Side-chain effect of second monomer units on crystalline morphology, thermal properties, and enzymatic degradability for random copolyesters of (R)-3-hydroxybutyric acid with (R)-3-hydroxyalkanoic acids
Side-chain effect of second monomer units on crystalline morphology, thermal properties, and enzymatic degradability for random copolyesters of (R)-3-hydroxybutyric acid with (R)-3-hydroxyalkanoic acids
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DOI：
10.1021/bm0155975
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发表时间：
2002-01-01
影响因子：
6.2
通讯作者：
Doi, Y
中科院分区：
文献类型：
--
作者：
Abe, H;Doi, Y
采用生物合成技术合成了3种不同侧链长度的94mol%(R)-3-羟基丁酸(3HB)和6mol%(R)-3-羟基烷酸(3HV)、(R)-3-羟基己酸(3HHx)和中链(R)-3-羟基烷酸(MCL-3HA，C8-C12)无规共聚物。采用广角X射线衍射仪、小角X射线散射仪、差示扫描量热仪和光学显微镜等手段对共聚物熔融结晶薄膜的固态结构和热性能进行了表征。除了共聚酯中的3HV外，无规分布的第二单体单元是P(3HB)晶体的缺陷，被排除在P(3HB)晶片之外。随着第二单体单元侧链长度的增加，共聚物的片层厚度减小。在相同的结晶温度下，随着第二单体单元碳数的增加，球晶的生长速率降低。这些结果表明，第二单体单元的空间膨胀影响了无规共聚酯中(R)-3HB链段的结晶。在粪产碱菌T1PHB解聚酶存在下，对熔融结晶共聚物膜进行了酶降解试验。共聚酯的侵蚀速率与样品的结晶度和片层厚度有关。结果表明，随着第二单体单元碳数的增加，共聚物膜的酶降解速率增加。
Three types of random copolymers with 94 mol % (R)-3-hydroxybutyric acid (3HB) and 6 mol % (R)-3-hydroxyalkanoic acids with different side-chain lengths, (R)-3-hydroxypentanoic acid (3HV), (R)-3-hydroxyhexanoic acid (3HHx), and medium-chain-length (R)-3-hydroxyalkanoic acids (mcl-3HA, C8-C12), were prepared by biological synthetic techniques. The solid-state structure and thermal properties of melt-crystallized films for copolymers were characterized by means of wide-angle X-ray diffraction, small-angle X-ray scattering, differential scanning calorimetry, and optical microscopy. The randomly distributed second monomer units, except for 3HV in copolyesters, act as defects of the P(3HB) crystal and are excluded from the P(3HB) crystalline lamellae. The lamellar thickness of copolymers decreased with an increase in the side-chain length of second monomer units. In addition, the growth rate of spherulites decreased with an increase in the carbon numbers of second monomer units at an identical crystallization temperature. These results indicate that a steric bulkiness of the second monomer unit affects the crystallization of (R)-3HB segments in random copolyesters. An enzymatic degradation test of melt-crystallized copolymer films was carried out in the presence of PHB depolymerase from Alcaligenes faecalis T1. Erosion rate of copolyesters was dependent on both the crystallinity and the lamellar thickness of samples. As the result, the rate of enzymatic degradation for copolymer films increased with an increase in the carbon numbers of second monomer units.