A systematic experimental and modeling study of several emulsion copolymerization systems has been performed, and will be reported in a series of papers. Ten binary and three ternary copolymerizations involving styrene, methyl methacrylate, butyl acrylate, butadiene, vinyl acetate, acrylic acid, and ethylene were studied varying polymerization temperature, monomer composition, water to monomer ratio, initiator and emulsifier concentrations. Conversion, particle size, copolymer composition, and gel content were measured at several reaction times. The goal of this series of papers is to assess our quantitative understanding of emulsion copolymerization expressed in the form of a comprehensive mathematical model applied to monomers widely used in industry. In this first paper of the series, a global comparison of the experimental results is made. It is observed that the gel content is higher in systems containing butyl acrylate and butadiene, and smaller in systems containing methyl methacrylate. Larger particle numbers are obtained for lattices containing acrylic acid and butadiene. It is also shown that, for most of the systems, integration of the simple Mayo–Lewis equation is adequate to explain the drift in copolymer composition observed experimentally. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2360–2379, 2001

ABSTRACT:Using a previously published model and continuing the series of papers started with styrenic copolymers, predictions for evolution of conversion and average particle diameter in batch experiments are compared against experimental data for four emulsion copolymerizations involving at least one acrylic monomer: (1) methyl methacrylate/butyl acrylate, (2) methyl methacrylate/butadiene, (3) methyl methacrylate-vinyl acetate, and (4) butyl acrylate/vinyl acetate. For each system a fraction of factorial experiments were run covering simultaneous variations in five variables: initiator [I] and surfactant [E] concentrations, water to monomer ratio (W/M), monomer composition, and temperature. Data fitting is performed to represent the experimental data as several parameters are not available from independent experimental sources. The model is able to explain the effects of simultaneous changes in emulsifier concentration, initiator concentration, and water to monomer ratio on conversion and average particle size histories, although in some cases only qualitatively. An assessment of the degree in which a general emulsion copolymerization model is useful for practical applications is made. Physical insight is also gained by observing the trends of adjusted parameters with temperature and copolymer composition.

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Using a model previously published, predictions for evolution of conversion and average particle diameter in batch experiments are compared against experimental data for four emulsion copolymerizations of styrene with the following monomers: (1) methyl methacrylate, (2) butyl acrylate, (3) butadiene, and (4) acrylic acid. For each copolymerization system the experiments covered simultaneous variations in five variables: initiator and surfactant concentrations, water to monomer ratio, monomer composition, and temperature. It is shown that after data fitting for unknown or uncertain parameters, the model is capable of explaining quantitatively the experimental observations for conversion evolution and only qualitatively the particle size evolution data. This points out to the possible contribution of particle nucleation mechanisms other than the micellar one, which is the only mechanism included in the model. Some of the adjustable parameter values were found to depend on the copolymer composition. The only case in which the model does not perform well is in the prediction of the effect of initiator concentration on the copolymerization rate for butadiene‐rich formulations. It is also found that the model predictions are very sensitive to the value of the diffusion coefficients of monomeric radicals in the copolymer particle, which are not readily available in the literature. It is concluded that it is important to independently measure these parameters in order to enhance the predictive power of models. It is also concluded that the model can be useful for practical applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2380–2397, 2001

Reversible addition fragmentation chain transfer (RAFT) polymerization is a well-known control/living radical polymerization (CLRP) 1,2 and has been used for the synthesis of well defined (co)polymers with specific architectures 3,4 in both solution 5 and heterophase polymerizations to form (nanostructured) polymeric particles. 6,7 The combination of RAFT polymerization with miniemulsion processes have also been demonstrated as very successful for the synthesis of many polymeric systems, 1,2,6-13 particularly toward the generation of polymers with industrial applications. 7,8,14 Nevertheless, while the "living" nature of polymerizations in solution was successfully exploited for the synthesis of block copolymers following continuous processes, 15,16 we were unaware of a controlled non-stop block copolymerization in miniemulsion. For example, the conventional way to synthesize these block copolymers in miniemulsion is based on the following approach: 7,14,17,18 the first step is the RAFT polymerization in miniemulsion of the nanoparticles to be used as seeds, the polymerization must then be stopped also in a controlled fashion, and subsequent steps to grow a second or successive block(s) include addition of the second monomer and initiator, a "swelling time" for the seeds to incorporate that second monomer, and finally a re-initiation of the polymerization. A very important point to take into consideration has been reported explaining that in miniemulsion polymerizations of block copolymers, the prevention of an increased amount of dead chains of the first block (especially in the case of polystyrene (PS)) is achieved by stopping the polymerization at relatively low monomer conversions. 7,14,17 Thus, we were interested in tackling this complex objective, the synthesis of block copolymers of industrial interest following a controlled non-stop one-pot RAFT polymerization in miniemulsion. To this end, we targeted the symmetric poly(styrene)-block-poly(butadiene)-block-poly(styrene) triblock copolymer (SBS).Our approach was based on a different strategy, in which the symmetric dibenzyl trithiocarbonate (DBTTC) was chosen as chain transfer agent and still taking into consideration a low monomer conversion during the polymerization of the polystyrene (PS) (first) block. Thus, the full amount of butadiene (Bd) monomer was injected at once at incomplete conversion of styrene (St), without stopping the polymerization. The result is, therefore, that we performed a non-stop block copolymerization in miniemulsion establishing for the first time a continuous process for the synthesis of block copolymers in miniemulsion.Samples were taken at different reaction times to study the evolution of the polymerization as a function of time, the monomer conversion, the particle sizes, and molecular weights with their respective molecular weights distributions. Figure 1(a) presents the conversion versus time profile for pure PS showing that it takes around 75 h to reach a conversion near 60%. Based on this result, it was decided for th...

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Summary: A simple model based on elastic and attraction forces is proposed to describe the spreading of a cross-linked polymer particle on one or two surfaces. The model considers the internal elastic forces between the knots of reticulation and the external attraction forces between the particle and the mineral surface. The deformation and therefore the final shape of the particle is a resultant of the applied forces. The model is validated by fitting with experimental data of latex spreading on mineral surfaces, and the next steps towards using this knowledge to help design new particle structures and morphology are outlined.

In this work an experimental and simulation study of batch and semicontinuous styrene/butadiene emulsion copolymerization process was developed. The mathematical model combines the classical emulsion copolymerization equations, with mass balances, partitioning of components among all liquid phases, micellar and homogenous nucleation mechanisms and mass transfer equations between liquid and gaseous phases. Simulation results show good agreement with experimental measurements of conversion, average particle diameter and pressure.