Abstract: An antithrombogenic synthetic polymer has repeat structural units represented by the following structural formula consisting of portions I and II: ##STR1## a microdomain structure composed of crystalline phases and amorphous phases, each phase having an average size of 5 to 10 nm, and a molecular weight in the range of about 10,000 to about 300,000. The polymer exhibits little adhesion of blood platelets thereto, an excellent antithrombogenic property and a sufficient mechanical strength.

Abstract: Antithrombogenic synthetic elastomer having repeat units comprising portion I which is a soft segment unit containing a polyether and portion II which is a hard segment unit: ##STR1## R is a straight-chain or branched-chain alkylene group containing 2 to 4 carbon atoms, R' is amide a urethane, an urea, n ranges up to 180, m is an integer of 1 to 20, l is an integer of 1 to 10, said polymer having a microdomain structure composed of soft and hard segments, the domains of which have an average size of 10 to 20 nm, and a molecular weight of about 80,000 to about 500,000.The polymer shows little adhesion of blood platelets thereto, little deformation of adhering blood platelets and an excellent antithrombogenic property. This polymer has excellent mechanical properties as an elastomer.

Abstract: An acetalized polyvinyl alcohol having a molecular weight of 10,000 to 1,000,000 represented by the formula: ##STR1## wherein: R.sup.1 represents a halogen-containing residue of an aldehyde or a ketone; R.sup.2 represents a hydrogen atom, which may partially be substituted with an acetyl group; R.sup.3 represents naught or a monomeric unit copolymerizable with vinyl acetate; and l, m, n are integers indicating polymerization degrees, has excellent characteristics such as high sensitivity, high resolving power and excellent dry etching resistance and is suitable as a negative-type resist in ionizing radiation lithography.