纳米粒子交联类玻璃高分子材料的动力学行为和流变行为研究

Dynamic and Rheological Behavior of Particle Crosslinked Vitrimers

研究了纳米粒子动态交联端羧基聚丁二烯的动力学行为.除了利用传统的熔融重塑以及应力松弛行为来研究其动态行为和可加工性,着重通过线性和非线性动态流变学,研究揭示了粒子交联类玻璃高分子材料与分子交联类玻璃高分子、粒子填充高分子复合材料的差异.与分子交联体系相比,粒子交联体系末端区的松弛主要来源于粒子的扩散运动,可逆共价网络对模量的贡献较弱,但减慢了粒子扩散的速度.与粒子填充体系相比,在粒子交联体系中,粒子需要在动态共价键解离之后才能从粒子笼中逃出.

Dynamic reversible covalent bonds introduced into the polymer networks enable the materials to undergo structural rearrangement and obtain processability under suitable conditions,endowing it with considerable applications in polymeric materials.In this work,particle-crosslinked vitrimer and molecular crosslinked vitrimer were obtained through the crosslinking reaction between carboxy-terminated liquid polybutadiene rubber and epoxy-containing crosslinkers(molecular crosslinker and nano-particle crosslinker).The reversibility and reprocessability of crosslinked polymer were proved by stress relaxation and melt remolding.Furthermore,linear and nonlinear dynamic rheology were used to study the influences of the size differences of crosslinker on the dynamic characteristics of vitrimer composites.In linear rheology,the double relaxation processes in dynamically cross-linked systems were observed,where fast relaxation process at high frequencies could be attributed to the contribution of the pendant chain.In contrast to the molecular cross-linked system,whose terminal relaxation was determined by the scission of active network strands,the terminal relaxation of particle cross-linked system was due to particle diffusion out of particles cage.The reversible covalent network had a weaker contribution to the modulus as compared to the particles’contribution,but greatly slowed down the particle diffusion.In nonlinear oscillatory rheology,the comparison of Lissajous curves and strain overshoot of loss modulus among particle-crosslinked vitrimer,molecular crosslinked vitrimer and particle-filled polymer composites also verified the above results.