Surface modification method and surface-modified elastic body

A surface modification method for surface-modifying an object of a rubber vulcanizate or a thermoplastic elastomer, the method comprising:

• step 1 of forming polymerization initiation points A on a surface of the object by adsorbing a polymerization initiator A onto the surface of the object;
• step 2 of radically polymerizing a non-functional monomer, starting from the polymerization initiation points A, to grow non-functional polymer chains;
• step 3 of forming polymerization initiation points B on the surface of the object where the non-functional polymer chains are formed by adsorbing a polymerization initiator B onto the surface of the object where the non-functional polymer chains are formed;
• and
• step 4 of radically polymerizing a functional monomer, starting from the polymerization initiation points B, to grow functional polymer chains,
• wherein
• the rubber vulcanizate or thermoplastic elastomer contains an allylic carbon atom,
• the non-functional monomer is at least one member selected from the group consisting of acrylic acid, acrylic acid esters, acrylic acid alkali metal salts, acrylic acid amine salts, methacrylic acid, methacrylic acid esters, methacrylic acid alkali metal salts, methacrylic acid amine salts, acrylonitrile, acrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, hydroxyacrylamide, acryloyl morpholine, methacrylamide, dimethylmethacrylamide, diethylmethacrylamide, isopropylmethacrylamide, hydroxymethacrylamide, and methacryloyl morpholine, and
• the functional monomer is at least one member selected from the group consisting of a fluoro group-containing monomer, a zwitterionic monomer that has a carboxybetaine group, a sulfobetaine group, or a phosphobetaine group in a side chain thereof, 2-(meth)acryloyloxyethyl phosphorylcholine, 2-(meth)acryloyloxyethyl carboxybetaine, 2-(meth)acryloyloxyethyl sulfobetaine, silver acrylate, and silver methacrylate.