Palladium-catalyzed hydrosilylation polymerization of dihydrosilanes with diynes affording silylene-divinylene polymers

The Pd-PCy₃ (Cy=cyclohexyl) system effectively catalyzed hydrosilylation polymerization of dihydrosilanes with p- or m-diethynylbenzene to give silylene-divinylene polymers with Ph, Me, and/or vinyl substituents at the silicon atoms. The resulting polymers showed characteristic absorption and fluorescence spectra in ultraviolet to visible region. p-Phenylene polymers displayed λ_max peaks in longer wavelength region than the corresponding m-phenylene polymers. In TGA, the 5% weight loss temperatures (Td₅) ranged from 436 to 501 °C, indicating rather high thermal stability of these polymers. Vinyl group-containing polymers exhibited higher Td₅ values and char yields than other polymers.     

Efficacy of chitin-PAA-GTMAC gel in promoting wound healing: animal study

Acrylic grafted chitin (chitin-PAA) was modified with glycidyltrimethylammonium chloride (GTMAC) with the aim of promoting wound healing. The chitin-PAA-GTMAC gels with different GTMAC contents were compared with the original chitin-PAA gel and Intrasite gel for their efficacy in deep wound healing of Wistar rats. Four full-thickness wounds were made on the dorsal skin of rats and then each was treated with 4 materials; chitin-PAA, chitin-PAA-GTMAC(1:4), chitin-PAA-GTMAC(1:10) and Intrasite gel. During 18 days of treatment, the wounds were visually observed and calculated for wound size using image analysis program. Skin wound tissues of sacrificed rats were processed for routine histological observation and immunohistochemistry of proliferating cell nuclear antigen (PCNA). The wounds covered with the chitin derivatives either with or without GTMAC showed a significant reduction in wound size in day 9 in comparison with day 12 for those covered with Intrasite gel. The faster rate and the better pattern of epidermal development observed in histological study as well as the higher dermal cell proliferation (PCNA expression) also demonstrated the better efficiency in wound healing of the chitin derivatives than Intrasite. The earliest epidermal development of the wounds treated with chitin-PAA-GTMAC (1:4) among the tested materials suggested the most promising of this material for the treatment of full-thickness open wound.     

Xylan/polyvinyl alcohol blend and its performance as hydrogel

Xylan was first modified with maleic anhydride (MA) to obtain xylan‐MA. The derivative was then blended with polyvinyl alcohol (PVA) to generate xylan‐MA/PVA hydrogel. Xylan‐MA was prepared by reacting xylan with MA under an acidic condition. A ring opening of MA occurred, yielding ester linkages between xylan and MA, as verified by ¹³C‐NMR and FTIR. The effects of reaction temperature and weight ratio of xylan to MA on esterification were examined. Thermal stability of modified xylan derivatives was compared with that of pure xylan using TGA. The blends of xylan‐MA with PVA became crosslinked gel after being heated at high temperature. The influences of MA and PVA contents on strength and swelling behaviors of the gels were investigated. The cytotoxicity of the gels was also evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1914–1918, 2006