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At least 145 records · Page 8Linked to original sources
PubMed1976

Surface hydroxylation of styrene-butadiene-styrene block copolymers for biomaterials.

This work pertains to the development of high strength elastomers potentially useful as nonthrombogenic cardiovascular prostheses. Triblock copolymers of the styrene-butadiene-styrene type have been subjected to surface hydroxylation which provide reactive sites at the surface for the subsequent coupling of heparin while retaining the unique mechanical properties of the SBS copolymers. Curves of hydroxyl content versus the copolymer film thickness demonstrate the effect of swelling in the surface region on the product distribution and on the time dependence of the hydroxylation process. In addition, the effect of time, temperature, and the composition of the reaction bath on the diffusion/reaction process is shown. Finally, the general applicability of this surface modification scheme to the development of biomaterials is discussed.

Adsorption↗
PubMed2006

Self-assembly of mixtures of block copolymers of poly(styrene-b-acrylic acid) with random copolymers of poly(styrene-co-methacrylic acid).

The effects of the addition of random copolymers of poly(styrene-co-methacrylic acid) [P(S-co-MAA)] on the self-assembly of block copolymers of poly(styrene-b-acrylic acid) (PS-b-PAA) are described. The effects of variation of five factors, including the MAA content, the weight fraction and molar mass of the P(S-co-MAA), the initial concentration of the mixture, and the length of the PAA segment in the block copolymer, were investigated. With increasing MAA content, the localization of the random copolymer in the aggregate changed from the core to the interface, which led to a morphological transition from spheres to vesicles. Vesicles, mixtures of vesicles and large spheres, and large spheres alone were formed with increasing weight fraction of the random copolymer. When the molar mass of the random copolymer was high, both rods and vesicles were observed at low water contents; otherwise, only vesicles were observed. The vesicle size increased (from 100 to 140 nm) with increasing initial polymer concentration, whereas the vesicle membrane thickness remained constant. The size of the vesicles prepared from the mixtures increased with water content but decreased with the length of PAA in the diblock.

Journal Article↗
PubMed2002

Optical properties of the synthetic nanocomposites SiO2/CdS/poly(styrene-co-maleic anhydride) and SiO2/CdS/poly(styrene-co-maleimide).

Hybrid materials consisting of SiO2/CdS particles dispersed in poly(styrene-co-maleic anhydride) and poly(styrene-co-maleimide) have been synthesized and characterized. The polymer nanocomposites were synthesised in situ in the presence of previously prepared inorganic fillers (SiO2/CdS). The nanocomposites were synthesized with the use of as-prepared or surface-modified SiO2/CdS fillers. For both types of nanocomposites, the optical properties were evaluated and the observation of size quantization effects in the optical spectra is discussed. In this context, the influence of the inorganic fillers and polymer matrices on the optical properties of the final nanocomposites was investigated.

Cadmium Compounds↗
PubMed2002

[Analysis of confined crystalline behaviors of poly(styrene)-poly(ethyleneoxide)-poly(styrene) triblock copolymers by inverse gas chromatography].

The confined crystalline behaviors of the triblock copolymers, poly(styrene)-poly(ethyleneoxide)-poly(styrene) (PS-PEO-PS), were studied by using inverse gas chromatography(IGC) probe technique, including phase-transformation of melting crystalline, crystallinity (Xc), melting temperature(Tm) and melting range of temperature. The effects of the molecule-chain length of linear alkane probes on the results are discussed. Results showed that micro-phase separation of PS-PEO-PS had a greater influence on crystallization of PEO molecule-chain. Crystalline-structure of PS-PEO-PS had interphase formed by some kinds of imperfect PEO crystal and amorphous PS. The molecule-chain length of linear alkane probes had no effect on the determination of melting temperature and melting range of temperature of PS-PEO-PS, but had a greater influence on the determination of crystallinity of PS-PEO-PS and investigation phase-transformation of melting crystalline. Crystallinity of PS-PEO-PS determined by IGC was decreased with the increase of molecule-chain length of linear alkane probes. By suitable shorter molecule-chain length of linear alkane probes, it was truer to reflect the existence of interphase of PS-PEO-PS and multi-phase-transformation of melting crystalline presenting in interphase.

