Inhibiting the Thermal Gelation of Copolymer Stabilized Nonaqueous Dispersions and the Synthesis of Full Color PMMA Particles

Abstract

Polymeric particle dispersions have numerous potential applications; currently one of the most relevant is their use as inks in electrophoretic displays. These colloidal particles are synthesized from the appropriate monomer using nonaqueous dispersion (NAD) polymerization in a nonpolar solvent, which requires a stabilizer to control particle size and morphology. We have previously reported the facile synthesis of poly(methyl methacrylate)-block-poly(octadecyl acrylate) (PMMA-b-PODA) by atom transfer radical polymerization (ATRP), and its use in the NAD polymerization of MMA in hexane/dodecane solvent mixtures. Here we report the synthesis of monodisperse PMMA particles in dodecane following a standard "industrial" procedure using these PMMA-b-PODA stabilizers. However, it was observed that the particle suspensions solidified when they were left at temperatures below ∼18 °C yet redispersed upon being heated. Differential scanning calorimetry, dynamic light scattering, and rheological studies demonstrated that this thermoresponsive behavior was due to a liquid-gel transition occurring at 17.5 °C as a consequence of the upper critical solution temperature of PODA in dodecane being traversed. Consequently, new copolymers were synthesized by ATRP with an ethylhexyl acrylate (EHA) co-monomer incorporated into the lyophilic (dodecane compatible) block. Dispersions stabilized by these PMMA-b-P(ODA-co-EHA) polymers with high EHA contents exhibited lower gelation temperatures because of the greater solvent compatibility with dodecane. The use of a PMMA65-b-(ODA10-co-EHA45) copolymer stabilizer (with the highest EHA content) gave PMMA dispersions that showed no gelation down to 4 °C and monodisperse cross-linked PMMA particles containing organic dyes (cyan, magenta, red, and black) giving colored particles across the size range of approximately 100-1300 nm.

Exploring the Upper Size Limit for Sterically Stabilized Diblock Copolymer Nanoparticles Prepared by Polymerization-Induced Self-Assembly in Non-Polar Media

“…Moreover, there is a strong correlation between the target DP of the PBzMA block and the mean particle diameter, which means that a desired particle size can be readily obtained. Given their ease of synthesis, such sterically stabilized nanoparticles are expected to be used as model systems for fundamental studies in the field of colloid and interface science, , as well as potential commercial applications. − …”

The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents

“…Poly(methyl methacrylate) (PMMA) latexes, originally developed through an industrial-academic collaboration between the University of Bristol and ICI [22,23], have proved an essential tool for colloid scientists to develop new technologies and study fundamental interactions in nonpolar media. These PMMA latexes are typically sterically-stabilized with poly(12-hydroxystearic acid) (PHSA) brushes, although there is active research into developing other effective steric stabilizers [8,[24][25][26][27][28]. They are generally dispersed in either n-alkanes or in mixed solvents to achieve density or refractive index matching (typically decalin and either brominated cycloalkanes or carbon disulfide) [29][30][31][32][33][34].…”

Polymerization and Applications of Poly(methyl methacrylate)–Graphene Oxide Nanocomposites: A Review

“…20,78,79 At room temperature to the boiling point of the solvent, PMMA is miscible with toluene even at normal pressure. 80,81 Application of PMMA-GO. Bone Cement.…”