Synthesis of Poly(p-hydroxy-α-methylstyrene) by Cationic Polymerization and Chemical Modification

High molecular weight, soluble poly(p-hydroxy-α-methylstyrene) has been synthesized for the first time by cationic polymerization of p-[(tert-butoxycarbonyl)oxy]-'-methylstyrene with boron trifluoride etherate as an initiator in liquid sulfur dioxide followed by thermolytic deprotection. Cationic polymerization of p-acetoxy-α-methylstyrene in dichloromethane followed by hydrazinolysis afforded the title compound, but the polymerization was accompanied by partial cleavage of the protecting group. Conventional cationic polymerization of p-[(tert-butoxycarbonyl)oxy]-α-methylstyrene in dichloromethane resulted in formation of low molecular weight polymer accompanied by partial cleavage of the protecting group. Ether monomers, such as p-methoxy- and p-(ethoxymethoxy)-α-methylstyrenes, readily underwent cationic polymerization, while the p-(2-methoxyethoxy)methyl derivative suffered from partial deprotection and cross-linking. Removal of the ether protecting group was, in all cases, accompanied by chain degradation and/or cross-linking. Chemical modification of poly(α-methylstyrene) and poly(p-bromo-α-methylstyrene) by lithiation followed by hydroxylation produced cross-linked materials.