Preparation Of Functional Silicone Materials Via Thiol-ene Click Reaction And Their Wastewater Treatment

Water pollution problems become more and more serious with the rapid growth of the economy and population,posing a major threat to human health.According to the survey by World Health Organization,80%of the diseases spreading in developing countries are related to water pollution.Therefore,rapid removal of contaminants from wastewater is essential for human health and environmental protection,and wastewater purification is of great significance.Among the water pollutants,oils and other organic substances,dyes,heavy metals and other pollution hazards are the most common and endangered.Adsorbent materials are most widely used to clean up pollution at present among all the methods to dealing with water pollution,because of its advantages of easy processing,low cost,good selectivity.reusability and environmental harmlessness..Silicone materials possess many unique properties such as non-toxicity,physiological inertness,flame retardancy,high-and low-temperature resistance,weather resistance,aging resistance,electrical insulation and ozone resistance,and thus are widely used in aerospace,electrical and electronic,light industry,chemical industry,construction,textile,machinery manufacturing,medical care,daily chemical industry etc.in the national economic sectors.Functional silicone materials have many special applications in addition to the general advantages of silicone materials due to their special properties.Among them,silicone materials have great potential in wastewater treatment based on the above properties.The thiol-ene click reaction is one of the click reactions.The reaction conducts in air at room temperature with the mild reaction conditions,the fast reaction speed,the high yield,the less side reaction and the high stereoselectivity.Furthermore,metal catalyst is not needed in the reaction process and the commercial raw materials are very abundant.Therefore,it has been widely used in various aspects of polymer synthesis.Compared with carbon-based materials,there are fewer types of reactions in the synthesis of silicone materials,and the reaction conditions are more rigorous,which limits the widespread use of new silicone materials.The application of thiol-ene click reaction to functional silicone materials is of great significance for promoting the development of silicones.In this paper,a few functionalized silicone materials including small molecules,polymers and silicone networks will be prepared by thiol-ene click reaction and studied via a series of tests.We will also study their applications in oil-water separation,dye and metal ion adsorption,etc.The main contents are as follows:1.A few kinds of functional polysiloxanes were first obtained by reacting functional alkenes with 3-(dimethoxy(methyl)silyl)propane-1-thiol in near-quantitative yields using a simple,efficient and photoinitiated thiol-ene click reaction.Then,functional polysiloxanes are synthesized from their corresponding functional dialkoxysilane monomers.This two-step method is a novel and efficient way of synthesizing functional polysiloxanes.The functional polysiloxanes show obvious fluorescence properties,which are assumed to be generated from unconventional chromophores.Furthermore,a series of copolymers(PETHs)with mercaptopropyl and polyether side chains are also obtained.They are successfully used for hydrophilic modification of a poly(styrene-b-butadiene-b-styrene)triblock copolymer.The PETH-based blue-light-emitting silicone elastomer is synthesized first via a thiol-ene click reaction,and it exhibits wonderful hydrophilicity,which may be useful in biomedical fields.2.The unconventional chromophore S→Si coordination bond was firstly found in water-soluble polysiloxanes modified with polyether groups via thiol-ene click reaction.The fluorescence was preliminarily assumed to be generated from through-space charge transfer because the S→Si coordination bonds made it easier to occur.The existence of S→Si coordination bond was firstly proved by experiments.including synthesizing model compound and testing via quantum-chemical modeling,Si NMR,XPS spectra.and fluorescence spectra.Furthermore,the changing law of fluorescence intensity of those compounds with temperature,concentration and solvent are investigated.Fluorescence intensity improves with the temperature dropped down.This unconventional chromophore shows the AIEE(aggregation-induced emission enhancement)phenomenon.The mercapto and thioether groups in PETHs can act on Hg2+ and Fe3+,breaking the S→Si interaction and quenching the fluorescence.The quenching constant is determined by the Stern-Volmer equation.Therefore,the PETHs are used as fluorescence probes for Hg2+ and Fe3+ in water with low detection lilmits which is applicable to metal detection.3.A novel oil-absorptive silicone-based material was synthesized through the efficient thiol-ene click reaction and simple post-processing to deal with waste oil.The silicone-based material possesses high adsorption ability for various oils,short adsorption time,excellent reusability,and high-and low-temperature resistance.Furthermore,this silicone-based material presents hydrophobicity and oleophilicity,which is useful for oil/water and oil/oil separation.The adsorption ability for different oils is evaluated according to the polarity of the oils.A novel and efficient reuse method is presented based on the selective adsorption.The absorption mechanism is strudied through surface observations via scanning electron microscopy and dynamic and thermodynamic analyses.It is found that the adsorption process is divided into two steps,and the adsorption power mainly comes from the van der Waals force between the material and the oil.4.We first report a novel and simple method for the synthesis of macroporous silicone sponges via one-pot thiol-ene click reaction at-10 ℃.The sponge has high porosity,low density,durably and high hydrophobicity,super-oleophilicity,good thermal insulation,and excellent compressibility(11.01 MPa at 93%strain,superior to all the previously reported silicone sponges)in addition to conventional advantages of silicone such as non-flammability,excellent stability,and non-toxicity.The morphology,pore size,density,and compression properties of the sponge are also controllable by adjusting the synthesis conditions.Furthermore,the sponge could be used for rapid oil/water separation with good absorption ability,excellent reusability and separation efficiency(>99%).It also has good application potential in the fields of shock absorption,buffering and pressure sensing.5.Super-amphiphilic 3D silicone sponge are first synthesized by the efficient two-step thiol-ene click reaction.The shape-controllable sponges possess high porosity,low weight density,good compressibility,excellent adsorption ability and reusability for water,oil,and water/oil emulsions in addition to conventional advantages of silicone such as excellent stability,non-flammability.and non-toxicity.The sponge as a block can selectively adsorb Hg2+ from solution containing various ions with a very high adsorption amount(941.3 mg/g)and nearly 100%removal efficiency.The pH did not affect the removal efficiency,indicating the wide application field.Cation dyes can also be selectively and rapidly captured by the sponge with a high yield.Furthermore,the sponge is designed as a filter element for a filtration system,and the filtrate is drinkable after the Hg2+ and dye solutions are processed.The filter can be reused with almost unchanged filtration efficiency after a simple washing process.