The side-chain-substituted poly (lactic acid)s (SPLAs) having C3–C4 alkyl side chains (Pr, iPr, n-Bu, iBu, and s-Bu for propyl, isopropyl, n-butyl, isobutyl, and sec-butyl groups, respectively) were synthesized from l-amino acids, and their crystallizability was systematically investigated (unknown for Pr, n-Bu, and s-Bu but already known for iPr and iBu). s-Bu was found to be a crystalline polymer like iPr, whereas Pr and n-Bu had little or no crystallizability like iBu. The crystal structure, melting behavior, and crystallization rate of s-Bu were examined in detail. The crystal structure and crystallinity (ca. 60%) of s-Bu were not affected at all by the crystallization temperature and casting solvent. The melting temperature and spherulite growth rate of s-Bu were compared with those of iPr and referenced data of SPLA with methyl side chains (Me) [i.e., poly (l-lactic acid)] and that with ethyl side chains (Et) [i.e., poly (L-2-hydroxybutanoic acid)]. The magnitude relation among melting temperatures of SPLAs would be iPr > s-Bu > Me > Et, and that among spherulite growth rates iPr > Me ≈ s-Bu > Et.

具有C3–C4烷基侧链（Pr，iPr，n-Bu，iBu和s-Bu的丙基，异丙基，正丁基，异丁基和仲丁基）的侧链取代聚乳酸（SPLA）-丁基分别）由l合成对α-氨基酸及其结晶性进行了系统研究（Pr，n-Bu和s-Bu未知，但iPr和iBu已知）。发现s-Bu是一种结晶聚合物，如iPr，而Pr和n-Bu却很少或没有结晶性，如iBu。详细检查了s-Bu的晶体结构，熔融行为和结晶速率。s-Bu的晶体结构和结晶度（约60％）完全不受结晶温度和浇铸溶剂的影响。比较了s-Bu的熔融温度和球晶生长速率与iPr的熔融温度和球晶生长速率，并比较了具有甲基侧链（Me）[即，聚（l-乳酸）]和带有乙基侧链的（Et）[即，聚（L-2-羟基丁酸）]。SPLA熔化温度之间的大小关系为iPr> s-Bu> Me> Et，球晶生长速率之间的大小关系为iPr> Me≈s-Bu> Et。