Polymers for Light-Activated Mechanical Actuators

由分子链段组成的聚合物在受光照射时会变形，为将光直接转化为机械功提供了一个框架。这种材料可以用来设计新型的机械执行器，这些机械执行器完全由光触发和控制。正在研究的一种更有前景的光响应聚合物可以在光照射下产生巨大的力，但受到缓慢驱动速度的困扰。该奖项将支持有关分子结构对液晶共聚物光机械性能影响的基础研究。这项研究将验证如下假设：在偶氮苯功能化液晶聚合物(ALCP)中，控制偶氮苯功能化交联剂中柔性间隔物的结构可以调制光机械驱动，并帮助实现驱动速率、功密度和光机械应力的阶跃变化。为了研究这一点，我们将合成刚性核中含有偶氮苯基和不同链长的柔性间隔基的丙烯酸酯基交联介质物。利用这些材料，我们将制作一系列液晶聚合物薄膜，测量它们的光机械驱动能力，并考察它们在致动器中的应用。在这些研究中，将考察诱导/擦除光致机械应变的物理基础作为光化光的强度和偏振的函数。最终，定制的向列型导向器将被设计成支持新的驱动模式，并为新型光机械机械元件奠定基础。

Polymers composed of molecular segments that can distort when irradiated with light offer a framework for directly converting light into mechanical work. Such materials can be used to engineer new classes of mechanical actuators that are triggered and controlled exclusively with light. One of the more promising light-responsive polymers being studied can generate significant forces upon irradiation with light but is plagued by slow actuation speeds. This award will support fundamental research into the effect of the molecular structure on the photomechanical properties for liquid crystalline copolymers. The insights that emerge can spawn a new class of polymers that could be deployed in systems over a range of length scales where contactless actuation could be enabled such as "soft machines", integrated optomechanical devices, optically-driven microfluidics and microrobots.This research will test the hypothesis that in azobenzene-functionalized liquid crystal polymers (ALCP), controlling the structure of the flexible spacer in mesogenic azobenzene-functionalized crosslinkers can modulate photomechanical actuation and help realize step-changes in actuation rates, work densities and photomechanical stresses. To study this, acrylate-based crosslinking mesogens with azobenzene-group in the rigid core and flexible spacers of various chain lengths will be synthesized. Using these, a range of liquid crystal polymer films will be created, their photomechanical actuation will be measured and their utility in actuators will be examined. During these studies, the physical underpinnings of inducing/erasing photomechanical strains as a function of intensity and polarization of actinic light will be examined. Ultimately, customized nematic directors will be engineered to enable new actuation modes and set the foundation for novel photomechanical machine elements.