High molecular weight syndiotacticity-rich poly(vinyl alcohol) gel in aging process |
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Authors: | J H Choi W S Lyoo H D Ghim S-W Ko |
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Institution: | (1) Department of Fiber and Polymer Science College of Engineering Seoul National University Seoul 151–742, Korea e-mail: sohkwonk@gong.snu.ac.kr, KR;(2) School of Textiles, Yeungnam University Kyongsan 712–749, Korea, KR |
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Abstract: | The properties of the aged gels of high molecular weight syndiotacticity-rich poly(vinyl alcohol)s (HMW S-PVAs) with different
syndiotactic diad (s-diad) contents were investigated. HMW S-PVA gels with s-diad content of 61.5% and 58.2% showed the rapid increases of the syneresis and the turbidity from the early stage of aging
time, which is ascribable to the phase separation, while that with s-diad content of 55.7% did not. From the morphological study, it was confirmed that the phase separation in HMW S-PVA gel
with s-diad content of 61.5% occurred without the liquid-liquid phase separation in sol state, whereas both the liquid-liquid phase
separation in sol state and the subsequent phase separation in gel state occurred in the case of HMW S-PVA gel with s-diad content of 58.2%. On the other hand, HMW S-PVA gel with s-diad content of 55.7% showed neither the liquid-liquid phase separation in sol state nor the phase separation in gel state
in the long period of time. It was also confirmed from wide angle X-ray diffractogram that the crystallization was accompanied
by the phase separation in gel state in the aging process of PVA gel. However, the crystallization was hindered by the fast
network formation at the initial stage of time. Later the syndiotacticity promoted the crystallization. The tensile modulus
of HMW S-PVA gel with higher syndiotacticity increased more significantly with time.
Received: 2 December 1999/Accepted: 12 July 2000 |
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Keywords: | Aging Poly(vinyl alcohol) Gel Syndiotacticity High molecular weight |
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