Programmable pattern transformation of reconfigurable polymer membranes

非技术总结：该项目涉及合成聚合物材料，该材料可以通过重新配置其形状来响应外部刺激。这些聚合物将被加工成具有规则间隔孔的有图案的微结构膜。研究响应外部刺激的结构变化将为如何设计可重构纳米材料提供重要的科学见解。这些可以用来制造更复杂、多功能的微结构。由此产生的物理性质变化（例如透明度和颜色变化）也可能使这些材料与新技术相关，包括可调光学窗口、传感器、可编程声音和热传递、催化、药物输送和软机器人。所有层次的学生都将接触到化学、材料科学与工程、物理、软力学、纳米制造和计算建模等各种主题。外展将包括当地高中和社区大学中代表性不足的群体，以在宾夕法尼亚大学校园开展研究。研究成果将在费城材料日和其他公共宣传活动中展示。技术概述：该项目涉及对外部刺激（如pH值、温度和光）有响应的微结构聚合物膜的合成和研究，旨在更深入地了解材料在复杂几何形状（各向同性和各向异性）下的机械响应。反过来，这将允许通过考虑聚合物的分子结构，膜中孔阵列的几何参数以及外力的应用来编程复杂手性结构的演变。具体来说，研究包括1)制备一系列基于聚（2-羟乙基甲基丙烯酸酯）（PHEMA）的水凝胶膜，这些膜具有任意特征尺寸、间距、纵横比和排列的微观孔阵列；2)不同pH和温度下溶剂溶胀引起的模式转变及其与模型的比较；3)合成向列液晶单体及交联剂制备微结构向列液晶弹性体（NLCEs）；4)控制膜内液晶分子的表面锚定以最大化应变响应并与建模比较；5)探索不同温度下NLCE膜的内部不稳定性，并与基于phema的水凝胶膜的模式转化进行比较；6)应用相同的变形原理研究具有光和偏振局部空间控制的光响应NLCE膜。

NON-TECHNICAL SUMMARY:This project involves synthesizing polymeric materials that can respond to external stimuli by reconfiguring their shapes. These polymers will be processed so as to yield patterned microstructured membranes with regularly spaced holes. The study of structural change in response to external stimuli will provide important scientific insights into how to design reconfigurable nanomaterials. These could be used to create more complex, multifunctional microstructures. The resulting changes in physical properties (e.g. transparency and color change) may also make these materials relevant to novel technologies, including tunable optical windows, sensors, programmable sound and heat transfer, catalysis, drug delivery, and soft robotics. Students at all levels will be exposed to a diverse range of topics in chemistry, materials science and engineering, physics, soft mechanics, nanofabrication and computational modeling. Outreach will include underrepresented groups at local high schools and community colleges to carry out research on campus at the University of Pennsylvania. Research results will be showcased at the Philadelphia Materials Day and at other public outreach events. TECHNICAL SUMMARY:This project involves synthesis and study of microstructured polymer membranes that are responsive to external stimuli (e.g. pH, temperature and light), aimed at providing deeper understanding of the materials' mechanical responses in complex geometries (both isotropically and anisotropically). This in turn will allow for programming the evolution of complex chiral structures by considering the molecular structures of the polymers, the geometric parameters of the pore arrays in the membranes, and the application of external forces. Specifically, the research includes 1) preparation of a range of poly(2-hydroxyethyl methacrylate) (PHEMA) based hydrogel membranes with microscopic hole arrays of arbitrary feature size, spacing, aspect ratio, and arrangement; 2) examination of the solvent-swelling induced pattern transformation at different pH and temperature and its comparison to modeling; 3) synthesis of nematic liquid crystal monomers and crosslinkers to prepare microstructured nematic liquid crystal elastomers (NLCEs); 4) control of surface anchoring of the liquid crystal molecules within the membranes to maximize the strain response and comparison to modeling; 5) exploration of the internal instability in NLCE membranes at different temperatures in comparison to pattern transformation in PHEMA-based hydrogel membranes; 6) application of the same deformation principles to investigate light-responsive NLCE membranes with local spatial control of light and polarization.