Synthesis And Properties Of Silicon-titanium Ologomers

Silicone materials have been resistant to high and low temperature properties and other excellent properties,so it has been an important part of high temperature resistant adhesive.When introducing certain metal heteroatoms into the silicone,a new type of modified silicone material-polymetalorganosilicon was obtained.The introduction of metal heteroatom silicone polymer has a more excellent resistance thermal and high temperature adhesion than the simple silicone polymer.Polytitanium organosiloxane is a kind of typical silicon-titanium polymers in which the main chain contains the silicon and titanium inorganic element and the side chain is the organic groups.Thus Polytitanium organosiloxanes have the properties of both organic and inorganic materials.Silicon-titanium polymer has a very wide range of applications in industry.In this paper,we use hydroxyl-terminated polydimethylsiloxane and 1,4-bis(dimethylhydroxysilyl)benzene as raw materials and tetrabutyl titanate as Ti source to synthesize silicon-titanium oligomer.At the same time,we study its related properties.1.Hydroxyl-terminated polydimethylsiloxane and tetrabutyl titanate were reacted at a molar ratio of 4:1 to successfully synthesize the cruciform silicon-titanium oligomer without benzene ring.Comparing the yield,molecular weight and thermal properties of the product,we determined the best method for synthesizing cruciform silicon-titanium oligomers without benzene ring.2.We studied the thermal stability of cruciform silicon-titanium oligomers without benzene ring.The results show that the initial decomposition temperature of the oligomer is 350 ℃.The residual amount after 800 ℃ is 10%,and the heat resistance is excellent.This is mainly due to the introduction Ti atoms into the siloxane system to form a Si-O-Ti bond with a higher stability than the Si-O-Si bond,while the main structure of the siloxane is not destroyed.3.1,4-bis(dimethylhydroxysilyl)benzene and tetrabutyl titanate were reacted at a molar ratio of 4:1 to successfully synthesize the cruciform silicon-titanium oligomer containing benzene rings in the main chain.Based on the discussion of the synthesis conditions,it is determined that tetrahydrofuran is used as solvent and the cruciform silicon-titanium oligomer containing benzene rings is synthesized at 50 ℃.4.The initial decomposition temperature of the cruciform silicon-titanium oligomer containing benzene rings is 270 ℃ and the residual amount after 800℃ was 62%.The initial decomposition temperature of the cruciform silicon-titanium oligomeris is relatively lower than that of the cruciform silicon-titanium oligomer without the benzene ring,but the final residue is higher and the heat resistance is more excellent.The main reasons:the benzene ring introduced into the main chain has a negative effect on the Si-C bond,and the temperature at which the organic group dissociates from the silicon atom is shifted to the low temperature region.In addition,the degradation process of the silicon-titanium oligomer is a free radical process.There are no silicon compounds in the volatile material.The methyl is easy to form free radicals and the volatile substances,but the structure of Si-phenyl-Si is more difficult broken,and it can form free radicals containing silicon.Further combined it can form the non-volatile substances.5.Hydroxyl-terminated polydimethylsiloxane and tetrabutyl titanate were reacted at a molar ratio of 2:1 to successfully synthesize the spirocyclic silicon-titanium oligomers without benzene rings.The reaction is very fast and the conversion rate is very high,meanwhile the final product can be well dissolved in tetrahydrofuran,toluene,benzene and deuterium reagents,so it further shows the occurrence of cyclization reaction,resulting in spirocyclic silicon-titanium oligomers.We studied the thermal stability of the spirocyclic silicon-titanium oligomers without benzene rings.The results show that the initial decomposition temperature of the oligomer is 300 ℃ and the final residue is 27%.When the oligomers were pyrolyzed at different temperatures,the most severe pyrolysis occurred between 5 and 20 minutes,and after 400 ℃ the trend of weight loss was significantly reduced.6.1,4-bis(dimethylhydroxysilyl)benzene and tetrabutyl titanate were reacted at a molar ratio of 2:1 to successfully synthesize the spirocyclic silicon-titanium oligomers containing benzene rings.Its thermal stability is excellent:the initial decomposition temperature is 240 ℃ and the final residue is 61%.The initial decomposition temperature of the spirocyclic silicon-titanium oligomers containing benzene rings is lower than that of the spirocyclic silicon-titanium oligomers without the benzene rings,but the final residue is higher and the thermal stability is better,which is mainly caused by the introduction benzene rings into the main chain.7.Compared the thermal stability of the cruciform silicon-titanium oligomers with the spirocyclic silicon-titanium oligomers,the results show that the thermal stability of the spirocyclic titanium-titanium oligomers without the benzene rings are better and the cruciform silicon-titanium oligomers containing benzene rings are better.