Preparation Of Soap-Free Emulsion By Semi-Continuous RAFT Polymerization-Induced Self-Assembly

The soap-free emulsion polymerization is a method without emulsifier or only using emulsifier at a critical micelle concentration?CMC?.Soap-free emulsions can produce clean polymer products that avoid the adverse effects of emulsifiers on polymer properties?such as electrical,optical,and water-resistant properties?,giving polymers more possibilities in terms of application.For example,antibacterial groups can be introduced into the polymer chains by chemical reaction to prepare an antibacterial latex.Reversible Addition-Fragmentation Chain Transfer?RAFT?polymerization belonging to“living”radical polymerization is a highly efficient and convenient method for the preparation of polymers with controllable molecular weights and pre-designed structures.It can be suitable for a wide range of monomers,work in moderate conditions and can be terminally functionalized.Polymerization-induced self-assembly?PISA?developed on the basis of“living”radical polymerization is an efficient method for the synthesis of amphiphilic block copolymer nanoparticles,which can be used in the preparation of soap-free emulsion.Moreover,RAFT polymerization is mostly used in the PISA process.Herein,a high solid content soap-free emulsion and another antibacterial,crosslinked soap-free emulsion were prepared by semi-continuous RAFT PISA process.Some fundamental work and conclusions are shown as follows.System I:Semi-continuous feeding method to prepare RAFT-controlled PISA soap-free emulsion.The water-soluble monomer,poly?ethylene glycol?monomethyl ether methacrylate?PEGMA?,was used to prepare poly?poly?ethylene glycol?monomethyl ether methacrylate??PPEGMA?in water mediated by 4-cyano-4?thiobenzoylthio?pentanoic acid?CTBCOOH?.The conversion of PEGMA was nearly up to 100%so that purification of PPEGMA was unnecessary and the polymer solution could be used directly as a macromolecular chain transfer agent in subsequent reaction.After the semi-continuous addition of the second monomer?oil-soluble methyl methacrylate?MMA??,RAFT polymerization was carried out to produce diblock linear copolymer,where polymer latexes formed by PISA process in situ in the aqueous solution.Moreover,a series of different solid content of stable latexes can be prepared by adjusting the feeding ratio.When the solid content was 10–50%,the latex size was about 20 nm and the highest solid content reached up to 60%.System II:Semi-continuous feeding method to prepare RAFT-controlled PISA cross-linked soap-free emulsion with antibacterial property.In order to prepare antimicrobial soap-free emulsion,we firstly conducted radical copolymerization to prepare soap-free emulsion using quaternary ammonium salt monomer?MAQAC₆?,oil-soluble monomer styrene?St?and a cross-linking agent,divinyl benzene?DVB?by batch way.Consequently,emulsion with good,antibacterial activity was obtained.On this basis,we still adopted the semi-continuous feeding method established in the system I to prepare a higher solid content of antibacterial,crosslinking soap-free emulsion.In this system,PDMAEMA was first prepared by solution polymerization using 2-cyanoprop-2-yl 1-dithionaphthalate?CPDN?as the RAFT agent and N,N-dimethylaminoethyl methacrylate?DMAEMA?as the monomer.MMA and cross-linker ethylene glycol dimethacrylate?EGDMA?were semi-continuously fed bearing the mechanism of PISA aqueous emulsion polymerization with PDMAEMA as the macro-RAFT agent at acidic condition.A stable cross-linked,soap-free emulsion was prepared,and the polymer was quaternized.Gram-negative bacteria were used as experimental strains to verify antimicrobial properties of polymer by plate coating method.