Thermodynamically-Driven Depolymerization

There are three mechanisms for initial backbone cleavage that cascades into complete depolymerization (Fig. 107) [110,328]  

Poly(a-acetoxystyrene) is an acetophenone enol ester and its acidolysis involves the polymer backbone in contrast to the side chain deprotection discussed earlier (Fig. 30). Protonation of the side chain carbonyl oxygen results 

The depolymerization mechanism from the polymer end has been recently revisited in the design of positive electron beam resists. 2-Phenylallyl-termi-nated poly(a-methylstyrene) was prepared by living anionic polymerization, which exhibited a significantly lower depolymerization temperature on TGA than the H-terminated counterpart [340]. The 2-phenylallyl-terminated polymer depolymerized completely when treated with n-BuLi in THF at room temperature. A single-component resist (without PAG) formulated with the 2-phenylallyl-terminated poly(a-methylstyrene) demonstrated a higher e-beam sensitivity (500 pC/cm2 at 20 keV) than the one based on the H-terminated polymer when developed with methanol/methyl isobutyl ketone (2/3 vol/vol) [340]. However, the sensitivity of the non-catalyzed single-component system 

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