二茂铁疏水改性支化聚乙烯亚胺水溶液的聚集结构与流变行为

MICROSTRUCTURE AND RHEOLOGICAL BEHAVIOR OF FERROCENE-MODIFIED BRANCHED POLY (ETHYLENE IMINE) IN AQUEOUS SOLUTIONS

通过将二茂铁接枝在大分子链上制备了疏水改性支化聚乙烯亚胺(Fc-BPEI),用动态光散射、透射电镜及旋转流变仪研究了其水溶液中大分子的聚集态结构与流变行为.考察了剪切作用、浓度、温度对溶液中大分子结构和形态及流变行为的影响.研究结果表明,二茂铁改性的聚乙烯亚胺分子尺寸明显增大,且随浓度增大体系中大分子逐渐从分子内疏水缔合为主向分子间疏水缔合为主转变,形成分子间缔合体.上述原因使得Fc-BPEI溶液黏度显著增大,但是该体系却呈现典型的牛顿流体特征.对样品进行连续升-降温循环热处理,发现经过升降温处理后的Fc-BPEI体系黏度明显增大,且增幅随热循环次数增加而逐渐减小.动态流变测试结果表明,这种现象缘于热处理使得大分子链缔合方式和形态发生变化,体系中出现穿插于多个分子间缔合体的PEI大分子,产生了类似网络结构的大分子聚集结构.经热处理的Fc-BPEI溶液呈现显著的剪切变稀现象,高浓度溶液的抗剪切能力显著提高.

Microstructure and rheological properties of ferrocene modified branched poly（ethylene imine） （Fc- BPEI） in aqueous solutions were investigated through dynamic light scattering, transmission electron microscopy （TEM） and rheometry. The influences of shear, concentration and temperature on microstructure and rheological behavior of Fc-BPEI aqueous solutions were also explored. Compared with pure BPEI, the molecule size of Fc-BPEI obviously increases. It is found that the dominate association in aqueous solutions transfers from intramolecular to intermolecular association with the increase of concentration and intermolecular associations are formed,inducing a considerable increase in viscosity of Fc-BPEI aqueous solutions. However, these Fc-BPEI aqueous solutions represent a typical rheological behavior of Newtonian fluid. After undergoing continuous heating-cooling treatments, the viscosities of Fc-BPEI aqueous solutions increase significantly. Furthermore, the increment of viscosity gradually decreases as the heating-cooling treatment repeats. The dynamic rheological resuhs indicate that heating-cooling treatment could lead to the changes in maeromolecular association and resulting microstructure of polymers. Some Fc-BPEI macromolecules could simultaneously participate in multiple intermolecular association structures and consequently a large structure of macroscopic network-like forms. Fc-BPEI aqueous solutions present obvious shear-thinning due to the occurrence of associative network after thermal treatments and anti-shear ability of high concentration solutions of Fc-BPEI remarkably improves.