Formation And Polymerization Of The Polyperoxides

Polymeric peroxide is a kind of polymer containing several peroxy linkages in a single macromolecular chain.The polyperoxide can be divided into acid polyperoxide and vinyl poleperoxide.Among the polyperoxide,the vinyl polyperoxide can often be used as solid fuels and initiator because of the unusual characteristics of their exothermic degradation,their autopyrolysis and their autoacceleration.Compared with the traditional initiators,the vinyl polyperoxide can not only initiate polymerization,but also synthesize polymers with special structures such as blocks and grafts.Usually,the vinyl polyperoxide can be formed by vinyl monomers and oxygen at low temperature and atmospheric pressure.The molecular weight and yield of the vinyl polyperoxide synthesized by the above method are very low,and the molecular weight is only 4000-5000,the yield is only about 10%.In addition,the initiation efficiency of the vinyl polyperoxide is extremely low at low temperature.Therefore,the vinyl polyperoxide has not been widely used as inititor.However,recent studies have shown that the vinyl polyperoxide may be a suitable high temperature initiator,which may have higher initiation efficiency at high temperature.And if the molecular weight of the vinyl polyperoxide is sufficiently large,a longer block copolymer can be synthesized by free radical polymerization with the vinyl polyperoxide as an inititor.According to the above idea,the synthetic method of high molecular weight poly(methyl methacrylate)peroxide,PMMAP,with methyl methacrylate as vinyl monomer and oxygen as a comonomer was firstly studied in this paper.After that,the initiating ability of different PMMAP samples was also studied.These apart,the structure and properties of the polymer obtained from the above polymerization were also investigated.Then the core-shell structure PMMA-b-PS block copolymer was prepared by in-situ polymerization of styrene with high molecular weight PMMAP as initiator in the selective solvent.Through the above discussion,the final conclusions of this work are drawn as follows:(1)High molecular weight poly(methyl methacrylate)peroxide can be synthesized by high temperature free radical polymerization in the absence of initiator.The molecular weight of PMMAP is between 1.78×104 and 6.35×104.The suitable synthetic temperature is from 120? to 140?,and the oxygen pressure is from 0.1MPa to 0.7MPa.(2)The high molecular weight PMMAP,formed at different conditions,can induce the high temperature free radical polymerization of methyl acrylate,hydroxyethyl acrylate and styrene at the temperature higher than 110?.And the polymerization rate gradually accelerated with increasing the polymerization temperature.The optimum temperature range for initiating the polymerization is from 120? to 150?.(3)The synthesis conditions,initial concentration and initiation temperature of PMMAP have an effect on the polymerization rate when PMMAP was used as initiator.At the same polymerization temperature,the higher the initial concentration and the initiation temperature are,the faster the polymerization rate and the higher the final reaction conversion.(4)The block copolymer with controllable block length can be prepared with poly(methyl methacrylate)as initiator.The ratio of the block copolymer was greater than 90wt%.The length of PMMA segments in block copolymers can be controlled by adjusting the molecular weight of PMMAP.The core-shell structure PMMA-b-PS block copolymer microspheres with particle size of 100 nm to 800 nm can be synthesized by in-situ self-assembly in a suitable solvent.