English Abstract↗
PubMed1993

32P-postlabelling of DNA adducts in styrene oxide-modified DNA and in workers exposed to styrene.

Lamination workers are exposed to large amounts of styrene. A postlabelling method was developed in order to detect DNA adducts in white blood cells from such workers. First, styrene oxide was reacted with DNA, and the adducts were characterized by the nuclease P1 version of the 32P-postlabelling technique. The adducts in human samples were transferred magnetically during chromatography. The 2'-deoxyguanosine 3'-monophosphate (dGMP) adduct standards, including N2 and O6 adducts, were shown to be resistant to the action of nuclease P1. The O6 adducts were detected in the femtomole range at about 10% labelling efficiency. In lamination workers, the level of O6 adducts, adjusted for adduct recovery, was 5/10(8) nucleotides, which was five times the level in controls.

Autoradiography↗
PubMed1982

Studies on metabolism and toxicity of styrene. IV. 1-Vinylbenzene 3, 4-oxide, a potent mutagen formed as a possible intermediate in the metabolism in vivo of styrene to 4-vinylphenol.

1-Vinylbenzene 3,4-oxide, a putative intermediate in the metabolism of styrene to 4-vinylphenol, was synthesized and examined for its obligatory intermediacy to the phenol, its physical properties, and its mutagenicity toward Salmonella typhimurium TA98 and TA100. The 3,4-oxide had a half-life of 4.3 sec at pH 7.4 in an aqueous solution, and yielded 4-vinylphenol quantitatively without concomitant formation of any trace amount of 3-vinylphenol. The 3,4-oxide had a potent mutagenicity toward the TA100 bacteria but not toward the TA98 strain, whereas it showed a potent cytotoxicity to both of them His+ revertant colonies induced by the 3,4-oxide were 7233/plate at a total dose of 1.0 micromole/plate when it was applied in a sequential manner to the bacterial suspension during the pre-incubation of the testing system. Under the same conditions, benzo[a]pyrene 4,5-oxide and phenyloxirane showed 1283 and 1657 of His+ revertant colonies/plate at 19 nmoles and 10 micromoles/plate, respectively, as the maximal activities. The isomeric arene oxide, 1-vinylbenzene 1,2-oxide, had a longer half-life (1.63 min) than the 3,4-oxide at pH 7.4 in aqueous solution and was specifically rearranged to 2-vinylphenol. The 1,2-oxide also showed more potent mutagenicity to the TA100 strain bacteria than phenyloxirane but weaker than the 3, 4-oxide. 4- and 2-vinylphenols were neither mutagenic nor cytotoxic to the bacteria at concentrations ranging up to 4 micromoles/plate.

Drug Stability↗
PubMed2000

Styrene oxide-induced 2'-deoxycytidine adducts: implications for the mutagenicity of styrene oxide.

The reaction between 2'-deoxycytidine and styrene 7,8-oxide (SO) resulted in alkylation at the 3-position and at the O(2)-position through the alpha- and beta-carbons of the epoxide but at the N(4)-position only through the alpha-carbon. The 3-alkylated adducts were found to deaminate to the corresponding 2'-deoxyuridine adducts (37 degrees C, pH 7.4) with half-lives of 6 min and 2.4 h for the alpha- and beta-isomers, respectively. The N(4)-alkylated products were stable at neutral pH. The O(2)-alkylated products were unstable being prone to depyrimidation and to isomerisation between alpha- and beta-isomers. In SO-treated double-stranded DNA, enzymatic hydrolysis allowed the identification of the beta3-deoxyuridine and alphaN(4)-deoxycytidine adducts (1.9 and 0.5% of total alkylation, respectively), in addition to the previously identified DNA-adducts. The 3-substituted uracil may have implications for the mutagenicity of SO.

Animals↗