Structural evolution of polymers swollen by supercritical CO2

Our project is based on the SAXS/WAXS study of the structural evolution of polymers during a swelling kinetic by scCO2 in order to follow
simultaneously during the swelling, the relaxation and the crystallinity (when present) by WAXS and the large scale structure by SAXS with
polymers of industrial interest. We will focus our study on polymer families with major industrial interest namely a polyethylene (PE), a polycarbonate (PC) and a polyamide (PA12) and ethylene-vinyl acetate (EVA) known to swell rapidly and commonly used in industry (e.g.
encapsulation of solar panels). The objectives are to characterize the swelling kinetics, to understand the origin of the structural reorganization
at the origin of the CO2 desorption after a latency period and to determine if a general behavior can be observed comparing different types of
polymers. The underlying question is: Is there a common mechanism or the different behaviors may have different physical origins?

本项目围绕超临界二氧化碳（supercritical CO₂, scCO₂）作用下聚合物溶胀动力学过程中的结构演化展开研究，采用小角X射线散射（Small-Angle X-ray Scattering, SAXS）与广角X射线散射（Wide-Angle X-ray Scattering, WAXS）两种表征手段，旨在在溶胀过程中同步追踪两类结构信息：通过WAXS表征聚合物的松弛行为与结晶度（若存在），通过SAXS表征其宏观尺度结构，研究对象为具有重要工业应用价值的聚合物体系。本研究将聚焦几类主流工业聚合物，即聚乙烯（polyethylene, PE）、聚碳酸酯（polycarbonate, PC）、聚酰胺12（polyamide 12, PA12），以及溶胀速率快且工业应用广泛的乙烯-醋酸乙烯酯共聚物（ethylene-vinyl acetate, EVA，例如用于太阳能电池板封装）。本项目的研究目标包括：表征聚合物的溶胀动力学过程；阐明潜伏期后二氧化碳脱附过程中结构重构的内在成因；通过对比不同类型的聚合物体系，探究是否存在普适性的结构演化行为。本研究的核心科学问题为：聚合物在scCO₂溶胀过程中的结构演化是存在统一的作用机制，还是不同聚合物体系的行为差异源于各自不同的物理本质？