화학공학소재연구정보센터
Macromolecules, Vol.51, No.4, 1260-1271, 2018
Synthesis of Various Poly(2-hydroxyethyl vinyl ether)-Stabilized Latex Particles via Surfactant-Free Emulsion Polymerization in Water
Following the recent success of the controlled radical polymerization of hydroxy-functional vinyl ethers [Macromolecules 2016, 49, 1563; 2017, 50, 8346], we report a surfactant-free, batch emulsion polymerization stabilized by the poly(hydroxy-functional vinyl ether)s. A series of emulsion polymerizations of various hydrophobic monomers such as vinyl acetate (VAc), methyl methacrylate (MMA), ethyl acrylate (EA), and styrene (St) were performed using poly(2-hydroxyethyl vinyl ether) (PHEVE) with hydrophilic azoinitiator, 2,2'-azobis(2-amidinopropane) dihydrochloride. In the emulsion polymerization in water using PHEVE as a steric stabilizer, the polymerization proceeded smoothly to form PHEVE-stabilized spherical particles without any coagulation. The mean particle diameter could be controlled over a size range (261 nm-ca. 1 mu m) with relatively narrow size distributions by varying the synthesis parameters. Furthermore, one-pot emulsion polymerization was also conducted from HEVE to poly(vinyl acetate) (PVAc) latex particles through PHEVE. However, in the case of other analogous stabilizers such as poly(4-hydroxybutyl vinyl ether) (PHBVE) and poly(2-metoxyethyl vinyl ether) (PMOVE) as a more hydrophobic stabilizer than PHEVE, highly stable latex particles were not formed, with the exception of PMOVE-stabilized PSt latex particles (micelles). The dispersing ability of PHEVE was further confirmed by RAFT emulsion polymerization of VAc. The RAFT emulsion polymerization of VAc using PHEVE macromolecular chain transfer (macro-CTA) proceeded in water to form PHEVE-b-PVAc latex particles with 71-293 nm size depending on degree of PVAc block. However, using binary mixed PHEVE and thermoresponsive PHBVE macro-CTAs, the resulting latex particles formed small aggregate of particles at 20 degrees C due to the decrease in stability and hydrophilicity relative to PHEVE. All the products using PHEVE successfully prepared are core-shell particles with PHEVE shells which give high dispersion stability for hydrophobic core. Such PHEVE-stabilized particles resulted in highly ordered three-dimensional colloidal crystals owing to the interaction of their hydrophilic PHEVE surfaces.