Stereocomplex formation between enantiomeric poly(lactic acid)s. 12. Spherulite growth of low-molecular-weight poly(lactic acid)s from the melt
Stereocomplex formation between enantiomeric poly(lactic acid)s. 12. Spherulite growth of low-molecular-weight poly(lactic acid)s from the melt
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DOI：
10.1021/bm049835i
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发表时间：
2004-07-01
影响因子：
6.2
通讯作者：
Tezuka, Y
中科院分区：
文献类型：
--
作者：
Tsuji, H;Tezuka, Y
在来自低分子量聚（L-丙交酯）的共混物中立体复合物微晶的球晶生长[即，聚（L-乳酸）（PLLA）]和聚（D-丙交酯）[即，用偏光显微镜研究了聚（D-乳酸）（PDLA）]熔体中的共混物，以及纯PLLA和PDLA薄膜中的共混物。与均方晶系（≤ 140 ℃）相比，立构复合物的球晶生长在更宽的温度范围内（≤ 190 ℃）。在140 ℃时，立体复合物微晶的球晶半径生长速率（G）（136.4 mum min（-1））比PLLA的同嵌段共聚物高一个数量级（11.8 mum min（-1））和PDLA（15.7 μ m min（-1）），而对于立构复合物的球晶，诱导期较短（0.0分钟）比PLLA（2.6分钟）和PDLA（0.7分钟）的均晶球度要高。除了这两个因素外，与PLLA和PDLA的均方晶相比，立体复合物微晶的较高球晶密度导致立体复合物的整体结晶快速完成。在140-190 ℃温度范围内，立体复合物微晶的前沿因子（G（0））和成核常数（K-g）分别估计为3.56 × 10（12）μ mmin（-1）和8.42 × 10（5）K-2。立体复合物微晶的G（0）值比PLLA的同型微晶高1和2个数量级（9.69 × 10（11）μ m min（-1））和PDLA（8.79 × 10（10）μ m min（-1）），而立构复合物微晶的K-g值是PLLA（4.95 × 10（5）K-2）和PDLA（4.20 × 10（5）K-2）的同嵌段共聚物的K-g值的两倍。
The spherulite growth of stereocomplex crystallites in the blend from low-molecular-weight poly(L-lactide) [i.e., poly(L-lactic acid) (PLLA)] and poly(D-lactide) [i.e., poly(D-lactic acid) (PDLA)] from the melt, together with that of the homocrystallites in pure PLLA and PDLA films, was investigated using polarization optical miscroscopy. The spherulite growth of stereocomplex crystallites occurred at a wider temperature range (less than or equal to190degreesC) compared with that of homocrystallites (less than or equal to140degreesC). At 140degreesC, the spherulite radius growth rate (G) for the stereocomplex crystallites (136.4 mum min(-1)) was an order of magnitude higher than those for the homocrystallites of PLLA (11.8 mum min(-1)) and PDLA (15.7 mum min(-1)), whereas the induction period was shorter for the spherulties of stereocomplex crystallites (0.0 min) than for the spherulties of homocrystallites of PLLA (2.6 min) and PDLA (0.7 min). In addition to these two factors, the higher spherulite density of stereocomplex crystallites compared with those of the homocrystallites of PLLA and PDLA resulted in rapid completion of overall crystallization of stereocomplex. The front factor (G(0)) and nucleation constant (K-g) for the stereocomplex crystallites in the temperature range of 140-190 degreesC were estimated to be 3.56 X 10(12) mum min(-1) and 8.42 x 10(5) K-2, respectively. The G(0) value for stereocomplex crystallites was 1 and 2 orders of magnitude higher than those for the homocrystallites of PLLA (9.69 x 10(11) mum min(-1)) and PDLA (8.79 x 10(10) mum min(-1)), whereas the K-g value for stereocomplex crystallites was twice those for the homocrystallites of PLLA (4.95 x 10(5) K-2) and PDLA (4.20 x 10(5) K-2).