Synthesis and characterization of stereoblock poly(lactic acid)s with nonequivalent D/L sequence ratios
Synthesis and characterization of stereoblock poly(lactic acid)s with nonequivalent D/L sequence ratios
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DOI：
10.1021/ma070156k
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发表时间：
2007-05-01
期刊：
影响因子：
5.5
通讯作者：
Kimura, Yoshiharu
中科院分区：
文献类型：
--
作者：
Fukushima, Kazuki;Hirata, Masayuki;Kimura, Yoshiharu
以中等分子量的聚L-乳酸（PLLA）和聚D-乳酸（PDLA）共混物为原料，采用固相缩聚法合成了由不同比例的D-和L-序列组成的立构嵌段聚乳酸（sb-PLA）。PLLA和PDLA预聚物首先分别通过L-和D-乳酸的直接熔融缩聚制备。将这些预聚物以不同的比例熔融共混，其中它们各自的部分立体络合可以有助于富聚合物的结晶。然后使熔融共混物在140-160 ° C的温度下经受SSP，该温度低于纯手性聚合物的熔融温度。所得的聚合物由较长的嵌段链的丰富的成分，并具有高于100 kDa的分子量时，无论是PLLA或PDLA的比例在饲料中较大。
Stereoblock poly(lactic acid)s (sb-PLA) consisting of different ratios of D- and L-sequences were synthesized by a process involving solid-state polycondensation (SSP) of polymer blends of poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) of medium molecular weight. Both PLLA and PDLA prepolymers were first prepared by direct melt-polycondensation of L- and D-lactic acids, respectively. These prepolymers were melt-blended in different ratios where their respective partial stereocomplexation could aid in the crystallization of the rich polymer. The melt-blends were then subjected to SSP at a temperature of 140-160 degrees C, which was lower than the melting temperature of the homochiral polymers. The resultant polymers consisted of longer block chains of the rich components and had molecular weights of higher than 100 kDa when either the PLLA or PDLA ratio in the feed was larger.