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Photopolymerization kinetics and monomer diffusion in polymer matrix

1990; Elsevier BV; Volume: 31; Issue: 6 Linguagem: Inglês

10.1016/0032-3861(90)90262-w

1873-2291

Vadim V. Krongauz, Robert M. Yohannan,

Advanced Polymer Synthesis and Characterization

A direct and non-destructive method for observing reaction kinetics and monomer transport in photopolymers during photopolymerization is presented. This method is based on monitoring a change in intensity of the fluorescence emitted by plasticized vinylacetate film containing fluorescent monomer, N-vinylcarbazole. The film used in the experiments had high optical density at 295 nm. Illumination of one side of the film led to polymerization of the dispersed monomer and reduction of its concentration predominantly near the illuminated surface. Thus, during this photopolymerization reaction, which produces a monomer concentration gradient, the monomer diffuses across the film toward the illuminated surface. Since only the monomer and resulting polymer are fluorescent, an increase in concentration of the polymer near the illuminated surface increases the fluorescence intensity. This increase in fluorescence intensity is used to monitor the photopolymerization kinetics. It is demonstrated here that upon excitation at 295 nm at room temperature the polymerization kinetics of N-vinylcarbazole in a plasticized vinyl acetate film are controlled by N-vinylcarbazole diffusion. The diffusion coefficient for this monomer, as measured in the present work, is 6 × 10−9 cm2s−1.