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Nucleation and Crystallization of PLDA‐ b ‐PE and PLLA‐ b ‐PE Diblock Copolymers
Author(s) -
Müller Alejandro J.,
Castillo Reina V.,
Hillmyer Marc
Publication year - 2006
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/masy.200651025
Subject(s) - crystallization , nucleation , materials science , lamellar structure , crystallinity , copolymer , amorphous solid , chemical engineering , polymer chemistry , polyethylene , isothermal process , composite material , crystallography , polymer , chemistry , thermodynamics , organic chemistry , engineering , physics
The nucleation and crystallization of two types of strongly segregated poly(lactide)‐ block ‐polyethylene diblock copolymers with an approximate 50/50 composition has been investigated. One material contains an amorphous PLDA block (PLDA‐ b ‐PE) and the other contains a semicrystalline PLLA block (PLLA‐ b ‐PE). The overall isothermal crystallization rate of the PLLA block was slowed down as compared to homo‐PLLA by the covalently bonded PE chains that were molten at the PLLA crystallization temperatures. This crystallization rate depression of the PLLA block produces a coincident crystallization process when PLLA‐ b ‐PE is cooled down from the melt at rates larger than 2 °C/min. The overall crystallization rate of the PE block is faster when it is covalently bonded to previously crystallized PLLA than when it is attached to a rubbery PDLA block, this results from a nucleation effect of PLLA on the PE block. Polarized Light Optical Microscopy (PLOM) confirmed the confined nature of the crystallization process within lamellar microdomains for both diblock copolymers, since neither PLLA nor PE are capable of breaking out and spherulites can not be formed.