Synthesis of Long-Chain Polyamides via Main-Chain Modification of Polyethyleneketones.

Long-chain polyamides (polyethyleneamides) were prepared from polyethylenes bearing in-chain carbonyl groups (polyethyleneketones) by the oxime formation and successive Beckmann rearrangement. (Diethylamino)sulfur trifluoride (DAST) was utilized as a promoter, which allowed mild conversion of the oxime group in spite of low solubility of the polymers. The polyethyleneamide exhibited different tensile property compared to a commercial HDPE.

Effects of Alkyl Ester Chain Length on the Toughness of PolyAcrylate-Based Network Materials.

Polyacrylate-based network materials are widely used in various products owing to their facile synthesis via radical polymerization reactions. In this study, the effects of alkyl ester chains on the toughness of polyacrylate-based network materials were investigated. Polymer networks were fabricated via the radical polymerization of methyl acrylate (MA), ethyl acrylate (EA), and butyl acrylate (BA) in the presence of 1,4-butanediol diacrylate as a crosslinker.

Linking microscopic structural changes and macroscopic mechanical responses in a near-ideal bottlebrush elastomer under uniaxial deformation.

Bottlebrush (BB) elastomers, in which load-bearing network strands are densely grafted with side chains, are gaining much attention due to their unique mechanical properties. Herein, we used small-angle X-ray scattering coupled with tensile tests to investigate the microscopic structural changes induced in a model BB elastomer with a controlled network structure under uniaxial deformation. The model BB elastomer was synthesized by end-linking a monodisperse star-shaped BB polymer, which ensured a controlled network structure.

Synthesis of a Bottlebrush Polymer Gel with a Uniform and Controlled Network Structure.

A structurally controlled polymer gel was synthesized by end-linking a monodisperse star polymer in which each arm was a bottlebrush (BB) polymer densely grafted with side chains. The combination of atom transfer radical polymerization and postpolymerization modification yielded a four-arm star-shaped BB polymer with a controlled polymerization degree of the backbone and side chains. The reactive end groups introduced at the end of each arm reacted with small bifunctional linkers in solution, leading to the formation of a BB polymer gel.

A Simple and Versatile Method for the Construction of Nearly Ideal Polymer Networks.

Polymer networks usually contain numerous inhomogeneities that deteriorate their physical properties and should be eliminated to create reliable, high-performance materials. A simple method is introduced for the production of nearly ideal networks from various vinyl polymers through controlled polymerization and subsequent crosslinking. Monodisperse star polymers with bromide end groups were synthesized by atom-transfer radical polymerization and end-linked with dithiol linkers using thiol-bromide chemistry.

Thermoelectric Enhancement of Silicon Membranes by Ultrathin Amorphous Films.

We propose a simple, low-cost, and large-area method to increase the thermoelectric figure of merit (ZT) in silicon membranes by the deposition of an ultrathin aluminum layer. Transmission electron microscopy showed that short deposition of aluminum on a silicon substrate covers the surface with an ultrathin amorphous film, which, according to recent theoretical works, efficiently destroys phonon wave packets. As a result, we measured 30-40% lower thermal conductivity in silicon membranes covered with aluminum films while the electrical conductivity was not affected.

Fabrication of Water-Resistant Nacre-like Polymer/Clay Nanocomposites via in Situ Polymerization.

Fabrication and characterization of water-resistant nacre-like polymer/clay nanocomposites, in which clay platelets and hydrophobic polymer chains are alternately stacked in parallel, are reported. Hydrophilic clay was converted by an ion-exchange reaction with a methacrylate monomer having a long alkyl chain and a quaternary ammonium salt group at the end. The subsequent in situ polymerization bound the neighboring clay surfaces, leading to the preferential orientation of the clay platelets owing to their high aspect ratio.

Tunicate-Inspired Gallol Polymers for Underwater Adhesive: A Comparative Study of Catechol and Gallol.

Man-made glues often fail to stick in wet environments because of hydration-induced softening and dissolution. The wound healing process of a tunicate inspired the synthesis of gallol-functionalized copolymers as underwater adhesive. Copolymers bearing three types of phenolic groups, namely, phenol, catechol, and gallol, were synthesized via the methoxymethyl protection/deprotection route.

Reversible Hydride Transfer to N,N'-Diarylimidazolinium Cations from Hydrogen Catalyzed by Transition Metal Complexes Mimicking the Reaction of [Fe]-Hydrogenase.

[Fe]-hydrogenase is a key enzyme involved in methanogenesis and facilitates reversible hydride transfer from H to N,N-methenyltetrahydromethanopterin (CH-HMPT). In this study, a reaction system was developed to model the enzymatic function of [Fe]-hydrogenase by using N,N'-diphenylimidazolinium cation (1) as a structurally related alternative to CH-HMPT. In connection with the enzymatic mechanism via heterolytic cleavage of H at the single metal active site, several transition metal complex catalysts capable of such activation were utilized in the model system.

