Method for preparing transparent and heat-sensitive polycaprolactam coatings on polymer substrates

A method for the preparation of transparent and thermosensitive polyvinyl-caprolactam coatings on polymeric substrates comprising the following steps:

• a) synthesizing a polyvinyl-caprolactam copolymer containing caprolactam and benzophenone groups,
• where this synthesis is carried out through one of the following synthetic routes:
• (a.1) the synthesis of the copolymer from N-vinylcaprolactam (VCL) and a vinyl monomer selected from N-vinylformamide and 3-aminopropyl vinyl ether, followed by acid hydrolysis only in the case of the copolymer obtained from VCL and N-vinylformamide in order to hydrolyse the amide groups to amine, and subsequent reaction of benzophenone 4-isocyanate with the copolymer obtained from VCL and 3-aminopropyl vinyl ether or that obtained after acid hydrolysis, or
• (a.2) synthesis of a vinyl monomer incorporating benzophenone from 3-aminopropyl vinyl ether, or 2-hydroxyethyl vinyl ether, and isocyanate from 4-benzophenone and subsequent copolymerization reaction of the formed vinyl monomer and VCL,
• (b) contacting the copolymer synthesized in step (a) with the surface of the substrate whose surface is to be coated, and
• (c) exposing to UV light of the substrate that has come into contact with the copolymer.