Effect of Carboxylic Acid Monomer Type on Particle Nucleation and Growth in Emulsifier-free Emulsion Copolymerization of Styrene-Carboxylic Acid Monomer

Abstract

ABSTRACT:Carboxylated polystyrene latexes were prepared by emulsifier-free emulsion copolymerization of styrene with various carboxylic acid monomers (AA, MAA and IA). DLS analysis and SEM observations were used to investigate the effect of various carboxylic acid monomers on the particle formation and growth processes. It was found that number of particles per unit volume of aqueous phase (N p ) increases with increasing hydrophobicity of carboxylic acid monomers in order of IA < AA < MAA. There was significant difference in polymerization rate per particle (R p =N p ) in all the experiments also. The results revealed that both particle nucleation and growth processes are dependent on the hydrophilic nature of carboxylic acid monomers. SEM studies showed that N p is almost constant in the particle growth stage (conversion above 10%). Through some calculations by data obtained from DLS technique, average diameter of monomer swollen polymer particles (d pswol ) of all the carboxylated polystyrene latexes at the same conversion of 0.4 was obtained to be 325.24, 199.30 and 661.02 nm for AA, MAA and IA respectively. Attempt was made to calculate the average number of propagating radicals per particle and to determine its relevance to the kinetics of particle growth by various carboxylic acid monomers.

A robust computational method based on the thermodynamic approach for determining monomer partitioning in emulsion polymerization systems

“…These variable changes ensure that the volume fraction of monomers in particle and droplet phases will be limited in the interval [0,1] and the values of in the interval . For solving the system of nonlinear equations (i.e., Equations –(16)), we used the Levenberg‐Marquardt and trust‐region‐reflective methods.…”

“…In these systems, the primary reaction locus is inside the particles and the polymerization in the aqueous phase is usually ignorable. However, many industrial processes usually use one or more functional monomers with significant water solubilities such as acrylic acid and methacrylic acid . The rate of polymerization, copolymer composition, conversion, and molecular weights are strongly affected by monomer partitioning in emulsion polymerization systems.…”

Exploiting catalytic chain transfer polymerization for the synthesis of carboxylated latexes via sulfur‐free RAFT

“…The distribution of the acid is influenced by a number of factors, such as the reactivity ratio of the monomers, or the partitioning behavior of the carboxylic acid over the pH range of the Carboxylic acid monomers are often highly soluble in water . Nevertheless, they will still partition to varying degrees into the organic phase, subject to their relative hydrophobicity . AA, IA, and FA tend to be highly partitioned to the aqueous phase, even at pH levels below their pKa's, and produce significant amounts of water‐soluble polymer.…”

Fundamentals of chemical incorporation of ionic monomers onto polymer colloids: paving the way for surfactant-free waterborne dispersions

“…However, strong adsorption makes them inefficient for particle nucleation. 6 Functional monomers and initiators containing ionic groups such as carboxylate, 7,8 sulfate, 8,9 amino, 10 phosphate, 11 phosphonate 12 and sulfonate [13][14][15] are used in emulsion polymerization formulations to minimize the amount of surfactant used, and also to impart special properties such as better adhesion to substrates and biological tissues and better mechanical properties. 16,17 In this context, it is appealing to use functional monomers as the sole source of stabilizing moieties.…”