Real-time measurements of crystallization processes in viscoelastic polymeric photonic crystals

摘要

We present a study of the dynamic shear ordering of viscoelastic photonic crystals, based on core-shell polymeric composite particles. Using an adapted shear-cell arrangement, the crystalline ordering of the material under conditions of oscillatory shear is interrogated in real time, through both video imaging and from the optical transmission spectra of the cell. In order to gain a deeper understanding of the macroscopic influences of shear on the crystallization process in this solvent-free system, the development of bulk ordering is studied as a function of the key parameters including duty cycle and shear-strain magnitude. In particular, optimal ordering is observed from a prerandomized sample at shear strains of around 160%, for 1-Hz oscillations. This ordering reaches completion over time scales of order 10 s. These observations suggest significant local strains are needed to drive nanoparticles through energy barriers, and that local creep is needed to break temporal symmetry in such high-viscosity nanoassemblies. Crystal shear-melting effects are also characterized under conditions of constant shear rate. These quantitative experiments aim to stimulate the development of theoretical models which can deal with the strong local particle interactions in this system.

赵其斌

副教授

研究兴趣包括胶体光子晶体组装、材料结构规则度调控、规则及不规则结构在不同条件下的演变过程及物理机理、光学材料及能源类材料制备、微纳结构材料的大面积制备方法、自然界中的功能结构及其在跨种演变视角下的生物进化学等。