Thiol/ene free-radical reactions are highly effective when compared with complicated synthesis methods and precise sequence control. Investigation of mercapto-olefins for N-phenylacrylamide (NPA) by thiol/ene free-radical mechanism has not been reported so far. Herein, we report the thiol/ene free-radical reaction of N-phenylacrylamide (NPA)/pentaerythritol tetra(3-mercaptopropionate) (PETMP) by ultraviolet irradiation to give the final product (abbreviation: NPP). The preliminary applications of the NPP were also explored including photoluminescence, adhesive, and thermoresponsive. The adhesion of the NPP has been validated in various substrates. Moreover, it has a strong ability to stick to glass surfaces, even when submerged in water for an extended time. The better adhesion may be attributed to functional groups forming dynamic crosslinks based on hydrogen bonding, van der Waals interactions, and π-π interactions and high hydrophobicity of the phenyl group. This strategy opens an avenue for NPA by thiol-ene click reaction.