| Vinyl polyperoxide is a type of polymer which contains peroxy bonds in the main chain.It can be used as a radical polymerization initiator to initiate the polymerization of vinyl monomers.Since vinyl peroxide has a lower molecular weight and a much larger molecular weight organic peroxide,the polymer synthesized by its initiation polymerization contains a longer initiator residue,and the obtained polymer belongs to a block copolymer.This characteristic of vinyl peroxide has attracted much attention.However,due to the current technical problems in the synthesis of vinyl peroxides,it has not been widely used.There are three problems that vinyl peroxide has not been widely used as an initiator for free radical polymerization to synthesize block copolymers:one is that the molecular weight is low,and the formation of block segments is short and uncontrollable;the other is that the structure is a vinyl monomer and Alternating copolymers formed by oxygen lead to poor thermal stability of the prepared block copolymers;thirdly,the synthesis cycle is too long and the yield is low,which cannot meet the needs of a wide range of applications.If the molecular weight of the vinyl peroxide polymer can be increased,and the chain structure of the product can be controlled to contain only a small amount of peroxy bonds,it can be used to synthesize a block copolymer with a controllable structure and good thermal stability.If this goal is achieved,it will not only enrich the types of peroxygen initiators,but also make the synthesis of block polymers more convenient and controllable,with a richer variety,and broaden its application fields and scope of application.In view of this,based on the structure and decomposition characteristics of vinyl polyperoxide,this article puts forward the idea of high-temperature polymerization to synthesize high molecular weight vinyl peroxide,and explores its feasibility by using styrene as a monomer.By investigating the effects of reaction temperature,oxygen pressure and solvent dosage on the product structure,molecular weight,number of peroxy bonds and thermal properties,the chain structure of PSP synthesized by high-temperature free radical polymerization was clarified,and the main chain of synthesis had a small amount of peroxy bonds and high molecular weight The polymerization conditions and formula of PSP,and its ability to initiate polymerization were evaluated at the same time,and the following conclusions were studied:(1)High-molecular-weight polystyrene peroxide containing a small amount of peroxy bond in the main chain can be synthesized by high-temperature free radical polymerization.Under the conditions of reaction temperature of 120°C,oxygen pressure of 0.3 MPa,and solvent content of 5%,a polystyrene peroxide with a molecular weight of up to 1.52×10~5and main chain which contains 2 to 4 peroxy bonds can be synthesized.(2)The molecular weight of PSP synthesized by high temperature free radical polymerization is significantly higher than that of low temperature free radical polymerization products used in the literature.Its molecular weight is affected by polymerization temperature,oxygen pressure and solvent dosage,and solvent dosage has a greater influence on its molecular weight.(3)PSP synthesized by high-temperature free radical polymerization is polystyrene peroxide with a small amount of peroxy bonds in the main chain,and the average number of peroxy bonds per molecular chain does not exceed 7.The number of peroxy bonds is affected by the polymerization temperature,oxygen pressure and the amount of solvent.The number of peroxy bonds can be controlled by adjusting the sizes of the three.(4)PSP synthesized by high temperature free radical polymerization can initiate high temperature free radical polymerization to synthesize block copolymers.The higher the polymerization temperature,the greater the polymerization rate,and the highest yield of prepared block copolymers can reach 94.5%. |
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