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In the case of a monomer having a hydroxyl group, the hydroxyl group may be replaced by an acetal group suscep› tible to deprotection with acid, typically ethoxyethoxy, prior to polymerization, and the polymerization be followed by deprotection with weak acid and water. Alternatively, the hydroxyl group may be replaced by an acetyl, formyl, piv› aloyl or similar group prior to polymerization, and the poly› merization be followed by alkaline hydrolysis. 

In another preferred embodiment, the copolymer may have further copolymerized therein recurring units ( d) selected from units of indene, benzofuran, benzothiophene, acenaph› thylene, chromone, coumarin, and norbomadiene, or deriva› tives thereof. Suitable monomers are exemplified below. 

