Kramer Thomas, Schweins Ralf, Huber Klaus
Department Chemie, Fakultät für Naturwissenschaften, Universität Paderborn, Warburger Strasse 100, D-33098 Paderborn, Germany.
J Chem Phys. 2005 Jul 1;123(1):014903. doi: 10.1063/1.1946751.
The present work investigates the structure of large polystyrene (PS) chains in solutions of small poly(ethyl methacrylate) (PEMA) microgel particles in toluene. Toluene is a good solvent for the PS chains. The PEMA colloids have an outer radius of R=11 nm which is much smaller in size than the radius of gyration Rg=58 nm of the PS chains. The system is considered to represent the protein limit of polymer-colloid mixtures. Structural investigation is performed by small-angle neutron scattering (SANS) using an appropriate contrast matching. This could be achieved by dissolving fully deuterated PS chains (D8-PS) in solutions of hydrogenated PEMA colloids in hydrogenated toluene (H-toluene). It is first demonstrated that PEMA colloids are satisfactorily contrast matched for SANS in H-toluene if the PEMA concentration does not exceed 200 g/l. Based on these findings, D8-PS is investigated by SANS in pure H-toluene and three different PEMA concentrations in H-toluene. The results indicate a drastic shrinking of D8-PS chain dimensions with increasing PEMA content. Comparison with model curves of star-branched Gaussian chains and Gaussian rings suggest a striking similarity of the respective density-density correlation of those models with the shrunken D8-PS chains. Along with this, a shrinking as large as 0.5 was estimated when the PEMA content reached 200 g/l.
本研究调查了大尺寸聚苯乙烯（PS）链在小尺寸聚甲基丙烯酸乙酯（PEMA）微凝胶颗粒的甲苯溶液中的结构。甲苯是PS链的良溶剂。PEMA胶体的外半径R = 11 nm，其尺寸远小于PS链的回转半径Rg = 58 nm。该体系被认为代表了聚合物 - 胶体混合物的蛋白质极限情况。通过小角中子散射（SANS）并采用适当的对比匹配进行结构研究。这可以通过将完全氘代的PS链（D8 - PS）溶解在氢化PEMA胶体的氢化甲苯（H - 甲苯）溶液中来实现。首先证明，如果PEMA浓度不超过200 g/l，PEMA胶体在H - 甲苯中对于SANS能实现令人满意的对比匹配。基于这些发现，通过SANS研究了D8 - PS在纯H - 甲苯以及H - 甲苯中三种不同PEMA浓度下的情况。结果表明，随着PEMA含量的增加，D8 - PS链尺寸急剧收缩。与星型支化高斯链和高斯环的模型曲线比较表明，这些模型各自的密度 - 密度相关性与收缩后的D8 - PS链具有显著相似性。与此同时，当PEMA含量达到200 g/l时，估计收缩率高达0.5 。
