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Featured researches published by Toshio Kitao.


Journal of Membrane Science | 1995

Molecularly imprinted polymeric membranes for optical resolution

Masakazu Yoshikawa; Jun-ichiro Izumi; Toshio Kitao; Susumu Koya; Shunji Sakamoto

Abstract d -Tryptophan permeated faster than l -tryptophan through the molecularly imprinted polymeric membranes bearing tetrapeptide derivative as a molecular recognition site.


Polymer | 1989

Preparation of block copoly (ester-ether) comprising poly (L-lactide) and poly (oxypropylene) and degradation of its fibre in vitro and in vivo

Yoshiharu Kimura; Yuji Matsuzaki; Hideki Yamane; Toshio Kitao

Abstract The A-B-A triblock copoly(ester-ether)s comprising poly( l -lactide) (A) and poly(oxypropylene) (B) were prepared by the copolymerization of l -lactide and polypropylene glycols (PPG) with mono-dispersed molecular weights of 2000 and 4000. A Me3AlH2O catalyst system was utilized as the initiator. When the feed ratios of PPG 2000 and 4000 were over 5 and 10 wt% relative to l -lactide, respectively, the polymerization of l -lactide took place from the PPG hydroxy terminals to give the desired A-B-A block copolymers in high yields. Their molecular weights were found to be coincident with the values estimated from the monomer conversions and the feed ratios of PPG. At the lower feed ratios of PPG, the poly( l -lactic acid) (P l LA) homopolymer was formed together with the block copolymers. The copolymers were melt-spun by the conventional method and the fibres obtained were extended by drawing at 80–90°C. At the same draw ratio the modulus of the fibres was decreased with increasing PPG content in the copolymers. The fibres of the P l LA-PPG 4000 copolymers with different content of PPG were subjected to degradation both in vitro and in vivo. Upon immersion in a phosphate buffer (pH = 7.2) the fibres showed a time-dependent decrease in tensile strength with accompanying surface erosion. The rate of this degradation was much higher than that of the fibre of P l LA ( M n = 62 000 ). The same fibres, implanted under the dorsal skin of rats, caused a degradation similar to that observed in vitro without eliciting a significant rejection and inflammation. The block copolymers comprising P l LA and PPG, therefore, were shown to have high potentiality as the biodegradable polymers with improved flexibility and biodegradability.


Polymer | 1993

Copolymerization of 3-(S)-[(benzyloxycarbonyl)methyl]-1,4-dioxane-2,5-dione and l-lactide: a facile synthetic method for functionalized bioabsorbable polymer

Yoshiharu Kimura; Kenji Shirotani; Hideki Yamane; Toshio Kitao

Abstract The copolymerization of 3-(S)-[(benzyloxycarbonyl)methyl]-1,4-dioxane-2,5-dione (BMD) and l -lactide (LAC) was carried out in bulk at relatively low BMD/LAC feed ratios with stannous 2-ethylhexanoate as the catalyst. The resulting copolymers were subjected to hydrogenolysis at atmospheric pressure in the presence of a palladium on charcoal catalyst to remove the pendant benzyl groups quantitatively. The deprotected copolymers consisted of l -lactic (L), glycolic (G) and l -α-malic acid (M) repeating units, with the copolymer composition being almost identical to the monomer feed composition.13C n.m.r. spectroscopy revealed that the BMD units (G–M) had been randomly incorporated into the copolymer (L–L). These poly(α-hydroxy acid)s with pendant car☐yl groups were found to hydrolyse more rapidly than poly( l -lactide), because of the water-absorbing and catalytic activities of the car☐yl moieties. They were allowed to react with p-azidophenacyl bromide in the presence of triethylamine to form photo affinity labelling groups at the car☐yl functionalities. These findings suggested that the malic-acid-containing poly(α-hydroxy acid)s should have a high potential for use as functionalized bioresorbable polymers.


Polymer | 1992

Degradation of azo-containing polyurethane by the action of intestinal flora: its mechanism and application as a drug delivery system

Yoshiharu Kimura; Y. Makita; T. Kumagai; Hideki Yamane; Toshio Kitao; H. Sasatani; S.I. Kim

Abstract Several segmented polyurethanes comprising azo aromatic and hydrophilic groups were synthesized by reaction of m -xylylene diisocyanate with a mixture of m , m ′-dihydroxyazobenzene, poly(ethylene glycol) (PEG, M a = 2000) and 1,2-propanediol (propylene glycol, PG). Their polymer films were made by solution casting, and pellets of a hydrophilic drug (FOY-305) were coated with these polymers. Both the films and the coated pellets were incubated anaerobically in a culture of human intestinal flora. It was found that the azo groups in the polymer were reduced to hydrazo groups during incubation, which induced degradation of the films and the coatings without decreasing the molecular weight of the polymer. The rate of drug release from the pellets depended on both the azo and PEG compositions. Based on these findings, a new degradation mechanism of the polyurethane films and coatings is proposed.


