Monomer hard phase-forming

A detailed description of AA, BB, CC step-growth copolymerization with phase separation is an involved task. Generally, the system we are attempting to model is a polymerization which proceeds homogeneously until some critical point when phase separation occurs into what we will call hard and soft domains. Each chemical species present is assumed to distribute itself between the two phases at the instant of phase separation as dictated by equilibrium thermodynamics. The polymerization proceeds now in the separate domains, perhaps at differen-rates. The monomers continue to distribute themselves between the phases, according to thermodynamic dictates, insofar as the time scales of diffusion and reaction will allow. Newly-formed polymer goes to one or the other phase, also dictated by the thermodynamic preference of its built-in chain micro — architecture. 

Second example was obtained from the copolymerization initiated with starch. The results were shown in Fig. 12. The copolymer isolated from the monomer phase was produced by the thermal polymerization and the composition curve was completely similar to the ordinary curve of the radical copolymerization product. The copolymer isolated from the water phase differed from the usual copolymer. The upper curve indicated that the HA formed by starch were soft, and soft MMA was much more easily incorporated than hard St. 

In general, block copolymers are heterogeneous (multiphase) polymer systems, because the different blocks from which they are built are incompatible with each other, as for example, in diene/styrene-block copolymers. This incompatibility, however, does not lead to a complete phase separation because the polystyrene segments can aggregate with each other to form hard domains that hold the polydiene segments together. As a result, block copolymers often combine the properties of the relevant homopolymers. This holds in particular for block copolymers of two monomers A and B. 

PMMA particles with hollow structures were synthesised by water-in-oil-in-water emulsion polymerisation. Sorbitan monooleate was used as a primary surfactant and sodium lauryl sulphate and Glucopen (a polypeptide derivative) were used as secondary surfactants. Urethane acrylate, with a hard segment in the molecular backbone, a long soft segment in the middle and vinyl groups at both ends was used as a reactive viscosity enhancer. Only a few particles contained a void in the polymer phase at low concentrations of urethane acrylate, but as the concentration of urethane acrylate increased, so did the number of particles containing the void. This was because urethane acrylate increased the viscosity of the monomer mixture and helped to form the stable emulsion droplets. At concentrations of urethane acrylate above 7 wt%, multi-hollow structured particles were produced. The mechanism of formation of the hollow particles was discussed. 7 refs. 

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