Photomelt and photoinduced tacky resins comprising disulfide and photoinitiators as easy-to-release, pressure-sensitive, and separator-free adhesives

Abstract

Photomelt resins (PMRs) can be liquefied by light exposure, which is promising for applications such as pressure-sensitive adhesives. From the perspectives of environmental friendliness, worker health, and cost, there is a need to develop PMRs that are recyclable and customizable for use with specific substrates, that melt upon exposure to low-energy light, and that use a more economical synthesis method. In this study, we fabricated various PMRs comprising polysulfides cured by isocyanates and commercial photoinitiators via a thiourethane reaction at room temperature. The exchange reactions between the disulfide groups and radicals generated from the photoinitiators alter the mechanical properties of the polymer chains. Upon light exposure, the polymer changes from an elastomer to a pressure-sensitive adhesive, which makes these PMRs promising for use as reworkable and easy-to-release adhesives. Moreover, these PMRs exhibit photoinduced tackiness, which enables the design of separator-free adhesive tape. As separator films are currently used to cover one or both sides of pressure-sensitive adhesive tapes, adhesive films with photoinduced tackiness could significantly reduce the global usage of separator film, thus reducing the environmental impact of these adhesives.