Synthesis and characterization of functionalized polymer latex particles through a designed semicontinuous emulsion polymerization process

Abstract

AbstractMonodispersed noncarboxylated and carboxylated poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) latices were synthesized with a well‐defined semicontinuous emulsion polymerization process. A modified theory to correlate the polymerization rate to the instantaneous conversion of the monomer or comonomer mixture was developed. The resulting equation was used to determine the maximum polymerization rate only below or equal to which the polymerization could be operated in the highly monomer‐starved regime, which corresponded to an instantaneous conversion of 90% or greater. Experimental data from reaction calorimetry supported that the polymerization was under highly monomer‐starved conditions when the model latices were synthesized with the modified model. The estimation of the average number of free radicals per latex particle(n̄) during the feeding stage revealed that n̄ was as high as 1.4 in the actual polymerization, which showed that the original selection of 0.5 as the n̄ value was not accurate in the developed model. From the conductimetric titration experiments, we found that most of the carboxyl groups from the methacrylic acid (MAA) were buried inside the latex particles, and the surface carboxyl group coverage increased as the MAA concentration in the comonomer feed increased. The glass‐transition temperatures of the synthesized polymers were close to the designed value from the Pochan equation, and only one glass transition was observed in the polymer samples in the differential scanning calorimetry measurements, indicating a homogeneous copolymer composition in the functionalized shell. Particle size characterization and transmission electron microscopy confirmed the uniformity in the latex particle size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 248–256, 2005