Articles in 2012

π-Conjugated polymers are synthesized by C–H and C–X polycondensation of 2-(4-haloaryl)thiophene monomers with a nickel catalyst and Knochel–Hauser base (TMPMgCl·LiCl (chloromagnesium 2,2,6,6-tetramethylpiperidide lithium chloride salt)). The C–H functionalization polycondensation reaction of a monobrominated monomer undergoes dehydrobrominative polymerization with an equimolar amount of TMPMgCl·LiCl and a catalytic amount of NiCl₂dppp to afford poly(2,5-thienylene-1,4-phenylene) and poly(2,5-thienylenepyridine-2,5-diyl) in reasonable yields. Polycondensation with triflate as a leaving group proceeds under similar conditions to afford poly(thienylenephenylene) with excellent yield. Poly(benzodithiophene) is also found to be obtained by the reaction of the corresponding monobrominated benzodithiophene in the presence of a nickel-catalyst-bearing N-heterocyclic carbene as a ligand.

An isotope-labeled hornet (Vespa) cocoon in which the Ala carbons of silk proteins were substituted with ¹³C was successfully obtained by feeding a mixture of larval saliva with [¹³C₃]Ala to mature larvae. The Ala fraction in the α-helix conformation of hornet silk was estimated by obtaining high-resolution ¹³C solid-state NMR spectra of the labeled cocoon, which also helped in understanding the molecular structure of hornet silk.

Monodispersed spherical silver nanoparticles with 35±5 nm diameter were prepared by microwave irradiation of an AgNO₃ aqueous solution in poly(ethylene glycol) (PEG). Thanks to the hydroxyl groups at the chain-ends of the PEG, the matrix of the Ag nanoparticles suspension was well incorporated into a polyurethane backbone, allowing a good distribution of the metal particles inside the final nanocomposite without aggregation. An optimal antibacterial activity was observed for a 35 p.p.m. Ag concentration against P. aeruginosa and E. faecalis without significant variation of the intrinsic physicochemical properties of polyurethane material.

m-Terphenyl-based random copolymers of chiral and achiral amidines and its complementary homopolymer of achiral carboxylic acids self-assembled to form complementary double helices with a preferred-handed helical sense via interstrand amidinium–carboxylate salt bridges, thus showing induced cotton effects in the π-conjugated main-chain chromophore regions. A unique amplification of the helical chirality (‘the sergeants and soldiers effect’) was, for the first time, observed during the double-helix formation.

The crystalline structure and molecular mobility of PVDF blended with PMMA at various fractions were investigated by solid-state ¹⁹F MAS NMR spectroscopy. The origin of the characteristic peaks observed for typical polymorphs of PVDF (α-, β- and γ-forms) are explained based on DFT calculations. The dominant crystalline form in the blends of [PVDF/PMMA]=[80/20], [70/20] and [50/50] is α-form containing a small portion of β-form, whereas that of [65/35], [60/40] and [55/45] consists of β-form and γ-form. In contrast, no crystalline structure is found in [45/55], [40/60] and [20/80], indicating that PVDF and PMMA chains are miscible at the molecular level.

A multivariate analysis was used to extract components in solid-state nuclear magnetic resonance (NMR) spectra from bacterial cellulose (BC). Polymers such as cellulose have several domain structures, and their structure and dynamics are reflected in the variety of solid-state spectra derived from different parameters. Multivariate analysis, such as principle component analysis (PCA), is suggested as an option to improve analyses of complex NMR spectra from relaxation measurements. In this study we demonstrate the extraction of peak components using PCA from cross polarization experiment data with variable contact time spectra of BC.

Poly(styrene derivative) particles, average diameter of which is <30nm, were prepared without ionic emulsifier with nonionic emulsifier polyoxyethylene alkyl phenyl ether by polymerizing monomer, emulsifier, water and initiator mixture at around PIT. Effects of initiator concentration, temperature and monomer type on the average diameter of the generated polymer particles are investigated. Smaller particles are obtained with higher rate of radical generation at PIT. The particles of poly(p-methylstyrene) which have an average diameter of 21 nm and a polymer weight fraction of 5% were prepared.

An enzyme electrode was fabricated by covalent immobilization of acid phosphatase (ACP) on a polyaniline/poly(acrylic acid) composite film for use as the anode of a fuel cell driven with L-ascorbic acid 2-phosphate (ASA2P). The enzyme electrode showed an activity in biochemical dephosphorylation of ASA2P to ascorbic acid (ASA), and succeeded in electrochemical oxidation of ASA. The ASA2P fuel cell equipped with the enzyme electrode gave a maximum power output of 6.0 μW cm⁻²-anode, reflecting the bioelectrochemical activity of the electrode.

Our PI/BaTiO₃ hybrid composites were prepared by mixing the organosoluble PI derived from one-step polymerization with BaTiO₃ in dimethylacetamide, screen printing the pastes to form composite films and drying at 90 °C for 24h. The low-temperature process is a key for the PI-based flexible devices to be integrated with flexible electronics. The reported PI/BaTiO₃ dielectric films were prepared by a two-step process, which needed to be further imidized at 300 °C.

