Synthesis, stereocomplex crystallization and homo-crystallization of enantiomeric poly(lactic acid-co-alanine)s with ester and amide linkagesElectronic supplementary information (ESI) available. See DOI: 10.1039/c7py02024d

α-Hydroxy acid and α-amino acid-derived poly( l -lactic acid- co - l -alanine)s and poly( d -lactic acid- co - d -alanine)s with different alanine unit contents were synthesized by copolymerization of l -lactide and (3 S ,6 S )-3,6-dimethyl-morpholine-2,5-dione and of d -lactide and (3 R ,6 R )-3,6-dimethyl-morpholine-2,5-dione, respectively. The effects of the incorporated alanine units in lactic acid units or amide linkages in ester linkages on the crystallization behavior of solution- and melt-crystallized 50/50 blended samples as well as that of solution- and melt-crystallized nonblended samples were investigated. This article reports for the first time a stereocomplex (SC) formation between enantiomeric random copolyesteramides poly(lactic acid- co -alanine)s with ester and amide linkages. The solution-crystallized nonblended samples crystallized in α- or δ-form homo-crystallites for an l -alanine unit content up to 6 mol% or a d -alanine unit content up to 3 mol%, whereas all the melt-crystallized samples crystallized in α- or δ-form homo-crystallites for the l - or d -alanine unit content at least up to 12 and 13 mol%. In contrast, the solution-crystallized blended samples with the alanine unit contents of 0-13 mol% and the melt-crystallized blended samples with the alanine unit contents of 4-13 mol% crystallized only in SC crystallites, whereas the melt-crystallized blended samples with an alanine unit content of 0 mol% [ i.e. , poly( l -lactic acid)/poly( d -lactic acid) blends] crystallized in both SC crystallites and homo-crystallites. The alanine units of melt-crystallized nonblended samples were incorporated into homo-crystalline regions, whereas those of solution-crystallized nonblended samples were excluded from homo-crystalline regions. In contrast, the alanine units of solution-crystallized blended samples were incorporated into SC crystalline regions, whereas those of melt-crystallized blended samples were excluded from SC crystalline regions. α-Hydroxy acid and α-amino acid-derived poly( l -lactic acid- co - l -alanine)s and poly( d -lactic acid- co - d -alanine)s with different alanine unit contents were synthesized and their stereocomplex crystallization and homo-crystallization were investigated.