Polymers for Light-Activated Mechanical Actuators

由分子片段组成的聚合物在受到光照射时会扭曲，这为直接将光转化为机械功提供了一个框架。这种材料可用于设计新型机械致动器，这些致动器完全由光触发和控制。正在研究的一种更有前途的光响应聚合物可以在光照射时产生显着的力，但受到驱动速度慢的困扰。该奖项将支持分子结构对液晶共聚物光机械性能影响的基础研究。由此产生的见解可以催生一类新的聚合物，这些聚合物可以部署在各种长度范围内的系统中，在这些系统中可以启用非接触式驱动，例如“软机器”、集成光机械设备、光驱动微流体和微型机器人。本研究将验证在偶氮官能化液晶聚合物（ALCP）中，控制介生偶氮官能化交联剂中柔性间隔层的结构可以调节光敏致动，并有助于实现致动速率、功密度和光敏应力的阶跃变化。为了研究这一点，将合成以丙烯酸酯为基础的交联中间体，其刚性核心为偶氮苯基，不同链长的柔性间隔剂。利用这些，一系列液晶聚合物薄膜将被制造出来，它们的光电驱动将被测量，它们在执行器中的效用将被检验。在这些研究中，作为光化光的强度和偏振的函数，诱导/消除光化应变的物理基础将被检查。最终，定制的向列定向器将被设计成新的驱动模式，并为新型光电机械元件奠定基础。

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.