Organic fillers by anionic dispersion polymerization

Abstract

Styrene-dMnylbenzene mixtures were anionically polymerized in the presence of block polymeric dispersing agents in aliphatic hydrocarbons. Cross-linked fine particles with sizes as small as several hundred angstroms could be readily prepared by this technique. By suitable control of reaction variables, either isolated particles or structured agglomerates were formed. The latter agglomerates were efficient thickeners for hydrocarbon liquids and appeared to maintain their integrity even under high shear conditions. The living nature of the anionic polymerization permitted the introduction of various functional groups on the polymer chain ends In the particle. This functionality was useful in modifying the properties of the particles. For example, colored pigments, water dispersible materials, and highly reinforcing fillers for SBR rubber were produced by the appropriate choice of functionality.

Dispersion polymerization in non-polar solvent: Evolution toward emerging applications

“…The ineffectiveness of Stereon 840A was due to (i) the triblock configuration causing entropic strain on the particle surface, (ii) the small polybutadiene block producing a thin steric layer and (iii) the tendency of adsorption of shorter stabilizer chains due to the broad molecular weight distribution of Stereon 840A. Murray and Schwab made a similar observation with the triblock copolymer, 'Kraton' rubber, which was showed to be less effective than a diblock stabilizer [80].…”

“…The particles can be redispersed if required. In some cases, 5 wt% paraffin wax has also been added to improve redispersion of cross-linked polystyrene particles [80].…”

“…This in turn contributes to the particle size and polydispersity. The polymeric stabilizer can either be preformed prior to particle synthesis, or made in situ via anionic polymerization with a polymeric organolithium compound [80].…”

“…Over a decade on, Murray and Schwab produced cross-linked polystyrene particles (50 -150 nm) in hexane [80].…”

“…This was due to higher initiation and polymerization rates [80,83], thus producing lower molecular weight chains. Together with a decrease in medium solvency, this encouraged more chain aggregation, producing larger particles at lower count.…”