Programmable oils feature tunable viscosity and therefore possess potential for technical improvements and innovative solutions in many lubricated applications. Herein, we describe the first assessment of the variability of rheological properties of light-programmable 9-anthracene ester-terminated polydimethylsiloxanes (PDMS-As), including implications that arise with UV-light as an external trigger. We applied a modified rheometer setup that enables the monitoring of dynamic moduli during exposure to UV-light. The reversible dimerization of anthracene esters is used to either link PDMS chains by UV-A radiation (365 nm) or cleave chains by UV-C radiation (254 nm) or at elevated temperatures (>130 °C). Thermal cleavage fully restores the initial material properties, while the photochemical cleavage of dimers occurs only to a limited extent. Prolonged UV radiation causes material damage and in turn reduces the range of programmable rheological properties. The incomplete cleavage contributes to a gradual buildup of viscosity over a course of several switching cycles, which we suggest to result from chain length-dependent reaction kinetics. Material property gradients induced during radiation due to attenuation of the light beam upon its passing through the oil layer have to be considered, emphasizing the need for proper mixing protocols during the programming step. The material in focus shows integrated photorheology and is suggested to improve the performance of silicone oils in friction systems.

中文翻译：

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硅油中的编程粘度：9-蒽酯封端的聚二甲基硅氧烷的流变性能的可逆调整

可编程油具有可调的粘度，因此在许多润滑应用中具有技术改进和创新解决方案的潜力。在本文中，我们描述了光可编程9-蒽酯封端的聚二甲基硅氧烷（PDMS-As）流变性质变异性的首次评估，包括紫外线作为外部触发物所引起的影响。我们应用了改进的流变仪设置，可以在暴露于紫外线的情况下监控动态模量。蒽酯的可逆二聚用于通过UV-A辐射（365 nm）连接PDMS链，或通过UV-C辐射（254 nm）或在高温（> 130°C）裂解链。热裂解完全恢复了初始的材料性质，而二聚体的光化学裂解仅在有限的程度上发生。长时间的紫外线辐射会造成材料损坏，进而减小可编程流变特性的范围。不完全的裂解会导致在几个转换循环过程中逐渐形成粘度，我们建议这是由链长相关的反应动力学引起的。必须考虑在辐射过程中由于光束在通过油层时的衰减而在辐射过程中引起的材料特性梯度，强调了在编程步骤中需要适当的混合方案。重点关注的材料显示出完整的光流变学，并被建议用于改善硅油在摩擦系统中的性能。不完全的裂解会导致在几个转换循环过程中逐渐形成粘度，我们建议这是由链长相关的反应动力学引起的。必须考虑在辐射过程中由于光束在通过油层时的衰减而在辐射过程中引起的材料特性梯度，强调了在编程步骤中需要适当的混合方案。重点关注的材料显示出完整的光流变学，并被建议用于改善硅油在摩擦系统中的性能。不完全的裂解导致在几个转换循环过程中逐渐形成粘度，我们建议这是由链长相关的反应动力学引起的。必须考虑在辐射过程中由于光束在通过油层时的衰减而在辐射过程中引起的材料特性梯度，强调了在编程步骤中需要适当的混合方案。重点关注的材料显示出完整的光流变学，并被建议用于改善硅油在摩擦系统中的性能。强调在编程步骤中需要适当的混合协议。重点关注的材料显示出完整的光流变学，并被建议用来改善硅油在摩擦系统中的性能。强调在编程步骤中需要适当的混合协议。重点关注的材料显示出完整的光流变学，并被建议用于改善硅油在摩擦系统中的性能。