Macromolecular Reaction Engineering
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Talents, Trends and Highlights
in Macromolecular Chemistry and Physics
Talent Articles highlight outstanding young scientists developing new, original ideas in the field of polymer science, explained by the authors of those new concepts.
Trend Articles are short overview contributions that highlight important contemporary developments in the field of polymer science, including the author's personal opinion on new directions, recent achievements and still open questions in the field.
Highlight Articles are short papers describing recent very important research results in the field of polymer science. They emphasize the importance of the presented research work and instruct readers on its significance.
TREND: Imaging of Polymeric Nanoparticles: Hard Challenge for Soft Objects
Patricia Renz, Maria Kokkinopoulou, Katharina Landfester, Ingo Lieberwirth*
The visualization of polymeric nanoparticles by means of electron microscopy methods is an important mainstay for the characterization. Simple drop casting is a commonly used preparation method but it meanly conserves the nanoparticle morphology. Alternatively, the nanoparticles can be embedded into a matrix consisting of trehalose or ionic liquid in order to achieve a better structure conservation.
Macromol. Chem. Phys., DOI: 10.1002/macp.201600246
TREND: Configuring Anion-Exchange Membranes for High Conductivity and Alkaline Stability by Using Cationic Polymers with Tailored Side ChainsPatric Jannasch,* Eva Annika Weiber
Polymeric anion-exchange membranes are crucial components in alkaline membrane fuel cells and other electrochemical energy systems. Recent results show that both OH− conductivity and alkaline stability of these materials are significantly enhanced by introducing flexible and hydrolytically stable alkyl side chains in the macromolecular design. Here, the latest trends in this research area are briefly reviewed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500481
TALENT: Molecular Polymer Brushes in NanomedicineMarkus Müllner
Molecular polymer brushes present an emerging class of polymer nanostructures with the potential to address persevering problems in nanomedicine. Recent improvements in the synthesis of these polymeric architectures allowed the tailoring of sophisticated nanomaterials for applications in drug and gene delivery, as well as the design of new imaging probes and prototype nanomaterials
Macromol. Chem. Phys., DOI: 10.1002/macp.201600086
TALENT: Use of Shewanella oneidensis for Energy Conversion in Microbial Fuel CellsA. Belen Jorge,* Rachael Hazael
Exoelectrogens are able to transfer electrons outside the cell to oxidize chemicals anareoebically through extracellular electron transfer mechanisms. This allows them to function in microbial fuel cells. However, there are still limitations and open questions about electron transfer mechanisms and biofilm-electrode interactions before this technology can be fully implemented in the real world.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500477
TREND: Engineering of Tough Double Network HydrogelsQiang Chen, Hong Chen, Lin Zhu, Jie Zheng*
Double network hydrogels (DN gels), consisting of two asymmetric, interpenetrating polymer networks, are considered as the toughest hydrogels. This Trend article summarizes the latest important findings of DN gels, covering new gel structures, functionalities, applications, and future perspectives.
Macromol. Chem. Phys., DOI: 10.1002/macp.201600038
TALENT: Polymeric Nanohybrids as a New Class of Therapeutic BiotransportersJonathan Whitlow, Settimio Pacelli, Arghya Paul*
Polymeric nanohybrids offer a useful platform to deliver drugs and genes in a selective and efficient manner. A variety of nanomaterials can be combined together with biomolecules in order to generate the next generation of biotransporters. This Talent article highlights the diverse innovative solutions in this direction with particular emphasis on the development of new biotransporters for drugs and gene delivery.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500464
TREND: Cationic Photoinitiators for Near UV and Visible LEDs: A Particular Insight into One-Component SystemsJing Zhang, Pu Xiao, Celine Dietlin, Damien Campolo, Frederic Dumur, Didier Gigmes, Fabrice Morlet-Savary, Jean-Pierre Fouassier, Jacques Lalevée*
The progress made along the last forty years in the design of one-component photoinitiators of cationic polymerization reactions is briefly described. A special emphasis is provided on the most recent development of ferrocenium salts based photoinitiating systems operating under near UV and visible LEDs.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500546
TREND: Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and ApplicationsTREND: Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and Applications
Alex Palma-Cando, Ullrich Scherf*
Assembling electroactive tetrapods into microporousthin films. Microporous polymer films produced by electrochemical oxidative polymerization of multifunctional, rigid monomers can be applied in fields that have been until now not accessible for the corresponding chemically synthesized bulk materials, e.g., organic electronic devices. High intrinsic surface area combined with a smooth surface represents a unique synergy, best-suited for applications where high quality films are required.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500484
TREND: Ferroelectric Polymers and Their Energy-Related ApplicationsQi Li, Qing Wang*
Ferroelectric polymers combine the unique physical properties of ferroelectrics and inherent advantages of organic materials. With highly tunable physical properties via tailoring chemical compositions and processing conditions, ferroelectric polymers are becoming the core components of advanced electronics, energy storage, and conversion devices.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500503
TREND: Cellulose-Based Gels
Hongliang Kang, Ruigang Liu,* Yong Huang*
Cellulose, the most available biomacromolecule in nature, is an excellent candidate for designing and constructing gels and microgels. This paper summarizes the methods for preparation of cellulose-based gels in detail. Chemical, physical, or both crosslinking approaches are introduced in the preparation of cellulose-based gels, which endows them with different properties for various applications.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500493
TREND: Configuring Anion-Exchange Membranes for High Conductivity and Alkaline Stability by Using Cationic Polymers with Tailored Side ChainsPatric Jannasch,* Eva Annika Weiber
Polymeric anion-exchange membranes are crucial components in alkaline membrane fuel cells and other electrochemical energy systems. Recent results show that both OH− conductivity and alkaline stability of these materials are significantly enhanced by introducing flexible and hydrolytically stable alkyl side chains in the macromolecular design. Here, the latest trends in this research area are briefly reviewed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500481
TALENT: Polymer and Particle Dynamics and Assembly in Varied Hydrodynamic FieldsEric D. Ruud, Nikolas A. Wilkinson, Cari S. Dutcher*
Polymer and particle dynamics and assembly play essential roles in both industrial and environmental aqueous processes. In this work, recent advancements in complex fluid dynamics and macromolecular assembly in varied hydrodynamic fields are highlighted, including viscoelastic (de)stabilization in Taylor–Couette flow, colloidal particle assembly in electrohydrodynamic flows, and polyelectrolyte–particle flocculation in turbulent flows.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500392
