Synthesis,Cyclization And Properties Of Phenyl-containing Diene Polymers

Polymers possessing rigid cyclic repeating units in the main chain have been attracting attention due to their excellent heat resistence,mechanical properties,and chemical stability.Among them,such polymers lacking polar heteroatoms can have a low dielectric constant and nonhygroscopicity and frequently exhibit favorable transparency,which make them attractive materials,especially in the extreme environment and optoelectronic field.The cationic cyclization modification of diene-polymers can avoid the use of cyclic monomers,as compared with the polymerization of cyclic monomers for preparation of hydrocarbon polymers possessing cyclic units in the main chain from cyclic monomers.The cost of cyclic monomers is usually high,and polymerization of these monomers is always accompanied by side reactions.Therefore,this post-modification method not only can avoid the above disadvantages,but also can utilize the designability of the cyclized precursor polymer to achieve high-performance polymer preparation and synthesis of various complex topological macromolecules.In this thesis,four 1,3-diene/diphenylethylene alternating copolymers and two poly(pheny 1-1,3-butadiene)polymers were designed and synthesized as precursor polymers for cationic cyclization.After cyclization,a series of high temperature hydrocarbon polymers were prepared.Based on the long sequence of hydrogenated acene structure of the cyclized polymer backbone,high carbon-yielding polymers were prepared through further dehydrogenation of cyclized polymers.At the same time,the inimer monomer with weak bond structure was introduced into the design and synthesis of precursor polymer for cationic cyclization.After cyclization,rigid macroinitiator with weak bond structure in the side group was prepared.Using this macroinitiator,two complex topological graft polymers with rigid backbone were designed and synthesized.Follows are mian results:1.Design and synthesis of phenyldiene polymers followed by cationic cyclization for high temperature hydrocarbon polymers.Based on the structure design of cyclized polymer backbone,four alternating copolymers(a-PBD,a-PBTs,a-PID,a-PITs)of butadiene(Bd)/isoprene(Ip)and 1,1-diphenylethylene(DPE)/trans 11,2-diphenylethylene(Ts)and poly(1-phenyl-1,3-butadiene)(P(1-PB))with different microstructures were designed and synthesized as precursor polymers for cationic cyclization.Using CF3SO3H as the catalyst,these precursors all can be completely cyclized without intermolecular linking occurred.The glass transition temperature(Tg)of cyclized product of alternating copolymer reached 200℃.The Tg of cyclized P(1-PB)increased substantially from 200 to 304℃ as the 3,4-structure content of its prepolymer increased,and the Tg of high temperature hydrocarbon polymer was firstly exceeded 300℃.Through cyclized results of various precursor polymers,it is proved that the key to preparation of high-Tg hydrocarbon polymer by cationic cyclization is the design of the chain regularity of precursor polymer.To prepare high-Tg hydrocarbon polymer,the design of the precursor polymer chain should follow the rule of minimizing spacer carbons between cyclic repeating units of cyclized polymer backbone.Finally,a structure model of rigid hydrocarbon polymer backbone containing cyclic repeating units is proposed.Using this structure model,based on the position design of pendant substituent group of cyclized polymer,poly(2-phenyl-1,3-butadiene)(P(2-PB))with different microstructures were designed and synthesized as precursor polymers.The Tg of cyclized product of highly 3,4-regulated(96.2%)P(2-PB)reached 325℃,and the hydrocarbon polymer with the highest Tg value was successfully prepared.It indicates that the Tg of cyclized polymer also can be increased by using its pendant substituent group to limit the backbone motion.In addition,the thermal stability of precursor polymer was obviously improved after cyclization modification.2.High carbon-yielding polymers were prepared through cyclization and dehydrogenation of poly(1-phenyl-1,3-butadiene).The dehydrogenation of P(1-PB)and its cyclized product CP(l-PB)were preformed using 2,3-dicyano-5,6-dichlorobenzoquinone(DDQ)at 100℃.The dehydrogenated product of P(l-PB)(TP(1-PB))and the dehydrogenated product of CP(1-PB)(TCP(1-PB))have high carbon yielding(carbon yield>60%)at 1000℃,and the highest carbon yield can reach 70%.Further research shows that the carbon yield of TCP(1-PB)decreases with the increase of the 3,4-structure content of P(1-PB),while the carbon yield of TP(1-PB)is not affected.When the microstructure of P(l-PB)was the same,the degree of graphitization of the carbon materials prepared from the corresponding TP(1-PB)and TCP(1-PB)increases with the increase of the carbonization temperature,and all the carbon materials were disordered carbon and involved turbostratic structure.When the carbonization temperature was the same,the microstructure of P(1-PB)had no obvious effect on the degree of graphitization of the carbon materials prepared from these dehydrogenated products.In addition,porous carbon material with uniform pore distribution was prepared from the direct dehydrogenation of P(1-PB)route.It is considered that this is due to the pore structure caused by the gelation phenomenon during this dehydrogenation process.3.Design and synthesis of rigid polymer with C-C weak bond in the side group and its application to graft polymer.Based on the design of the cyclized polymer backbone structure,altermating copolymers(a-PCS)of 1,3-cyclohexadiene(CHD)and styrene(St)with different compositions were designed and synthesized through anionic copolymerization as precursor polymers for cationic cyclization.Using CF3SO3H as the catalyst,the rigid polymer cPCS was obtained after cyclization.A styrene derivative p-(2,2,2-triphenylethyl)styrene(TPES)containing weak bond structure instead of St was selected to copolymerize with CHD,and random copolymer(r-PCT)with different compositions were designed and synthesized.Using CF3SO3H as the catalyst,the rigid polymer cPCT with C-C weak bond in the side group was prepared afiter cyclization.The TGA curves showed that the introduction of C-C weak bond lead to the two-step decomposition of cPCT,which is different from the one-step decomposition of cPCS.The initial decomposition temperature and 5%weight-loss temperature(Td5)of cPCT samples were obvious lower than those of cPCS samples,and the Td5 values of cPCT samples were around 336℃.The calculation based on the TGA data of cPCT samples confirmed that their first decomposition step resulted from the evaporation of triphenylmethane,which was attributed to the cleavage of C-C weak bond in the side group.These results confirmed that the rigid macroinitiator cPCT with weak bond structure in the side group can be prepared by introducing TPES instead of St to copolymerize with CHD followed by cationic cyclization modification.The radical polymerization of methyl methacrylate(MMA)was preformed in the presence of macroinitiator cPCT at high temperature,and a Rod-g-Coil brush polymer cPCT-g-PMMA was prepared through grafting from method.Hypergrafted PTPES with a rigid backbone was synthesized through self-condensing vinyl polymerization of TPES in the presence of macroinitiator cPCT.