Preliminary Research Of Several Fractural Carbon-Carbon Bond Radical Initiators:Design, Synthesis And Application

As an important method for the synthesis of block copolymers, living anionic polymerization (LAP) is difficult to application for the synthesis of nonpolar-polar block copolymers due to its hard implementation of polar monomers. The active monomer species applied by each polymerization method are limited. A series of novel structure polymers can be prepared through combined different polymerization methods together. As classic and hot living polymerization methods, combination of anion living polymerization and controlled/living radical polymerization to prepare nonpolar-polar block copolymer is a good approach.Lithium-based synthetic rubbers and styrene-based thermoplastic elastomers are not only the major industrial products of anionic polymerization (AP), but also the largest output and fastest growing thermoplastic elastomers worldwide. Compared with polyurethane, polyester and polyamide thermoplastic elastomer, they have the advantages of low cost and wide application. However, their defects are the low ceiling using temperature and the poor polarity. This thesis intends to seek an easy and cost-effective approach to modify the polarity of styrene-based thermoplastic elastomers, which would enhance their oil resistivity in hydrocarbon solvents, compatibility and adhesion with polar material.In this thesis, we take full advantage of the painstaking research for many years in LAP area of our research group, learn from the core ideas of iniferter method, then combine the two different types of polymerization mechanism together to compensate the lacks of each single polymerization mechanism. According to this train of thought, we synthesize nonpolar-polar block copolymers. The main contents are as follows.An unsymmetrical triphenylethane compound, ethane-1,1,2-triyltribenzene (ETB), was successfully prepared. As a model compound and an initiator, its characteristics and possible initiation mechanisms of the thermal radical polymerization were researched. Then the molecule structure of ETB was introduced into the end of various polymer chains by means of anionic polymerization initiated by ETB-Li to obtain a series of homo-, di-block and tri-block macroinitiators. The characteristics of the thermal radical polymerization initiated by macroinitiators were also researched. It is found that ETB could produce two radicals with different structures when heated, the relatively stable diphenyl methyl radical and the lively benzyl radical. The molecular weight distribution of PMMA can be controlled at1.12to1.48. The polymerization process has certain controllability. GPC curves of polymers initiated by macroinitiator present two peaks. After extraction, GPC curves regress to unimodal, and the molecular weight distribution can be controlled at1.12to1.57.An unsymmetrical triphenylethane compound,2,2,3-triphenylpropanoic acid (TPPA), was successfully prepared. As a model compound and an initiator, its characteristics and possible initiation mechanism of the thermal radical polymerization were researched, such as initiation temperatures, molecular weight and the molecular weight distribution, monomer conversion, radical structures generated. It is found that TPPA could produce two radicals with different structures when heated, the relatively stable1-carboxy1-1,1-diphenyl methyl radical and the lively benzyl radical. The molecular weight distribution of PMMA can be controlled at1.10to1.34. The polymerization process has certain controllability.An unsymmetrical compound including allyl structure, but-3-ene-1,1-diyldibenzene (BEDB), was successfully prepared. As model compounds and initiators, their characteristics of the thermal radical polymerization were researched. Then the molecule structure of BEDB was introduced into the end of various polymer chains by means of anionic polymerization initiated by BEDB-Li to obtain a series of homo-, di-block and tri-block macroinitiators. The characteristics of the thermal radical polymerization initiated by macroinitiators were also researched. It is found that BEDB could produce two radicals with different structures when heated. The molecular weight distribution of PMMA initiated by BEDB is less than1.5. GPC curves of polymers initiated by macroinitiator present two peaks. After extraction, GPC curves regress to unimodal, and the molecular weight distribution can be controlled at1.50to2.70.Two kinds of sulfur functionalized initiators for living anionic polymerization,2-methyl-1,3-dithiane-2-lithium (MDTL) and2-phenyl-1,3-dithiane-2-lithium (PDTL), were prepared through the directly reactions between n-butyllithium and organic sulfur1,3-dithiane compounds. Two types of polymers including sulfur-containing functional groups at the end were obtained through the anionic polymerization initiated by MDTL and PDTL. The end groups of polymer chains may be prone to fracture of carbon-carbon bond and formation of carbon-center radical at an appropriate temperature due to the big size of functional groups. The characteristics of the thermal radical polymerization initiated by macroinitiators were also researched. The study found that MDT-PB macroinitiator can not initiate radical polymerization of MM A at75℃to120℃, but PDT-PB macroinitiator with low content of1,2-structure (about8%) can do that and the content of PMMA in copolymer could reach5.8%～21.8%.