Synthesis And Properties Of Disulfide Bond-containing Organosilicon Acrylate UV-cured Materials

UV-curing technology has been widely concerned by academia and industry because of its characteristics of fast curing,low consumption,environmental protection,energy saving and wide application.Free radical photopolymerization systems have always been a research hotspot in UV-curing technology due to the advantages of fast curing speed and rich raw materials.However,free radical polymerization is a kind of chain polymerization by which liquid resins rapidly polymerize to solid polymers,and produces serious polymerization volume shrinkage,which is easy to bring harm to the dimensional stability,and physical and mechanical properties of photocured materials.Both of organosilicon acrylate and organosilicon polyurethane acrylate photocuring materials are favored and most widely applied currently because they possess features of both acrylate or polyurethane and organosilicon.However,as free radical photopolymeric materials,they inevitably face the problem of serious volume shrinkage caused by polymerization mechanism,which results in a great limitation on their application in the fields of high-performance materials and high-precision materials.In addition,most photopolymeric materials are crosslinked polymers,which are difficult to be degraded and will cause serious environmental pollution when they are abandoned.Therefore,it is still a challenge to develop photocurable organosilicon acrylate or polyurethane acrylate materials with low volume shrinkage and good degradability.Our previous work has proved that the introduction of disulfide bonds into the photopolymerization system can effectively reduce the volume shrinkage in the photopolymerization of acrylate monomers by taking advantage of the reversible properties of disulfide bonds under light irradiation,and the disulfide bonds can also endow the materials with good degradability.Based on the above background,this project aims to introduce disulfide bonds into the organosilicon acrylate or polyurethane acrylate photocurable materials to reduce the volume shrinkage of the materials,improve the comprehensive properties of the materials,and endow the materials with good degradability.The effects of disulfide bonds and organosilicon chain segment on the photopolymerization properties,volume shrinkage,heat resistance,glass transition temperature（T_g）,water resistance,mechanical properties and degradability of the materials were also explored.The research of this topic has important theoretical significance and application value.It will enrich the theoretical basis of photocurable materials,broaden the application field of disulfide compounds,and provide experimental data and technical support for the application of the materials in 3D printing,dental materials and other fields.The main research contents and conclusions are as follows:1.Three polymerizable polysiloxane acrylate monomers with different chain lengths（MA-Si_n）and a polymerizable disulfide monomer（SA）,a disulfide bond-containing polysiloxane polyurethane acrylate oligomer（SSiPUA）and a polysiloxane polyurethane acrylate oligomer without disulfide bond（SiPUA）were successfully synthesized.2.Using 2-hydroxy-2-methyl-1-phenyl-1-acetone（1173）as a photoinitiator,a series of photocuring formulations were obtained by mixing MA-Si_n,SA,2-hydroxyethyl acrylate（HEA）,isobornyl acrylate（IBOA）and triethylene glycol dimethacrylate（TEGDMA）in different proportions.The effects of contents and chain length of MA-Si_n,and SA as well as contents of IBOA and TEGDMA on the photopolymerization kinetics,volume shrinkage,water resistance,hardness,heat resistance,T_g and tensile properties and degradability of the photopolymerization system（S-Si-I-T）were investigated.The results showed that the S-Si-I-T system presented a good photopolymerization performance,and the final double bond conversion reached about 94%after 200 s of illumination.SA can significantly reduce the volume shrinkage and endow the photocured film with degradability.MA-Si_nimproved the water resistance,thermal stability and flexibility of the cured film,but reduced the hardness and T_g.The increase of contents of hard monomer IBOA and difunctional monomer TEGDMA enhanced the hardness and tensile strength of the film,but decreased the flexibility.The photocured film of S1-Si₉0.9-I1-T2 system showed the best comprehensive properties.Its volume shrinkage was 3.5%;the water contact angle was 90.8°;the pencil hardness was2H;T_g was 171.8℃.T_5%and T_max2of the cured film reached 291℃and 571℃,respectively;the tensile strength and elongation at break reached 19.5 MPa and83.5%,respectively.More importantly,after soaking in N,N-dimethylformamide solution with tributyl phosphate for 120 min,the cured film was degraded completely.3.Using 1173 as a photoinitiator,a series of photocurable formulations were obtained by mixing the SSiPUA or SiPUA,HEA,IBOA and TEGDMA in different proportions.The effects of SSiPUA or SiPUA,IBOA and TEGDMA on the photopolymerization kinetics,volume shrinkage,water-repellency,hardness,heat resistance,T_g,tensile properties and degradability of SSi-I-T system were investigated.The results showed that the SSi-I-T system exhibited an excellent photopolymerization performance,and the final double bond conversion reached about 92%after 200 s of illumination.SSiPUA can significantly reduce the volume shrinkage,hardness and T_g of the cured film,and effectively improve water-repellency,heat resistance and tensile properties,meanwhile,endowed the film with good degradability.The increase of the contents of hard monomer IBOA and difunctional monomer TEGDMA enhanced the hardness and tensile strength of the cured film,but reduced the flexibility.The cured film of SSi4-I1-T0.1 system showed the best comprehensive properties.Its volume shrinkage was 4.9%;the water contact angle was 79.2°;the pencil hardness was HB;T_g was 83.4℃.T_5%and T_max2of the cured film reached 282℃and 456℃,respectively;the tensile strength and elongation at break reached 1.8 MPa and 576.2%,respectively.More significantly,after soaking in N,N-dimethylformamide solution with tributyl phosphate for 90 min,the cured film was degraded completely.