SANS investigation of piezoelectric polymer assembly under combined ultrasound and electrical fields

Poly(Vinylidenediflouride) (PVDF) is a high performance polymer used in a multitude of applications such as filtration membranes, high temperature structural components, sensors, actuators and energy storage. The polymer exhibits 5 phase conformations, 3 of which are piezoelectric. Of all, the beta-phase has the highest piezoelectric response due to zigzag planar chain conformation. To synthesise this phase, mechanical or thermal treatment is typically used on the alpha phase form. However, ultrasound, with its capacity to generate cavitation on a small spatial scale, presents an efficient energy source for reorienting the polymer chains. This approach enables the formation of the desired (beta-phase) zigzag conformation by overcoming the crystallisation energy barrier. In addition, being semi-crystalline polymer, precise control of the amount, size distribution of the beta-phase crystallinity is critical for applications such as sensor,actuator design as it increase di-polar moments per volume. Understanding the time evolution of crystal structure and beta-phase conformation is critical to increase the beta-phase using energy efficient technique. The PI of the proposal has previously received early career research grant funding from The Royal Society (RGS\R2\222100) on advanced processing methods for high performance polymer sensors for condition monitoring applications in the offshore energy sector. The PI currently is supervising a PhD student on this research.

聚偏氟乙烯（Poly(Vinylidenediflouride), PVDF）是一类高性能聚合物，被广泛应用于过滤膜、高温结构部件、传感器、执行器以及储能等诸多领域。该聚合物存在5种晶型构象，其中3种具有压电特性。在所有晶型中，β晶型因具备锯齿状平面链构象而展现出最高的压电响应。
通常需通过机械或热处理对α晶型进行处理，以合成该β晶型。而超声波凭借其在微小空间尺度内引发空化效应的能力，可作为一种高效的能量来源实现聚合物链的重取向。该策略能够通过克服结晶能垒，形成目标的β晶型锯齿状链构象。
此外，作为半结晶聚合物，精准调控β晶型结晶度的占比与尺寸分布，对于传感器、执行器的设计等应用至关重要——这是因为提升β晶型占比可增大单位体积内的偶极矩。明晰晶体结构与β晶型构象的时间演化规律，对于采用节能技术提升β晶型占比而言同样关键。
本项目的项目负责人（Principal Investigator, PI）此前曾依托英国皇家学会（Royal Society, RGSR2222100）提供的早期职业研究资助金，开展面向海上能源领域状态监测应用的高性能聚合物传感器先进制备方法研究。目前，该项目负责人正指导一名博士生开展此项研究。