期刊
POLYMER
卷 185, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2019.121982
关键词
A(x)O(y)A(x) triblock copolymers; Enhanced phase separation; SAXS
资金
- National Natural Science Foundation of China [21674097, 21875214]
- second level of 2016 Zhejiang Province 151 Talent Project, China
- Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry [201601]
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, China
Enhanced phase separation and inverse order-to-order phase transition with increasing temperature was observed for a series of poly (acrylic acid)-b-poly (propylene oxide)-b-poly (acrylic acid) triblock copolymers with various block lengths by temperature-variable synchrotron small-angle X-ray scattering (SAXS). This abnormal phase behavior was attributed to the change of hydrogen (H)-bonding interaction in block copolymers upon increasing temperature and theoretically explained from thermodynamic viewpoint. The temperature-dependent FTIR analysis revealed that increasing temperature led to the weakening of overall H-bonding interactions and the increase of free C-O and C-O-C groups. The Flory-Huggins interaction parameter chi of PAA and PPO blocks was positive and increased with increasing temperature as determined from the SAXS profiles of disordered block copolymer. The thermodynamic calculation indicated that the increase of Delta H was larger than the decrease of -T Delta S with increasing temperature because of the relatively large value of chi, leading to the increase of overall Delta G(mix) and hence the enhanced phase separation at higher temperature.
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