No abstract

In this study, we have prepared predominantly syndiotactic poly([R,S]‐β‐hydroxybutyrate) using different distannoxane catalyst systems (1‐hydroxy‐3‐chlorotetrabutyldistannoxane, 1‐ethoxy‐3‐chlorotetrabutyldistannoxane, 1,3‐dichlorotetrabutyldistannoxane, and dibutyltin oxide). Copolymers poly([R,S]‐β‐hydroxybutyrate‐co‐ϵ‐caprolactone), P(BL‐co‐CL), and poly([R,S]‐β‐hydroxybutyrate‐co‐δ‐valerolactone), P(BL‐co‐VL), have also been synthetized from the ring‐opening copolymerization of (R,S)‐β‐BL with ϵ‐caprolactone (CL) and δ‐valerolactone (VL) using hydroxy‐ and ethoxydistannoxanes catalysts. The enzymatic degradability of these polymers was studied in aerobic medium. The objective of this work was to determine the influence of the tacticity and crystallinity of the corresponding polymers on their degree of aerobic biodegradation and on their initial degradation rate. It was shown that the degradation rate value measured for bacterial PHB 100% (R) was the highest and the degree of aerobic biodegradation reached around 94% after 36 days. A percentage of final biodegradation of about 35% was obtained for predominantly syndiotactic PHB. This result is agreement with the calculated result obtained from triads sequences. The influence of crystallinity on the initial degradation rate was observed for the copolymers P(BL‐co‐CL) and P(BL‐co‐VL) of various feed ratios. All these, copolymers, synthetized from distannoxane catalysts, exhibit a high degree of biodegradation of around 75–88%. © 2002 Society of Chemical Industry

Homogeneous and composite aromatic polyetherimide membranes were prepared by casting from N‐methylpyrrolidinone (NMP) solutions and by electrodeposition of polymer at the cathode, respectively. The membranes were evaluated for their sorption, diffusion and pervaporation separation of water from ethanol with emphasis on the breaking of azeotropic composition. The membrane performance was shown to be dependent on the feed concentration, but still selective towards water over the whole composition range of the feed mixture. By looking at the surface energy parameters, the determination of degree of swelling and the calculation of deviation coefficients (ε), an interesting insight was gained into the coupling effect in this solvent/membrane system. From the sorption, diffusion and temperature‐dependent permeation behaviour, it could be concluded that in this system the diffusivity of permeant plays a major role in determining the pervaporation performance, rather than the solubility. © 1999 Society of Chemical Industry

A systematic study was carried out to investigate the cataphoretic electrodeposition of polyetherimide from an aqueous medium onto an electrically conductive support (aluminum, steel mesh). The subsequent re-imidisation steps were also investigated. The yield and quality of deposited polyetherimide were found to be strongly dependent upon a number of formulation variables that are closely related to the emulsion composition and electrodeposition conditions. A polymer modi®ed to 70% with methylpiperazine and quaternised to 50% with lactic acid gave a stable emulsion at 6% w/w (seven days at 4±5°C). Maximum rate of deposition was obtained with an initial current density of 10 mA cm À2 in the voltage range of 40±68 V.

A systematic study was carried out to investigate the cataphoretic electrodeposition of polyetherimide from an aqueous medium onto an electrically conductive support (aluminum, steel mesh). The subsequent re‐imidisation steps were also investigated. The yield and quality of deposited polyetherimide were found to be strongly dependent upon a number of formulation variables that are closely related to the emulsion composition and electrodeposition conditions. A polymer modified to 70% with methylpiperazine and quaternised to 50% with lactic acid gave a stable emulsion at 6% w/w (seven days at 4–5 °C). Maximum rate of deposition was obtained with an initial current density of 10 mA cm−2 in the voltage range of 40–68 V. © 1999 Society of Chemical Industry