Effective charge and coil-globule transition of a polyelectrolyte chain.
Effective charge and coil-globule transition of a polyelectrolyte chain.
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DOI：
10.1021/ma9020888
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发表时间：
2010-03-09
期刊：
影响因子：
5.5
通讯作者：
Muthukumar, M.
中科院分区：
文献类型：
--
作者：
Kundagrami, Arindam;Muthukumar, M.
考虑反离子在孤立聚电解质(PE)链上的吸附，利用变分理论，计算了一阶线圈-球体转变的相界和临界点。这种转变是由反离子吸附和链构象协同诱导的，计算是自洽进行的。PE链的大小是电荷的单值函数。线圈尺寸的不连续转变伴随着电荷的不连续转变。由库仑强度(逆温度或介电常数)和离子强度(盐)引起的线团-球体转变的相界表明，在盐的存在下，PE链在低得多的库仑强度下崩溃。在线圈展开状态下，对于链构象与反离子吸附耦合较弱的情况，导出了链的有效电荷的解析公式。总的来说，靠近聚合物主链的溶剂的介电非均质性在电荷规则化和链崩溃中起着至关重要的作用。
Considering the adsorption of counterions on an isolated polyelectrolyte (PE) chain and using a variational theory, phase boundaries and the critical point for the first-order coil-globule transition are calculated. The transition is induced cooperatively by counterion adsorption and chain conformations and the calculation is done self-consistently. The size of the PE chain is a single-valued function of charge. The discontinuous transition of the coil size is accompanied by a discontinuous transition of the charge. Phase boundaries for the coil-globule transitions induced by both Coulomb strength (inverse temperature or dielectric constant) and ionic strength (salt) show that the PE chain collapses at a substantially lower Coulomb strength in the presence of salt. In the expanded state of the coil, an analytical formula is derived for the effective charge of the chain for conditions where the coupling between chain conformations and counterion adsorption is weak. In general, the dielectric heterogeneity of the solvent close to the polymer backbone is found to play a crucial role in the charge regularization and the chain collapse.
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