Synthesis of Polymer/Silica Hybrid Latexes by Surfactant-Free RAFT-Mediated Emulsion Polymerization

Abstract

The reversible addition−fragmentation chain transfer (RAFT) polymerization technique was used to synthesize random copolymers of poly(ethylene glycol) methyl ether acrylate) (PEGA) and n-butyl acrylate (BA) and terpolymers of acrylic acid (AA), PEGA and BA with a trithiocarbonate reactive end-group. These macromolecular RAFT agents (macro-RAFTs) were subsequently adsorbed at the surface of size-monodisperse colloidal silica particles with diameters varying between 40 and 450 nm. Adsorption isotherms for both macro-RAFTs could be well fitted to the Langmuir adsorption model, the AA-based macro-RAFT agent showing however a lower maximum adsorption. The adsorbed macro-RAFT agents were subsequently chain extended with a mixture of methyl methacrylate (MMA) and BA by starved feed emulsion polymerization. Cryo-TEM analysis of the resulting hybrid latexes synthesized in the presence of the P(AA-co-PEGAco-BA) terpolymers resulted in multipod-like particles while the P(PEGA-co-BA) copolymers showed the formation of individually and multiencapsulated silica particles depending on the silica particle size. Decreasing the total silica surface area available by decreasing the silica concentration or by increasing the silica particle size resulted in limited coagulation of the latex particles due to a less efficient use of the free nonadsorbing macro-RAFT agent. The feeding process also had a strong impact on particle morphology, and snowman-like particles could be successfully achieved under batch conditions. The use of commercial silica particles instead of homemade silica led to armored latexes illustrating the determinant role of the surface properties of the macro-RAFT-coated inorganic particles in controlling hybrid particle morphology. At last, core−shell particles with a rigid silica core and a soft copolymer shell were obtained for the first time by polymerizing a film-forming monomer mixture showing the high potential of the P(PEGA-co-BA) macro-RAFT agent for the elaboration of polymer-encapsulated silica particles for coating applications.

A Comparative Study of Chemical Routes for Coating Gold Nanoparticles via Controlled RAFT Emulsion Polymerization

“…Taking advantage of the amphiphilic character of the MR agent, which in this case can act as surfactant, the RAFT emulsion polymerization of the mixture of hydrophobic monomers (MMA:BA 10:1 w/w) was carried out from the surfaces of MR@Au NPs. The amount of initiator used in these experiments was estimated by following procedures reported for similar situations . Therefore adsorption studies were carried out to obtain the amount of MR agent adsorbed (0.4 mmol L –1 ) and then, the [MR]/[I] ratio was set at 2.8, which guarantees a polymerization under RAFT conditions.…”

Polymer-encapsulation of iron oxide clusters using macroRAFT block copolymers as stabilizers: tuning of the particle morphology and surface functionalization

“…The adsorbed macroRAFT agents not only encourage the polymerization to take place at the inorganic surface but also contribute to the stabilization of the resulting composite particles. This approach was first reported by the group of Hawkett for the encapsulation of titanium dioxide pigments 39 and gibbsite clay platelets, 40 and subsequently used by our group with success for the encapsulation of a large variety of inorganic particles such as cerium dioxide, 41 silica, 42 layered double hydroxides [43][44][45] and montmorillonite clay platelets. 46 REEP was also recently successfully used for the preparation of magnetic latex particles (MLPs) using poly(acrylic acid) (PAA)-based macroRAFT agents.…”

The morphology of poly(terminal vinyl dimethicone-co-methyl methacrylate-co-n-butyl acrylate)/pigment composite film and its application in pigment printing of polyester fabric

“…To overcome the above mentioned defects, encapsulation of organic pigment particles by an adhesive polymeric shell was regarded as one of the most effective methods. To date, encapsulation of organic pigment via emulsion polymerization, [13][14][15][16][17] miniemulsion polymerization [18][19][20][21] and suspension polymerization [22][23][24] has been reported by many researchers. It was found that the pigment dispersibility in the polymer lm was signicantly improved aer encapsulation.…”