| Recently,depending on the superiorities in controlling the propagation states of the polymerization,the switchable polymerization(SP)has been widely used in the preparation of functional and sequence defined polymers and modulating the polydispersity.However,because of the harsh conditions such as the catalysts with complex structures,the scarce monomers and the severe reaction environments,the usage of SP was fairly restricted.Moreover,the current studies for SP are mainly conducted on all the species in the system,but few publications were reported about the quantitative regulation on the“ON-OFF”state of the living chains.In this paper,based on the quantitative“Locked-Unlocked”phenomenon of 1-(triisopropoxymethylsilylphenyl)-1-phenylethylene(DPE-Si(OiPr)3)to the living species in the anionic copolymerization,the investigation on the features and applications of this kind of polymerization reaction are carried out and the results are as follows:(1)By changing the feeding ratio of DPE-Si(OiPr)3,the unlocking reactions at 50%and100%end-capped were studied.The chain growth process after unlocking was controlled by the kinetics,and when only styrene(St)was added,just moiety completed chain growth reaction.Otherwise,when the mixture of St and DPE was added,all the unlocking species completed chain propagation.The alkality of alkali metal alkaxide has an important influence on the unlocking efficiency.According to the experimental results,the unlocking efficiency of the three alkalis is t-Bu OLi<Na ODP<t-Bu OK,indicating that the stronger the alkality is,the better the unlocking efficiency is.On the other hand,the unlocking process is irreversible because the alkaxides cannot be extracted after it was added.(2)Because of the characteristic that DPE-Si(OiPr)3 monomer can quantitatively lock the living species in anionic polymerization,the living chains could be end-capped step by step with DPE-Si(OiPr)3 gradually added to the polymerization process of styrene.By adjusting the end-capping strategy,theDof the unimodal polystyrene(PS)can be regulated in the range of1.08–1.39.The symmetry of the curves and the number of peaks can be regulated in the range of 1–4.Moreover,the living polystyrene chains with broad distribution were unlocked and completed chain growth.Further combined with hydrosilylation reaction,the copolymer materials(narrow distribution)NP-PS-b-PSD-g-(PIp)n,(broad distribution)BP-PS-b-PSD-g-(PIp)n,(multimodal distribution)MP-PS-b-PSD-g-(PIp)n were obtained.By researching the thermodynamic properties,it's found that the elastic modulus NP>BP>MP.In addition,because the high tan?of MP-PS-b-PSD-g-(PIp)n is in a large temperature range,so this polymer may has a lot of prospects in damping materials.(3)By means of the coupling properties of DPE-Si(OiPr)3 and the efficient Ugi reaction of primary amine groups,the results of surface modification of nano-silica are as follows:DNPSDSi O was firstly grafted onto the surface of nano-substrate by“grafting onto”method.The grafting density of polymer brush can be adjusted at the range of 1.92-0.087 chains nm-2 by changing the molecular weight of the brush chains.Furthermore,the Ugi-4CR reaction was then introduced into this reaction system using the amino groups.By changing the molecular weight and feed ratio of PS-CHO(increasing the molecular weight,the reaction efficiency decreased,increasing the feeding,the efficiency also increased),the monomodal/bimodal polymer brush materials were synthesized,and the structure of the polymers grafted to the nanoparticles was precisely designed. |
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