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

我的研究关注软功能材料中的介观结构调控及其光学、热学与力学功能。我们以胶体、颗粒组装和聚合物复合体系为主要材料平台，研究剪切、弯曲、拉伸和循环形变等外部力学场如何驱动微结构重排、结晶、晶格转变与取向选择，并进一步调控材料的结构色、光谱响应、热辐射特性和力学响应。通过将软物质物理、可规模化加工和结构—性能分析相结合，研究旨在发展可编程软光子材料与功能涂层，为自适应光学表面、光热调控、传感和机械编码材料提供新的设计思路.