Photopolymerization-induced phase separation kinetics explored by intermittent irradiation
Photopolymerization-induced phase separation kinetics explored by intermittent irradiation
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DOI：
10.1016/j.polymer.2023.126526
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发表时间：
2023-11
期刊：
影响因子：
4.6
通讯作者：
Lauren Zakrzewski;Chang Y. Ryu;Chulsung Bae;C. Picu
中科院分区：
文献类型：
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作者：
Lauren Zakrzewski;Chang Y. Ryu;Chulsung Bae;C. Picu
在这项工作中，我们探索了由季戊四醇四丙烯酸酯(PETA)和甲基丙烯酸2-乙基己酯(2-EHMA)单体和聚丙二醇(PPG)线性聚合物添加剂和二苯基(2，4，6-三甲基苯甲酰基)氧膦(TPO)光引发剂组成的光敏树脂中光聚合诱导相分离(PIPS)过程的动力学和控制微结构发展的机理的相互作用。我们通过在过程的不同阶段中断照射和改变光强度来控制光聚合的动力学。通过对暴露在甲醇中的断口进行透过率测试和扫描电子显微镜(SEM)检查来监测微观结构的演变，目的是去除相分离的PPG含量。通过实时傅里叶变换红外(FTIR)光谱监测辐射过程中网络的演变，以及辐射停止后的间歇探测。确定了控制微结构演变的三种机制：相分离、光引发剂消耗和组织细化。相分离在网络发育开始后立即开始，并由于富含PPG的亚域的形成而导致透过率迅速降低。微观结构的细化在后期发生，导致这些亚区的减少，亚区内PPG浓度的逐渐增加和相关的透光率的增加。TPO消耗发生在辐射期间，在较小程度上占透过率恢复的比例。中断辐照可以产生具有不同程度的转化率和相分离亚区大小的材料，这为控制材料的性质提供了一种新的方法。
In this work, we explore the kinetics of the photopolymerization-induced phase separation (photo-PIPS) process and the interplay of mechanisms controlling the development of the microstructure in a photosensitive resin comprised of pentaerythritol tetraacrylate (PETA) and 2-ethylhexyl methacrylate (2-EHMA) monomers with polypropylene glycol (PPG, Mn= 4000 g/mol) linear polymer additive and diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiator. We control the kinetics of photopolymerization by interrupting the irradiation at various stages of the process and varying the light intensity. Evolution of the microstructure is monitored by transmittance testing and scanning electron microscopy (SEM) inspection of fractured surfaces that are exposed to methanol for the purpose of removing the phase-separated PPG content. The evolution of the network is monitored by real-time Fourier-transform infrared (FTIR) spectroscopy during irradiation and intermittent probing after the cessation of irradiation. Three mechanisms controlling the evolution of the microstructure are identified: phase separation, photoinitiator consumption, and microstructural refinement. Phase separation begins immediately after the onset of network development and leads to a rapid reduction of transmittance due to the formation of PPG-rich subdomains. Microstructural refinement takes place at later stages leading to a reduction of these subdomains, a gradual increase of the PPG concentration within subdomains and an associated increase of transmittance. TPO consumption takes place during irradiation and accounts, to a smaller extent, for the recovery of the transmittance. Interrupting the irradiation allows generation of materials with various degrees of conversion and sizes of phase-separated subdomains, which provides a new way to control material properties.