Characteristics in Copolymerization of Amine/Alkoxysilyl 1,1’-diphenylethylene(DPE)Derivatives Via Living Anionic Polymerization
Author:Liu Zuo Bo
Supervisor:li yang ma hong wei
The performance of polymer is determined by the interaction of their multi-level structures.Enrichment of the regulation method has become a way for preparing high-performance polymers.At present,there are many research reporting on the molecular weight,unit composition and topological structure of polymers,besides the sequential structure regulation of polymer monomers has gradually begun to attract attention.Therefore,it is of great theoretical and practical significance to develop novel sequence regulation methods and polymerization mechanisms.In living anionic polymerization,1,1-diphenylethylene(DPE)derivatives cannot self-polymerize and only can be copolymerized with other monomers.Hence,functional groups could be introduced into polymer chains clearly "qualitatively",accurately"quantitatively" and accurately "localized" via DPE derivatives.Taking advantage of DPE derivatives,sequence-controllable polymers can be conveniently and quickly prepared,which has become one of the current research hotspots in the field of living anionic polymerization.However,there are still some problems in the copolymerization of functionalized DPE derivatives possessing heteroatoms in living anionic polymerization,such as the lack of sequence-controlled methods and unclear polymerization mechanism.In order to solve the problems above,this study focused on a series of copolymerization of DPE derivatives possessing amine or alkoxysilyl groups via living anionic copolymerization,which established a method for regulating the statistical sequence distribution of polymers by regulators,and proposed a quantitative "locked-unlocked" mechanism via 1-[4-(triisopropoxysilyl)phenyl]-1’-phenylethylene(DPE-Si(OiPr)3),and then a series of end/in-chain amine functionalized styrene-butadiene rubbers were prepared.The main results are as follows:(1)The statistical sequence distribution of copolymers with 1-[4-(dimethylaminophenyl)]-1’-phenylethylene(DPE-NMe2)and styrene(St)at a feed ratio of 1/1 was regulated by two different regulators,tetrahydrofuran(THF)and sodium 2,3-dimethyl-3-pentanol(NaODP).The results of time sampling method showed that the rst of styrene to DPE-NMe2 under the action of THF(THF/Li=10),NaODP(NaODP/Li=2)and without a regulator,was 6.9,29.8 and 9.1 respectively.Kinetic analysis showed that the apparent copolymerization constants of DPE-NMe2 were KDPE-NMe2-THF<KDPE-NMe2-Neat<KDPE-NMe2-NaODP.By using the two different regulators,the distribution of DPE-NMe2 unit in polymer chains is efficiently and conveniently controlled,and a method of regulating sequence structure based on active anionic polymerization is established.(2)Firstly,three novel DPE derivatives possessing alkoxysilyl groups,1-[4-(dimethylethoxysilyl)phenyl]-1’-phenylethylene(DPE-Si(OEt)Me2),1-[4-(triethoxysilyl)-phenyl]-1-phenylethylene(DPE-Si(OEt)3)and 1-[4-(triisopropoxysilyl)phenyl]-1 ’-phenyl-ethylene(DPE-Si(OiPr)3)were prepared.And then by kinetic and substituent resistance control methods,the side reactions between alkoxysilyl groups and living reactive center were inhibited.Secondly,quantitative "locked-unlocked" mechanism via DPE-Si(OiPr)3 and NaODP regulator in living anionic polymerization was also studied.Based on the data of MALDI-TOF-MS characterization,it is confirmed that DPE-Si(OiPr)3 can quantitatively lock the anionic living center,and then NaODP can enable the partially closed active center unlocked and then re-participate in copolymerization.(3)In situ NMR was used to study the reaction kinetics behaviour of the end-capped reaction between the three amine functionalized DPE derivatives,1,1’-bis[(dimethylaminophenyl)]ethylene(DPE-(NMe2)2),1-[4-(dimethylaminopheny1-)]-1’phenylethylene(DPE-NMe2)and 1-[4-(dimethylsilyl)phenyl)]-l’-[4-(dimethylaminophenyl)]ethylene(DPE-SiH/NMe2),and living anionic center.The kinetic constants(kSD)of the end-capping reaction between three monomers and PS-Li were 0.155,1.26 and 6.24 L1/2 mol-1/2 s-1,respectively.Furthermore,DPE-(NMe2)2 was used to synthesize end-chain amine-functionalized styrene-butadiene rubber(SSBR)and DPE-NMe2 was used to prepare in-chain amine functionalized SSBR.The composition of DPE-NMe2 unit and the vinyl structural unit was controlled between 4.8%～16.4%and between 40.8%～67.3%respectively.The dispersion of silica in rubber matrix can be effectively improved by end/in-chain amine-functionalized soluble styrene-butadiene rubber.The amine functionalized SSBR not only meet the requirements of the green tire but also improve the rolling resistance by 7%.