Synthesis Of Polyimide-siloxane And Its Properties

Due to combined with the structure characteristics of two materials,Polysiloxane-imide polymer has remarkable flexibility,solubility,thermal stability and mechanical properties,which is capable of application in fields like aerospace and microelectronic industries.At present,polyimide was modified by a small of polymethylsiloxane,and the processing performance was improved,but the phase separation was easy to happen because of their poor compatibility,which affects the transparency of the material and display of polysiloxane characteristics.The main contents of this paper are as follows:In this paper,instead of aromatic diamine,a series of polyimide-siloxane were synthesized through amino propyl-terminated polymethylphenyl siloxane and aromatic tetracid dihydride.Its intermolecular forces and compatibility were improved by ?-? interaction between PMPS and DTD A,and then their structure and properties were also studied.Four kinds of amino propyl terminated polymethylphenyl siloxane were prepared by methyl phenyl cyclic siloxane and amino propyl siloxane monomer through anionic polymerization,1H-NMR was used to characteristic the structures of polysiloxane.Taking polymethylphenyl siloxane with four chains as an example,the effects on the molecular weight of raw materials were analyzed by charging sequence,catalyst dosage and reaction time.The result showed that it were favorable for process of reaction to add amino propyl siloxane monomer at first,when catalyst dosage were 0.04%of raw material weight,and the first reaction time was 1.5h,the molecular weight was closest to the theoretical value.A series of polyimide-siloxane were prepared by synthesized polymethylphenyl siloxane and four types of aromatic tetracid dihydrides that include PMDA,BPDA,BTDA,HQDPA.The structures were characterized by FT-IR,the properties of polymers are studied such as hydrophobicity,solubility,thermal stability and mechanical properties.(a)The results show that the series of polymers have good solubility in DMF,DMAc,NMP,and CHCl3.(b)The results of thermal stability test showed that the polymers had good thermal stability,the maximum weight loss temperature was 497?-513? in argon atmosphere.(c)The result of contact angle test showed that the hydrophobicity of the materials increases with increasing the molecular weight of polymethylphenyl siloxane.(d)The analysis of mechanical properties indicates that intermolecular forces decided the crosslinking density and mechanical properties,and the materials showed high elongation at break and good elasticity.Dynamic mechanical analysis of three kinds of flexible polymers showed that the polymers had very high Tan?.Two types of blend polymers,which were PMPS-2-PMDA and PMPS-12-PMDA,PMPS-2-BPDA and PMPS-12-BPDA,were obtained by thermal cyclization.The results showed that the thermal stability of two types of blends was among two kinds of polymers separately,and blends had good elasticity.