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A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0‐1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The synthesis, by two sequential inverse microemulsion polymerizations, of interpenetrating polymer networks (IPN) formed by polyacrylamide (PAM) and poly(acrylic acid) (PAA) and their response to changes in pH and temperature are reported here. The temperature and pH responses of the IPN nanoparticles are compared with those of polyacrylamide and random copolymers of polyacrylamide and poly(acrylic acid) P(AM-co-AA) nanoparticles also made by inverse microemulsion polymerization. We found that only the IPN nanogels exhibited a sharp swelling increase with temperature associated with its Upper Consolute Solution Temperature, driven by hydrogen bonding interactions, and with pH, driven by electrostatic repulsions of the PAA carboxylic groups, especially at pHs larger than the pKaof the PAA. The ς-potentials of the PAM, P(AM-co-AA) and IPN nanogels were measured as a function of pH and temperature, to determine the effects of these two variables, which in turn, affected the swelling of the nanogels. Field emission scanning electron microscopy revealed that the IPN nanogels were spheroidal with sizes similar to those determined by dynamic light scattering. [ABSTRACT FROM AUTHOR]

A generalized model is presented here for the semicontinuous heterophase polymerization of methyl and hexyl methacrylate, which have very different water solubility. In this polymerization technique, neat monomer is fed at a controlled rate over a monomer-free aqueous solution of surfactant and initiator, to produce nanometer size particles with controlled molar masses, and high polymer/surfactant ratios similar to those used in conventional emulsion polymerization. For the two monomers studied at three different addition rates, model predictions accurately reproduce conversion-versus-time curves, the evolution of particle size, and the number density of particles. The model reveals that the controlling nucleation mechanism shifts from micellar to homogeneous nucleation as the monomer solubility in water increases. [ABSTRACT FROM AUTHOR]