Boron–nitrogen coordination in polyurethane elastomers enhances the dynamics of the boronic ester while introduces inter- and intra-molecular interactions, leading to mechanical robustness and excellent self-healing efficiency simultaneously.

Supertough biocompatible and biodegradable polylactide materials were fabricated by applying a novel and facile method involving reactive blending of polylactide (PLA) and poly(ethylene glycol) diacylate (PEGDA) monomer with no addition of exogenous radical initiators. Torque analysis and FT-IR spectra confirm that cross-linking reaction of acylate groups occurs in the melt blending process according to the free radical polymerization mechanism. The results from differential scanning calorimetry, phase contrast optical microscopy and transmission electron microscopy indicate that the in situ polymerization of PEGDA leads to a phase separated morphology with cross-linked PEGDA (CPEGDA) as the dispersed particle phase domains and PLA matrix as the continuous phase, which leads to increasing viscosity and elasticity with increasing CPEGDA content and a rheological percolation CPEGDA content of 15 wt %. Mechanical properties of the PLA materials are improved significantly, for example, exhibiting improvements by a factor of 20 in tensile toughness and a factor of 26 in notched Izod impact strength at the optimum CPEGDA content. The improvement of toughness in PLA/CPEGDA blends is ascribed to the jointly contributions of crazing and shear yielding during deformation. The toughening strategy in fabricating supertoughened PLA materials in this work is accomplished using biocompatible PEG-based polymer as the toughening modifier with no toxic radical initiators involved in the processing, which has a potential for biomedical applications.

A family of air-stable (phenylbuta-1,3-diynyl)palladium(II) complexes were designed and prepared in a facile synthetic procedure. Their structures were characterized by (1)H and (13)C NMR, MS, and X-ray analysis. These Pd complexes were revealed to efficiently initiate the polymerization of phenyl isocyanides in a living/controlled chain growth manner, which led to the formation of poly(phenyl isocyanide)s with controlled molecular weights and narrow molecular weight distributions. (13)C NMR analysis indicated the isolated poly(phenyl isocyanide) was of high stereoregularity. The Pd unit at the end of the polymer chain could undergo further copolymerization with phenyl isocyanide monomers to give block copolymers. It was also found that incorporation of an electron-donating group on the phenyl group of the Pd complex could improve the catalytic activities. Furthermore, these Pd complexes were tolerant to most organic solvents and applicable to a wide range of isocyanide monomers including alkyl and phenyl isocyanides and even phenyl isocyanide with bulky substituents at the ortho position and diisocyanide monomers. Therefore, this polymerization system is versatile in the preparation of well-defined polyisocyanides with controlled sequence. Bi- and trifunctional Pd complexes with two and three Pd units incorporated onto the same phenyl ring were designed and synthesized. They were also able to initiate the living polymerization of phenyl isocyanide to afford telechelic linear and star-shaped polyisocyanides with controlled molecular weights and narrow molecular weight distributions.

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Vitrimer network polymers are very special in that, above a characteristic temperature T v , their dynamic covalent network connectivity allows macroscopic flow while remaining cross-linked. The vitrimer is able to change from being a typical elastomer to a network polymer with thermoreversible bond-exchange reactions. This has aroused enthusiastic interest, especially for designing novel materials to meet the increasing requirements of environmental protection, self-healing, and sustainable development. In this work, the viscoelasticity of the curing and cured epoxy vitrimer was investigated. Time-resolved multifrequency rheometry during the early stages of curing disclosed network ripening due to transesterification. After being fully cured, one of the most defining properties of vitrimers is a reversible, temperature-induced transition at T v , where the vitrimer assumes a pronounced critical state. Surprisingly, this transition state was found to behave like a critical gel having a relaxation modulus, G(t) = St −n , over a fairly broad temperature interval of 20 K. Viscoelastic moduli G′(ω,T) and G″(ω,T) can be approximately shifted into a single set of master curves for the entire experimental temperature range. Large strain behavior above T v becomes nonlinear very quickly. No resemblance was found with a glass transition near T v .

