Radiation-induced Graft-polymerization and Cocrystallization of Microbial Co-polyesters

以从活性污泥中分离得到的绿色植物Burkhoderia cepacia d1和Delftia acidovorans为原料，以丁酸和戊酸（VA）或γ-丁内酯（bl）为混合碳源，分别合成了共聚物聚（3-羟基丁酸-c0-3-羟戊酸）[P (3HB-co-3HV)]和聚（3-羟基丁酸-co-4-羟戊酸）[P (3HB-co-4HB)]。随着VA和γ-BL浓度的增加，3IIV和4IIB组分的含量增加。P （3HB-co-3HV）的熔点随3HV含量的变化曲线显示，在3HV约40%处存在共晶点，表明P （3HB）晶体中含有3HV成分。P （3HB）及其与甲基丙烯酸甲酯辐射接枝共聚物的生物降解速率减慢，与丙烯酸辐射接枝共聚物的生物降解速率提高。乙烯接枝的P （3HB）球晶生长速率略有下降，醋酸乙烯接枝的P （3HB）球晶生长速率明显减慢。通过接枝提高了材料的耐热性和力学性能。在3HV含量低于40%时，P （3HB-co-3HV）出现共结晶现象，而在其他范围P （3HB-co-3HV）或所有范围P （3HB-co-4HB）均未出现共结晶现象。后者的结晶度因共聚而降低。P （3HB-co-4HB）单晶的酶解不仅发生在晶体的横向，而且发生在折叠链区域。少量的4HB成分以晶体缺陷的形式存在于P （3HB）晶体中。最后，将被认为是商业化最快的聚l -乳酸和Bionolle辐照引入交联，以提高在玻璃化转变温度甚至熔点以上的温度范围内的热稳定性或耐热性。

Using Burkhoderia cepacia D1and Delftia acidovorans isolated from active sawage, the copolymers poly (3-hydroxybutyrate-c0-3-hydroxyvalerate) [P (3HB-co-3HV)] and poly (3-hydroxybutyrate-co-4-hydroxyvalerate) [P (3HB-co-4HB)] were biosynthesized from mixed carbon sources of butyric acid and valeric acid (VA) or γ-butyrolactone (γ-BL), respectively. The contents of 3IIV or 4IIB component increased with increasing in concentration of VA or γ-BL.. The curve of melting points of P (3HB-co-3HV) against the 3HV contents showed an eutectic point at ca. 40% 3HV, suggesting the 3HV component was included in P (3HB) crystal. Biodegradation rate of P (3HB) and its copolymer radiation-graft-polymerized with methyl methacrylate was retarded, while those with acrylic acid was promoted. The rate of spherulites growth of P (3HB) grafted with stylene was slightly decreased, while that grafted with vinyl acetate was significantly retarded. Heat resistance and mechanical property were improved by grafting. Cocrystallization was observed P (3HB-co-3HV) at 3HV content less than 40%, while it was not observed in other range of P (3HB-co-3HV) or all range of P (3HB-co-4HB). Crystallinity of the latter decreased by copolymerization. Enzymatic degradation of single crystals of P (3HB-co-4HB) occurredl not only at crystal laterals but also at folded chain regions. The small amounts of 4HB cornponents were included in P (3HB) crystals as crystal defects. Finally, poly (L-lactic acid) and Bionolle, which were considered to be the fastest ones to commercialize, were irradiated to introduce crosslinking in order to improve thermal stability or heat-resistance at temperature range above glass transition temperatures or even above melting points.