Journal of Polymer Science Part A: Polymer Chemistry

Polymeric materials possessing fluorescent moieties may act as effective chemosensors for various molecules in solution, based on either fluorescent quenching or enhancement effects observed upon interaction of the polymer with the molecule to be detected. On page 52, Maria Demetriou and Theodora Krasia-Christoforou demonstrate the capability of well-defined diblock copolymer systems possessing fluorescent (anthracene) and metal binding (β-ketoester) functionalities to act as effective dual-chemosensors for amines and transition metal ions in organic media.

A variety of alkene, diene, aromatic, and condensation type monomers currently utilize renewable resources. The Highlight article by Robert T. Mathers on page 1 discusses synthesis strategies for ethylene, propylene, α-olefins, methylmethacrylate, 1,3-butadiene, 1,3-cyclohexadiene, isoprene, 1,3-propanediol, 1,4-butanediol, and terephthalic acid as well as opportunities for other renewable-based monomers.

Biomass provides chemicals for many commodity monomers and polymers. This highlight discusses efforts to utilize renewable resources, such as cellulose, lignin, plant oils, starches, and monoterpenes.

A series of poly(globalide-caprolactone) copolymers were synthesized by enzymatic ring-opening polymerization from globalide, a naturally occurring macrolactone, using ε-caprolactone as intercalating monomer to provide linear multifunctional polyesters bearing different degrees in 1,2-disubstituted unsaturations along the main chain. The random copolymers were successfully photo cross-linked in the melt with a tri-functional thiol monomer via the thiol–ene coupling reaction affording thermoset film materials with a range of thermal and viscoelastic properties potentially useful for coating applications. The “green chemistry” concept is exemplified by combination of an environment-friendly 3-in-1 approach that serves as model platform in the formation of semi-synthetic cross-linked networks.

Hyperbranched polyesters are obtained via Baylis–Hillman polymerization of 2,6-pyridinedicarboxaldehyde and trimethylolpropane acrylate. These hyperbranched polymers contain chemically orthogonal vinyl and hydroxyl groups that are amenable to further postpolymerization modification, and which can be used to generate chemically diverse libraries of hyperbranched polymers or to prepare core–shell type architectures, among others.

Single electron transfer living radical polymerization of methyl acrylate in dimethyl sulfoxide was mediated using commercially available tris(2-aminoethyl)amine (TREN) as the ligand under a range of conditions. Bifunctional PMA was prepared. The polymerization outcomes were compared to with those obtained when Me₆-TREN was used as ligand, with particular focus on chain-end fidelity of the polymers.

A branched cationic polymer was synthesized by polyaddition of 4-chloromethyl-1,3-dioxolan-2-one and diethylenetriamine in molten salts. The polyaddition proceeded through nucleophilic addition of the primary amino group to the cyclic carbonate structure and quarternization of the secondary amino group with the chloromethyl group. The resulting cationic polymer was a good and recyclable catalyst for the reaction of carbon dioxide and epoxides owing to the ammonium structure. The complexation with DNA was confirmed by dynamic light scattering and zeta potential measurements, and it suggests the potential application as a carrier for drug delivery system.

The synthesis and characterization of a novel family of well-defined methacrylate-based diblock copolymers possessing (i) fluorescent (anthracene) and (ii) metal chelating (β-ketoester) side-chain functionalities prepared by reversible addition- fragmentation chain transfer-controlled radical polymerization is described. The poly(9-anthrylmethyl methacrylate)-block-poly(2-(acetoacetoxy)ethyl methacrylate)s (AnMMA_x-b-AEMA_y) are evaluated toward their ability to act as efficient dual chemosensors for amines and metal ions in organic media.

Solution-processable NIR electrochromic aromatic polyamides with anthraquinone units were prepared from the low temperature polycondensation. These electrochromic polyamides showed ambipolar behavior with reversible redox couples and high contrast ratio both in the visible range and near-infrared region.

The characteristics of arborescent polyisobutylenes (arbPIB) and arborescent polystyrene (arbPS) were analyzed and compared using several branching parameters. The g (R_g,branched/R_g,linear) parameter was compared to the theory developed by Zimm and Stockmayer. The log–log scale plot for the branching parameter g versus DP_i for arbPS and arbPIB displays a similar trend with the curve shifted by a factor related to the average chain length between branch points for the arborescent polymers.

Polyurethanes containing tertiary carbamate groups in their backbone are easily degradable by acidic and thermal treatment. Nanoparticles and nanocapsules consisting of these materials are obtained by different miniemulsion techniques and subsequently used in sensor and release experiments.

Synthesis of intergallery-surface-initiated ROMP poly(dicyclopentadiene)—montmorillonite nanocomposites leading to exfoliated nanocomposites with improved properties was achieved for the first time.

The thermal crosslinking of poly(dimethylsiloxane-co-methylvinylsiloxane) and 1,12-diazido-dodecane was studied. The influence of temperature and [N₃]/[C=C] ratio was investigated by rheological, swelling and insoluble fraction measurements for materials crosslinked in bulk and by comparison of the normalized thickness before and after elimination of extractibles for the crosslinked coatings. Even if the fraction of elastically effective crosslinks in bulk remained below 20%, the preparation of crosslinked elastomers and coatings was demonstrated.

