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Crystallization and Morphology of Autophobic Dewetted Poly( ε ‐caprolactone)‐ b ‐poly( L ‐lactide) Diblock Copolymer Ultrathin Films
Author(s) -
Yan Derong,
Huang Haiying,
He Tianbai
Publication year - 2012
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201200501
Subject(s) - crystallization , dewetting , nucleation , wetting , lamellar structure , wetting layer , chemical engineering , layer (electronics) , supercooling , materials science , morphology (biology) , transmission electron microscopy , crystallography , polymer chemistry , chemistry , composite material , nanotechnology , thermodynamics , organic chemistry , physics , genetics , biology , engineering
We have investigated the crystallization and morphological behaviors of poly( ε ‐caprolactone)‐ b ‐poly( L ‐lactide) (PCL‐ b ‐PLLA) in its autophobic dewetted ultrathin films (∼11 nm) using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The autophobic dewetting process creates a well defined film geometry containing an extremely thin wetting layer (∼4.5 nm) with densely distributed micrometer droplets atop, which restricts the primary nucleation process to occurring only in the droplets. In addition to the normally encountered flat‐on lamellae, the growth of edge‐on lamellae in such a thin wetting layer has been observed on both of two crystallization paths. In thermal crystallization, flat‐on lamellae are favored at small supercoolings while edge‐on lamellae appear at very large supercoolings both in the droplets and the wetting layer. For cold crystallization, the edge‐on lamellae can form easily in the droplets and grow into the wetting layer even at very small supercoolings. These observations are explained on the basis that the nucleation and lamellar orientation are strongly affected by the film geometry, the crystallization paths, and the applied supercoolings.