Journal of Polymer Science Part A: Polymer Chemistry

The cover image shows a schematic structure of a hyperbranched polyether. These dendritic polymers are a particularly interesting class of chemically stable and often highly biocompatible materials, as demonstrated in the Highlight article by Martina Schömer, Christoph Schüll, and Holger Frey on page 995. Furthermore, the image shows the two main types of monomers employed for the preparation of such multifunctional branched polyethers, i.e., hydroxyl-functional epoxides and oxetanes. Recent achievements by the authors in this area include a wide range of hyperbranched copolymers with established epoxide monomers, such as ethylene oxide and propylene oxide. Frey et al. review the progress in the preparation, characterization, and application of these uniquely versatile aliphatic polyols.

Synthesis, characterization, and transistor applications of PBTSB and PBTFN polymers containing stilbene and fumaronitrile moieties are presented on page 1029 by Dong-Yu Kim and colleagues. The cover image depicts the polarized optical microscopy (POM, micrometer scale), atomic force microscopy (AFM, nanometer scale), and time-dependent density functional theory (TDDFT, molecular scale) calculation images of PBTFN. The crystalline phase and self-assembly of PBTFN are attributed to the bithiophenefumaronitrile (donor-acceptor) intermolecular interaction. Electron transport is improved due to the well-ordered molecular packing in the fibrillar structure after thermal annealing.

Hyperbranched polymers combine several advantages of the perfectly branched dendrimers (e.g., multifunctionality) with easy accessibility, typically in a one-step synthesis. Amongst them, hyperbranched polyethers are a particularly interesting and established class of chemically stable and often biocompatible materials. They can be prepared via anionic and cationic polymerization mechanisms with comparably low polydispersities, using hydroxyl-functional epoxides or oxetanes. Their unusual mechanical, thermal, and solution properties render them useful for a variety of applications, e.g., as building blocks for various complex macromolecular architectures or in biomedical and electronic applications.

Pd-mediated polymerization of 1-pyrenylmethyl diazoacetates affords poly(1-pyrenylmethoxycarbonylmethylene) (poly4′), whose CC main chain is tightly surrounded by pyrene groups. The intensity ratio of excimer emission to monomer emission (I_E/I_M) of poly4′ was more than 20 times higher than that of its vinyl polymer counterpart of poly(1-pyrenylmethyl methacrylate) (polyPyrMA), clearly demonstrating much higher efficiency for excimer formation in poly4′, because of the tight arrangement of the pyrene groups around the main chain.

An efficient protocol, atom transfer radical nitroxide coupling chemistry, for the preparation of polymer/clay nanocomposites via grafting-onto strategy with well-defined polymer, which were synthesized via atom transfer radical polymerization, has been described. The radical coupling, taking place between the clay layers, not only leads to attached polymer chains but also to successful nanocomposite formation with highly exfoliated morphology.

The effects of electron-withdrawing cyano groups on the electronic properties of the new conjugated polymers are investigated. The lowering of the LUMO energy levels due to the electron-withdrawing properties of the cyano substituents could enhance electron injection capability. The fibrillar structure of PBTFN improved the electron transport.

Well-defined azobenzene-containing side-chain liquid crystalline diblock copolymers with polypeptide block were prepared by a combination of atom transfer radical polymerization, ring-opening polymerization, and click reaction.

Two donor/acceptor (D/A)-based benzo[1,2-b:4,5-b']dithiophene-alt-2,3-biphenyl quinoxaline copolymers of P1 and P2 were synthesized pending different functional groups (thiophene or triphenylamine) in the 4-positions of phenyl rings. A power conversion efficiency (PCE) of 3.43%, an open-circuit voltage of 0.80 V and a short-circuit current of 9.20 mA cm^-2 were achieved in the triphenylamine-containing P2-based cell under the illumination of AM 1.5, 100 mW cm^-2.

An acrylamide-type copolymer containing catechol, amino, and hydroxyl groups was synthesized as a mimetic of the natural mussel adhesive protein (MAP). An aqueous solution of the obtained copolymer formed a hydrogel within 2 h under air. Two aluminum plates were adhered by the gelation of the MAP mimetic copolymer solution under humid air at room temperature. The interfacial region between the two aluminum plates failed at a lap shear strength of 0.46 MPa.

A series of dodecyl-based monofunctional trithiocarbonate chain transfer agents (CTAs) are successfully synthesized toward the RAFT polymerization of styrene. The CTAs are used as initiators for RAFT polymerization, in the absence of the conventional free radical initiator, at higher temperature. Polystyrene of narrow PDI is synthesized. Subsequently, poly(styrene-b-benzyl methacrylate) diblock and poly(styrene-b-benzyl methacrylate-b-2-vinyl pyridine) triblock copolymers are synthesized from the polystyrene macro-RAFT agent by simply heating with the second and third monomer, respectively.

Polymer brush pendent photolabile thiols were designed for postpolymerization surface modification. Addressing the protecting groups with light enables a plethora of thiol-mediated transformations with isocyanates and maleimides via thiol-isocyanate and thiol-Michael click reactions providing a versatile route to create complex, functional polymer surfaces.

A well-defined amphiphilic graft copolymer, bearing hydrophobic polyallene-based backbone and hydrophilic poly(N-isopropylacrylamide) side chains, was synthesized by the combination of living coordination polymerization, single electron transfer-living radical polymerization, and the grafting-from strategy.

A series of well-defined amphiphilic graft copolymers, bearing hydrophobic polyallene-based backbone and hydrophilic poly(2-(diethylamino)ethyl acrylate) side chains, was synthesized by the combination of living coordination polymerization, single electron transfer-living radical polymerization, and the grafting-from strategy.

