Preparation Of Long Chain Hydrocarbon-Organic Silicon Alternate Copolymer And Temperature Performance Research

Long-chain hydrocarbons were hydrocarbons with a carbon number of 8 or higher,which had certain compatibility and hydrophobicity.They were mainly used in petrochemical fields such as lubricants,paraffin oil,petroleum solvents,and also in daily necessities such as pesticides,medicines,and surfactants.However,the long-chain hydrocarbons had poor high and low temperature resistance.Polysiloxane,commonly known as silicone,was a type of polymer with silicon-oxygen bonds as the main chain.It had strong chemical bonding energy and molecular flexibility,so general silicone products had excellent high and low temperature resistance.If long-chain hydrocarbons were combined with silicones,not only could the product's temperature resistance be improved,but its application fields could also be expanded.There were two main types of combined products of long chain hydrocarbons and silicones.1)Long chain hydrocarbons was used as bridges,grafts silicones to short chain polyolefins to form silicone-modified polyolefin products containing long chain hydrocarbon units.2)This kind of combined products was based on hydrogen-containing polysiloxanes.Long-chain alkane was grafted into the polysiloxane to form a long-chain alkane-modified polysiloxane structure.Existing literature reports also focused on these two types of products,but these two types of products were mainly block copolymers.what's more,there were few reports on products of alternating copolymers of long chain hydrocarbon silicones.In this paper,a series of long-chain alkenyl alternating copolymers were prepared by the hydrosilylation method with?-long-chain monoolefin,?,?-long-chain diolefin and M^HM^H as raw materials,such as long-chain alkenyl group terminated,dimethylsiloxyl group terminated,long-chain alkyl group terminated,both long-chain alkenyl and dimethylsiloxyl group terminated alternating copolymers and so on.Low molecular weight components were gained by gel chromatography where the polymer was separated,which was characterized by ¹H-NMR,¹³C-NMR,and MALDI-TOF MS.The results showed that long-chain hydrocarbons and silicones were copolymerized alternately.According to the GPC results of the higher molecular weight long-chain hydrocarbon-silicone copolymer,while under the condition that the molar ratio of the long-chain olefin to the silicone monomer was 1:1 and the reaction time was 4h,the conclusion of the copolymer reaction was drawed:The copolymer having the largest molecular weight?M_n=3787 g/mol?was prepared when the amount of catalyst was used with 20?L and the reaction temperature was 75?.At the same reaction temperature,the narrowest molecular weight distribution of the copolymer?PDI=1.91?was obtained if 30?L catalyst wasused.When the amount of catalyst is 30?L,higher molecular weight of the product was obtained if the reaction temperature increased from 25?to 75?,and the molecular weight distribution of the product was narrower.Compared with the same temperature,the molecular weight distribution of the copolymer obtained by the reaction of 30?L catalyst was relatively small,and the molecular weight distribution is relatively narrow,as is relatived to 20?L and 40?L catalyst amount.Thus,by changing the reaction temperature and the amount of catalyst,the controllability of the molecular weight and distribution of the copolymer could be achieved.The results of the study on the heat resistance of oligomers showed that as the molecular weight of the oligomer increased,the thermal stability also increased,and the lowest phase transition temperature in the cooling section was lower than-80?.The oligomer had strong cold resistance and overall performance,which was better than liquid paraffin and poly alpha olefins.It was shown that the introduction of silicone could improve the temperature resistance of the product and enhance the flexibility of the oligomer molecular chain.The research on the temperature resistance of higher molecular weight copolymers found that the thermal decomposition trend of high molecular weight copolymers was basically similar to that of oligomers,and the overall high temperature resistance was close to that of oligomers with larger molecular weights.When the molecular weight of the copolymer exceeded 965 g/mol,the thermal properties of the copolymer no longer increased as the molecular weight increases.The main factor affecting the thermal properties of the copolymer was the cohesive energy density.The molecular weight distribution of the copolymer was related to the weight loss rate of the product under a nitrogen atmosphere.For a long chain hydrocarbon-silicone copolymer with a narrow molecular weight distribution,the weight loss rate tended to be more moderate with temperature.The thermal decomposition tendency of these copolymers in the air atmosphere was almost the same,and the copolymer could withstand a high temperature of nearly 400?as a whole,and be applied to new heat-resistant agents.