Horkay Ferenc, Douglas Jack F
Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Material Measurement Laboratory, Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Gels. 2022 Feb 4;8(2):96. doi: 10.3390/gels8020096.
Simulation studies of aqueous polymer solutions, and heuristic arguments by De Gennes for aqueous polyethylene oxide polymer solutions, have suggested that many-body interactions can give rise to the 'anomalous' situation in which the second osmotic virial coefficient is positive, while the third virial coefficient is negative. This phenomenon was later confirmed in analytic calculations of the phase behavior and the osmotic pressure of complex fluids exhibiting cooperative self-assembly into extended dynamic polymeric structures by Dudowicz et al. In the present study, we experimentally confirm the occurrence of this osmotic virial sign inversion phenomenon for several highly charged model polyelectrolyte gels (poly(acrylic acid), poly(styrene sulfonate), DNA, hyaluronic acid), where the virial coefficients are deduced from osmotic pressure measurements. Our observations qualitatively accord with experimental and simulation studies indicating that polyelectrolyte materials exhibit supramolecular assembly in solution, another symptomatic property of fluids exhibiting many-body interactions. We also find that the inversion in the variation of the second () and third () virial coefficients upon approach to phase separation does not occur in uncharged poly(vinyl acetate) gels. Finally, we briefly discuss the estimation of the osmotic compressibility of swollen polyelectrolyte gels from neutron scattering measurements as an alternative to direct, time-consuming and meticulous osmotic pressure measurements. We conclude by summarizing some general trends and suggesting future research directions of natural and synthetic polyelectrolyte hydrogels.
对水性聚合物溶液的模拟研究以及德热纳对聚环氧乙烷水性聚合物溶液的启发式论证表明，多体相互作用可能导致“异常”情况，即第二渗透维里系数为正，而第三维里系数为负。这种现象后来在杜多维茨等人对表现出协同自组装形成扩展动态聚合物结构的复杂流体的相行为和渗透压的解析计算中得到证实。在本研究中，我们通过实验证实了几种高电荷模型聚电解质凝胶（聚丙烯酸、聚苯乙烯磺酸盐、DNA、透明质酸）中这种渗透维里系数符号反转现象的存在，其中维里系数是通过渗透压测量推导出来的。我们的观察结果在定性上与实验和模拟研究一致，这些研究表明聚电解质材料在溶液中表现出超分子组装，这是表现出多体相互作用的流体的另一个特征性质。我们还发现，在接近相分离时，第二（）和第三（）维里系数变化的反转在不带电的聚醋酸乙烯酯凝胶中不会发生。最后，我们简要讨论了从中子散射测量估计溶胀聚电解质凝胶的渗透压缩性，作为直接、耗时且细致的渗透压测量的替代方法。我们通过总结一些一般趋势并提出天然和合成聚电解质水凝胶的未来研究方向来得出结论。
