Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids Derivatives of such polymer