Journal of Membrane Science | 2000

Specialty polymeric membranes

Masakazu Yoshikawa; Shin-ichi Kuno; Takashi Wano; Toshio Kitao

SummaryPervaporation of acetic acid/water mixture was investigated through uncrosslinked and crosslinked polybutadiene membranes. Crosslinked polybutadiene membrane permeated acetic acid in preference to water indicating that polybutadiene must be a candidate for a permselective membrane material for acetic acid separation from its aqueous solution.


Journal of Membrane Science | 1994

Specialty polymeric membranes 2. Pervaporation separation of aqueous lower alcohol solutions throuh modified polybutadiene membranes

Masakazu Yoshikawa; Takashi Wano; Toshio Kitao

Abstract Uncrosslinked and crosslinked polybutadiene membranes were used to investigate the pervaporation of lower alcohol/water mixtures (alcohol: methanol, ethanol, 1-propanol, 2-propanol, and t-butanol). Crosslinked polybutadiene membrane permeated lower alcohols in preference to water indicating that polybutadiene must be a candidate for permselective membranes for alcohol/water mixtures.


European Polymer Journal | 1997

Speciality polymeric membranes—VI. Pervaporation separation of benzene/cyclohexane mixtures through nylon 6-graft-poly(ethyl methacrylate) membranes

Masakazu Yoshikawa; Toshio Kitao

A novel pervaporation membrane was prepared by radical graft polymerization of ethyl methacrylate onto Nylon 6. The permselectivity toward benzene was increased by the introduction of poly(ethyl methacrylate) on to a Nylon 6 membrane. The membrane from Nylon 6-graft-poly(ethyl methacrylate), whose (PEMA)/(N6) ratio was 0.06, gave a separation factor over 220 toward benzene at the weight fraction of benzene in the feed of ca 0.1. From the pervaporation data and sorption experiments, it was made clear that both the solubility selectivity and the diffusivity selectivity are preferable to benzene.


Journal of Membrane Science | 1993

Specialty polymeric membranes. 1. Modified polybutadiene membranes for alcohol separation

Masakazu Yoshikawa; Takashi Wano; Toshio Kitao

Pervaporation of lower alcohol/water mixture (alcohol: methanol, ethanol, or 1-propanol) through uncrosslinked and crosslinked polybutadiene membranes was investigated. Crosslinked polybutadiene membranes permeated lower alcohols in preference to water indicating that polybutadiene is a candidate for permselective membranes for the separation of alcohol/water mixtures.


Separation Science and Technology | 1999

Specialty Polymeric Membranes. VIII. Separation of Benzene from Benzene/Cyclohexane Mixtures with Nylon 6-graft-Poly(Butyl Methacrylate) Membranes

Masakazu Yoshikawa; Keisuke Tsubouchi; Toshio Kitao

A novel pervaporation membrane was prepared by radical graft polymerization of butyl methacrylate onto nylon 6. The permselectivity toward benzene was increased by the introduction of poly(butyl methacrylate) onto a nylon 6 membrane. From pervaporation and sorption experiments, it was shown that the introduction of poly(butyl methacrylate) onto a nylon 6 membrane leads to the enhancement of permselectivity toward benzene. The solubility data for benzene were described by a combination of simple sorption and specific sorption, while cyclohexane solubility was described by simple sorption.


Polyhedron | 1990

Coordination structure of the aluminium atoms of poly(methylaloxane), poly(isopropoxylaloxane) and poly[(acyloxy)aloxane]

Yoshiharu Kimura; S. Tanimoto; Hideki Yamane; Toshio Kitao

Abstract Poly(methylaloxane) ( 1 ), prepared by hydrolytic polymerization of trimethyl-aluminium (TMA), was reacted with isopropanol (IP) to obtain poly(isopropoxylaloxane) ( 2 ). This was further reacted with propionic acid (PA) to prepare poly[(propionyloxy) aloxanel ( 3 ), with various ratios of PA ligands. By gasmetry of the methane produced in the reaction, as well as by the 1 H NMR spectroscopy of the products, both 1 and 2 were found to contain less reactive terminal A1Me and AlOH groups. For 3 , the unit structure and molecular weight were controlled by the PA/TMA ratio reacted. The 27 A1 NMR spectra of these products revealed that the coordination states of the aluminium atoms are different, depending on the O/A1 atomic ratio in the products. In the case of 1 , which has a low O/A1 ratio, the aluminium atoms are penta-coordinated, while in 2 and 3 hexa-coordination is involved. Based on these data the structures of poly(aloxanes) ( 1 – 3 ) are discussed.

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Yoshiharu Kimura

Kyoto Institute of Technology

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Masakazu Yoshikawa

Kyoto Institute of Technology

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Hideki Yamane

Kyoto Institute of Technology

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Jun-ichiro Izumi

Kyoto Institute of Technology

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Shunji Sakamoto

Kyoto Institute of Technology

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Masakazu Konda

Kyoto Institute of Technology

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Takashi Wano

Kyoto Institute of Technology

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Eri Yoshida

Toyohashi University of Technology

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Isoji Taniguchi

Kyoto Institute of Technology

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