Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
J Am Chem Soc. 2010 Nov 17;132(45):16107-11. doi: 10.1021/ja106332g. Epub 2010 Oct 26.
Spiropyran (SP) mechanophores (mechanochemically reactive units) can impart the unique functionality of visual stress detection to polymers and have potential for use in smart materials with self-sensing capabilities. These color-generating mechanophores were incorporated into polyurethane via step growth polymerization. Polyurethane, which is inherently a versatile engineering polymer, possesses an optimized balance of mechanical toughness and elasticity to allow for investigation of the kinetics of the mechanochemical response of the SP mechanophore in the bulk polymer via fluorescence and absorbance measurements. The stress-induced 6-π electrocyclic ring-opening to the colored merocyanine (MC) form of the mechanophore was quantified by measuring the change in absorbance of the polymer, while it was held at constant strain. The closing kinetics of the mechanophore was also studied by fluorescence imaging. Finally, the effects of mechanical strain on the equilibrium between the SP and MC forms are reported and discussed.
螺吡喃（SP）机械增感剂（机械化学反应单元）可以赋予聚合物独特的视觉压力检测功能，并且有可能用于具有自感测功能的智能材料。这些产生颜色的机械增感剂通过逐步聚合反应被引入到聚氨酯中。聚氨酯本身是一种多功能的工程聚合物，具有优化的机械韧性和弹性平衡，允许通过荧光和吸光度测量来研究 SP 机械增感剂在大块聚合物中的机械化学响应动力学。通过测量聚合物在恒应变速率下的吸光度变化，定量研究了机械增感剂的应力诱导 6-π电环化开环到有色甲川（MC）形式。还通过荧光成像研究了机械增感剂的关闭动力学。最后，报告并讨论了机械应变对 SP 和 MC 形式之间平衡的影响。
