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Thermal behavior and spherulitic superstructures of SBC triblock copolymers based on polystyrene (S), polybutadiene (B) and a crystallizable poly(ε‐caprolactone) (C) block
Author(s) -
Balsamo Vittoria,
von Gyldenfeldt Friederike,
Stadler Reimund
Publication year - 1996
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1996.021971021
Subject(s) - polybutadiene , materials science , crystallization , copolymer , polymer chemistry , polystyrene , caprolactone , differential scanning calorimetry , chemical engineering , nucleation , melting point , composite material , polymer , chemistry , thermodynamics , organic chemistry , physics , engineering
The dynamic crystallization and the melting behavior of polystyrene‐ block ‐poly(ε‐caprolactone) (PS‐ b ‐PCL, short notation SC), polybutadiene‐ block ‐poly(ε‐caprolactone) (PB‐ b ‐PCL, BC) and polystyrene‐ block ‐polybutadiene‐ block ‐poly(ε‐caprolactone) (PS‐ b ‐PB‐ b ‐PCL, SBC) have been studied using differential scanning calorimetry. The copolymers with high molecular weight exhibit microphase separation into microphases consisting of polystyrene, polybutadiene and poly(ε‐caprolactone) and partial crystallization of the corresponding PCL block. The crystallization occurs at temperatures below the PS glass transition. Depending on the block copolymer composition, crystallization takes place through a combination of heterogeneous and homogeneous nucleation. Isothermal crystallization was studied in order to determine the equilibrium melting point, T m 0 , of the PCL block, which depends on the weight ratio w PB : w PCL . The crystallization kinetics was analyzed in terms of Avrami equation. A general decrease in the overall crystallization rate in the block copolymers relative to the equivalent PCL homopolymer was found. Additionally, the growth rate of the spherulites was followed using polarized optical microscopy. Depending on the composition and flexibility of the block connected to PCL, some copolymers showed ring‐banded spherulites.