TALENT: Polymer Photocatalysts for Water Splitting: Insights from Computational ModelingPierre Guiglion, Cristina Butchosa, Martijn A. Zwijnenburg*
The ability of polymers to act as water splitting photocatalysts for the production of renewable hydrogen from water and sunlight is discussed based on insights from computational chemistry calculations. The role of exciton dissociation in these materials is considered, as well as the effect of oligomer length and the presence of heteroatoms on the photocatalytic activity.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500432
TALENT: Amphiphilic Hyperbranched Polymers: Synthesis and Host-Guest Supermolecular Coloring ApplicationYaochen Zheng, Aijin Tang, Zhulin Weng, Shengying Cai, Yu Jin, Zhengguo Gao, Chao Gao*
A novel amphiphilic hyperbranched poly(propargyl quaternary ammomium methacrylate)-co-polymethyl methacrylate is facilely synthesized via SCVP-RAFT polymerization and a sequential Menschutkin reaction. With a loose structure, tunable hydrophilic/hydrophobic segments, and strong interaction between binding site and guest molecule, it is used as an efficient dye-encapsulation additive and for common polymer coloring. The dyed polymer exhibits good uniformity, high transparency, and low dye release.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500321
TALENT: Side-Chain Amino-Acid-Derived Cationic Chiral Polymers by Controlled Radical PolymerizationKamal Bauri, Saswati Ghosh Roy, Priyadarsi De*
The synthesis of amino acids incorporating different types of main-chain and side-chain polymers is presented in this article. Here, mainly the synthesis, properties, and applications of side-chain amino acid/peptide containing cationic chiral polymeric architectures and 3D gel networks made by reversible addition-fragmentation chain transfer polymerization are reviewed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500271
TALENT: 2D or not 2D-Layered Functional (C, N) Materials "Beyond Silicon and Graphene"Michael J. Bojdys*
As of 2015, the number of mobile phone subscriptions outstrips Earth's human population. Critical raw materials and silicon, won in energy intensive refinement, make up the electronics in all these devices. While graphene still has to deliver on its potential in electronic applications, the present study looks to 2D polymer materials that go beyond silicon and graphene.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500312
TALENT: Functional Materials Design through Hydrogel Encapsulation of Inorganic Nanoparticles: Recent Developments and ChallengesMatthias Karg*
Hydrogel encapsulation of inorganic nanoparticles is a powerful strategy to render nanoparticles with high colloidal stability, compatibility with different media, and to gain controlled interparticle distances upon particle assembly. 2D and 3D assembly of these particles allows access to new functional materials with applications in sensing, photovoltaics, lasing, and all-optical computing.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500334
TALENT: Brief Timelapse on Dendrimer Chemistry: Advances, Limitations, and ExpectationsCatia Ornelas*
Dendrimer timelapse demonstrates constant evolution in dendrimer chemistry enabling their application in nanomedicine, protein mimic, catalysis, light harvesting systems, and sensing. Increasing the variety of functionalities in dendrimers located at precise sites of the dendritic backbone result in versatile multifunctional nanomaterials that in the future might approach the conceptual nanobots.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500393
TALENT: An Emerging Unified View of Dynamic Interphases in PolymersDavid S. Simmons*
An emerging understanding of dynamic interphases in multiple classes of polymeric materials is described. Near-interface alterations in dynamics are controlled in large part by interfacial energy and the mismatch of high-frequency modulus across the interface, and alterations propagate into the material over a range controlled by the size of cooperative segmental rearrangements characteristic of these materials’ dynamics during glass formation.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500284
TALENT: Bioactive Nanofiber Matrices Functionalized with Fibronectin-Mimetic Peptides Driving the Alignment and Tubular Commitment of Adult Renal Stem CellsAnna G. Sciancalepore, Maria Moffa, Simonetta Carluccio, Luigi Romano, Giuseppe S. Netti, Clelia Prattichizzo, Dario Pisignano*
The design and realization of electrospun nanofibers coupled with a fibronectin-mimetic peptide is described. The effect of the scaffolds on the behavior of renal stem cells is analyzed. These bioactive fibers might be useful for the definition of new biomimetic platforms to effectively culture and commit renal stem cells, allowing confluent and functional cell layers to be generated which are analogous to the renal proximal tubule epithelium.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500370
TALENT: Orchestrating Molecular Motion with Light - From Single (macro)Molecules to Materials
The ability to optically control synthetic systems using photochromic compounds holds much promise for the fields of materials and life sciences. This article highlights recent advances in that direction including the optimization of azobenzene photoswitches and their integration into oligomers, polymers, and 3D frameworks.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500330
TALENT: Investigations in Fundamental and Applied Polymer MechanochemistryMichael B. Larsen, Andrew J. Boydston*
Mechanochemistry continues to experience tremendous growth over the past decade. Major emphasis focuses on molecular-level design to understand how functional groups and polymeric materials transduce mechanical input. Additionally, applications-oriented research holds promise for translating mechanoresponsive materials into real world devices. Described herein are some of our efforts to develop mechanophores and mechanoresponsive materials.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500292
TALENT: Fluorescent Unimolecular Conjugated Polymeric Micelles for Biological ApplicationsFeng Qiu, Yu Huang, Xinyuan Zhu*
Unimolecular conjugated polymeric micelles, including wormlike copolymers and spherical copolymers, have been reviewed. The basic structure concepts, molecular design principles, synthesis strategies, and biological applications in the last ten years are introduced.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500283
TALENT: Aqueous Polymer Self-Assembly Based on Cucurbit[n]uril-Mediated Host-Guest InteractionsJi Liu, Cindy Soo Yun Tan, Yang Lan and Oren A. Scherman*
In recent years, cucurbit[n]urils (CB[n]) have attracted considerable attentions on account of their unique structure and host-guest binding properties. In this article, recent research progress in the Scherman group, on CB[n]-mediated polymeric self-assembly, is summarized. It covers supramolecular macromolecular engineering and corresponding self-assemblies, supramolecular polymerization, single polymer chain nanoparticles, supramolecular polymer microcapsules, supramolecular polymer hydrogels, colloidal clusters, and surface engineering.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500295
TALENT: Just Antimicrobial is not Enough: Toward Bifunctional Polymer Surfaces with Dual Antimicrobial and Protein-Repellent FunctionalityWibke Hartleb, Julia S. Saar, Peng Zou, and Karen Lienkamp*
Bifunctional antimicrobial and protein-repellent polymer surfaces can prove beneficial for the prevention of biofilm formation, particularly in the medical field. To obtain the desired dual functionality, the antimicrobial and the protein-repellent moiety of the polymer surfaces need to be precisely balanced. In this article, two possible surface architectures are described.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500266
