Comparative structure-property characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s films under hydrolytic and enzymatic degradation: finding a transition point in 3-hydroxyvalerate contentстатья
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Аннотация:The hydrolytic and enzymatic degradation of polymer films of poly(3-hydroxybutyrate)(PHB) of different molecular mass and its copolymers with 3-hydroxyvalerate (PHBV) of different3-hydroxyvalerate (3-HV) content and molecular mass, 3-hydroxy-4-methylvalerate (PHB4MV),and polyethylene glycol (PHBV-PEG) produced by theAzotobacter chroococcum 7Bby controlledbiosynthesis technique were studied underin vitromodel conditions. The changes in thephysicochemical properties of the polymers during theirin vitrodegradation in the pancreaticlipase solution and in phosphate-buffered saline for a long time (183 days) were investigatedusing different analytical techniques. A mathematical model was used to analyze the kineticsof hydrolytic degradation of poly(3-hydroxyaklannoate)s by not autocatalytic and autocatalytichydrolysis mechanisms. It was also shown that the degree of crystallinity of some polymers changesdifferently during degradationin vitro. The total mass of the films decreased slightly up to 8–9%(for the high-molecular weight PHBV with the 3-HV content 17.6% and 9%), in contrast to thecopolymer molecular mass, the decrease of which reached 80%. The contact angle for all copolymersafter the enzymatic degradation decreased by an average value of 23% compared to 17% after thehydrolytic degradation. Young’s modulus increased up to 2-fold. It was shown that the effect ofautocatalysis was observed during enzymatic degradation, while autocatalysis was not availableduring hydrolytic degradation. During hydrolytic and enzymatic degradationin vitro, it was foundthat PHBV, containing 5.7–5.9 mol.% 3-HV and having about 50% crystallinity degree, presentscritical content, beyond which the structural and mechanical properties of the copolymer haveessentially changed. The obtained results could be applicable to biomedical polymer systems andfood packaging materials.