Hybrid Photopolymerization :: Chemistry

Hybrid photopolymerization has the potential for solving the oxygen inhibition and moisture problem that plagued the free-radical and cationic photopolymerization reactions respectively. The problem, however, with the hybrid system is the deficiency in the fundamental knowledge of the reaction in the system. This project tends to address these deficiencies by studying hybrid systems in order to understand how experimental variables affect oxygen, moisture and alcohol sensitivity. This understanding will be archived by the following objectives; Determine the kinetic rate constants for the hybrid systems. The kinetic rate constant, activation energy and Arrhenius constant of the hybrid systems will be obtained from Raman spectroscopy method. Model oxygen- diffusion-effect in hybrid systems. An oxygen-diffusion-model will be developed incorporating energy balance, specie balance and light attenuation parameters. Reduce oxygen diffusion in hybrid monomer films through formulation and processing variable selections. Hybrid monomer molecule and monomer mixture will be polymerized to obtain the conversion profile; the cure sample will be investigated to obtain the functional group conversion versus depth by Raman spectroscopy and microscopy respectively. The physical properties of the resulting product will be checked in order to determine the least oxygen diffused product. Develop practical hybrid monomer formulations for industrial applications. Hybrid systems that can be replicated on the industrial scale will be formulated. These systems will be suggested based on availability, cost and resulting physical properties displayed as investigated in Objective three. IV. Research Plan A Overview In this study, a series of hybrid systems will be considered; monomers of these systems will have different functionality present, like those in Figure 5. Hybrid monomer molecule, that is, a single monomer molecule with two moieties (such as acrylate and epoxide) and hybrid mixture formulation that will contain separate molecules for each moiety (i.e. acrylate will be mixed with epoxide). The photoinitiator systems for this study will be expanded to include ÃŽ ±-cleavagable free-radical photoinitiator, such as dimethoxyphenylacetophenone (DMPA) shown in Figure 1, and cationic photoinitiator salts as shown in Figure 3. Raman spectroscopy will be used for in-situ investigation of polymerization of samples. Raman microscopy will be used to obtain profiles of functional group conversion at various depths. These methods are based upon a non-destructive Raman scattering technique which provides information about the vibrational and electronic states in a confined system.{{8 Cai,Ying 2006}} The method is particularly well suited for detection of chemical bonds and their changes during reaction. B. Objective #1 Kinetic Study of the Hybrid Systems