Untethered small actuators have drawn tremendous interest owing to their reversibility, flexibility, and widespread applications in various fields. For polymer actuators, however, it is still challenging to achieve programmable structural changes under different stimuli caused by the intractability and single-stimulus responses of most polymer materials. Herein, multi-stimuli-responsive polymer actuators that can respond to light and solvent via structural changes are developed. The actuators are based on bilayer films of polydimethylsiloxane (PDMS) and azobenzene chromophore (AAZO)-crosslinked poly(diallyldimethylammonium chloride) (PDAC). Upon UV light irradiation, the AAZO undergoes trans-cis-trans photoisomerization, causing the bending of the bilayer films. When the UV light is off, a shape recovery toward an opposite direction occurs spontaneously. The reversible deformation can be repeated at least 20 cycles. Upon solvent vapor annealing, one of the bilayer films can be selectively swollen, causing the bending of the bilayer films with the directions controlled by the solvent vapors. The effects of different parameters, such as the weight ratios of AAZO and film thicknesses, on the bending angles and curvatures of the polymer films are also analyzed. The results demonstrate that multi-stimuli-responsive actuators with fast responses and high reproducibility can be fulfilled.

中文翻译：

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光开关和溶剂控制的定向驱动器：超分子组装和交联聚合物

不受束缚的小型执行器由于其可逆性、灵活性和在各个领域的广泛应用而引起了极大的兴趣。然而，对于聚合物执行器而言，由于大多数聚合物材料的难处理性和单刺激响应，在不同刺激下实现可编程结构变化仍然具有挑战性。在此，开发了可以通过结构变化响应光和溶剂的多刺激响应聚合物致动器。致动器基于聚二甲基硅氧烷 (PDMS) 和偶氮苯发色团 (AAZO) 交联聚（二烯丙基二甲基氯化铵）(PDAC) 的双层膜。在紫外光照射下，AAZO 会发生反式-顺式-反式光致异构化，导致双层膜弯曲。当紫外线关闭时，会自发地向相反方向恢复形状。可逆变形可以重复至少 20 个循环。在溶剂蒸汽退火时，其中一个双层膜可以选择性地溶胀，导致双层膜的弯曲方向由溶剂蒸汽控制。还分析了AAZO的重量比和薄膜厚度等不同参数对聚合物薄膜弯曲角度和曲率的影响。结果表明，可以实现具有快速响应和高再现性的多刺激响应执行器。