Macromolecular Rapid Communications

Front Cover: Peptide-based ABA triblock copolymers exhibit pH-responsive sphere–vesicle and sphere–disk morphology transitions. These changes result from the energy penalty associated with folding the core B block to form a sphere in relation to the interfacial curvature associated with different charged states of the A block. Further details can be found in the article by J. G. Ray, S. S. Naik, E. A. Hoff, A. J Johnson, J. T. Ly, C. P. Easterling, D. L. Patton, and D. A. Savin* on page 819. Artwork: Courtesy of James Goetz.

Star polymers enjoying the advantages of facile synthesis, flexible compositions, and tunable sizes are an important material to be used as unimolecular containers and reactors. This Feature Article highlights the recent development on synthesis and application of core-shell structured star polymers for applications in drug delivery, catalysis, and templates for hybrid nanomaterials.

The swelling behaviour of surface- tethered weak polyelectrolytes in salt solutions is studied by both ellipsometry and quartz crystal microbalance (QCM). Ellipsometry studies support the proposed solidified liquid layer (SLL) model. QCM experiments designed according to the SLL model are highly sensitive: a 0.18 nm thickness change of the SLL will lead to a 1 Hz frequency change.

Glycopolymers have unique recognition properties and can be used in various bioapplications. The well-defined structures of glycopolymers effect their binding to proteins significantly. It is crucial to gain absolute control over their structure to control specific carbohydrate–lectin interactions. These interactions can be best determined by advanced techniques, QCM and SPR.

This article presents a chemistry-based method to transform frozen aggregates of amphiphilic block copolymers into dynamic micelles by introducing pH-sensitive hydrophilic units into the hydrophobic block of the block copolymer. The figure represents the reversible aggregation of micelles formed by a P(nBMA_50%-stat-DMAEMA_50%)-block-PDMAEMA diblock copolymer as a function of the ionization degree of the DMAEMA units.

Well-dispersed biodegradable star polymers are described for conjugating drugs via a pH-responsive linker. Doxorubicin was conjugated to the star cores using amine–aldehyde coupling reactions. Subsequently, the star polymer–doxorubicin conjugates were subjected to in vitro analyses to assess toxicity and doxorubicin release.

This work reports a POSS-based supramolecular amphiphile generated through the host–guest inclusion complexation between a mono adamantane-functionalized POSS and a cyclodextrin oligomer, which further self-assembles into hollow nanospheres, sphere layers, and nanoporous films in a hierarchical way. The obtained supramolecular structures have demonstrated great potential in biomedical applications, e.g., as matrix materials for cell adhesion and proliferation.

Chiral regulation has been achieved through the co-assembly of PCDA with different azobenzene derivatives, or by the photo-isomerization of the azobenzene chromophores, combining supramolecular chemistry and the LB technique. The hydrogen bonding interaction between PCDA and PAzo is suggested to be responsible for the regular helical packing of PCDA molecules in the monolayer, resulting in chiral amplification of PDA LB films.

The interactions of thermoresponsive poly[oligo(ethyleneglycol)methacrylates] with phospholipid bilayers as the polymers are heated above their lower critical solution temperature (LCST) are studied. Above the LCST, the polymers are lipophilic and can, therefore, insert in lipid bilayers, as probed by a series of complementary assays. This provides insight into the role of “smart” polymers in biotechnological applications.

Meso- and microporous poly(DVB) resins can be synthesized by a simple hard-templating method. The resulting resins have high surface areas combined with a high porosity, typically exceeding 60%. The resins can be functionalized without loss of porosity and show good performance for adsorption applications. Because of their spherical pore shape, they can also be used as model systems for the analysis of pore stability in ultraporous systems.

Supramolecular block copolymers are prepared by reversible addition fragmentation transfer (RAFT) polymerization followed by oxidative doping with oligomer aniline. These microphase-separated supramolecular block copolymers exhibit much higher permittivity and lower dielectric loss than undoped neat block copolymers.

A novel fully-branched hyperbranched polymer with a diselenide catalytic core is successfully synthesized by post modification of the focal point. The cored polymer demonstrates prominent glutathione peroxidase (GPx) activity, due to the interaction between the densely branched and core-shell structured hyperbranched polymer and the substrates.

Control over the nitroxide-mediated polymerization of isoprene initiated by acid-functional alkoxyamines is significantly improved by carrying out the polymerization in the hydrogen-bond-accepting solvents 1,4-dioxane or pyridine. Both solvents increase the rate of initiator consumption, while the overall rate of polymerization of isoprene is increased in pyridine solution.

The biocompatible ampholytic copolymer has been grafted onto the mesoporous silica nanoparticles via surface RAFT polymerization. The dual thermo-sensitive copolymer shell behaves specially with the increasing temperature. Thermoresponsive release of payload from the novel nanocarrier has been studied in this paper.

Poly(L-lysine)-b-poly(propylene oxide)-b-poly(L-lysine) triblock copolymers exhibit sphere-vesicle and sphere-disk micelle transitions as a function of pH. The unique responsive behavior for these triblock systems can be utilized in areas such as drug delivery, whereby a delivered drug could be spontaneously released upon pH-driven morphology transitions.

A methodology for controlled and selective hydrolysis of (co)poly(2-oxazoline)s is developed. The influence of the ethanol–water solvent mixture on the hydrolysis is highlighted, even yielding enhanced selectivity for block copolymers of poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline).

Multifunctional star polymer ruthenium catalysts are designed to enhance activity, controllability, and functionality tolerance in living radical polymerization. Typically, the formation of pseudo hetero P,N-chelating ruthenium complexes in a star core is quite effective for methyl methacrylate and unprotected methacrylic acid.

A Pd catalyst that can mediate a living, chain-growth polymerization of π-conjugated monomers is reported. Using (IPr)Pd(3-chloropyridine)Cl₂ as a precatalyst, both homopolymers and block copolymers of phenylene- and thiophene-based monomers were prepared. Although a living, chain-growth mechanism is observed during polymerization, the catalyst resting state is somewhat unstable after the monomer is consumed.

A platform of well-defined azlactone-functionalized copolymers was elaborated via the RAFT process using 2-styryl-4,4-dimethylazlactone (SDA) and styrene as comonomer. Highly effective ring-opening reactions are executed in mild conditions with a wide range of functionalized amines in order to provide materials with interesting properties via the anchorage of NMR-, fluorinated-, fluroescent- and electroactive- probes as well as sugars and biological peptides.

Novel maleimide-containing styrenic copolymers that are “orthogonally” reactive toward thiol- and amine-containing molecules, as well as two different thiol-containing molecules via the nucleophilic thiol-ene and the radical thiol-ene “click” reactions are reported.

Microwave-assisted surface-initiated radical polymerization (μW-SIP) enables the rapid synthesis of polymer brush surfaces with significant enhancement in film growth over conventional heating.

Hyperbranched polymers with peripheral alkyl bromide groups were prepared by the copolymerization of styrene and a crosslinker in the presence of CBr₄ (chain transfer agent which delayed gelation and served as the source of terminal Br atoms). The alkyl bromide groups were used in further chemical reactions (ATRP or azidation followed by click coupling) that yielded star copolymers.