环形高分子单链塌缩的熔球中间态及其热力学解释
发布时间：2019-02-26 08:37
【摘要】：采用动态蒙特卡洛分子模拟研究了环形高分子单链在不良溶剂中发生塌缩转变时可逆地出现具有核-壳结构特征的熔球中间态,发现该结构特征与相同链长的线形单链基本相同,表明其只与链的长短有关,而与链端基的特殊效应无关.本工作将这一现象与单链单晶在其平衡熔点附近出现的类似现象相互关联,采用表面预溶模型来解释单链塌缩出现熔球中间态的热力学机理.分子量越低,熔球越小,表面预溶现象就越显著,塌缩转变随热力学条件变化就越缓慢.实际的高分子体系由于链内拓扑缠结,在表面未必能充分释放片段链,达不到理论预期的平衡态.表面预溶使得相分离临界点或晶体熔点附近在界面厚度方向上存在链单元能量状态不连续分布,这在微观分子水平上与临界界面连续浓度梯度的传统理论处理不一致,为我们深入理解高分子流体界面的微观结构带来帮助.
[Abstract]:In this paper, dynamic Monte Carlo molecular simulation was used to study the reversible intermediate state of core-shell structure in the core-shell structure of circular polymer single chain during collapse transition in bad solvent. It is found that the structure is basically the same as the linear single chain with the same chain length, indicating that it is only related to the length of the chain, but has nothing to do with the special effect of the end group of the chain. In this paper, this phenomenon is related to the similar phenomenon of single-chain single crystal near its equilibrium melting point, and the thermodynamic mechanism of the intermediate state of single-chain collapse is explained by surface pre-dissolving model. The lower the molecular weight is, the smaller the melting ball is, the more obvious the surface pre-dissolution phenomenon is, and the slower the collapse transition changes with the thermodynamic conditions. Because of the topological entanglement in the chain, the actual polymer system may not release the fragment chain sufficiently on the surface, which can not reach the equilibrium state expected by the theory. The surface pre-dissolution results in the discontinuous distribution of the chain element energy in the direction of interface thickness near the critical point of phase separation or near the melting point of the crystal, which is inconsistent with the traditional theoretical treatment of the continuous concentration gradient at the critical interface at the micro-molecular level. It is helpful for us to understand the microstructure of polymer fluid interface.
【作者单位】： 南京大学化学化工学院高分子系;
【基金】：国家自然科学基金(基金号21474050)资助项目
【分类号】：O631.11
本文编号：2430614
[Abstract]:In this paper, dynamic Monte Carlo molecular simulation was used to study the reversible intermediate state of core-shell structure in the core-shell structure of circular polymer single chain during collapse transition in bad solvent. It is found that the structure is basically the same as the linear single chain with the same chain length, indicating that it is only related to the length of the chain, but has nothing to do with the special effect of the end group of the chain. In this paper, this phenomenon is related to the similar phenomenon of single-chain single crystal near its equilibrium melting point, and the thermodynamic mechanism of the intermediate state of single-chain collapse is explained by surface pre-dissolving model. The lower the molecular weight is, the smaller the melting ball is, the more obvious the surface pre-dissolution phenomenon is, and the slower the collapse transition changes with the thermodynamic conditions. Because of the topological entanglement in the chain, the actual polymer system may not release the fragment chain sufficiently on the surface, which can not reach the equilibrium state expected by the theory. The surface pre-dissolution results in the discontinuous distribution of the chain element energy in the direction of interface thickness near the critical point of phase separation or near the melting point of the crystal, which is inconsistent with the traditional theoretical treatment of the continuous concentration gradient at the critical interface at the micro-molecular level. It is helpful for us to understand the microstructure of polymer fluid interface.
【作者单位】： 南京大学化学化工学院高分子系;
【基金】：国家自然科学基金(基金号21474050)资助项目
【分类号】：O631.11
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1 樊克,吴大诚;端基附壁高分子模型链的塌缩转变[J];高分子学报;2001年01期
，本文编号：2430614
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