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Nucleation and crystallization of PS‐ b ‐PEO‐ b ‐PCL triblock copolymers
Author(s) -
Müller Alejandro J.,
Arnal Maria Luisa,
LópezCarrasquero Francisco
Publication year - 2002
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200207)183:1<199::aid-masy199>3.0.co;2-s
Subject(s) - nucleation , copolymer , crystallization , materials science , supercooling , polystyrene , phase (matter) , polymer chemistry , chemical engineering , homogeneous , nanoscopic scale , crystal (programming language) , crystallography , polymer , thermodynamics , chemistry , nanotechnology , composite material , organic chemistry , physics , engineering , computer science , programming language
We have recently prepared a series of Polystyrene‐ b ‐Poly(ethylene oxide)‐ b ‐Polycaprolactone (PS‐ b ‐PEO‐ b ‐PCL or SEOCL) triblock copolymers of varying compositions and molecular weights. These ABC triblock copolymers present the peculiarity that two of the three blocks are able to crystallize upon cooling from an already phase segregated melt. When either of the crystallizable blocks or both are a minor phase, a fractionated crystallization process develops. The confinement of crystallizable blocks in the nanoscopic scale enables the clear observation in some cases of exclusive crystallization from homogeneous nuclei of two components within the triblock copolymer. The homogeneous nature of the nucleation was deduced since the supercooling attained is the maximum possible before vitrification of the material takes place. The self‐nucleation domains were also found to depend on the composition and molecular weight of the copolymers. The block copolymers exhibited a marked decrease in crystalline memory and when the crystallizable blocks constitute minor phases, the self‐nucleation domain disappears. The reason behind this behavior is that only at lower self‐nucleation temperatures the density of self‐nuclei becomes high enough to include at least one crystal fragment per confined microdomain in view of their vast numbers (e.g., 10 16 /cm 3 ).