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Two t-butyloxycarbonyl (t-BOC) protected maleimide monomers, N -(t-butyloxycarbonyloxy)maleimide (t-BOCOMI) and N -[ p -(t-butyloxycarbonyloxy)phenylmaleimide (t-BOCOPMI), have been synthesized and polymerized. The t-BOC group was used to protect the hydroxy groups of the starting N -substituted maleimides, N -hydroxymaleimide (HOMI) and N-(p -hydroxyphenyl)maleimide (HOPMI). t-BOCOMI and t-BOCOPMI were copolymerized with styrene derivatives (X-St) to obtain the t-BOC protected polymers P(t-BOCOMI/X-St) and P(t-BOCOPMI/X-St) in high conversions. P(t-BOCOMI/St) and P(t-BOCOPMI/St) were cleanly deprotected by heating the polymers to 110 and 175°C, respectively. The deprotection temperature of the copolymers of t-BOCOMI (ca. 100°C) is the lowest among the known t-BOC protected polymers. Deprotection of P(t-BOCOMI/X-St) and P(t-BOCOPMI/X-St) produced the corresponding polymers having HOMI and HOPMI structures, respectively, and resulted in large changes in physical properties. The deprotected polymers have very high glass transition temperatures (above 250°C) and good solubility in aqueous base solutions, whereas the t-BOC polymers are only soluble in organic solvents. P(t-BOCOMI/St) was found to have desirably low ultra-violet absorption and high sensitivity in resist formulations. |
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