Pigment Encapsulation by Emulsion Polymerization Using Macro-RAFT Copolymers

Abstract

A new method is described, based on living amphipathic random macro-RAFT copolymers, which enables the efficient polymeric encapsulation of both inorganic and organic particulate materials via free-radical polymerization. The mechanism for this new approach is examined in the context of the polymer coating of zirconia- and alumina-coated titanium dioxide particles and its breadth of application demonstrated by the coating of organic phthalocyanine blue pigment particles. The particulate materials were first dispersed in water using a macro-RAFT copolymer as a stabilizer. Monomer and water-soluble initiator were then added to the system, and the monomer polymerized to form the coating. If nucleation of new polymer particles in the aqueous phase was to be avoided, it was found necessary to use a macro-RAFT copolymer that did not form micelles; within this constraint, a broad range of RAFT agents could be used. The macro-RAFT agents used in this work were found not to transfer competitively in the aqueous phase and therefore did not support growth of aqueous-phase polymer. Successful encapsulation of particles was demonstrated by TEM. The process described enables 100% of the particles to be encapsulated with greater than 95% of the polymer finishing up in the polymeric shells around the particles. Moreover, the coating reaction can be carried out at greater than 50% solids in many cases and avoids the agglomeration of particles during the coating step.

Living Radical Polymerization by the RAFT Process - A Second Update

“…In the case of bis-RAFT agents sequential polymerization of two monomers will yield a triblock. [269] BA [270] MA [270] NIPAM [269,[271][272][273] 420 [274] BA [281] DA [281] St [71,275] 2VP [276] NVP [103] NIPAM/274 [153] DEHEA [280] MA [281] TMAPMA/PEGMA/NIPAM [277] (PEGMA/320) [165] tBA [280] BA/AA [279] (PEGMA/344) [165] 331 [159] AEMA/325/328 [278] DEHEA-b-ODA [280] DMAM-b-331 [159] DMAM-b-331-b-NIPAM [159] DEHEA-b-tBA [280] NIPAM-b-DMAM [272] 2VP-b-EA [276] tBA-b-DEHEA [280] AEME/328/342 [278] 105 [282] [282] PEGA-b-St [282] 106 [188] [188] EHA-b-MA [188] S S S…”

“…St [72] VAc [389] VB [389] NVPI [220] VAc [391] VAc/VB [389] (NIPAM/369) [390] (Continued) [60] BA/AA [279] VAc [283] O S S 217* [381] 218 [392] O N 3 S S (NVCL) [384] (NVPI) [220] NVP [381] 366 [380] 367 [380] 368 [380] VAc [392] NVP-b-VAc [381] S O S O 219* OH 220 [169] …”

Synthetic and Physicochemical Aspects of Advanced Stimuli‐Responsive Polymers

“…Use of amphiphilic macro-RAFT agents in miniemulsion polymerization has been reported frequently. For example, RAFT-controlled/living ab initio emulsion polymerization by amphiphilic macro-RAFT self-assembly was reported [133] along with encapsulation of hydrophobic or hydrophilic pigments by emulsion polymerization using butyl acrylate/AAc random macro-RAFT copolymers [134]. In addition, poly(ethylene oxide) (PEO) macro-RAFT agent was used as both a stabilizer and a control agent in styrene polymerization in aqueous dispersed systems [135,136].…”

Surface protection of an organic pigment based on a modification using a mixed-micelle system

“…A number of methods have been developed to improve the dispersibility of organic pigments, such as surfactant adsorption [4][5][6][7][8][9], emulsion polymerization [10][11][12][13], polymer and copolymer surfactant adsorption [10,[14][15][16][17][18][19], the super fluid technique [20][21][22], or phase separation methods [23][24][25][26].…”