Abstract: A vinyl acetylsalicylate-vinyl alcohol based copolymer which comprises a structural unit having the following formula (1): ##STR1## and a structural unit having the following formula (2): ##STR2## optionally with at least one member selected from the group consisting of a structural unit having the following formula (3): ##STR3## and a structural unit having the following formula (4): ##STR4## In the copolymer, the amounts of vinyl acetylsalicylate units and vinyl alcohol units, degree of polymerization and the like can be controlled, whereby the efficacy of acetylsalicylic acid can be easily controlled as desired. Therefore, the copolymer is expected to be widely applicable as medicament.

Abstract: Novel cellulose derivative, process for preparing the same and sulfur dioxide gas permselective membrane comprising said derivative.Hydrocarbysulfinylethyl cellulose represented by the formula (I): ##STR1## wherein, X may be the same or different and represents hydrogen atom or hydrocarbylsulfinylethyl group represented by the formula (II): ##STR2## wherein, R may be the same or different and represents an alkyl group having 1 to 6 carbon atoms or a phenyl group,with the average substitution degree with the hydrocarbylsulfinylethyl group of the formula (II) per glucose unit being at least 0.05, and sulfur dioxide gas permeation membrane comprising said cellulose derivative. This membrane is excellent in sulfur dioxide gas permselectivity.

Abstract: Materials for forming a hydrogel when contacted with water having improved anti-thrombogenic properties and a highly improved mechanical strength are obtained by the copolymerization of a free radical-polymerizable vinyl monomer capable of forming a hydrophilic polymer and a hydrophobic macromolecular compound having a chain-terminated polymerizable double bond and a molecular weight of 1,000 to 100,000.