Dispersion polymerization of styrene in polar solvents. IV. Solvency control of particle size from hydroxypropyl cellulose stabilized polymerizations

Abstract

SynopsisChanging solvent has a dramatic effect on the outcome of HPC stabilized dispersion polymerization of styrene in polar solvents. In methoxyethanol/ethanol mixtures, particle size varies from essentially infinity for unstabilized reactions (below 30% ethanol) to about 3 microns in ethanol. In a series of n-alcohols, there was a maximum in particle size at intermediate chain length particle size increased from 2 microns in methanol to 8.3 microns in pentanol, then decreased again to 1 micron in octadecanol. These results were rationalized in terms of the three-component Hansen solubility parameters. The largest particles were obtained in solvents with Hansen polarity and hydrogen bonding terms closest to HPC. The generality of the three-component solubility parameter approach was examined by reactions performed in eight mixed solvents with the same values of all three Hansen terms. Seven of the eight solvents gave particles of similar size and molecular weight. The two critical effects of solvent on both particle size and molecular weight appear to be: ( a ) the solubility properties of the grafted HPC-PS formed, and ( b ) the partitioning of monomer and initiator between solution and particle phases subsequent to nucleation.

Dispersion polymerization of acrylamide: Part II. 2,2?-Azobisisobutyronitrile initiator

“…28,29 The molecular weight increases but with a gradually reduced rate as the conversion increases. These results suggest that the gel effect (the so called solid phase polymerization) [5][6][7] is operative.…”

Graft copolymers having hydrophobic backbone and hydrophilic branches. XXIII. Particle size control of poly(ethylene glycol)-coated polystyrene nanoparticles prepared by macromonomer method

“…Larger particles were synthesized using DMF/water mixtures. Paine 35 and Baines et al 36 observed that the particles in ethanol compared to those in methanol in dispersion polymerization of St with poly(vinylpyrrolidone) or poly(2-dimethylamino) ethyl methacrylate-b-methyl methacrylate as a stabilizer were larger. Ober et al 34 noted that particle size could be broadly correlated with the solubility parameter of the initial polymerization mixture, though quantitative correlations between different solvent types could not be observed.…”

Dispersion polymerization of n‐butyl acrylate

“…7 During the past 15 years, there has been a considerable interest in generalizing these results to more polar solvents as the continuous phase, by which the range of monomers that can be polymerized using this method have been greatly expanded. Hydroxypropyl cellulose (HPC), 23 poly(acrylic acid) (PAA), 24 and polyvinylpyrrolidone (PVP) 10,11,25 are the most frequently used stabilizers in polar media. The relative extent of the interaction between the reaction medium, the stabilizer, and the polymer that is being produced is considered to be one of the key factors that controls the final particle size.…”