Journal of Polymer Science Part A: Polymer Chemistry

Thick photosensitive films with sufficient light penetration are required for improving the capacity of recording media based on azopolymers. Block copolymers having an azo liquid crystalline block allow the dilution of azo chromophores but maintain the cooperativity among them. On page 1716, Jesús del Barrio, Eva Blasco, Luis Oriol, Rafael Alcalá, and Carlos Sánchez-Somolinos describe the self-assembly of azo chromophores and pyridine units of commercial polystyrene-b-poly(4-vinylpyridine)s to obtain photoresponsive supramolecular block copolymers. This approach offers a versatile and facile method for the preparation of photoresponsive block copolymers for volume holographic storage.

Polymerizable deep-eutectic solvents (DESs) formed between a variety of ammonium salts and hydrogen-bond donors containing acrylic acids and acrylamides are capable of sustaining frontal polymerization, as presented by Gabriel Luna-Bárcenas et al. on page 1767. After complete conversion, the non-polymerizable counterpart of DES can be released from the polymer in controlled fashion. For instance, the cover image depicts a monolith of poly(acrylic acid) loaded with lidocaine hydrochloride (a common anesthetic) that plays the role of ammonium salt. Since the swelling behavior of polyacrylates depends on the pH, the release of lidocaine hydrochloride can be tuned by modifying the pH of the medium.

Photo-initiated radical polymerization has several advantages that qualify this process for application in many industrial fields, but suffers from oxygen (O₂) inhibition. The prohibitive cost of existing methods to prevent O₂ inhibition has hampered their widespread use in industrial applications involving free radical polymerization in air. A novel approach based on an enzymatic pathway in which glucose oxidase acts as catalyst for glucose oxidation using O₂ is described to overcome O₂ inhibition of radical polymerizations.

A universal high reactive ligand, Me₆TREN, was successfully explored as the reducing agent for the ambient temperature copper-mediated LRP of AN. The key to success is ascribed to the optimized Me₆TREN amount and reaction conditions employed, producing ideal living free radical polymerization characteristics. The very high chain-end functionality of the resultant polymer has been confirmed by GPC and ¹H NMR analyses as well as the chain-extension reaction.

Several new triptycene-containing polyetherolefins were synthesized via acyclic diene metathesis polymerization. Inclusion of triptycene was found to increase the glass transition temperature over 100 °C from the control polymer without any triptycene. Varying the amounts and orientations of triptycene was found to increase the stiffness, toughness, and ductility of the polymer at room temperature.

Poly(benzylidene-ether)esters containing a photoreactive benzylidene chromophore in the main chain were synthesized from 2,6-bis(4-hydroxy-3-methoxybenzylidene) cyclohexanone. The influence of the length of methylene spacer on phase transition was investigated using DSC and an odd-even effect has been observed. The photolysis of liquid crystalline poly(benzylidene-ether)esters revealed that the α,β-unsaturated ketone moiety in the main chain dimerises through 2π + 2π cycloaddition reaction to form a cyclobutane derivative and leads to crosslinking. The rate of photocrosslinking decreases significantly on increasing methylene carbon chain length of the acid spacer.

The preparation of a series of photoaddressable supramolecular block copolymers is demonstrated by mixing a carboxy-terminated azobenzene derivative, AZO, and two PS-b-P4VP block copolymers. Homogeneous liquid crystalline materials were obtained for ratios of AZO to vinylpyridine repeating unit, x, lower or equal to 0.50. Mixtures with higher x resulted in heterogeneous materials showing clear macrophase separation. Photoinduced orientation of the azobenzene units was obtained in films of PS-b-P4VP(AZO)_x with x = 0.25 and 0.50.

A series of near-infrared (NIR) emissive conjugated polymers with boron di(iso)indomethenes were synthesized. Quantitative demethylation of the polymer was carried out to transform the polymer to a NIR emissive polymer. The obtained polymer gave both a drastically larger red-shifted and a sharper PL spectrum than the parent polymer in the NIR region (Φ_PL = 0.37, full width at half maximum height Δλ_1/2 = 460 cm⁻¹, λ_PL = 758 nm).

An organosoluble polyetherimide (PEI) (4) containing an allyl group was successfully prepared. PEI (5), obtained from the thermal curing of PEI (4) at 300 °C, displays a much higher T_g value (307 °C) and a lower coefficient of thermal expansion (29 ppm/°C) than the PEI (4) (T_g 253 °C, CTE 52 ppm/°C).

Self-aggregated sodium deoxybenzoin (Na-DB) molecules can form a trimeric aggregator in tetrahydrofuran and vacuum state. Upon addition of hexyisocyanate, a single molecule of Na-DB initiates the monomers and two other molecules to form a complex with a growing amidate anion of polyisocyanate. Thus, Na-DB can perform dual functions: initiation and additive effects.

The thiol-ene reaction is characterized with respect to the polymerization rate, rate-limiting step, and termination mode (i.e., bimolecular vs. unimolecular events) for functionalized siloxane systems of varying structural compositions.

Microporous molecular networks containing spirobifluorene and tetraphenylmethane units are synthesized by the organic sol-gel method. The network materials are produced in different forms and porosities varying with the processing conditions for the sols consisting of nanoparticle dispersions of the molecular networks as well as the composition of comonomers.

