Sunlight-Induced Cross-Linked Luminescent Films Based on Polysiloxanes and D-Limonene via Thiol-ene "Click" Chemistry

The increasing pursuit of biocontained elastic materials led the investigation of the potential use of the monoterpene limonene in film synthesis via thiol-ene reaction. Poly[(mercaptopropyl) methylsiloxane] (PMMS) is first synthesized. By controlling the molar ratio of PMMS and functional monomers, such as polyethylene glycol allyl methyl ether or rhodamine-B, PMMS is partially functionalized while leaving spare mercapto groups that could be further used as cross-linking sites. On the basis of the functionalized PMMS, novel transparent silicone luminescent films with hydrophilic tunable properties are prepared by natural-sunlight-triggered thiol-ene "click" chemistry by using D-limonene as a cross-linker. Their structures and properties are thoroughly characterized. Transparent luminescent films are coated on commercially available UV-light emitting diode (LED) cell from solution medium followed by an in situ cross-linking step; a colorful LED cell is obtained through this facile and efficient method. The UV-LED coated by films show very intense photoluminescence under normal visible light or the light is on, and has very high coloric purity.