Chain structure evolution, rationalizing

The structure of itaconic acid bears some resemblance to methacryllc acid. While It Is know that methacryllc acid and methacrylic anhydride do enhance sensitivity when copolymerized with methyl methacrylate, some of the Increase In speed may be due to porosity (7,12). The gas formation may cause a higher rate of dissolution then can be attributed to chain scission alone. Pittman and co-workers have reported G(s) values for poly(methacryllc anhydride) of 0.4 (10) and 1.8 and 2.9 (14) based on gamma radiation experiments. Hiroaka (12) measured G(s) by gas evolution on Irradiation of films with electron beams and established values In the ration 1 2 6 for the methyl methacrylate. A terpolymer with the three components In the molar ratio of 70 15 15 (same three monomers) was selected by Moreau et al (13) on the basis of complete lithographic evaluation. The speed Is 4 to lOx that of PMMA. As aforementioned, an Increase In G(s) may be only partially responsible. 

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