Deep eutectic solvents (DESs), based upon mixtures of a variety of ammonium salts – the active fillers – and hydrogen bond donors containing acrylic acids and acrylamides, are capable of sustaining frontal polymerization (FP) with full conversion. For instance, after FP of acrylic acid-lidocaine hydrochloride DES, the lidocaine hydrocloride can be released in a controlled fashion.

Naturally occurring bulky terpenes were quantitatively copolymerized with various maleimide derivatives via selective 1:2-alternating propagation governed by the penultimate effect, which resulted in 1:2-sequence regulated polymers with relatively high glass transition temperatures and optical activities. Similar petroleum-derived bulky olefins possessing α-methyl substituents were copolymerized with phenylmaleimide via preferential 1:2-alternating propagation with a slightly lower selectivity. A further decrease in the bulkiness of non-polar olefins increased the 1:1-alternating sequence.

Electron spin resonance analysis of in situ nitroxide-mediated polymerization of styrene promoted by the benzoyl peroxide/N-tert-butyl-α-isopropylnitrone pair is investigated to elucidate the structure of the nitroxides responsible for the polymerization control.

ABA-type triblock copolymers and AB-type star-shaped diblock copolymers with poly(2-adamantyl vinyl ether) [poly(2-AdVE)] hard outer segments and poly(n-butyl vinyl ether) [poly(NBVE)] soft inner segments were synthesized by sequential living cationic copolymerization. Although they are totally composed of poly(vinyl ether) backbones and hydrocarbon side chains, the two polymer segments were segregated into a microphase-separated structure to form thermoplastic elastomers with good mechanical and thermal properties and wide service temperatures.

New flame retardant phosphorus-containing thermosetting resins have been prepared by phospha-Michael addition of a difunctional secondary phosphine oxide, the 1,3-bis(phenylphosphino)propane dioxide, and aza-Michael addition of 4,4′-diaminodiphenylmethane. Different materials with 0–4.2% of P were obtained starting from a high oleic sunflower oil enone derivative. The kinetics of the phospha and aza-Michael additions under various conditions was investigated using model compounds and the thermal stability and flame retardant properties of the final materials were evaluated by TGA and LOI measurements.

The biocompatibility of poly(2-methyl-2-oxazolines) is systematically investigated with regards to cyto- and hemotoxicity. With its excellent biocompatibility profile PMeOxs can compete with other non-ionic hydrophilic polymers applied in the medical field.

The first graft copolymers with poly(vinyl cyclopropane) backbones were produced by first preparing a poly(dimethyl siloxane) with an allyl carbonate at one end group. This was then polymerized with 1,1-bis(ethoxycarbonyl)-2-vinyl cyclopropane (ECVP). The materials have low glass transition temperatures that were dependent on polymer composition.

A novel procedure through composite inner salts is presented based on the design and preparation of poly(phenylene benzobisoxazole) (PBO) copolymer fibers with well-dispersedgraphene oxide (GO). Three dimensional networks of PBO molecular chains and well dispersed GO particles are successfully constructed in GO-co-PBO copolymer fibers. The intensified interface strength and increased load transfer capacity between GO nanoparticles and PBO matrix result in GO-co-PBO copolymer fibers with significantly higher mechanical and thermal properties than PBO fiber.

New naphthalene-quinoxaline-based polymers are developed and showed remarkable photovoltaic performance with V_oc of >0.9 V and power conversion efficiency up to ∼3% for the cell upon addition of 1,8-diiodoctane additive.

Reported here is a novel synthetic strategy for preparing gradient fluorinated copolymers with statistical structure of azeotropic or gradient composition from styrene (S) and 2,2,2-trifluoroethyl methacrylate (T) with very similar reactivity ratios via heterogeneous ATRP.

This new benzoin derivative performed significantly better in photo-polymerization experiments of bulk solutions or films of acrylate monomers than the unsubstituted benzoin, a popular photoinitiator. Studies suggest that a slow α-cleavage mechanism from the electronic triplet state with a quantum yield of 0.1 is the primary photoreaction to generate the initiating free radicals.

Ligand-free single-electron transfer and degenerative chain transfer mediated living radical polymerization (SET-DTLRP) for methyl methacrylate (MMA) was realized by the initiation of an iodine-based initiator, 2-iodo-2-methylpropionitrile (CPI), in DMSO at ambient temperature. The polymerization produced acceptable controls over molecular weights with relatively narrow distributions (M_w/M_n ≤ 1.35). The polymers were obtained with high fidelity (∼ 96%) and active chain end groups. This work offered a more economical and eco-friendly SET-DTLRP technique.

A well-defined amphiphilic graft copolymer, containing a hydrophobic polyallene- based backbone and hydrophilic poly(2-(dimethylamino)ethyl methacrylate) side chains, was synthesized by the combination of living coordination polymerization, single electron transfer-living radical polymerization, and the grafting-from strategy.

Polystyrene-graft-poly(p-benzamide) was synthesized by free radical copolymerization of poly(N-octyloxybenzyl-p-benzamide) macromonomer and styrene, followed by the removal of the octyloxybenzyl groups from amide nitrogen. The glass transition temperature (T_g) of polystyrene-graft-poly(p-benzamide) increased dramatically by 50–60 °C when the content of poly(p-benzamide) exceeded a threshold of about 4%.