Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/17202
Title: Structure and shape memory properties of polyurethane copolymers having urethane chains as soft segments
Authors: Ji, FL
Hu, JL 
Yu, WMW 
Chiu, SSY
Issue Date: 2011
Source: Journal of macromolecular science, Part B : physics, 2011, v. 50, no. 12, p. 2290-2306
Abstract: Shape memory polyurethanes are usually fabricated with low-molecular weight polyols through a two-step copolymerization, which often results in difficulty attaining both desired shape memory switch temperature and optimal thermomechanical properties. Here we present a series of shape memory polyurethane copolymers having urethane chains as soft segments. The structure and shape memory properties of copolymers were investigated with differential scanning calorimetry, dynamic mechanical analysis, small angle x-ray scattering, and thermomechanical tests. Increasing the length of the urethane soft segments enhanced phase separation, while it brought little change to the glass transition temperature (T g). Based on the urethane soft segments, some rigid chain extenders could be readily introduced into the backbone of copolymers, resulting in better phase separation. All polyurethane copolymers exhibited more than 90% of shape recovery. The shape recovery of the materials was proved to be inversely proportional to the fraction of hard phase and directly proportional to the stability of hard domains. The copolymers containing longer soft and hard segments and rigid chain extenders exhibited higher deformation stress and thus larger recovery stress. The copolymerization employing urethane chains as soft segments can greatly expand flexibility for molecular design and favor the optimization of shape memory properties.
Keywords: copolymerization
phase separation
polyurethane
recovery stress
SAXS
shape memory
Publisher: Taylor & Francis
Journal: Journal of macromolecular science, Part B : physics 
ISSN: 0022-2348
EISSN: 1525-609X
DOI: 10.1080/00222348.2011.562091
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