Controlled free radical polymerization of a set of ferrocene (meth)acrylate monomers was successfully performed via the RAFT and ATRP processes. The monomers were found less reactive than their ferrocene-free analogues, and polymerizations resulted mostly in moderate molar masses only. The reasons for this behavior are not entirely clear; indications point to sterical hindrance of the active center being the most probable explanation.

For the first time fullerene can be oxidized in water and under environmentally friendly reaction conditions by new biocatalysts, constructed from laccase and linear-dendritic copolymers. The oxidation products are formed in 50-78 % yield and the copolymer-enzymatic complex can be recycled by simple filtration and reused.

The co- and ter-polymerization of alicyclic and aliphatic epoxides catalyzed by a (salan)CrCl/onium salt catalyst system are described. The activation barriers for copolymer synthesis for reactions performed in toluene were found to be significantly larger than those previously reported under solventless conditions; furthermore, a reverse in selectivity is seen for propylene oxide. Temperature-dependent Fineman-Ross analyses of the terpolymerization process of cyclohexene oxide/propylene oxide/CO₂ reveal a reactivity ratio greatly favoring propylene oxide incorporation into the polymer at 25 °C, whereas, a more equal distribution of monomers is seen at 40 °C.

The novel N-substituted-N-vinylformamides were synthesized to investigate the radical polymerizability of monomers and the polymer structure. Chiral substituents affected on the polymer chain structure, examined by ¹H NMR spectra, ¹³C NMR spectra, and circular dichroism. N-(p-Methoxybenzyl)-N-vinylformamide generated polymers, while it was known that their N-vinylacetamide derivatives did not. The chiral polymers, which were obtained by the radical polymerization of N-(S)-2-methylbutyl-N-vinylformamide and N-(S)-2,3-dihydroxypropyl-N-vinylformamide at 0 °C, showed sharper spectral patterns in ¹³C NMR and the intensities of their positive cotton effects on circular dichroism increased, suggesting that the substituent bulkiness influenced the polymer structures.

Novel biodegradable polymer-–drug nanoparticles (NPs) were synthesized by azide-–alkyne click-linking of acetylene-functionalized polylactide (PLA) with diazide-functionalized paclitaxel (PTXL) in oil-in-water miniemulsion. Well-defined nanostructure of these NPs was verified by dynamic light scattering, transmission electron microscopy, and atomic force microscopy characterizations. Their biodegradability was confirmed by degradation study in enzyme solution.

A class of 2,7-polyfluorene derivatives with carbazole and oxadiazole pendants were modified by the blue-emitting iridium complex pendants incorporated in the C-9 position of fluorene and exhibited better electroluminescence properties in the single-emissive-layer polymer light-emitting devices. The current efficiency and brightness levels of these iridium complex-modified 2,7-polyfluorene derivative-based devices were 2.1 and 1.7 times higher than the corresponding levels from the parent 2,7-polyfluorene derivative-based devices, respectively.

The presence of hexafluorobenzene or octafluorotoluene lead to π–π stacking interactions that decreased the rate of the atom transfer radical polymerization of styrene in nonaromatic solvents. By interacting with the aromatic group at the dormant chain end, π–π stacking agents reduced the stability of the active polymer radical and shifted the equilibrium further toward the dormant species.

A series of styrenic phosphonium ionic liquids possessing various alkyl substituents and counterions were synthesized and copolymerized with butyl acrylate. Dynamic mechanical analysis curves of phosphonium ionomers possessing tributyl substituents appeared two tan δ peaks, suggesting microphase separation due to strong ionic association between phosphonium cations. Longer alkyl chains hindered ionic association and increased ionic domain spacing based on wide-angle X-ray diffraction results. Large counterions provided liquid-like, viscous behavior.

The synthesis of acrylonitrile-butadiene rubbers via reversible addition fragmentation chain transfer polymerization of acrylonitrile and butadiene in solution under azeotropic conditions (38/62) was investigated for a broad range of common solvents. The rates of polymerization are shown to correlate with the decomposition rate of the used initiator in the respective solvent system.

The fast and controlled polymerization of different acrylamide monomers through the use of copper chloride and tris(2-dimethylaminoethyl)amine as a metal/ligand pair to yield high molecular weight polymers (degrees of polymerization ranging from 50 to 5000) is reported. Characterization of high molecular weight poly(NIPAm) demonstrated large changes in the LCST observed on heating and cooling, and this hysteresis was exploited for the controlled release of doxorubicin from poly(NIPAm) spheres. Access to these high molecular weight water-soluble polymers, as well as to stimuli-responsive poly(NIPAm), opens new doors for interesting applications in a variety of fields including tissue engineering, drug delivery, and controlled solution viscosity.

We demonstrate the ability of the reversible addition-fragmentation chain transfer (RAFT) process to produce well-defined amphiphilic block co-oligomers with narrow molecular weight distribution and degrees of polymerisation below 50. A detailed study shows that the amphiphilic diblock co-oligomers self-assemble in solution and form micelles or polymeric particles, depending on the hydrophobicity of the diblock. These oligomers present an excellent alternative to traditional amphiphilic molecules, by combining the properties of polymers to those of single molecule surfactants.