Synthesis And Properties Of Poly (Siloxane Imide) Copolymers

Organosilicon polymers exhibit various excellent properties,such as good flexibility,chemical stability,weather resistance and biocompatibility.Related products have been widely used in aerospace,electronics,biomedicine,chemical industry,construction and other fields.With the development of economy and society,the demand for silicone products is increasing.At the same time,the requirements for the higher performance are increasing.Therefore,it is imperative to develop new silicone-based products.It is important to expand the types of organosilicon products and promote the development of organosilicon industry by synthesizing high-performance siloxane-containing polymers via combining organosilicon polymers with organic polymers.Polyimide is an important special engineering material with outstanding thermal stability,mechanical properties,radiation resistance and so on.And it plays an important role in aerospace,automobile industry,machinery and other fields.Imide-containing polysiloxanes with excellent comprehensive properties can be obtained by introducing the imide structures into the polysiloxanes,which can combine the advantages of the two polymers.In this thesis,the imide structures were introduced into the main chains of polysiloxanes,and a series of poly(siloxane imide)copolymers were synthesized by adjusting the structures of diamine and dianhydride monomers and the molecular weight of polysiloxanes,and the properties were studied.The main contents of the thesis are as follows:First,aminopropyl-terminated polysiloxane was synthesized by ring-opening polymerization of octamethylcyclotetrasiloxane;second,anhydride-terminated poly(siloxaneimide)was synthesized by adding excess dianhydride oligomers to the Aminopropyl-terminated polysiloxane;finally,the product was copolymerized with diamine monomers to prepare poly(siloxane imide)copolymers(PSI).By adjusting diamine monomers with two benzene rings,one benzene ring and no benzene ring in the structure,and the molecular weight of polysiloxanes,the properties of copolymers were studied.DSC results showed that PSI possessed two glass-transition temperatures.The imide structures enhanced the rigidity of the copolymers,and PSI exhibited excellent thermal stability,and the decomposition temperature reached above 440℃.They also exhibited good mechanical properties,and the tensile strength reached 5.25 MPa.In addition,the copolymers exhibited good solubility,reprocessabity and reusability.Based on the synthesis method above,three kinds of dianhydrides with planar structure,non-coplanar structure and non-coplanar carbonyl-containing structure were selected to synthesize a series of poly(siloxane imide)copolymers.And the properties of copolymers were investigated.It was found that different imide structures endowed copolymers with different properties.The copolymer synthesized from carbonyl-containing dianhydride exhibited better solubility in polar solvents such as DMF and DMAc,and had higher mechanical strength(4.60 MPa).When the dianhydride had the planar structure,the copolymer synthesized from it exhibited better thermal stability and hydrophobicity,and its decomposition temperature was 469℃,and the contact angle was 110°.In addition,the copolymers had both mechanical strength and flexibility,and exhibited good mechanical properties.