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讨论了大分子溶致凝聚过程中体系熵变的特点和影响。在分子链无规凝聚形成无定形聚合物时,正是熵增的贡献使体系自由能下降,无规凝聚过程得以进行。在有规凝聚形成结晶聚合物时,熵变对结晶过程产生复杂影响。由于熵变和内能变化相互竞争,使溶致结晶时最优生成的晶体结构为松散折叠链片晶;而从熔体结晶时则得到晶相和非晶相(无定形相)两相并存的复杂结构。区分了两类不同性质的熵变:阶跃性熵变导致熵致相变发生;渐变性熵变使体系力学性质变化或发生力学状态转变。
The characteristics and influence of the entropy change of the system during the process of the macromolecular lytic condensation are discussed. When the molecular chains are randomly aggregated to form amorphous polymers, it is the contribution of entropy increase that decreases the free energy of the system and the random coalescence proceeds. Entropy changes have a complex effect on the crystallization process during the regular condensation to form crystalline polymers. Due to the competition between entropy change and internal energy change, the optimal crystal structure for lytic crystallization is loosely folded lamellar crystals, while the two phases of crystalline phase and amorphous phase (amorphous phase) coexist when melt crystallizes. Complex structure. Two types of entropy change of different nature are distinguished: the step-wise entropy change leads to the occurrence of entropy-induced phase change; the gradient entropy change causes the change of mechanical properties or the change of the mechanical state.