TREND: Recent Advances in Alkyne-Based Multicomponent Polymerizations
Rongrong Hu,* Weizhang Li, Ben Zhong Tang*
Recent progress on the alkyne-based multicomponent polymerization (MCP) is reviewed, including the A3-polycouplings of alkynes, aldehydes, and amines; the MCPs of alkynes, sulfonyl azides, and amines/alcohols; the multicomponent tandem polymerizations of alkynes, carbonyl chlorides, and thiols/amines; and the metal/catalyst-free alkyne-based MCPs. Such efficient polymerizations provide a powerful tool for the construction of functional polymers with well-defined structures and unique properties.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500291
TALENT: Engineering Bioresponsive Hydrogels toward Healthcare ApplicationsYun-Long Wu, Xiaohong Chen, Wenzhu Wang and Xian Jun Loh*
Bioresponsive hydrogels are polymeric materials, designed to influence specific interactions with cellular systems during their biologically environmental dependent sol-to-gel transition process. Several key hydrogel materials developed in our group are discussed with reference to promising healthcare applications.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500172
TREND: Dynamics of Biopolymers: Role of Hydration and Electrostatic InteractionsJoon Ho Roh*
Water serves as the integral medium of biologically relevant dynamics of biopolymers. It is found that water-coupled dynamics of protein and RNA vary with thermodynamic balance between dynamical flexibility and structural stability determined in the chemical and physical responses of biopolymers to hydration and charge screening. This provides insight into the general concept of biologically important dynamics which remain elusive.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500279
TREND: Versatile Protein Nanogels Prepared by In Situ Polymerization
Yanqi Ye, Jicheng Yu, Zhen Gu*
The in situ polymerized nanogels with encapsulated proteins have great promises for storage and release of cargos in a spatial, temporal, and dosage-controlled manner. The preparation method and stimuli-responsive properties of the protein nanogels are listed and explained herein.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500296
TREND: Synthesis of Monodisperse Sequence-Defined Polymers Using Protecting-Group-Free Iterative Strategies
Thanh Tam Trinh, Chloé Laure, Jean-François Lutz*
Protecting-group-free iterative strategies that have been recently reported for the synthesis of monodisperse sequence-defined polymers are described. In such approaches, the monomers are attached one-by-one to a growing chain, which is immobilized on a solid- or soluble support. The uses of protecting-group-free coupling chemistries permit the simplification of these multistep growth processes. These promising concepts are listed and explained herein.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500072
TREND: Click Functionalization of Aromatic Polymers for Organic Electronic Device ApplicationsTsuyoshi Michinobu
Optical and electrochemical properties of aromatic polymers are tuned by the novel click reactions using cyano-acceptor reagents. The resulting polymers contain donor–acceptor chromophores and accordingly can be applied to organic electronic devices including thin film transistors, organic solar cells, and polymer memory devices. A series of device studies reveal the characteristic electronic features of the formed donor-acceptor chromophores.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500086
TREND: Interfacial RAFT Miniemulsion Polymerization: Architectures from an InterfaceAdrian V. Fuchs,* Kristofer J. Thurecht
The design of polymer architectures using macro reversible addition–fragmentation chain-transfer agents in a miniemulsion polymerization requires an understanding of the processes occurring at the droplet interface. The development of interfacially confined reversible addition–fragmentation chain-transfer in miniemulsion can selectively produce nanoparticles or nanocapsules. This article summarizes the developments that have led to the production of novel, functional polymer platforms using this technique.
Macromol. Chem. Phys., DOI: 10.1002/macp.201500061
TALENT: Regioselective Metal-Free Click Polymerization of Azides and AlkynesAnjun Qin,* Yong Liu, Ben Zhong Tang*
Metal-free click polymerization (MFCP) has been developed to circumvent the problems inherent in the broadly-applied Cu(I)-catalyzed azide-alkyne click polymerization reactions. The regioselective MFCP of azides and alkynes to produce regioregular polytriazoles is summarized, and the properties and applications of the resultant polymers are also discussed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400571
TALENT: Bioinspired Polymeric Nanocomposites for Regenerative MedicineJames K. Carrow and Akhilesh K. Gaharwar*
Designing bioinspired nanomaterials for tissue-engineering applications requires a fundamental understanding of the interactions between polymers, nanostructures, and cells. Biomimetic structures composed of fibrous architectures are discussed, the emerging trends in designing complex nanocomposites with multiple functionalities are assessed and finally, some of the most critical challenges that come with the design and fabrication of bioinspired polymeric nanocomposites are highlighted.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400427
TREND: Supramolecular Assembly-Assisted Synthesis of Responsive Polymeric Materials with Controlled Chain TopologiesJinming Hu, Shiyong Liu*
Recent advances concerning the fabrication of stimuli-responsive polymeric materials under the assistance of supramolecular self-assembly are summarized. The templated synthesis of linear (multiblock) copolymers, non-linear shaped copolymers, as well as crosslinked nanostructures on the basis of supramolecular assemblies is discussed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400578
TREND: Polymers and Ionic Liquids: A Successful WeddingSébastien Livi,* Jannick Duchet-Rumeau, Jean-François Gérard, Thi Nhan Pham
Different pathways for development of nanostructured and advanced materials are summarized, based on the use of ionic liquids (ILs) as multifunctional agents of polymer matrices. The true potential of ILs in the design of new polymeric materials with unprecedented mechanical performance, thermal stability, and barrier properties is highlighted.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400425
TREND: Benzothiadiazole-Containing Conjugated Polyelectrolytes for Biological Sensing and ImagingRuoyu Zhan*, Bin Liu*
This article summarizes the recent advances of benzothiadiazole (BT)-containing conjugated polyelectrolytes (CPEs) for biological sensing and imaging. After a brief introduction of the molecular design principles, the application of linear BT-containing CPEs as multicolor or light-up probes for visual sensing of biomolecules is reviewed. Then, linear, grafted, and hyperbranched BT-containing CPEs that can self-assemble into nanoparticles or have intrinsic 3D structures for in vitro and in vivo imaging are summarized. The future outlook of BT-containing CPEs for biomedical applications is also discussed at the end.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400408
TALENT: Effect and Evolution of Nanostructural Complexity in Sensitive Polymer GelsSebastian Seiffert
Sensitive and supramolecular polymer gels can be selectively swollen and deswollen or gelled and degelled in response to external stimulation; to truly benefit from this ability, the impact of nanometer-scale structural heterogeneity in the constituent polymer networks must be understood and accounted for in materials design.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400410
