Study of the dissolution process of polystyrene in concentrated cyclohexane solution by MNR relaxation |
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Authors: | S-Z Mao H-Q Feng |
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Institution: | (1) Laboratory of Magnetic resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics The Chinese Academy of Sciences Wuhan 430071 P.R. China, CN |
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Abstract: | 13C-NMR relaxation times of polystyrene (PS) chains in its theta solvent, cyclohexane, have been measured at different temperatures.
It was found that relaxation of carbon nuclei of the side-chain-phenyl groups and those of main chains have remarkably different
temperature-dependent relaxation behaviors in the solvent. A two-step model for the dissolution process is proposed. According
to the model, swelling of the polymer below θ temperature corresponds mainly to the gradual dispersion of the side-chain phenyl
groups; while the complete dissolution above θ temperature corresponds mainly to the gradual dispersion of the main chains
at a molecular level. These dispersions reflect the fact that cohesional interaction among side-chain-phenyl rings or main
chains are weakened by solvent molecules, which shows the existence of the cohesional entanglements among polymer chains.
The results of T
1(C) are confirmed by the biexponential dependence of 1H-NMR spin–spin relaxation on temperature.
Received: 2 July 1997 Accepted: 21 October 1997 |
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Keywords: | NMR relaxation time cohesional entanglement polystyrene theta solvent |
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