Preparation and characterization of polystyrene and styrene-butyl acrylate copolymer latices

Abstract

Emulsion polymerization of styrene (S) and emulsion copolymerization of styrene with butyl acrylate (BuA) using potassium persulfate (KPS)/different aromatic aldehydic sodium bisulfite adducts as developed redox pair initiation systems were investigated at variable initiator, emulsifier concentrations and feed monomer compositions for studying the morphological characteristics of the obtained latices. It was found that the developed redox pair initiation system increased the number of polymer particles per unit volume of water ( Nt) more than the classical system. Also, N t , decreased with increasing initiator concentration, but increased with increasing emulsifier concentration for both the classical and developed ones. The volume-average particle diameter D ̄ v was found to be dependent on the different redox initiators: potassium persulfate/methylbenzaldehyde sodium bisulfite (KPS/MeBSBS), potassium persulfate/chlorobenzaldehyde sodium bisulfite (KPS/CBSBS), potassium persulfate/methoxybenzaldehyde sodium bisulfite (KPS/MBSBS), potassium persulfate/benzaldehyde sodium bisulfite (KPS/BSBS) and potassium persulfate/sodium bisulfite (KPS/SBS) to the powers 0.15, 0.27, 0.30, 1.80 and 0.70, respectively, while N t , is dependent on emulsifier concentration to the powers 0.48, 1.00, 2.08, 3.33 and 4.41 with respect to the different redox systems KPS/SBS, KPS/MBSBS, KPS/CBSBS, KPS/BSBS and KPS/MeSBSB. The polydispersity index ( D w D w ) for the emulsion latices prepared using different emulsifier concentrations was found to be in the range 1.00–1.29, i.e. they are relatively narrow. This means that the emulsion polymerization of styrene was not in the so-called induction period. Increasing BuA ratio in the feed monomer composition of the prepared S/BuA copolymer lattices led to a decrease in N t .