TALENT: Toughening Polylactide with Phase-Separating Complex Copolymer ArchitecturesWilliam M. Gramlich
Block and graft copolymers of polylactide (PLA) and a rubbery polymer can create nanometer-scale phase separation that leads to tough plastics, but past work has relied on a non-sustainable rubbery material. Through novel chemistry and copolymerizations, graft copolymers of sustainable polyisoprene and PLA can create a fully sustainable nanometer-scale phase-separated plastic.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400350
TREND: The Interaction Between Amphiphilic Polymer Materials and Guest Molecules: Selective Adsorption and Its Related ApplicationsBing Yu, Xuesong Jiang,* Jie Yin
Amphiphilic polymer materials possess selective adsorption to guest molecules, such as dyes, drugs, proteins, and other biomolecules, which is beneficial for their application in the separation, temporally controlled release, and patterning of guest molecules
Macromol. Chem. Phys., DOI: 10.1002/macp.201400389
TREND: Polymers for Luminescent Sensing ApplicationsHyungwoo Kim, Youngdo Kim andJi Young Chang*
Polymers are widely used for chemical sensing applications, as a receptor or as a signal transducer. Fluorescent conjugated polymers are extensively studied for signaling. Molecularly imprinted polymers are artificial receptors fabricated using the molecular-imprinting technique. In this article, the recent developments on luminescent polymeric sensors are briefly summarized.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400128
TALENT: The Renaissance of Side-Chain Ferrocene-Containing Polymers: Scope and Limitations of Vinylferrocene and Ferrocenyl MethacrylatesMarkus Gallei
The combination of metals and polymers is an intensively explored field for the formation of so-called next-generation materials. Metal-containing polymers featuring the ferrocene motif in the side chain, such as poly(vinylferrocene) and poly(ferrocenyl methacrylates), have been known for a long time but, due to recent synthetic efforts, the first steps toward fruitful applications have only been investigated in the last few years.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300762
TREND: "Heavy-Atom" Donor-Acceptor Conjugated PolymersGregory L. Gibson and Dwight S. Seferos*
Donor-acceptor polymers containing "heavy" atoms below the first row of the periodic table are widely studied with an eye to organic electronics. These polymers demonstrate desirable optical and electronic properties, including high charge-carrier mobility. This article elucidates trends in heavy-atom polymer structure–property relationships by examining single atom substitutions in select donor–acceptor architectures.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400042
TREND: Polysaccharide Biocatalysis: From Synthesizing Carbohydrate Standards to Establishing Characterization MethodsJelena Ciric, Dejan M. Petrovic and Katja Loos*
In vitro enzymatic synthesis is the future for polysaccharide production. By synthesizing and characterizing various polysaccharides with complicated structures, they are understood better and a much closer understanding of nature is reached. The characterization of widely used natural carbohydrates, such as starch and cellulose, can be improved after a detailed analysis of their enzymatically synthesized analogs. An overview of both enzymatic synthesis and various characterization techniques of polysaccharides is presented in this article.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300801
TREND: Recent Trends and Future Outlooks in the Field of Clay-Containing Polymer Nanocomposites
Suprakas Sinha Ray
This article highlights recent developments in academic and industrial research in the field of clay-containing polymer nanocomposites, including current commercial successes, providing a short overview on key research challenges, as well as future outlooks and open questions in the field.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400069
TALENT: Two Non-covalent Methods to Decorate Nanoparticles with Block CopolymersChristophe Schatz
Two novel approaches of particle functionalization with block copolymers are introduced. The first method is based on the physical adsorption of a charged block copolymer with two adsorbing blocks. The second method consists of self-assembling a bilayer of amphiphilic block copolymer at the particle surface through a change of solvent polarity.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300756
TALENT: Composing Well-Defined Stimulus-Responsive Materials Through Postpolymerization Modification ReactionsPeter J. Roth
Choosing the right building blocks is the key to designing novel smart materials. This article combines theoretical fundamentals of different types of stimulus-responsiveness, emphasizing lower and upper critical solution temperature (LCST and UCST) behavior, with a range of illustrations of postpolymerization modification reactions in order to provide guidance on how to compose well-defined smart polymers with tailored properties.
Macromol. Chem. Phys., DOI: 10.1002/macp.201400073
TALENT: Facile One-Pot Synthesis of New Functional Polymers through Multicomponent Systems
Shiqi Wang, Changkui Fu, Yen Wei and Lei Tao*
One-pot strategies, which combine in situ monomer synthesis and controlled radical polymerization together, are applied into innovative functional polymer preparation. This methodology is simple, efficient, and versatile. In this talent article, most advances in one-pot synthesis strategies are summarized and their further applications are discussed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300738
TREND: Mechanism and Kinetics of Dithiobenzoate-Mediated RAFT Polymerization - Status of the Dilemma
Developments in the understanding of the mechanism and kinetics of dithiobenzoate-mediated reversible addition-fragmentation chain-transfer (RAFT) polymerization over the period 2006–2013 are critically assessed with specific reference to choice of reagents and polymerization conditions, reagent and product stability, side reactions and factors that may lead to retardation.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300562
TALENT: Self-Assembly of Globular-Protein-Containing Block CopolymersBradley D. Olsen
The direct self-assembly of globular-protein-containing block copolymers provides an attractive method for the fabrication of biofunctional nanostructures; a variety of different solid state and block copolymer gel nanostructures may be formed. The thermodynamics and processing of these systems are heavily influenced by the folded, biofunctional structure of the protein.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300235
TALENT: Tailoring Cellulose Surfaces by Controlled Polymerization MethodsAnna Carlmark
To expand the utilization of cellulose beyond its traditional uses, it is necessary to modify the surface of the fibers. This paper summarizes the modification of cellulose by controlled polymerization methods such as ATRP, RAFT, ROP, and ROMP. The combination of the excellent properties of cellulose with functional polymers creates new materials of great potential in advanced material applications.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300272
TREND: The Solvent in Physical Gelation: Polymers Versus Organogelators
Debarshi Dasgupta, Jean-Michel Guenet*
A discussion of the gelation mechanisms involved in polymer thermoreversible gels and organogels is presented. The implication of the solvent as an active actor and not only a mere diluent is shown.
