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

以洋葱伯克霍尔德菌（Burkhoderia cepacia）D1和从活性锯木中分离的食酸代尔夫特菌（Delftia acidovorans）为原料，分别以丁酸和戊酸（VA）或γ-丁内酯（γ-BL）为碳源，生物合成了聚（3-羟基丁酸酯-co-3-羟基戊酸酯）[P（3 HB-co-3 HV）]和聚（3-羟基丁酸酯-co-4-羟基戊酸酯）[P（3 HB-co-4 HB）]。3 IIV和4 IIB组分的含量随VA或γ-BL浓度的增加而增加。P（3 HB-co-3 HV）的熔点随3 HV含量的变化曲线表明，P（3 HB-co-3 HV）的共晶点约为300 ℃。40%3HV，表明P（3 HB）晶体中含有3 HV组分。P（3 HB）及其共聚物与甲基丙烯酸甲酯辐射接枝聚合后，其生物降解速率受到抑制，而与丙烯酸辐射接枝聚合后，其生物降解速率受到促进。接枝苯乙烯的P（3 HB）球晶生长速率略有下降，而接枝醋酸乙烯酯的P（3 HB）球晶生长速率明显减慢。通过接枝改性提高了材料的耐热性和力学性能。P（3 HB-co-3 HV）在3 HV含量小于40%时发生共沉淀，而在其它范围或所有范围的P（3 HB-co-4 HB）中均未发生共沉淀。后者的结晶度降低共聚。P（3 HB-co-4 HB）单晶的酶降解不仅发生在晶面，也发生在折叠链区。少量的4 HB组分以晶体缺陷的形式存在于P（3 HB）晶体中。最后，聚（L-乳酸）和Bionolle，这被认为是最快的商业化，辐照引入交联，以提高热稳定性或耐热性的温度范围以上的玻璃化转变温度，甚至高于熔点。

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.