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

Copolymers of racemic β‐butyrolactone (β‐BL) with ε‐caprolactone (ε‐CL) (P(BL‐co‐CL)) and δ‐valerolactone (δ‐VL) (P(BL‐co‐VL)) were prepared by ring‐opening polymerization reactions using the commercial aluminoxane catalyst tetraisobutyldialuminoxane (TIBAO). The yields, molecular weights, compositions and crystallinities were determined for both copolymers by gel permeation chromatography (GPC), nuclear magnetic resonance (1H NMR) spectroscopy and differential scanning calorimetry (DSC). A detailed study by 13C NMR spectroscopy has been made to determine monomer diad sequence distributions. These results and those of reactivity ratios indicate that the co‐polymers may consist of compatible blocks of BL units and VL units of variable size. © 1998 SCI.

No abstract

In this study, we have prepared poly([R,S ]‐β‐hydroxybutyrate) (P([R,S ]‐β‐HB) or PHB) from [R ,S]‐β‐butyrolactone ([ R,S]‐β‐BL), using different aluminoxane catalyst systems (triethylaluminium/water, triisobutylaluminium/water, trioctylaluminium/water and tetraisobutyldialuminoxane/water). By varying the ratio of catalyst to water and using a method of fractionation of polymers, PHB with different isotactic diad fractions (i) (from 0.41 to 0.72) and crystallinities were obtained. Copolymers poly(butyrolactone‐co‐caprolactone) (P(BL‐co‐CL)) and poly(butyrolactone‐co‐valerolactone) (P(BL‐co‐VL)) have also been synthesized from the ring‐opening copolymerization of [ R,S]‐β‐BL with either ε‐caprolactone (CL) or δ‐valerolactone (VL) using tetraisobutyldialuminoxane (TIBAO) catalyst. The enzymatic degradability of these polymers was studied in aerobic and anaerobic media. The objective of this work was to determine the influence of the tacticity and crystallinity of the polymers on their degree of biodegradation and on their initial degradation rate. It was shown that the degradation rate measured for bacterial PHB 100% [R] was the highest and the degree of aerobic biodegradation reached after 36 days was around 94%. A 40–50% biodegradation was obtained for synthetic PHB, highly isotactic and predominantly syndiotactic. The non‐crystalline and atactic PHB synthesized from TIBAO catalyst had a very high degree of biodegradation of around 88%. This result may suggest that not only are the [R ]‐BL units hydrolysed but also the [S ]‐BL units. The influence of the 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 synthesized from TIBAO catalyst, exhibit a high degree of biodegradation of around 85% except for copolymers containing a very high portion of unsubstituted units, CL or VL. The anaerobic biodegradation of PHB and copolymers P(BL‐co ‐CL) is much lower than the aerobic biodegradation, as are the initial rates, even for bacterial P([R ]‐HB). © 1999 Society of Chemical Industry