PHYSICAL-PROPERTIES AND ENZYMATIC DEGRADABILITY OF COPOLYMERS OF (R)-3-HYDROXYBUTYRIC AND 6-HYDROXYHEXANOIC ACIDS
PHYSICAL-PROPERTIES AND ENZYMATIC DEGRADABILITY OF COPOLYMERS OF (R)-3-HYDROXYBUTYRIC AND 6-HYDROXYHEXANOIC ACIDS
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DOI：
10.1021/ma00127a007
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发表时间：
1995-11-06
期刊：
影响因子：
5.5
通讯作者：
YAMAGUCHI, A
中科院分区：
文献类型：
--
作者：
ABE, H;DOI, Y;YAMAGUCHI, A
以1-乙氧基-3-氯四丁基二锡氧烷为催化剂，通过（R）-β-丁内酯与ε-己内酯在不同进料比下的开环聚合，合成了（R）-3-羟基丁酸（（R）-3HB）与6-羟基己酸（6 HH）的共聚物，其组成范围为11 ~ 91mol%。P[（R）-3 HB-co-6 HH]的结构和物理性质通过H-1和C-13 NMR光谱、X射线衍射、差示扫描量热法和光学显微镜表征。共聚酯显示出具有（R）-3HB和6 HH单体单元的无规序列分布。P[（R）-3 HB-co-6 HH]的玻璃化转变温度随着6 HH组成从0增加到100摩尔%而从+4线性降低到-67 ° C。P[（R）-3 HB-co-6 HH]样品的熔融温度随着6 HH级分从0摩尔%增加到43摩尔%而从179 ° C降低到48 ° C。然后，随着6 HH分数从81摩尔%增加到100摩尔%，所述混合物的熔融温度从36 ° C增加到60 ° C。随着6 HH组成从0增加到43mol%，溶剂浇铸的共聚酯膜的X射线结晶度从62%降低到18%，并且共聚酯显示出P[（R）-3HB]晶格。另一方面，具有81-100摩尔%的6 HH分数的共聚物的X射线堆积度随着6 HH分数从31%增加到55%，并且这些样品显示出P（6 HH）晶格。具有53-70摩尔% 6 HH的P[（R）-3 HB-co-6 HH]样品是无定形聚合物。P[（R）-3 HB-co-6 HH]膜的酶促降解在25 ℃下在0.1M磷酸钾缓冲液（pH 7.4）中在从粪产碱菌纯化的PHB解聚酶或来自德氏根霉的脂肪酶的存在下进行。在11 ~ 43mol%6HH范围内的共聚物膜的PHB解聚酶的酶降解速率高于细菌P[（R）-3HB]膜。在11mol%6HH时，观察到通过PHB解聚酶的最高酶水解速率。对于在53至100摩尔%的6 HH级分范围内的SiO2膜，观察到很少的侵蚀。相比之下，具有脂肪酶的P[（R）-3 HB-co-6 HH]膜的重量损失曲线显示出与PHB解聚酶相反的共聚物组成的趋势。在91mol%6HH下观察到脂肪酶的最高酶解速率。在共聚物膜的酶促降解期间释放的水溶性产物的HPLC分析显示（R）-3HB和6 HH单元的单体、二聚体和三聚体的混合物。在此基础上，提出了一个聚羟基丁酸酯解聚酶水解聚酯链的模型。
Copolymers of (R)-3-hydroxybutyric acid ((R)-3HB) and 6-hydroxyhexanoic acid (6HH) with a wide range of compositions varying from 11 to 91 mol % 6HH were synthesized by the ring-opening polymerization of (R)-beta-butyrolactone with epsilon-caprolactone at various feed ratios in the presence of 1-ethoxy-3-chlorotetrabutyldistannoxane as a catalyst. The structure and physical properties of P[(R)-3HB-co-6HH] were characterized by H-1 and C-13 NMR spectroscopy, X-ray diffraction, differential scanning calorimetry, and optical microscopy. The copolyesters were shown to have a random sequence distribution of(R)-3HB and 6HH monomeric: units. The glass-transition temperature of P[(R)-3HB-co-6HH] decreased Linearly from +4 to -67 degrees C as the 6HH composition was increased from 0 to 100 mol %. The melting temperature of P[(R)-3HB-co-6HH] samples decreased from 179 to 48 degrees C as the 6HH fraction was increased from 0 to 43 mol %. Then, the melting temperature of the copolyester increased from 36 to 60 degrees C with an increase in the 6HH fraction from 81 to 100 mol %. The degree of X-ray crystallinity of solvent-cast copolyester films decreased from 62 to 18% as the 6HH composition was increased from 0 to 43 mol %, and the copolyesters showed a P[(R)-3HB] crystal lattice. On the other hand, the X-ray crystallinities of copolymers with 6HH fractions of 81-100 mol % increased from 31 to 55% with the 6HH fraction, and those samples showed a P(6HH) crystal lattice. The P[(R)-3HB-co-6HH] samples with 53-70 mol % 6HH were amorphous polymers. Enzymatic degradations of P[(R)-3HB-co-6HH] films were carried out at 25 degrees C in 0.1 M potassium phosphate buffer (pH 7.4) in the presence of PHB depolymerase purified from Alcaligenes faecalis or of lipase from Rhizopus delemar. The rates of enzymatic degradation by PHB depolymerase of copolymer films ranging from 11 to 43 mol % 6HH were higher than that of bacterial P[(R)-3HB] film. The highest rate of enzymatic hydrolysis by PHB depolymerase was observed at 11 mol % 6HH. Little erosion was observed for the copolyester films ranging in 6HH fractions from 53 to 100 mol %. In contrast, the weight loss profile of P[(R)-3HB-co-6HH] films with a lipase showed a trend in the copolymer composition opposite to that of a PHB depolymerase. The highest rate of enzymatic hydrolysis by Lipase was observed at 91 mol % 6HH. HPLC analysis of the water-soluble products liberated during the enzymatic degradation of copolymer films showed a mixture of monomers, dimers, and trimer of (R)-3HB and 6HH units. A model for the enzymatic hydrolysis of the polyester chain by PHB depolymerase was proposed on the basis of the results.