Organic field-effect transistors (OFETs) without any encapsulation of polymer semiconductor layers that still exhibit unipolar n-type characteristics under air conditions are very rare. In this study, we use fluorinated bithiophene as a donor, and bis(2oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF, P1) and azasubstituted BIBDF (P2) as acceptor units to develop air-stable and unipolar electron transport polymer semiconductors. Unencapsulated OFETs based on P1 and P2 were fabricated and directly evaluated under air conditions. The highest effective mobility (μ e,max eff ) of 0.23 cm 2 V −1 s −1 was obtained for P2-based devices with high I on /I off ratio of >10 6 and low threshold voltage of 1.1 V. Moreover, P2 had high air stability and maintained unipolar electron transport with μ e,max eff of up 0.1 cm 2 V −1 s −1 and I on /I off ratio of >10 6 during the 60 days of air storage. The work provides an effective molecular design strategy to develop air-stable and high-performance n-channel unencapsulated polymer transistors that can be directly operated under air conditions.

In this contribution, we report on the facile synthesis of hybrid silica nanoparticles grafted with helical poly(phenyl isocyanide)s via both "grafting from" and "grafting to" strategies. First, triethoxysilanyl functionalized alkyne− Pd(II) initiator was anchored onto the surface of bare silica nanoparticles through silanization coupling reaction. Polymerization of phenyl isocyanide using the Pd(II)−anchored silica nanoparticles lead to the formation of hybrid nanoparticles grafted with helical poly(phenyl isocyanide)s. The surfaceinitiated polymerization was revealed to proceed in a living/controlled chain-growth manner, afforded the hybrid nanoparticles with controlled thickness. 31 P NMR analysis indicated the initiation efficiency of the surface-anchored Pd(II) initiators is very high, and almost quantitative. The grafting density was determined to be ∼0.89 nm 2 /chain based on the thermal gravity analysis (TGA). Polymerization of optically active phenyl isocyanide bearing an L-alanine with a long decyl chain using the Pd(II)anchored silica nanoparticles formed chiral hybrid nanoparticles grafted with helical poly(phenyl isocyanide) arms in preferred handedness. Second, the hybrid silica nanoparticles were prepared via "grafting to" strategy. Well-defined triethoxysilanyl terminated poly(phenyl isocyanide) was prepared in controlled manners. The polymer was grafted to the surface of bare silica nanoparticles via the silanization coupling reaction, afforded hybrid silica nanoparticles grafted with helical poly(phenyl isocyanide). TGA indicates the grafting density is ∼0.76 nm 2 /chain. Taking advantage of this synthetic method, left-handed helical poly(phenyl isocyanide) was grafted to the surface of silica nanoparticles, generated chiral hybrid silica nanoparticles with high optical activity. Such chiral nanoparticle exhibited good performance in enantioselective crystallization of racemic Bocalanine. The enantiomeric excess (ee) of the induced crystal is up to 95%.

Aggregation-induced emission (AIE) active tetraphenylethene (TPE) functionalized phenyl isocyanide (PI) derivatives, such as TPE pendent PI monomers (TPE-NC) and TPE-based Pd­(II) catalysts (TPE-Cat. a and TPE-Cat. b) were synthesized. The corresponding linear (poly­(TPE-NC) n ) and four-armed (TPE-[poly­(TPE-NC) m ]4) conjugated polymers were subsequently prepared through the living polymerization of TPE-NC with TPE-Cat. a or TPE-Cat. b in THF, respectively. All of them have good solubility in common organic solvents, such as THF and CHCl3, and exhibited tunable AIE property, which can be facilely tuned through the variations on the concentration and the molecular weights (MWs) of the polymers. They also showed excellent thermal stability with a 5% of their weight loss as high as 380–405 °C and significant mass loss in the range of 350–650 °C. Stable helical assemblies could be formed by poly­(TPE-NC)n at high concentration conditions. However, four-armed TPE-[poly­(TPE-NC) m ]4 could self-assemble into an apparent bumpy “caterpillar” like assembly, which was very different from the ordinary ones. Moreover, these conjugated polymers could be employed to generate a vapochromism phenomenon and act as good dispersants for carbon agglomerates in poor solvents. It is expected that this work can enrich the family of luminescent materials based on the helical poly­(phenyl isocyanide) main chains and guide the future design of optical materials with attractive structures and special purposes, such as heat-resistant materials, security materials, and dispersed materials.