科研之友
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摘要
Dynamic networks constructed by physical cross-links between polymer chains can change their structure through the association and dissociation of cross-linking points. This paper yields experimental data about the transient change of the dynamic storage modulus G' for a molten random copolymer of vinyl acetate and vinyl alcohol with a vinyl alcohol content of 60 mol%, in which physical cross-links are formed via hydrogen bonding. As the cross-link density depends on temperature, the storage modulus G' of the system slowly evolves toward equilibrium at the experimental temperature, T-a, after changing the temperature from higher or lower than T-a. The characteristic time scale for the equilibration is on the order of 10(3) similar to 10(4) s (depending on T-a) and the time evolution curves of G' are dependent on the thermal history. The 'memory effect' (the structure developed at a certain temperature is preserved after changing the temperature) found in the system is discussed in detail.
- 出版日期2017-2