Poly(ɛ-caprolactone) (PCL) microfiber meshes containing embelin, a poorly water-soluble biactive agent, were prepared by electrospinning. Thermal properties revealed that the crystallinity of embelin was significatively decreased being the drug almost completely dissolved in the PCL fibers. Drug-loading content resulted appropriate for topical applications. Drug-loaded fibrous scaffolds exhibited an increase of 86% in the area-to-volume ratio and provided an effective area per unit mass that was 5.8-fold higher than that presented in drug-loaded films. This polymeric carrier would allow a better in situ bioavailability of embelin.

Microscopic behaviors of explicit water molecules on biocompatible zwitterionic self-assembled monolayer (SAM) surfaces were investigated by molecular dynamics simulations. The orientational distribution of water molecules near the surfaces was evaluated to analyze its structural properties. Consequently, water molecules on the zwitterionic SAMs are randomly oriented. In contrast, those near the surface of poly(vinyl alcohol) are highly oriented, resulting from the structured hydrogen bonding network. Microscopic properties of water molecules on the interfaces would have a key role in the suppression of protein adsorption for zwitterionic biomaterials.

We present a molecular design of a preprogrammed supermolecule that can stabilize frustrated molecular organization of an isotropic liquid-crystalline phase. The tapered amphiphilic compound exhibited an unusual smectic A to cubic phase transition. The chiral T-shaped compound showed amorphous blue phase III with a temperature range of 25 K. We demonstrate high-transmittance, sub-millisecond response and hysteresis-free switching in room temperature amorphous blue phase stabilized by a designed LC supermolecule.

A retardation film consists of optical polymer to control polarized light by the oriented birefringence. One of the issues of the films is wide-banding of birefringence. We have researched a novel molecular design to control dispersion, and found that the wide-band properties appear in a narrow range near the birefringence zero point, which is determined by the volume fractions of the positive monomer units to the negative units. The wide-band retardation film has been industrialized using a novel co-PC with a fluorene ring based on the molecular design.

Pd complexes with diimine ligands promote controlled cyclopolymerization of 1,6-dienes and 1,6,11-trienes to afford the polymers containing 1,2-trans-cyclopentane groups with well-regulated stereochemistry. Copolymerization of the dienes with ethylene and α-olefins also proceeds to give functionalized polyolefins. The polymerization of the monomers with oligomethylene spacer yields the polymers with five-membered rings in accurate density and distribution along the polymer chain. 4-Alkylcyclopentenes and alkenylcyclohexanes also get polymerized by the Pd complex to afford polymers with 1,3-trans-cyclopentane groups and 1,4-trans-cyclohexane groups, respectively. Isotactic polymer of 4-alkylcyclopentenes show liquid crystalline properties.

The slopes of G″–G′ decreased to 1.21 for the long-chain branched-polypropylene (LCB-PP) and 1.07 for PP-F07-S5. A decreased slope indicates an increase in elasticity, shear thinning effect and melt strength. The extending Avrami analysis proposed by Ozawa applied to PP, LCP-PP and the composite. The exponents were 3.6 for PP, 2.4 for LCB-PP and 1.5 for the composite.

Un-expected large increase in crystallization temperature (c.a. 53 °C) was found for Nylon-6 nanocomposites with both kind of carbon nanotubes (CNTs) and plasma-polymerized CNTs (CNTM) compared with Nylon-6 homopolymer. This behavior was associated with a high level of dispersion of CNT in all nanocomposites and the ability of CNT to act like a nucleating agent for semi-crystalline polymers. Besides, the steps involved in polymerization procedure help in dispersion of CNT, which is reported for the first time.

An inorganic metal salt, copper sulfate (CuSO₄), was mechanically mixed with acrylate rubber (AR) and heat pressed to prepare a novel crosslinkable AR/CuSO₄ composite. The coordination reaction between the ester lateral groups and the copper (II) ions was carried out at elevated temperatures. A straightforward method of vulcanizing AR was explored via the introduction of in situ coordination crosslinking.

The orientation of nanoscale double-helical morphologies of SBM triblock terpolymer at various film thicknesses (h) were studied using transmission electron microtomography, following solvent annealing and drying at a controlled solvent evaporation rate (R). The combination of h and R were found to be essential factors to determine orientation of the double-helical microdomains in thin films. Perpendicularly aligned double-helical morphology extending several micrometers from the substrate to the air surface was achieved.

Molecular self-assembly in IL is promoted by controlling cohesive energies of amphiphiles and ILs.

Macroscopic liquid crystal structures have been developed in hydrogels by self-assembly of a semi-rigid polyion complex. During the polymerization of isotropic precursor solution of a cationic monomer in the presence of a semi-rigid polyanion, the polycation will interact with oppositely charged polyanion to form polyion complexes. These semi-rigid complexes self-assemble further to form macroscopically ordered structure that is frozen in a nanoscale network by the following chemical cross-linking reaction.