Synthesis of Various Poly(2-hydroxyethyl vinyl ether)-Stabilized Latex Particles via Surfactant-Free Emulsion Polymerization in Water

Abstract

Following the recent success of the controlled radical polymerization of hydroxy-functional vinyl ethers [Macromolecules 2016[Macromolecules , 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 μm) 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 °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.

Controlled Radical Homopolymerization of Representative Cationically Polymerizable Vinyl Ethers

“…The use of CTA 1 as a RAFT agent is known to provide good control and little or no retardation of the RAFT radical homopolymerizations of hydroxy-functional VEs. ,, Thus, polymerization using either CTA 1 or 2 in which the radical-generating site is dissolved in the organic phase of VE was conducted. Figure shows the polymerization results using CTA 1 (and Figure S14 for CTA 2 ).…”

Silica nanoparticle-loaded thermoresponsive block copolymer vesicles: a new post-polymerization encapsulation strategy and thermally triggered release

“…[31][32][33][34][35][36] Such amphiphilic diblock copolymers can be conveniently prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization. [37][38][39][40][41][42][43] It is well-known that PISA syntheses based on RAFT aqueous emulsion polymerization oen lead to kinetically-trapped spheres. 15,34,44,45 There are various strategies that enable this morphological constraint to be overcome [46][47][48][49][50] but the resulting worms or vesicles normally do not exhibit thermoresponsive character.…”

“…31–36 Such amphiphilic diblock copolymers can be conveniently prepared using reversible addition–fragmentation chain transfer (RAFT) polymerization. 37–43…”

Radical homopolymerization of vinyl ethers activated by Li+-π complexation in the presence of CH3OLi and LiI

“…It is not strange that, aside from the studies on cationic living polymerization of vinyl ethers, there have been a few attempts to realize radical polymerization of non-radically polymerizable vinyl monomers through stabilizing the radical species. [4][5][6][34][35][36] Sugihara et al 4,5 first realized the radical homopolymerization of hydroxyl-functional vinyl ethers with the aid of hydrogen bonds between the oxygen atom and hydroxyl of the vinyl ether monomer, which effectively reduces the reactivity of growing chain radicals and inhibits side reactions such as β-scission. Then, they performed aqueous phase radical suspension polymerization of alkyl vinyl ethers with LiOH as a complexing agent (Li + ).…”

“…RAFT polymerization of vinyl ethers using a switchable chain transfer agent has also been realized. 15,35,[39][40][41] So far, the radical polymerization of vinyl ethers has been mainly limited to monomers miscible in LiOH or vinyl ethers bearing a hydroxyl group which could form hydrogen bonds with the solvent. Recently, with CH 3 OLi as a complexing agent, we realized the surface graft-polymerization of vinyl ether onto various substrates using benzophenone as a photoinitiator.…”