Seawater-Assisted Self-Healing of Catechol Polymers via Hydrogen Bonding and Coordination Interactions.

It is highly desirable to prevent crack formation in polymeric materials at an early stage and to extend their lifespan, particularly when repairs to these materials would be difficult for humans. Here, we designed and synthesized catechol-functionalized polymers that can self-heal in seawater through hydrogen bonding and coordination. These bioinspired acrylate polymers are originally viscous materials, but after coordination with environmentally safe, common metal cations in seawater, namely, Ca(2+) and Mg(2+), the mechanical properties of the polymers were greatly enhanced from viscous to tough, hard materials.

Formation of Hierarchical Lamellae-in-Lamella Nanostructures from Polymer Blends Via Controlled Nonequilibrium Freezing.

The creation of hierarchical nanostructures in polymeric materials has been intensively studied due to the great potential to tailor their physicochemical properties. Although much success has been achieved over the past decades in block copolymers, hierarchical structure engineering in polymer blends remains a great challenge. Here, the formation of hierarchical lamellae-in-lamella nanostructures from polymer blends via controlled nonequilibrium freezing is reported.

Polymers with multishape memory controlled by local glass transition temperature.

A multishape memory polymer with flexible design capabilities is fabricated by a very simple method. Local glass transition temperatures of a loosely cross-linked polymer film are changed by immersing sections of the film in a cross-linker solution with a different concentration. Each section memorizes a temporary shape, which recovers its permanent shape at a different recovery temperature depending on the local glass transition temperature.

A simple modification creates a great difference: new solid-base catalyst using methylated N-substituted SBA-15.

A simple modification, methylation of the nitrogen-substituted mesoporous silica SBA-15, enhances the basicity of a solid-base catalyst. The methyl group donates an electron to the nitrogen atom in the silica framework. This catalyst accelerates Knoevenagel condensation using benzaldehyde and diethyl malonate, which conventional solid-base catalysts reported to date cannot do.

Synthesis of readily recyclable biobased plastics by Diels-Alder reaction.

Readily recyclable biobased plastics were designed and synthesized utilizing the thermally reversible DA reaction. Furyl-telechelic poly(butylene succinate) prepolymers (PBSF(2)) were extended with bis- and tris-maleimide linkers (M(2) and M(3)) by the DA reaction in the bulk state to produce linear and network polymers, respectively. The DA reaction was able to proceed at 25-80 degrees C, at which crystalline domains of PBSF(2) were present.

Correlation between solid-state structures and enzymatic degradability of cocrystallized blends.

Solid-state structures and enzymatic degradability have been investigated for cocrystallized blends between poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBV] and poly(3-hydroxybutyrate-co-3-hydroxypropionate) [PHBP]. From wide-angle X-ray diffraction patterns, small-angle X-ray scattering data, and the comparison of the enzymatic degradability of these blends, the solid-state structures of PHBV/PHBP blend samples, in which the PHBV component has higher isothermal crystal growth rate (G) value than the PHBP one, might be similar to those of the component PHBVs; while those of the PHBP/PHBV blend samples, in which PHBP component has higher G value, were similar to the component PHBPs. Normalized one-dimensional correlation functions gamma(x) of PHBV/PHBP binary blends crystallized at 90 degrees C.

Comonomer-unit compositions, physical properties and biodegradability of bacterial copolyhydroxyalkanoates.

The comonomer-unit compositions and their distribution of as-produced bacterial copolyesters, including poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxy-butyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) are described in this paper. Each copolyester sample can be comonomer-unit compositionally fractionated into several fractions, indicating that the original copolymers are mixtures of copolymers with different comonomer-unit compositions. The effects of comonomer-unit compositional distribution on thermal properties, crystallization, biodegradability and solid-state phase behavior are investigated using comonomer compositionally fractionated copolymers.

Change of surface structure of poly(3-hydroxybutyrate) film upon enzymatic hydrolysis by PHB depolymerase.

The change in the surface structure of poly[(R)-3-hydroxybutyrate] [PHB] films upon the enzymatic hydrolysis was analyzed by attenuated total reflection infrared [ATR/IR] spectrometry. As enzymes, PHB depolymerases isolated from Ralstonia pickettii T1 and Pseudomonas stutzeri were used. By curve decomposition of the carbonyl stretching band of ATR/IR spectra, the change in the surface crystallinity of PHB films by exposure to buffer containing 0, 1, and 4 microg of PHB depolymerases was estimated.