Ring‐opening homopolymerization and copolymerization of lactones. Part 2. enzymatic degradability of poly(β‐hydroxybutyrate) stereoisomers and copolymers of β‐butyrolactone with ɛ‐caprolactone and δ‐valerolactone

Abstract

In this study, we have prepared poly([ R,S ] -b-hydroxybutyrate) (P( [ R,S ] -b-HB) or PHB) from [ R,S ] -b-butyrolactone ( [ R,S ] -b-BL), using diþ erent 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 diþ erent 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 ringopening copolymerization of [ R,S ] -b-BL with either e-caprolactone (CL) or d-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 inýuence 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 inýuence 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).

Continuous Synthesis of γ-Valerolactone in a Trickle-Bed Reactor over Supported Nickel Catalysts

“…γ-Valerolactone (GVL) is a versatile platform molecule, which can be directly used as a fragrance, green solvent, monomer for the production of plastics, or as a gasoline blending component. In addition, several biobased fuels or fuel additives (2-methyltetrahydrofuran, aromatics, and alkenes of different chain lengths) can be produced from GVL. − Two possible reaction pathways exist for the synthesis of GVL from levulinic acid (LA) . In the presence of acid functionalities, LA can be first dehydrated to angelica lactone, which is subsequently hydrogenated to GVL over transition metal catalysts.…”

Cationic copolymerization of racemic -β-butyrolactone with L,L-lactide: One-pot synthesis of block copolymers

“…Random copolymers of R ‐(3)‐HB and l,l ‐lactide (LA) with a wide range of compositions were prepared by the copolymerization in the presence of 1‐ethoxy‐3‐chlorotetrabutyldistannoxane as catalyst. It was observed that both the degree of crystallinity and the rate of degradation depended strongly on the copolymer composition . Random copolymers of HB and LA were also obtained by the transesterification of corresponding homopolymers performed in solution …”