Controlled Radical Polymerization And Properties Of Amphiphilic Block Polymers

The study of controlled radical polymerization methods and the structure and properties of amphiphilic block copolymers are the hot issues in the field of polymer science in recent years.On the other hand,with the rapid development and high performance of waterborne coatings,adhesives and inks,amphiphilic block copolymer has attracted increasing attention in the field of aqueous dispersants because of their special properties.However,there are few systematic studies on the relationship between the structural properties of the block polymer and dispersion effects.In this paper,a series of AB-type and ABA-type amphiphilic block polymers were synthesized by RAFT polymerization and photo-iniferter polymerization,and used as waterborne dispersants,and the relationship between the structure of amphiphilic block copolymers and the dispersion effect of inorganic powders in water were systematically studied.This result has important reference for the structural design of amphiphilic block copolymer dispersants.The main research contents of this paper are as follows:Two trithioester RAFT chain transfer agents were synthesized which contain double leaving groups and single leaving group,respectively.Solution polymerization was carried out using dioxane as the solvent under thermally initiated conditions,polyacrylic acid(PAA)homopolymers and AB type diblock polymers with PAA as A block were prepared by the use of the chain transfer agent containing a single leaving group;PAA homopolymers and ABA triblock polymers with PAA as A block were prepared by the use of the chain transfer agent containing double leaving groups,the B block hydrophobic monomer can be selected from fluorocarbon trifluoroethyl acrylate(TFEA),hexafluorobutyl acrylate(HFBA)and hydrocarbon monomer butyl acrylate(BA),ethyl acrylate(EA).The results showed that the synthesized AB-type and ABA-type block polymers had controllable molecular weights and a narrow molecular weight distribution(PDI less than1.60),and the lengths of hydrophilic and hydrophobic blocks within a certain range could be regulated.The monomer conversion can reach more than 70%.2.We use the trithioester synthesized above as a starting material to synthesize a trithioester iniferter and introduce the optically controlled iniferter reaction into the synthesis of amphiphilic block copolymer.We used dioxane as solvent,with the trithioester TTC as the iniferter,10-phenylphenothiazine as the catalyst,and ascorbic acid as the oxygen quencher added to the system and the reaction was completed in an air atmosphere,we succeeded in photo-iniferter polymerization with highly polar AA monomer to obtain PAA macro-iniferter.The dioxane/water mixed solution was used as solvent,and the synthesized PAA homopolymer with the trithioester end group was used as macro-iniferter,in-situ chain extension is performed using different hydrophobic monomers to obtain various amphiphilic triblock copolymers.The GPC and Monomer conversion conversion results show that these polymerization processes conform to the characteristics of controlled/living radical polymerization.Compared with solution polymerization process,emulsion polymerization reactions have faster rate and higher monomer conversion,therefore it is an effective method for the synthesis of amphiphilic block polymers.3.We characterized the surface tension of aqueous solutions of seven ABA or AB block copolymers with the same length of hydrophilic and hydrophobic blocks,and the effects of block composition and structure on the critical micelle concentration and aqueous surface tension were discussed.The synthesized ABA and AB amphiphilic block polymer were used as dispersants,the random copolymer was used as a comparison,to study the effect of polymer dispersant concentration and structure on the dispersion and stability of the system,and the applicability of ABA amphiphilic copolymer dispersants to different filler systems was discussed.The results showed that there is an optimal dispersant concentration in the dispersion system,when the dispersant dosage is at the optimal concentration,the suspension system has the best dispersion stability.When the hydrophilic block of the polymer is 100 units and the hydrophobic block is 50 units,the dispersing effect and stability of the suspension are the best.Compared with the AB diblock copolymers and random copolymers,the dispersions obtained with ABA triblock copolymers as dispersion stabilizers have smaller particle sizes or higher stability.