Study on Near-Infrared Light Induced Thiol-Epoxy Step Photopolymerization
摘要: 基于上转换材料辅助近红外光聚合技术，开展了近红外（NIR）光诱导硫醇-环氧逐步光聚合的研究。通过红外热成像仪监测了聚合体系的温度变化，利用实时红外测定近红外光辐照下巯基和环氧基的反应速率，采用凝胶渗透色谱表征了所得聚合物的分子量。结果表明，在近红外光辐照下上转换粒子发出紫外-可见光，引发光产碱剂光解产生碱性物质，在近红外光的光-热协同效应下，催化硫醇-环氧体系发生逐步聚合。Abstract: Epoxy resin is widely used in coatings and adhesives for its excellent mechanical performance, heat resistance and bonding property. Thiol-epoxy “click” reaction has become one of the hotspots in the field of photocuring due to its mild and efficient reaction conditions. As a latent photoinitiator, the photobase generator improves the storage stability of the formulation when it catalyzes the thiol-epoxy reaction. However, due to the low dose rate and poor solubility of the photobase generator, thiol-epoxy reaction rate is slow under light conditions. To solve this problem, a novel kind of near infrared (NIR) light induced thiol-epoxy photopolymerization system was established in this paper using the up-conversion particles (UCPs) as upconversion material, 980 nm NIR light as irradiation source. The up-conversion material assisted near infrared photopolymerization (UCAP) technology was used to study the NIR light-induced thiol-epoxy step photopolymerization, and the effect of photothermal synergistic effect of NIR light on thiol-epoxy reaction catalyzed by photobase generator was explored. The temperature change of the polymerization system was measured by infrared thermal imager, the reaction rate of sulfhydryl group and epoxy group under NIR irradiation was measured by real-time infrared, and the molecular weight of the polymer was measured by gel permeation chromatography (GPC). Results show that under the irradiation of NIR light (980 nm), the photobase generator absorbs the light emitted by the UCPs to generate a strong base which catalyze the step photopolymerization of thiol and epoxy monomers. Under the photothermal synergistic effect of NIR, the typical step polymerization of thiol-epoxy system catalyzed by photobase generator takes place. Kinetics and molecular weight studies show that the polymerization exhibits typical step growth characteristics, and proves the time controllability of the polymerization. The results are expected to promote the application innovation of photoalkali-producing material system in the fields of photocuring 3D printing and adhesives.
表 1 光聚合条件对硫醇 环氧近红外光逐步聚合的影响
Table 1. Effect of photopolymerization conditions on NIR induced step polymerization of thiol-epoxy
Mw 1 7×10-2 - 0 - 2 - 62 0 - 3 7×10-2 62 42.6 8000
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