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Yonezawa, Noriyuki; Okamoto, Akiko
doi: 10.1295/polymj.PJ2007210pmid: N/A
The structural design strategy and the synthetic approaches for the wholly aromatic polyketones and the monomers are described. Electrophilic aromatic aroylation substitution polycondensation and aromatic coupling polycondensation have been investigated as synthetic routes for wholly aromatic polyketones by the author's group. Acyl-acceptant arene molecules as the electrophilic aromatic aroylation substitution polycondensation type monomers and the aromatic nuclei for bis(chlorobenzoylated) compounds as the aromatic coupling polycondensation one were designed and synthesized employing 2,2′-dioxybiphenyl, 2,2′-dioxy-1,1-binaphtyl, and o-terphenyl skeletons. Determining factors for monomers, which enable regioselective polycondensation, are also discussed. The properties of polyketones are also discussed briefly on the basis of polymer repeating unit structures.
doi: 10.1295/polymj.PJ2009148pmid: N/A
Dynamic physical properties of homopolymer liquids relax through global motion of the polymer chains over their dimension. This motion is affected by a variety of factors. For high molecular weight (M) chains, the entanglement retards the global motion to affect the properties. This entanglement effect changes with the chain architecture as well as the molecular weight distribution. The effect of the chain architecture on the global chain dynamics is found also for non-entangled low-M chains as well. This article gives a very brief summary of the experimental facts and molecular interpretations for these effects.
Sun, Yuejian; Wu, Yaoying; Chen, Liguo; Fu, Zhifeng; Shi, Yan
doi: 10.1295/polymj.PJ2008269pmid: N/A
Stable free radical polymerization (SFRP) of styrene was carried out using bis(4-bromomethylbenzoyl)peroxide (BBMBPO)/4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (HTEMPO) or 4,4′-azobis(4-cyanopentyl)-α-bromoisobutyrate (ABCBIB)/HTEMPO as bimolecular initiating system. It was found that the molecular weights of obtained polystyrenes were controlled by the concentration of HTEMPO. Besides those generated by the initiators, some polystyrene chains were formed via thermal initiation. Polystyrene chains generated by the initiator had initiating groups for atom transfer radical polymerization (ATRP) at their ends, so they grew to higher molecular weights in ATRP of styrene. While the molecular weights of polystyrene chains generated by thermal initiation kept constant in ATRP conditions because of their inert terminals for ATRP. The amount of polystyrenes generated by thermal initiation was investigated quantitatively via gel permeation chromatography technique.
Kashimura, Yumi; Aoyama, Satoshi; Kawakami, Hiroyoshi
doi: 10.1295/polymj.PJ2009108pmid: N/A
We have synthesized fluorinated block copolyimides with different block chain lengths by chemical imidization in a two-pot procedure and prepared the asymmetric coployimide membranes using the dry-wet phase inversion process. The gas transport properties of the asymmetric membranes were measured using a high vacuum apparatus equipped with a Baratron absolute pressure gauge at 76 cmHg and 35 °C. We demonstrated that the skin layer thicknesses and the gas transport properties of the asymmetric membranes depended on the copolyimide structures. The phase separation in the block copolyimide solution instantaneously occurred so that the skin layer of the asymmetric block copolyimide membrane became thinner than that of the asymmetric random copolyimide membrane and the gas permeance of the asymmetric block copolyimide membrane had a high value. The apparent skin layer thickness of the asymmetric block coployimide membrane was 230 nm. The asymmetric copolyimide membrane indicated an O2 permeance of 2:7 × 10−4 [cm3(STP)/(cm2 sec cmHg)] (270 [GPU]) and an O2/N2 selectivity of 4.3.
Kawatsuki, Nobuhiro; Nobuhitani, Mami; Kondo, Mizuho
doi: 10.1295/polymj.PJ2009146pmid: N/A
The cooperative molecular reorientation in methacrylate copolymer films with hexamethylene spacer groups terminated with photoreactive hydrogen (H) bonded 4-oxycinnamic acid (CA) and photoinactive 4-oxy-4′-methoxybiphenyl (MB) in their side chains was investigated by irradiating with linearly polarized ultraviolet light (LPUV) and subsequent annealing. A thermally enhanced cooperative in-plane orientation of both CA and MB side groups perpendicular to the polarization (E) of LPUV light was obtained when the annealing temperature was in the liquid crystalline temperature range of both mesogenic side group. On the other hand, thermal enhancement of the in-plane molecular reorientation did not occur when the annealing temperature was out of the LC temperature range of the MB. It was clarified that the amount of axis-selectively photoreacted H-bonded CA groups and the LC mesomorphism of the copolymer film play an important role in the thermally enhanced cooperative molecular reorientation.
Maehara, Takayuki; Ohshita, Joji; Taketsugu, Ryo; Hino, Koichi; Kunai, Atsutaka
doi: 10.1295/polymj.PJ2009128pmid: N/A
Hydrosilylation of diethynylbenzene with bis(dihexylsilylpropoxy)-, bis(diphenylsilylpropoxy)-, and bis(methylphenylsiloxy)-adamantane (1a, 1b, and 1c) afforded the corresponding hydrosilylated polymers. A similar reaction of bis(allyloxy)-adamantane with 1b also gave a polymer with repeating units of Ad-propylene-silanylene-propylene (Ad = adamantanediyl). Heat-resistance of the resulting polymers was examined by the thermogravimetric analysis and the highest T d5 and T d10 (temperatures of 5 and 10% weight loss) among the present polymers were noted to be 370°C and 393°C, respectively, for the polymer prepared from the reaction of diethynylbenzene with 1c. Cross-linking hydrosilylation of a vinylsiloxane polymer with 1c was also studied.
Buruiana, Tinca; Melinte, Violeta; Stroea, Lenuta; Buruiana, Emil C.
doi: 10.1295/polymj.PJ2009131pmid: N/A
New urethane dimethacrylate oligomers functionalized with carboxylic acid groups (CAd-1÷4) were synthesized and evaluated as co-monomers in dental resin composites. Photopolymerization of these oligomers containing polyethylene oxide spacer was monitored by FT-IR spectroscopy comparatively with the low molecular monomer (CAd-M), as well as by fluorescence technique. The polymerization shrinkage for several mixtures including the urethane oligomers and BisGMA/TEGDMA system was determined and, for some cured specimens, the equilibrium water uptake, water sorption and contact angle were measured to establish their behaviour into a wet environment. The compatibility between the organic and inorganic phase was investigated by SEM analysis in fractured surfaces indicating the formation of compact homogeneous materials. Aspects of the crack propagation behaviour of some composites subjected to Vickers indentation were examined by polarizing optical microscopy (POM) and atomic force microscopy (AFM), a visible crack being visible only in AFM image. Mechanical properties (compressive and diametral tensile strengths), determined for several resins composites, sustains the formation of materials with a hardness comparable to those frequently encountered in dental practice.
Aoki, Ken'ichi; Ichimura, Kunihiro
doi: 10.1295/polymj.PJ2009005Rpmid: N/A
The self-developable formation of photoinduced surface relief was achieved by the post-exposure baking (PEB) of pattern-wise UV-exposed films consisting of a photobase generator, a branched base amplifier and an epoxy resin. A photogenerated amine triggered the self-catalytic fragmentation of a branched base amplifier to give branched molecules substituted with ω-amino groups, which reacted with an epoxy resin during PEB to form crosslinked networks. The consumption of ingredients as a result of the fragmentation and the crosslinking reactions during PEB generates the concentration gradients of components, leading to the mass transfer from unexposed areas to exposed ones to give surface relief structures.
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