Solvent-induced crystallization behaviors of PLLA ultrathin films investigated by RAIR spectroscopy and AFM measurements.
Solvent-induced crystallization behaviors of PLLA ultrathin films investigated by RAIR spectroscopy and AFM measurements.
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DOI：
10.1021/jp506840e
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发表时间：
2014-10
期刊：
影响因子：
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通讯作者：
Ningjing Wu;S. Lang;Hong Zhang;Meichun Ding;Jianming Zhang
中科院分区：
文献类型：
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作者：
Ningjing Wu;S. Lang;Hong Zhang;Meichun Ding;Jianming Zhang
利用反射吸收红外光谱（RAIR）和原子力显微镜（AFM）研究了不同溶剂对聚L-乳酸（PLLA）薄膜结晶行为的影响。由于PLLA链段与溶剂分子之间的强相互作用，不规则的PLLA枝晶薄片在二氯甲烷溶剂中以平对取向生长，然后在较长的诱导时间后再溶解。更快地形成PLLA球晶诱导丙酮比与二氯甲烷，这些保持不变，随着诱导时间的增加，因为PLLA片段和丙酮分子之间的极性差异。由于氯仿（CHCl 3）分子与PLLA无定形链之间存在很强的相互作用，导致CHCl 3溶剂分子迅速渗透PLLA无规线团并溶解无定形链，因此氯仿不能诱导PLLA无规线团薄膜结晶。这些现象是由于溶剂诱导的结晶和溶解的效果在PLLA薄膜，最终导致更高程度的结晶度与丙酮比与二氯甲烷之间的溶剂特异性的竞争。
The crystallization of poly(L-lactide acid) (PLLA) ultrathin films induced by different solvents was investigated using reflection-absorption infrared (RAIR) spectroscopy and atomic force microscopy (AFM). Irregular PLLA dendrite lamellae grew in the flat-on orientation with dichloromethane solvent before being redissolved after longer induction times owing to the strong interaction between the PLLA segments and solvent molecules. Faster formation of PLLA spherulites was induced with acetone than with dichloromethane, and these remained unchanged with increasing induction time because of the polarity difference between the PLLA segments and acetone molecules. PLLA ultrathin films could not be induced to crystallize using chloroform because of the very strong interactions between the chloroform (CHCl3) molecules and PLLA amorphous chains, which caused the CHCl3 solvent molecules to rapidly permeate the PLLA random coils and dissolve the amorphous chains. These phenomena are attributed to solvent-specific competition between solvent-induced crystallization and dissolution effects in PLLA ultrathin films, which ultimately leads to the higher degree of crystallinity obtained with acetone than with dichloromethane.