Macromol. Chem. Phys., DOI: 10.1002/macp.201300094
TALENT: Non-Natural Amino Acids for Protein Engineering and New Protein ChemistriesInchan Kwon,* Sung In Lim
Two distinct strategies, residue-specific and site-specific incorporation, allow biosynthesis of a protein containing non-natural amino acids. Non-natural amino acids introduced into a protein can be used to manipulate spectral and catalytic properties of a protein and provide new protein chemistries for bioconjugation with versatile molecules.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200710
TREND: MAPLE Deposition of MacromoleculesKimberly B. Shepard, Rodney D. Priestley*
Matrix-assisted pulsed laser evaporation (MAPLE) is used to deposit thin films of a vast range of macromolecules, including polymers, proteins, and composite materials. The numerous advantages of MAPLE are discussed, and recent reports of MAPLE-deposited films for electronic and medical applications are highlighted.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200621
TREND: Recent Trends in the Chemistry of Shape-Memory Polymers
Konstanze K. Julich-Gruner, Candy Löwenberg, Axel T. Neffe, Marc Behl, Andreas Lendlein*
Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand. This trend article highlights current approaches in the chemistry of SMPs (e.g., tailoring segment chemistry to integrate additional functions). It is illustrated that SMPs can be constructed on the molecular level as a modular system of different building blocks and netpoints.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200607
TREND: Can the Structures of Semicrystalline Polymers be Controlled Using Interfacial Crystallographic Interactions?Haixin Zhou, Shouke Yan*
Epitaxy based on crystallographic interaction can govern the crystal structure of overgrowing polymers. It therefore provides a simple and efficient way to fabricate ordered structures of homopolymers with controlled chain orientation, crystal modification, and spatial arrangement of the backbone chain. An expansion of this method to control structures of polymer blends is a trend and challenge in the field of polymer science.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200530
TREND: Microstructure Control: An Underestimated Parameter in Recent Polymer Design
Nezha Badi, Delphine Chan-Seng, Jean-François Lutz*
Macromolecular parameters such as tacticity, regioregularity, and co-monomer sequences determine, in large parts, the properties of polymer materials. However, these crucial aspects are currently overlooked by polymer chemists. The present article emphasizes the extreme importance of these parameters in 21st century polymer research.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200475
TREND: Chemical Vapor Deposition for Solvent-Free Polymerization at SurfacesJose Luis Yagüe, Anna Maria Coclite, Christy Petruczok, Karen K. Gleason*
Initiated chemical vapor deposition (iCVD) polymerization is a very elegant technique for designing new patterns and tuning the chemistry available on any kind of surface. These polymers attract considerable attention in many different fields of application. This trends article highlights the latest achievements in the fabrication of new surfaces and functional materials via iCVD and presents significant insights in its scale-up process.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200600
TALENT: Renewable Polyols for Polyurethane Synthesis via Thiol-ene/yne Couplings of Plant OilsGerard Lligadas
Nowadays, the utilization of chemicals derived from renewable feedstock is in the spotlight of the polymeric industry. Plant oils and derivatives are important platform chemicals due to their amazing chemical versatility. Herein, these materials together with thiol-ene/yne couplings are presented as a perfect ecofriendly combination to prepare hydroxyl building blocks for polyurethane technology.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200582
TREND: Thieno[3,4-c]pyrrole-4,6-dione-Based Polymers for Optoelectronic ApplicationsAgnieszka Pron, Philippe Berrouard, Mario Leclerc*
Recently, push–pull type conjugated polymers consisting of thieno[3,4-c]pyrrole-4,6-dione (TPD) motif as an electron-deficient moiety gained a lot of attention for applications in plastic electronics. For instance, incorporation of TPD-based polymers into bulk heterojunction (BHJ) solar cells resulted in devices with power conversion efficiency (PCE) up to 8.5%. This Trend Article summarizes current research on such TPD-based polymers with special emphasis on structure–property relationships.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200549
TALENT: New Applications of Photolabile Nitrobenzyl Groups in PolymersSamuel W. Thomas III
New approaches to photoresponsive materials with nitrobenzyl esters are described using conjugated polymers and polyelectrolyte multilayer films that respond to UV light. Photocleavage of cations from polyelectrolytes in layer-by-layer (LbL) films disrupts their integrity, while conjugated materials with nitrobenzyl pendants show photochemically controlled fluorescence efficiency and solubility.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200486
TALENT: Polymers as Probes for Multimodal Imaging with MRIKristofer J. Thurecht
Polymeric systems are an ideal platform for developing multimodal molecular imaging agents due to the ability to tailor their chemo-physical properties. Polymers facilitate marrying imaging modalities that provide high resolution such as MRI, with highly sensitive modalities such as positron emission tomography or fluorescence, through manipulation of the chemical structure of the macromolecules.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200420
TREND: Bioinspired Microorigami by Self-Folding Polymer FilmsLeonid Ionov
Recent advances in the development and application of biomimetic self-folding polymer films, which mimic natural mechanisms of movement and form complex 3D structures, are discussed in this manuscript.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200246
TREND: Combinations of Elements: a New Paradigm for Fire Retardancy
Thirumal Mariappan, Charles A. Wilkie*
The presence of a nanodimensional material, together with a conventional fire retardant, leads to increased char formation and better fire retardancy.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200363
TREND: Emergence of Polymer Stereocomplexes for Biomedical ApplicationsAnnabelle Bertin
Stereocomplexes of polylactide and poly(methyl methacrylate) are poised to have a big impact in the biomedical field because they offer improved properties and additional possibilities compared to the individual polymers in terms of tunable drug release and degradation rate as well as mechanical strength, not to mention their potential in terms of engineering of macromolecular constructs and surfaces.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200143
TREND: Chemical Routes Toward Multicompartment ColloidsDaniel Crespy,* Roland Hinrich Staff, Tanja Becker, Katharina Landfester
Complex colloidal structures can be elaborated via a cornucopia of synthetic pathways. The different routes are classified in: assembly of colloids, synthesis with the use of sacrificial templates, and internal phase separation in colloidal droplets. A tentative analogy between the basic arithmetic operations and these routes is proposed.
Macromol. Chem. Phys., DOI: 10.1002/macp.201200124
TREND: Beyond Orientation: The Impact of Electric Fields on Block CopolymersClemens Liedel, Christian W. Pester, Markus Ruppel, Volker S. Urban, Alexander Böker*
Since 1991, electric fields have been shown to strongly affect block copolymer structures. Aside from alignment, morphological distortions, order–order, and order–disorder transitions have been described both in bulk and thin films. Important findings of the last two decades are summarized and perspectives for future progress in the field of block copolymers in electric fields are outlined.
Macromol. Chem. Phys., DOI: 10.1002/macp.201100590
TREND: Current Trends in the Field of Self-Healing MaterialsNathalie K. Guimard, Kim K. Oehlenschlaeger, Jiawen Zhou, Stefan Hilf, Friedrich Georg Schmidt,* Christopher Barner-Kowollik*
The development of self-healing materials has become of increasing interest to material scientists in the last 20 years, given the extraordinary advantages that such systems offer in a wide range of applications. The design of an optimal self-healing material depends on many factors, including material application, stability, and production cost.
Macromol. Chem. Phys., DOI: 10.1002/macp.201100442
TALENT: Novel Controlled Polymerization of Cyclo-olefins, Dienes, and Trienes by Utilizing Reaction Properties of Late Transition MetalsDaisuke Takeuchi
Diimine Pd complexes promote polymerization of cyclopentenes, non-conjugated dienes, and trienes to produce polymers with controlled structure. The polymers show characteristic properties including thermoreversible gelation and liquid crystalline formation. Diimine Ni complexes bring about cyclopolymerization of diallylfluorene to yield polymers containing five- and/or six-membered rings in controlled stereochemistry.
Macromol. Chem. Phys., DOI: 10.1002/macp.201100182
TREND: Externally Induced Thermal Actuation of Polymer NanocompositesYing Hu, Wei Chen*
Thermally active polymers have attracted great attention because of the convenience and effectiveness of the thermal stimulation among the stimuli-responsive polymers. The trend article presents a brief overview of recent progress on externally induced thermal actuation of polymer nanocomposites, with emphasis on the influence of embedded nanomaterials which serve as "nanoantennas" and "nanoheaters" for harvesting and converting the external stimulus into thermal stimulation.
Macromol. Chem. Phys., DOI: 10.1002/macp.201100068
TREND: What Morphologies Do We Want? - TEM Images from Dilute Diblock Copolymer SolutionsHong Zhao, Qianjin Chen, Liangzhi Hong, Lei Zhao, Jianfang Wang, Chi Wu*
Various exotic morphologies of block copolymers in solutions have been reported only based on TEM imaging. Do they really exist in solutions or are they just some kinetically frozen structures formed during the TEM sample preparation? Fairly speaking, more and more people realize that it is necessary to use cryo-TEM to ascertain different morphologies of block copolymers in solutions. However, when a modern cryo-TEM is not accessible, a combination of different methods, such as LLS, freeze-drying, and TEM should be used.
