Synthesis And Properties Of Organosilicon Luminescent Materials Via Thiol "Click" Chemistry

According to Sharpless' characterization of click reactions,the synthetic chemistry communities as well as materials science have pursued many routes toward the identification of click reactions."Click" reaction is a fast and efficient chemical method which has high selectivity.Thiol-"click" reactions have all the fine characters of a click reaction.They are highly efficient,easy to execute and have no side products,proceeding fast to high yield.At present,thiol-"click" reaction has been widely applied in polymer synthesis and post-functionalization,including nano-imprinting,surface modification,synthesis of polymer microspheres,as well as the synthesis of gel.Organosilicon compounds are those with at least one organic group that is attached to the silicon atom.Organosilicon chemistry is the one of the fastest growing element-organic chemistry.For their unique properties,such as resistance to high temperature and moisture,electrical insulation,fine physical inertia and anti-aging properties,organosilicon materials have been widely used in many areas,such as electronics,aerospace,construction,energy and transportation.However,traditional functional organosilicon materials are mainly prepared by hydrosilylation reaction.The hydrosilylation reactions often need heavy metal catalysts,which have many shortcomings,such as the presence of heavy metals will limit the application of the products in medical or biology fields.Long reaction time and the rigor reaction conditions are demanding.Furthermore,the existence of the functional groups may cause catalyst poisoning and further affect the catalytic efficiency.Meanwhile,endowing organosilicon materials with superior luminescent properties may expand the application of traditional organosilicon materials.For these reasons,seeking for a kind of non-heavy metal catalysis,fast and efficient way to the preparation of organosilicon luminescent materials is crucial.In this dissertation,valuable explorations have been carried out and focused on the synthesis and properties of luminescent organosilicon-based materials via thiol"click" chemistry.The main contents are as follows:1.The photoinitiated radical-based thiol-yne click reaction provides a simple and efficient method for the formulation of diverse alkoxysilanes.Seven alkoxysilanes were synthesized by reacting either alkynes with 3-mercaptopropylalkoxysilane in the presence of a photoinitiator.The thiol-yne reactions were neatly ran in standard glassware under UV irradiation(100 W).The functionalized trialkoxysilanes were obtained in quantitative to near-quantitative yields with high purity.In addition,functionalized alkoxysilanes were selected to modify the surface properties of Si(1,0,0),which can then be used for further functionalization or the immobilization of polymers or biomolecules.2.Thiol-ene reaction was first introduced as a modular,very efficient and highly orthogonal method for polymerization.Novel polysiloxanes bearing sulfur atoms in main chain with controlled molecular weight were synthesized by thiol-ene "click"reaction of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane(MMVi)and 1,2-Ethanedithiol(EDT)subsequently functionalized using the same method.Finally,hybrid luminescent materials obtained from functionalized polysiloxanes and lanthanide ions exhibit excellent narrow-width red or green emissions.3.Polymerization reactions are very common in the chemical industry,however the depolymerization reactions are rarely researched.We revealed for the first time that oxone can break the Si-O-Si bond and induce further rearrangement to yield an ordered cyclic structure.The oxidation of the surfur-bridged polysiloxane-P1,which is afforded by the reaction of 2,2'-1,2-ethanediylbis(oxy)bis(ethanethiol)(DBOET)with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane(MMVi),with oxone yielded cyclic crystallized sulfone-siloxane dimer(P1-ox)after unexpected cleavage and rearrangement of the Si-O-Si bond.4.Side chain vinyl polysiloxanes were modified with several kinds of carbonyl groups.Additional coordination bondings of the lanthanide ions to the functionalized polysiloxanes were further achieved.Crosslinked silicone elastomers were fabricated by thiol-ene curing reactions at last.All these complexes can be cast into transparent,uniform,thin elastomers with good flexibility and thermal stability.The elastomer luminophores exhibited intense luminescence under UV excitation at room temperature,which is attributed to the transition of lanthanide ions.Besides,a series of high-efficiency full color fluorescent elastomers based on polysiloxane matrix were prepared by facile thiol-ene "click" reaction.It is demonstrated that a fluent change of emission colors is prospectable and conveniently reproducible by varying the stoichiometric ratio of the lanthanide ions and Rhodamine-B.The obtained elastomers were coated onto commercially available UV-LED cell from solution medium through an in situ cross-linking step.5.Poly[(mercaptopropyl)methylsiloxane](PMMS)was first synthesized.By controlling the molar ratio of PMMS and functional monomers,such as polyethylene glycol allyl methyl ether or rhodamine-B,PMMS was partially functionalized.On the basis of the functionalized PMMS,novel transparent silicone luminescent films with hydrophilic tunable properties were prepared by natural-sunlight-triggered thiol-ene"click" chemistry by using D-limonene as a cross-linker.Their structures and properties were thoroughly characterized.Transparent luminescent films were coated on commercially available UV-LED cell from solution medium followed by an in situ cross-linking step;a colorful LED cell was 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.6.Cross-linked silicone elastomers constructed with dynamic-covalent boronic esters were synthesized by photoinitiated radical thiol—ene "click" chemistry.Samples can could be cut with a sharp knife into two pieces,and then can healed by the reversibility of the boronic ester within 30 min under ambient conditions.Furthermore,the elastomers obtained exhibit intense fluorecent emission under UV light,which would expand their applications into photoluminescent materials.Luminescent properties regulation was also performed by incorporating organic dye through "one pot" thiol-ene reactions.The synthesis of these elastomers demonstrates a new strategy to produce boronic acid silicone materials capable of self-healing without external forces.