Molecular Level Study of Intra- and Inter-Particle Intractions in Polyelectrolyte Nanogel Systems

本研究项目旨在从分子水平上阐明聚电解质凝胶中体积-相变的本质。我们的实验策略是测量具有和不具有交联性的聚电解质纳米颗粒的尺寸变化，并将其与具有相同化学组成的聚电解质块状凝胶的体积变化进行比较。我们已经合成和使用了基于N-异丙基丙烯酰胺的交联型和直线型聚合物，其中阴离子和阳离子以及两者(两性阳离子)通过共聚或三聚作用结合在一起。用静态光散射、动态光散射和电泳光散射研究了以下几个方面：(1)pH、温度和离子强度对交联型聚电解质纳米颗粒(纳米凝胶)的流体动力学半径和半径回转的影响，以及作为聚电解质净电荷指示剂的电泳率的影响。(Ii)(i…)所得结果的比较更多)与那些线性聚电解质作为纳米凝胶的类似物。(3)聚电解质纳米凝胶与电荷相反的线性多离子的络合物形成(带电胶体体系中的聚合物-粒子相互作用)。(4)相反带电的纳米凝胶粒子之间的络合物形成(带电胶体系统中的粒子-粒子相互作用)。此外，我们还研究了中性聚合物与蛋白质的络合物的形成，目的是合成一种新型的离子纳米凝胶，其中球状多部分电荷(即蛋白质)处于中性聚合物网络(即带有蛋白质电荷的离子纳米凝胶)的“笼子”中。显然，根据我们的平衡模型[(A)Ilmain，F.；Tanaka，T.；Kokufuta，E.Nature 1991,349,400；(B)Kokufuta，E.in：多电解质的物理化学；Radeva，T.，Ed]，可以很好地解释从本研究获得的所有结果。也就是说，凝胶中的体积相变可以通过假设附着在网络上的官能团之间的排斥力和吸引力之间的平衡来确定-当排斥力(通常是静电的性质)克服吸引力时，凝胶经历溶胀变化；除了通常的静电吸引外，氢键和疏水相互作用被认为是吸引力。因此，目前的研究有力地支持了平衡模型，然后我们开始了一个新的项目，在该模型中，平衡模型允许设计响应性能与相应的接枝或嵌段共聚物相同的离子纳米凝胶。较少

This research project aims to elucidate at the molecular level the nature of volume-phase transitions in polyelectrolyte gels. Our experimental strategy is to measure the dimensional changes in polyelectrolyte nanoparticles with and without cross-links and to compare these with the volume change of polyelectrolyte bulk gels with the same chemical compositions. We have synthesized and used both cross-linked and linear polymers based on N-isopropylacrylamide, to which anions and cations as well as both (ampholytes) were bound via copolymerizations or terpolymerizations. Static light scattering, dynamic light scattering and electrophoretic light scattering were employed to study the following subjects : (i)Effects of pH, temperature and ionic strength on the hydrodynamic radius and radius gyration of cross-linked polyelectrolyte nanoparticles (nanogels) and on their electrophoretic mobilities as an indication of net charges of polyelectrolytes. (ii)Comparison of the results obtained in (i … More )with those of linear polyelectrolytes as an analog of the nanogels. (iii)Complex formation of polyelectrolyte nanogels with linear polyions whose charges are opposite each other (polymer-particle interactions in charged colloidal systems). (iv)Complex formation between oppositely charged nanogel particles (particle-particle interactions in charged colloidal systems). In addition, we studied the complex formation of neutral polymers with proteins with the intention of synthesis of a novel ionic nanogel in which globular multipartial charges (i.e., proteins) are in a "cage" of neutral polymer network (i.e., ionic nanogels with entrapped protein charges). It has become apparent that all of the results obtained from the present study can be well accounted for in terms of our balance model [(a)Ilmain, F. ; Tanaka, T. ; Kokufuta, E. Nature 1991,349,400 ; (b)Kokufuta, E. In : Physical Chemistry of Polyelectrolytes ; Radeva, T., Ed. ; Marcel Dekker, Inc., New York, Basel,2000;Chapter 17] ; that is, the volume phase transition in gels can be determined by hypothesizing a balance between the repulsion and attraction among functional groups attached to the network-When a repulsive force, usually electrostatic in nature, overcomes an attractive force, the gel undergoes a swelling change ; hydrogen bonding and hydrophobic interaction, other than the usual electrostatic attraction, are considered as the attractive force. As result, the present research strongly supports the balance model, then we have started a new project in which the balance model is allowing the design of ionic nanogels whose responsive performance is the same as observed in the corresponding graft or block copolymers. Less