This Trend Article is addtionally featured on MaterialsViews.
Macromol. Chem. Phys., DOI: 10.1002/macp.201000696
TALENT: Polymers for Control FreaksLaura Hartmann
Compared to biological polymers, most synthetic polymers utilized in medicine are often polydisperse in nature, statistically modified, and empirically optimized. Inherent distributions result in disperse structure-property relationships, which renders interpretation of the biological properties for such polymers difficult. Laura Hartmann presents in her Talent Article a novel synthetic strategy towards monodisperse, sequence-defined poly(amidoamine)s. Variations of the chemical structures are used to directly control the ability of such polycations to complex DNA and function as non-viral vectors. Her future work is expected to provide a deeper understanding of the interactions of fully synthetic with biological systems and using these interactions for the design of bioactive polymer-based materials.
This Talent Article is addtionally featured on MaterialsViews.
Macromol. Chem. Phys., DOI: 10.1002/macp.201000479
TREND: Optical Probes of Charge Generation and Recombination in Bulk Heterojunction Organic Solar CellsIan A. Howard, Frédéric Laquai*
Understanding the principles of charge generation and recombination in organic solar cells is a prerequisite for future material development and device optimization. Optical probes, especially transient absorption spectroscopy, are valuable tools to study the dynamics of excited states such as excitons and charges, over a wide-range of timescales. New insights from recent studies may help to guide the future material development without having to rely on entirely empirical strategies for device optimization.
Macromol. Chem. Phys. 2010, DOI: 10.1002/macp.201000353
TREND: Contemporary Mass Spectrometry and the Analysis of Synthetic Polymers: Trends, Techniques and Untapped PotentialGene Hart-Smith, Christopher Barner-Kowollik*
The current Trend article - written in an easily accessible tutorial style fashion - provides an introduction to the fundamental principles of polymer mass spectrometry from the ionisation process itself to the choice of mass analyser. In addition, selected applications are highlighted and commented upon.
Macromol. Chem. Phys. 2010, DOI: 10.1002/macp.201000107
TALENT: Diels-Alder Cycloaddition-Cycloreversion: A Powerful Combo in Materials DesignAmitav Sanyal
Incorporation of the reactive maleimide group into macromolecular structures enables the fabrication of thiol reactive polymeric materials. Until recently, challenge in preserving the maleimide group during synthetic manipulations such as polymerization has hampered the development of such materials. The Diels-Alder/retro Diels-Alder reaction combination offers a viable solution to this problem. Furthermore, the reaction combination also enables the design of thermoreversible materials.
Macromol. Chem. Phys. 2010, DOI: 10.1002/macp.201000108
TREND: In situ Synthesis of Polymer/Clay Nanocomposites by Living and Controlled/Living PolymerizationMehmet Atilla Tasdelen, Johannes Kreutzer, Yusuf Yagci*
The present trend article reports on the recent progress of the in situ synthesis of polymer/clay nanocomposites with well-defined structures and highly exfoliated morphologies. The methods used for the preparation are classified according to the individual polymerization mechanisms. Other possibilities such as multi-mode polymerization that combines different polymerization methods and click chemistry are also described. A special emphasis is devoted to the structures and morphologies of the obtained nanocomposites rather than their practical properties.
Macromol. Chem. Phys. 2010, DOI: 10.1002/macp.200900590
TREND: Organometallic-Mediated Radical Polymerization: Developing Well-Defined Complexes for Reversible Transition Metal-Alkyl Bond HomolysisKevin M. Smith, W. Stephen McNeil, Alaa S. Abd-El-Aziz*
Organometallic-mediated radical polymerization (OMRP) has emerged as a powerful new class of living controlled radical polymerization. In order to fulfill its potential in the polymerization of vinyl acetate (VOAc) and other challenging monomers, the effects of ancillary ligands on the metal-alkyl bond dissociation energy in OMRP reagents must be thoroughly explored. Recent results investigating structure-activity relationships in well-defined cobalt, iron and chromium complexes will be discussed. The involvement of radical intermediates in oxidative addition of secondary alkyls for catalytic cross-coupling reactions catalyzed by first row transition metals will also be examined for relevant design concepts.
Macromol. Chem. Phys. 2010, DOI: 10.1002/macp.200900581
TALENT: Plant Oils as Renewable Resources in Polymer ScienceMichael A. R. Meier
Due to depleting fossil resources, the ever increasing emission of greenhouse gases and toxic waste, as well as the inefficient utilization of our available resources, we have to implement the principles of green chemistry whenever and wherever possible. Plant oils are already the most important renewable resource for the chemical industry. Due to their inherent doublebond functionality, they offer the possibility of being transformed via several very efficient catalytic processes. Especially, new developments in olefin metathesis allow the chemist to directly polymerize or introduce a variety of functional groups to these renewable resources in an efficient manner.
Therefore, olefin metathesis with plant-oil-derived fatty acids and their derivatives can contribute to a sustainable development of our future, since this approach has great potential for the substitution of currently used petrochemicals and a variety of value-added chemical intermediates, especially for the polymer industry, can be derived from these resources in a straightforward fashion. This contribution will address and discuss the most recent developments in this field of research.
Macromol. Chem. Phys. 2009, DOI: 10.1002/macp.200900168
TREND: Has Click Chemistry Lead to a Paradigm Shift in Polymer Material Design?Christopher Barner-Kowollik,* Andrew J. Inglis
Has the introduction of the click chemistry concept by Sharpless and colleagues in 2001 lead to a paradigm shift in how we approach the design of macromolecular materials; or is it simply a relatively inconsequential re-branding exercise of already existing and slightly optimized but well-tried and tested reactions as some critics would have it?
The current Trend Article analyses the situation by examining a series of select macromolecular research fields to shed light on this question, providing an unambiguous answer: The focusing of polymer chemists through the click concept on what constitutes a powerful modular chemical transformation to generate a specific polymeric material is a defining element in contemporary synthetic polymer chemistry, transcending a specific reaction. Without the introduction of the click philosophy several classes of innovative materials and polymer designs would not have been realized.
