Mavila Sudheendran, Sinha Jasmine, Hu Yunfeng, Podgórski Maciej, Shah Parag K, Bowman Christopher N
Department of Chemical and Biological Engineering, University of Colorado at Boulder, Boulder, Colorado 80309, United States.
Department of Chemistry, University of Colorado Boulder, Boulder Colorado 80309, United States.
ACS Appl Mater Interfaces. 2021 Apr 7;13(13):15647-15658. doi: 10.1021/acsami.1c00831. Epub 2021 Mar 29.
A scalable synthesis of high refractive index, optically transparent photopolymers from a family of low-viscosity multifunctional thiol and alkyne monomers via thiol-yne "click" is described herein. The monomers designed to incorporate high refractive index cores consisting of aryl and sulfide groups with high intrinsic molar refraction were synthesized starting from commercially available low-cost raw materials. The low-viscosity (<500 cP) thiol-yne resins formulated with these new multifunctional monomers and a phosphine oxide photoinitiator underwent efficient thiol-yne polymerizations upon exposure to 405 nm light at 30 mW/cm. In contrast to the previously reported thiol-ene systems, the kinetic profile of these photopolymerizations showed significant dependence on the nature of the thiol and alkyne monomers. However, the ability of the thiol-yne reaction to introduce a large number of sulfide linkages compared to that of thiol-ene systems yielded cross-linked high optical quality photopolymers with a polymer refractive index that exceeds 1.68 (/20 °C). Interestingly, the photopolymer formed from the least sterically hindered alkynyl thioether monomer with flexible thioether core and the dithiol exhibited unprecedented difference in the polymer refractive index as compared to that of the resin with polymerization-induced changes reaching up to 0.08. Furthermore, the implementation of these low-viscosity thiol-yne resins was demonstrated by preparing two-stage photopolymeric holographic materials with a dynamic range of ∼0.02 and haze < 1.5% in two-dimensional high refractive index structures.
本文描述了一种通过硫醇-炔“点击”反应，由一系列低粘度多功能硫醇和炔单体可扩展合成高折射率、光学透明光聚合物的方法。从市售低成本原料出发，合成了旨在引入由具有高固有摩尔折射的芳基和硫化物基团组成的高折射率核心的单体。用这些新型多功能单体和氧化膦光引发剂配制的低粘度（<500 cP）硫醇-炔树脂，在30 mW/cm的405 nm光照射下能高效进行硫醇-炔聚合反应。与先前报道的硫醇-烯体系相比，这些光聚合反应的动力学曲线显示出对硫醇和炔单体性质的显著依赖性。然而，与硫醇-烯体系相比，硫醇-炔反应引入大量硫化物键的能力产生了交联的高光学质量光聚合物，其聚合物折射率超过1.68（/20 °C）。有趣的是，由具有柔性硫醚核心的空间位阻最小的炔基硫醚单体和二硫醇形成的光聚合物，与聚合诱导变化高达0.08的树脂相比，在聚合物折射率方面表现出前所未有的差异。此外，通过在二维高折射率结构中制备动态范围约为0.02且雾度<1.5%的两阶段光聚合全息材料，证明了这些低粘度硫醇-炔树脂的实用性。
