Novel derivatives of poly(4-hydroxystyrene) with easily removable tertiary, allylic, or benzylic ethers

Summary

The protection of poly(4-hydroxystyrene) and its 3,5-dimethyl analog through formation of its 2-cyclohexenyl, 1-phenyl-ethyl or t-butyl ether derivatives is easily accomplished. All of these ethers are selected as they contains structural features allowing for their facile elimination when deprotection is desired. In the case of the allylic and benzylic ethers,the monomers are easily prepared using a simple S_N2 substitution reaction on p-hydroxybenzaldehyde or its 3,5-dimethyl analog followed by a Wittig methylenation. Chemical modification of poly(4-hydroxystyrene) using etherification procedures is also done easily but usually only affords partial functionalization; the remaining hydroxyl functional groups may however be blocked in-situ by addition of a second reagent. The active ether pendant groups of the polymers can be cleaved easily and quantitatively by thermolysis, acidolysis, or acid hydrolysis suggesting that the ether protected polymers may be useful as resist materials.