Macromol. Chem. Phys. 2009, DOI: 10.1002/macp.200900139
TALENT: Electrostatic Self-Assembly as Route to Supramolecular StructuresFranziska Gröhn
We introduce and discuss the recently developed concept of electrostatic self-assembly for the formation of nanoscale assemblies in solution. As opposed to many approaches to self-assembly relying on amphiphilicity, the driving force here is electrostatics plus secondary interaction such as stacking of aromatic molecule parts: Polyelectrolyte dendrimers can be linked with multiply charged aromatic dye molecules as structural counterions yielding 100 nm scale aggregates of narrow size distribution and different shapes. We discuss competing interaction forces and the potential of this approach to lead to versatile and functional supramolecular structures.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200800290
TALENT: Challenges in Glassy Dynamics of PolymersAnatoli Serghei
This work is focused on the glassy dynamics of polymers under conditions of one-dimensional confinement (in thin films). Several important topics are addressed: (a) preparative factors with large impact on the molecular dynamics of thin polymer films (oxidative degradation, plasticizing effects, residual stresses leading to metastable states); (b) it is emphasized the necessity to characterize the glass transition by measuring relaxation time distribution functions; (c) it is shown that different experimental techniques do not necessarily deliver converging results when applied to characterise the dynamics of confined polymers; (d) a novel approach is demonstrated which grants a direct experimental access to interfacial polymer dynamics; (e) measurements on nearly isolated polymer chains are presented.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200800197
TREND: Trends in Polyolefin ChemistryWalter Kaminsky
Polyolefins have grown faster in recent years than many other polymers. The production of poly(propylene) increased rapidly when it was possible to optimize the isotacticity of the polymer chain. New fields for future polymer sciences are the defined short and long chain branched polyolefins, block copolymers by chain shuttling, living and emulsion polymerization, and polyolefin nanocomposite materials. These research fields will create polymers with new and specific properties and applications in the near future. Compared to the formation of polymers in nature, the possibilities are today very limited for the synthetic chemistry. Especially, there are great deficits in tailoring the microstructure of copolymers with two or more monomers in a well defined way. It will be a great challenge to solve this problem but then it opens up exciting advantages.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700575
TREND: Microstructured Reactors for Polymer Synthesis: A Renaissance of Continuous Flow Processes for Tailor-Made Macromolecules?Daniel Wilms, Johannes Klos, Holger Frey*
Organic synthesis in microfluidic devices has attracted increasing interest in recent years. However, little efforts had been undertaken to exploit this novel technology for polymer chemistry until several recent studies demonstrated the interesting potential of microreactors for the synthesis and modification of polymers. In fact, anionic polymerizations in continuous capillary flow-tube systems were established already in 1962 in pioneering work by Szwarc. Subsequent work focused on detailed kinetic analyses in such reactors. The present article explores different current strategies developed by several research groups to realize bulk and solution polymerizations using continuous flow microreactors. Inherent benefits and limitations of these systems compared to traditional laboratory set-ups are discussed. We present a variety of recent pioneering and advanced approaches to realize free radical, controlled radical, cationic and anionic polymerizations in microtechnological reaction devices. In some cases, surprisingly narrow molecular weight distributions have been obtained, demonstrating the promising potential of this approach for the tailoring of polymer structures.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700588
TREND: Combinatorial and High-Throughput Methods in Macromolecular Materials Research and DevelopmentDean C. Webster
Combinatorial and high-throughput experimentation is used to accelerate the rate of experimentation in macromolecular science. Combinatorial and high-throughput methods are used in macromolecular science to discover and optimize catalysts for polymerization reactions, discover compositions that have specific desired properties, and systematically explore polymer structure-property relationships. The use of high-throughput methods can enable the discovery of complex catalyst systems or polymer compositions that would not be feasible using conventional experimental methods. In addition, combinatorial data can be used as inputs into computer models to enable the accurate prediction of material properties as a function of composition.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700558
TALENT: Metallopolyyne Polymers as New Functional Materials for Photovoltaic and Solar Cell ApplicationsWai-Yeung Wong
The need to develop inexpensive renewable energy sources has stimulated intensive scientific research for efficient, low-cost, lightweight, photovoltaic devices. Organic polymer-based photovoltaic elements have offered the potential to obtain cheap and fabrication-easy methods to harvest energy from sunlight as compared to inorganic semiconductors. Encouraging progress has been made over the past few years in the field of photovoltaic solar cells using organic polymers. One attractive alternative discussed in this Talent Article is the development of photovoltaic and solar cells that are based on the exploitation of strongly absorbing metallopolyynes of platinum as the electron donors in bulk heterojunction devices. Power conversion efficiencies of over 4% have been achieved by blending polyplatinynes with electron-accepting methanofullerene. We predict that these conjugated organometallic congeners will make important contributions to identify environmentally friendly hi-tech solutions to the energy problem. This review includes a short summary of the recent achievements of the author in this field and relevant work by others. The ongoing challenges and future prospects of this research area are also discussed.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700563
TREND: Polymer Synthesis and Modification by Use of MicrowavesMareike Bardts, Nina Gonsior, Helmut Ritter*
Nowadays, microwave-assisted polymer chemistry is a rapidly growing field of research. In the last few years, various examples of reaction accelerations, selectivities, and higher yields have been reported. In this contribution, the current state of the art is summarized and an overview on microwave-assisted polymerizations is presented, whereby special attention is given to advantages and promising future trends in this intriguing field of research.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700443
TALENT: Synthetic Models of Weak Attractive Ligand-Polymer Interactions in Olefin Polymerization CatalystsMichael C. W. Chan
The subject of extremely weak hydrogen bonds such as CH...FC remains a contentious and topical area of research. The design and synthesis of a family of Group-4 post-metallocene catalysts supported by F-functionalized tridentate ligands that impose the fluorine substituent(s) in close proximity to the metal center is described, and for the first time, the elusive CH...FC interaction is characterized by a neutron diffraction study. The nature of the weak intramolecular CH...FC contacts in these complexes in solution and in the solid state is probed using multinuclear NMR spectroscopy in tandem with neutron and X-ray crystallography. These CH...FC interactions are important with regards to design implications and potential applications in olefin polymerization catalysts because they corroborate the proposed ortho-F...H() ligand-polymer contacts derived from density functional theory calculations for the Group 4 fluorinated phenoxyimine catalysts. Compared with the established agostic and cocatalyst-metal contacts, weak attractive non-covalent interactions between a non-innocent ligand and the polymer chain is a novel concept in polyolefin catalysis.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700322
TALENT: Recent Gelation Studies on Irreversible and Reversible Systems with Dynamic Light Scattering and Rheology - A Concise SummarySven Richter
This contribution is a short summary of the recent achievements of the author in the field of gelation research on irreversible gelling systems based on N-vinylcaprolactam and on thermoreversible systems (xanthan gum/locust bean gum, and gelatin) mainly based on dynamic light scattering and oscillatory shear rheology. These investigations are discussed in the framework of studies of other authors. It will be pointed out that both methods are well suited to detect the sol-gel transition, but some expectations that the two different methods can lead to different results will be given, which may be of importance to other systems. In the main focus is the comparison of dynamical critical exponents yielded from the two methods at the sol-gel transition.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700285
