Spatial and temporal evolution of the photoinitiation rate in thick polymer systems
Spatial and temporal evolution of the photoinitiation rate in thick polymer systems
复制标题
厚聚合物体系中光引发速率的时空演变
DOI：
--
复制
发表时间：
2006
期刊：
影响因子：
--
通讯作者：
N. Kenning
中科院分区：
文献类型：
--
作者：
N. Kenning
由于光在样品深处的光学衰减，人们一度认为光聚合厚度大于薄膜要么是不可能的，要么是效率低下的。然而，如果考虑到一些因素，这确实是可能的。三个特殊的修改是必不可少的，以提高光渗透到系统的深度。在没有其他组分吸收的光谱区域内吸收的引发剂使引发剂光解的入射光强度最大化。引发剂的浓度和/或摩尔吸收率低于薄膜中通常使用的浓度和/或摩尔吸收率，增强光穿透。最后，光漂白引发剂在光解时表现出降低的吸光度，从而使光随着时间的推移更深入地渗透到体系中。需要对这些系统进行建模是出于希望使用光来引发各种聚合，包括较厚的系统。在本项目中，建立了一套描述厚聚合物体系光强度梯度、光引发剂浓度梯度和光引发率分布的时空演变的微分方程。广义模型考虑了引发剂的消耗、光解产物的演化、引发剂和光解产物的扩散以及系统各组分的吸光度。这些研究的目的是进一步表征这些系统，以便结果准确地捕捉光引发过程。几个关键目标已经完成，包括多色入射光照明的影响，各种照明方案，并验证模型的预测能力。
It was once thought either impossible or inefficient to photopolymerize a thickness greater than a thin film because of the optical attenuation of light into the depth of the sample. However, if several considerations are allowed, it is indeed possible. Three particular modifications are essential to enhance light penetration into the depth of the system. An initiator that absorbs in a region of the spectrum where no other components absorb maximizes the incident light intensity for photolysis of the initiator. Concentration and/or molar absorptivity of the initiator lower than typically used in thin films enhance light penetration. Finally, photobleaching initiators exhibit decreased absorbance upon photolysis and thus allow light to penetrate more deeply into the system with time. A need to model these systems is born out of the desirability to use light to initiate polymerizations of all sorts, including thicker systems. In this project, a set of differential equations describing the spatial and temporal evolution of the light intensity gradient, photoinitiator concentration gradient, and the photoinitiation rate profile are developed for a thick polymer system. The generalized model accounts for the consumption of initiator, evolution of the products of photolysis, diffusion of the initiator and photolysis products, and absorbance by all system components. The purpose of these studies was to characterize further these systems so that results accurately capture the photoinitiation process. Several key objectives have been accomplished, including the effects of illumination with polychromatic incident light, various illumination schemes, and verification of the predicative ability of the model.