Fluorinated poly(AA-grad-HFBMA) gradient copolymer was prepared via the combination of semi-batch ATRcoP and hydrolysis reaction. Its surface properties, micellization behaviors and the effect of pH on the micellization behaviors were investigated experimentally.

Original amphiphilic poly(2-methyl-2-oxazoline)-b-poly(tert-butyl acrylate) (P(MOx)_n-b-P(t-BA)_m) copolymers are prepared from well-defined ω-N₃-P(t-BA) and α-alkyne-P(MOx) homopolymers by polymer–polymer coupling. Both homopolymers and resulting copolymers are fully characterized. Then, the self-assembly in water of amphiphilic P(MOx)_n-b-P(t-BA)_m is reported, showing the obtaining of well-defined monodisperse spherical micelles for which critical micellar concentration is determined.

The role of functional polysilanes with thioether side chains to facilitate the assembly formation of Au as well as Au–Pd bimetallic nanoparticles has been demonstrated.

Aluminum-based salen and salan complexes mediate the living and immortal ROP of rac-β-butyrolactone and rac-lactide with excellent control over the polymerizations, yielding polymers with controlled molecular weights and narrow PDIs. Copolymerization of these monomers to yield poly(lactic acid)-co-poly(3-hydroxybutyrate) is successful under neat conditions at 120 °C and in solution at 85 °C, representing the first systems to yield well-controlled copolymers. A strong bias for rac-lactide insertion over rac-β-butyrolactone is observed.

Amphiphilic brush polymers with different monomer sequence and chemical composition are synthesized and their application as macro-RAFT agent in the emulsion RAFT polymerization of styrene is explored. It is found that the monomer sequence in the brush polymers exerts great influence on the emulsion polymerization and the triblock copolymer colloidal morphology is firmly ascribed to the hydrophobic block extension.

Half-titanocene complexes were used for the polymerization of L-lactide, LLA. Most of these systems were proven to be very efficient initiators for the ring opening polymerization of LLA. The thermal properties of the produced polymers were examined by differential scanning calorimetry and thermogravimetric analysis. The activation energy of the thermal decomposition was calculated by the Ozawa–Flynn–Wall and Kissinger methods.

Several 4-vinyl phthalate esters are synthesized using Suzuki coupling. Nitroxide mediated-polymerization is used to form short homopolymers and random copolymers with n-butyl acrylate. These polymeric phthalates have the potential to act as nonmigratory plasticizers for PVC. Use in consumer products could address the health issues associated with monomeric phthalate plasticizers, which are implicated as endocrine disrupting compounds.

Ring-opening polymerization of cyclic esters, L-lactide, ε-caprolactone, ε-decalactone, β-butyrolactone by a series of heteroleptic bimetallic zinc complexes supported by NNO-tridentate ketiminate ligands has been reported.

A highly effective RAFT agent BCCDP was used to the RAFT polymerization of AN to synthesize well-defined high molecular weight PAN with controlled molecular weight and narrow molecular weight distribution. The PAN fibers with diameters from 247 to 1094 nm can be obtained via electrospinning.

Furan rings and maleimide rings were grafted to polyphosphazens respectively, and the two types of substituted polyphosphazenes were used to prepare self-healing inorganic ruubber. The self-healing properties were carried out by thermal treatment through the D-A reactions. Compared with the traditional cross-linked rubber, these materials could be renewable and re-processable.

A dual-functional copolymer, poly(4-styrenesulfonyl azide-co-t-butyl-methacrylate), with photoacid labile and photocrosslinkable components, was synthesized. The copolymers with photoacid generators were photopatterned at 365 nm, followed by exposure to 254nm DUV to immobilize the copolymers on an organic substrate. Selective wetting was observed in the patterned regions and a ratchet-wetting pattern was formed on the gradient line pattern.

A series of ansa-(fluorenyl)(cyclododecylamido) complexes of titanium was synthesized. Among them, 2,7-di-tert-butylfluorenyl complex 6 was found to show excellent comonomer incorporation in the copolymerization of ethylene with isobutylene, to give alternating copolymers. Complex 6 was also found to be effective as a catalyst precursor for the copolymerization of ethylene with limonene.

The five-membered cyclic carbonates were obtained from CO₂ and epoxides in the presence of dicyclohexylammonium iodide under mild conditions such as ordinary pressure and 25 to 45 °C. The iodides catalyzed efficiently the carbonate-forming reactions, whereas the bromide and chloride counterparts exhibited almost no catalysis. This metal-free system proceeded to give cyclic carbonate-rich polymers with high isolated yields by precipitation with water.

The cationic ring-opening polymerization of 3-allyloxymethyl-3-ethyloxetane (AllylEHO) leads to the formation of allyl functional polyoxetanes under simultaneous formation of cyclic oligomers as by-products. Their formation reveals the reason why the attempts for a controlled homopolymerization of oxetanes fail. However, the high versatility of poly(AllylEHO) for postpolymerization modification is proven by click-type thiol–ene reactions with 3-mercaptopropionic acid and N-acetyl-L-cysteine methyl ester.

The chemical incorporation of a minute amount (0.01–0.3%) of ally isocyanate functionalized hyperbranched polymer (HBP) into the polymer matrix of holographic polymer dispersed liquid crystals reduced the compound viscosity to about 1/3 of the HBP free and augmented the diffraction efficiency by threefold at low concentrations (0.01–0.05%). However, at high concentrations (0.10, 0.30%) HBP augmented the compound viscosity and reduced the grating formation kinetics and LC-polymer phase separation.