Crystallization and morphology of ultrathin films of poly(d-lactide) with BAB block copolymers in which the A block is made of poly(l-lactide)

• Published in: Polymer (Guilford) 2017-05, Vol.117, p.25-29
• Main Authors: Tien, Nguyen-Dung, Prud'homme, Robert E.
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Block copolymers; Copolymer; Copolymers; Crystallization; Crystals; Microscopy; Molecular weight; Morphology; Poly(L-lactide); Polylactic acid; Polylactide; Single crystals; Stereocomplexation; Stereocomplexes; Studies; Thin films
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2017.03.058

When poly(d-lactide) (PDLA) is mixed with poly(l-lactide) (PLLA) of similar molecular weight and crystallized from the melt in ultrathin films (30 nm), hexagonal single crystals are obtained at the equimolar composition, and triangular single crystals at non-equimolar compositions. Here, stereocomplexes are formed by blending PDLA with a PLLA incorporated as the central block of a triblock copolymer made with poly(2-dimethylaminoethyl methacrylate) (PDMAEMA-b-PLLA-b-PDMAEMA or BAB); the resulting single crystals are studied by in-situ atomic force microscopy. The imbalance between the PDLA and PLLA characteristics, due to the presence of the B blocks of the triblock copolymer, leads to triangular single crystals at equimolar compositions, the hexagonal single crystal morphology being shifted to off-equimolar compositions. The importance of the shift depends upon the A/B ratio and the molecular weight of each species. [Display omitted] •Stereocomplexes of PDLA and PDMAEMA-b-PLLA-b-PDMAEMA were successfully observed in ultrathin films (30 nm).•The single crystals are hexagonal or triangular depending on the PLLA/PDLA ratio and molecular weight of each species.•The shift in morphology depends upon the mobility of two species.