Morphology development of 10-?m scale polymer particles prepared by SPG emulsification and suspension polymerization

Abstract

Classicalparticle morphologies, core‐shell, hemisphere, sandwich, and so on, were all reproducible by starting from ca. 10‐μm uniform droplets composed of monomers, initiator, solvents, and polymer, and polymerizing them by subsequent suspension polymerization. SPG (Shirasu porous glass) membrane was employed to form uniform size droplets having the coefficient of variation (CV) around 10%. Styrene (ST) and acrylic monomers were used as monomers, and their polymers were dissolved in the droplets to investigate the development of phase separation. When hydrophilic methyl methacrylate (MMA) was polymerized in the droplets with a mixed solvent consisting of hydrophilic hexanol (HA) and hydrophobic benzene and hexadecane (HD), the resulting morphology shifted from hemisphere to sandwich and eventually to PMMA/solvent core‐shell with increasing hydrophilicity of the mixed solvent. The sandwich was converted to the core‐shell after several weeks elapsed. As styrene was added to MMA, the morphology shifted from hemisphere core/solvent shell to raspberry core/solvent shell as the fraction of ST increased. The domain of the mixed solvent in the raspberry core was reduced with increasing the hydrophilicity of the mixed solvent. All these morphologies were eventually converted to the copolymer core/solvent shell. When a mixed monomer of styrene and MMA dissolving polystyrene (PS) was polymerized, the resulting morphology shifted from salami to core‐shell with increasing the MMA fraction in the comonomer. The salami particles were then swollen with toluene, and after the swelling, toluene was removed under the different temperature and pressure. The final particle morphology converted to the core‐shell with a milder rate of toluene removal which was predicted from the thermodynamic model. When styrene and cyclohexyl acrylate (CHA), a pair with widely different reactivity ratios, were copolymerized, salami morphologies, with tiny CHA‐rich domains dispersed in the matrix, were obtained even at a higher fraction of CHA in comonomer. Effects of glass transition temperature of the polymers, molecular weight, and the composition of copolymers were taken in consideration whenever the final morphologies were discussed. By these experiments, the authors tried to demonstrate an advantage of using large uniform spheres for the particle morphology studies. SPG emulsification technique was a potential tool because of its free formulation of the droplets, and the subsequent polymerization could undergo without the breakup or coalescence of the droplets. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2200–2220, 2001

About morphology in ethylene–propylene(-diene) copolymers-based latexes

“…Morphology predictions Two-stage emulsion polymerization produces heterogeneous structures such as core-shell [26,27], 'inverted' core-shell [28,29] and phase-separated structures. Phaseseparated morphologies include 'sandwich-like' [30], 'snowman-like' [31], 'salami-like' [32], and 'raspberrylike' [33] particles, as exemplified in Fig. 5.…”

Synthesis of spike‐ball‐like polystyrene/poly(methyl methacrylate) composite particles via seeded polymerization

“…However, when the temperature of the system rises, Δ G m,p > 0 causes the monomer to be expelled from the PS particles/cores and PS/PMMA core(salami)/shell polymer particles are created. It should be noted that swollen shells are tacky and there might be some adhesion between some of the particles after the swelling by the monomer On increasing the temperature polymerization begins concomitantly in both the medium and the PS particles.…”

Core-shell poly(d,l-lactide-co-glycolide)/poly(ethyl 2-cyanoacrylate) microparticles with doxorubicin to reduce initial burst release

“…The size of emulsion that permeated through the SPG membrane was generally approximately 3~6 times membrane pore size. 27 However, the size of emulsion was gradually reduced when the volatile solvent was used. The coreshell structure was attributed to the interfacial polymerization of E2CA and the difference of hydrophobicity between the two polymers.…”