TREND: Charged Polymers via Controlled Radical Polymerization and their Implications for Gene DeliveryWilliam H. Heath, Askim F. Senyurt, John Layman, Timothy E. Long*
Non-viral gene delivery agents are notorious for their poor nucleic acid transfection efficiency and relatively high cell cytotoxicity. Thus, many investigators are exploring the important parameters involved in charged polymer-mediated gene delivery, such as chemical composition, molecular weight, structural architecture, surface charge, etc. It is important to develop clear structure-property relationships in order to design successful nucleic acid delivery agents for gene therapy. To elucidate these relationships, well-defined materials are necessary. Controlled radical polymerization methods offer a facile route to systematically produce well-defined, structurally distinct gene delivery agents. The use of charged polymers prepared via controlled radical polymerizations to elucidate transfection mechanisms or develop new delivery vectors will be reviewed herein.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200700216
TREND: Hierarchical Organization of Colloidal Particles: From Colloidal Crystallization to Supraparticle ChemistryErik W. Edwards, Dayang Wang,* Helmuth Möhwald
Recent developments in the hierarchical organization of micro- and nanoparticles suggest a categorical shift in which the focus has changed from colloidal crystallization based on van der Waals forces to the assembly of clusters of a well-controlled number of particles through various covalent and non-covalent interactions, referred to here as supraparticle chemistry. This article highlights some of the advances that have been made during this transition and discusses some of the promising future directions that should be realized.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200600655
TALENT: Functional Polymer-Bioconjugates as Molecular LEGO(R) BricksHans G. Börner
The controlled integration of sequence-defined oligopeptides into synthetic polymers leads to peptide-polymer conjugates with precisely defined, multifunctional peptide segments. These bioconjugates allow for the direct realization of bio-inspired polymer science. Peptides combine self-assembly properties with the potential to actively interact with biological systems. Hence conjugates can be exploited to program microstructure formation processes in polymeric materials by controlling secondary interactions between the peptide segments. Moreover, the programmable functionalities of the peptides can be used to tune specific interactions, e.g., between drugs and polymeric drug carriers or between inorganic crystal surfaces and polymeric crystal-growth modifiers.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200600559
TALENT: Poly(2-oxazoline)s: Alive and KickingRichard Hoogenboom
The development of various living/controlled polymerization techniques has allowed the synthesis of a large variety of well-defined (co)polymers with varied polymer length, composition, and architecture, for example. Screening this large possible parameter space for a polymer with certain properties can be a very demanding process. Therefore, we aim to rapidly synthesize and systematically screen libraries of copolymers to determine structure-property relationships that might allow the future design of novel (co)polymers with predictable properties. The cationic ring-opening polymerization of 2-oxazolines has been adapted for the synthesis of libraries of well-defined (co)polymers. In this contribution, the optimization of the polymerization procedure using both high-throughput experimentation and microwave irradiation is discussed. Subsequently, the microwave-assisted synthesis of well-defined libraries of (co)poly(2-oxazoline)s and the determination of structure-property relationships for these polymers is described. Moreover, the polymerization of a soy-based 2-oxazoline monomer will be illustrated as a green approach to replace current oil-based feedstock by renewable resources.
Macromol. Chem. Phys. 2008, DOI: 10.1002/macp.200600558
HIGHLIGHT: Catalytic Olefin Polymerization is a Mature Field. Isn't it?
We often hear that there is nothing left to discover in Ziegler-Natta chemistry, and that polyolefins have no more secrets to reveal. In reality, scientific research in the area has never been so much alive. Just as an example, a recent paper in Science (2006, 312, 714-719) introduces altogether a novel class of post-metallocene catalysts (see figure) and a revolutionary concept of polyolefin chain growth leading to materials with unprecedented microstructure and properties already bound for industrial production. This highlight aims at guiding the reader to the new challenging frontiers of Ziegler-Natta catalyst and material design.
HIGHLIGHT: New Methods for Anionic Polymerizations at Elevated Temperatures: "Retarded Anionic Polymerizations"
N. B. Bowden
Critical new advances in living anionic polymerizations, in particular retarded anionic polymerizations (RAP), which uses new reagents to initiate and control the polymerization, are highlighted here. The emergent area of RAP allows anionic polymerizations to be carried out under conditions that are more amenable to industrial synthesis (i.e., at elevated temperatures) and to synthesize new polymer architectures.
HIGHLIGHT: DNA-Synthetic Polymer Conjugates
The development of methods to prepare conjugated polymers in which functional moieties of DNA are connected to artificial polymers is a promising strategy to generate novel functional materials that combine the functions of both. Recent studies in the field are reviewed here with particular attention to the synthesis of a thymine-poly(thiophene) conjugated polymer, an example of a DNA function bound to a stable polymer backbone, which proved highly selective in the detection of Hg+ ions.
HIGHLIGHT: Styrene/Maleic Anhydride Macro-RAFT-Mediated Encapsulation
The encapsulation of a liquid by RAFT-mediated miniemulsion polymerization seems like a robust method. The use of a styreneûmaleic anhydride copolymer as a macro-RAFTagent offers potential for the further construction of nanostructured latex particles.
HIGHLIGHT: Towards Powering Nanometer-Scale Devices with Molecular Motors: Single Molecule Engines
Future nanodevices will require molecular motors to generate mechanical work. Single polymer chains for which an external stimulus changes the flexibility are possible candidates. The figure shows a possible working cycle of such a polymeric motor. The stimulus can be an electrochemical potential. As a proof of principle poly(ferrocenyldimethylsilane) was reversibly oxidized and reduced and its flexibility was shown to change accordingly.
HIGHLIGHT: Photodeformable Polymers - A New Kind of Promising Smart Material for Micro- and Nano-Applications
Y. Yu,* T. Ikeda*
The direct conversion of light energy into mechanical power (photomechanical effect) is achieved by deformations of photodeformable polymers. Recent developments in the field are presented, including the concept of using photo-crosslinking to prepare deformable polymers with various pre-determined shapes. The Figure shows a polymer film doped with SCAA molecules in its permanent shape (a), its temporary shape (b), and the recovered shape (c).
HIGHLIGHT: New Materials for Rapid Prototyping Applications
J. Stampfl,* R. Liska*
Rapid prototyping (RP) is a widely used manufacturing tool in the product development cycle. This Highlight gives a brief overview of the currently available RP techniques with special emphasis on three-dimensional (3D) printing. By using polymer ionomers some of the drawbacks of 3D printing can be eliminated. The article describes the chemical background of polymer ionomers and the relevance of these materials for future developments in RP.
HIGHLIGHT: Multicompartment Micelles: Has the Long-Standing Dream Become a Reality?
J.-F. Lutz,* A. Laschewsky*
The question as to whether the dream of realizing multicompartment micelles has been achieved is comprehensively answered here with the most recent advancements in this exciting field being highlighted. Multicompartment micelles are complex nanosized systems that possess a water-soluble shell and a hydrophobic core, which subsequently contains microdomains. Very recently, the morphology of such a multicompartment micelle was visualized for the first time by cryo-TEM. The future awaiting this exciting field is also discussed.
HIGHLIGHT: Multiblock Copolymers: PEO Stuck in the Middle
Robert B. Grubbs
A rare example of ABC triblock copolymer with poly(ethylene oxide) as the central block was recently reported. The copolymer was effectively prepared through the combination of living anionic polymerization, atom transfer radical polymerization, and polymer modification. This method will prove to have a great deal of versatility in allowing the incorporation of PEO blocks in interior positions of block copolymers.