Slightly and partially water-miscible monomers

Prediction of the instantaneous chemical composition as well as the rate of polymerisation during an emulsion copolymerisation of monomers 1 and 2 asks for the concentrations of the reacting monomers in the particle phase. Monomers 1 and 2 are only sparsely or moderately water soluble. The amounts of the monomers 1 and 2 in the droplet phase, the water phase and the particle phase are related by mass balances for the monomers. Equation 4.8 gives the mass balance for monomer 1  

Concentrations are expressed in moles per m of the phase involved, that is, the water phase, the droplet phase and the particle phase. Using the volume fraction of polymer in the particles, poi,p, the polymer volume in the particle phase, Vpoi,p and the volume fraction of monomer 1 in the particles, (/ i p, as well as in the droplets, Equation 4.9 can be rearranged into  

Vl stands for the molar volume of pure monomer 1. Note that molar volume changes of the monomers due to mixing with monomer 2 and/or the polymer have been neglected on going from Equations 4.9 to 4.10. For the mass balance of monomer 2 over the three phases analogous equations as 4.8-4.10 can be derived. Note that in the absence of monomer droplets, for example. Interval III for a batch emulsion polymerisation process. Equation 4.10 reduces to Equation 4.11  

For sparsely and moderately soluble monomers the following relations holds for the volume fractions of 1 and 2 in the droplet and the particle phase (Maxwell et al, 1992a)  

By negligible volume changes due to mutual mixing of the monomers 1 and 2 in the droplet phase and by mixing the monomers 1 and 2 with the polymer phase in the particles. Equation 4.12 can be rewritten in concentrations or mole fractions  

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