Monomer adsorption, differential

Copolymerization. The solid phase of the precipitation polymerization also influences copolymer composition, since differential monomer adsorption on the polymer particles considerably modifies the effective reactivity ratios of the comonomers. This problem has been discussed by several authors (22,23,24,25,26). 

Barrett and Thomas (10)proposed that these effects of differential monomer adsorption could be modeled by correcting homogeneous solution copolymerization reactivity ratios with the monomer s partition coefficient between the particles and the diluent. The partition coefficient is measured by static equilibrium experiments. Barrett s suggested equations are ... 

In summary the results observed in these studies [160] of poly(Sty-co-DVB) swelling in aromatic liquids serve to show that the method of measuring a is so sensitive that it can detect an effect caused by even the smallest modification in the molecular geometry of attached substituents, and that these differences correlate qualitatively with expectation based on the known principles of physico-organic chemistry of aromatic compounds. Since the observed a is the net effect of electronic attraction and steric hindrance between the sorbed molecule and the adsorption site, i.e. the monomer unit of the polymer, it would be impossible to separate quantitatively the electronic and steric contributions of a particular substituent. The ability to make such a differentiation, however, appears to be more promising with liquids that comprise homologous series of the type Z(CH2)nH (where Z is a phenyl, chloro, bromo or iodo substituent), since the added electronic contribution to Z by each additional methylene group is well known to be extremely small when n becomes >3 [165],... 

Application of numerical methods have been rather seldom in studies of adsorption kinetics from micellar solutions. The main difficulties are probably connected with the large number of independent parameters. The first work belongs to Miller [146]. Fainerman and Rakita also published numerical results of the solution of the boundary value problem (5.236), (5.237), (5.245) [85]. Recently Danov et al. proposed an original method for solving the boundary value problem for the diffusion of micelles and monomers [92]. The system of equations was reduced to a system of ordinary differential equations by using a model concentration profile in the bulk phase. The obtained results agree better with dynamic surface tensions of micellar solutions than equation (5.248). 

The Four Kinetic Regimes of Adsorption from Micellar Solutions In the theoretical model proposed in Refs. [149,150], the use of the quasi-equilibrium approximation (local chemical equilibrium between micelles and monomers) is avoided. The theoretical problem is reduced to a system of four nonlinear differential equations. The model has been applied to the case of surfactant adsorption at a quiescent interface [150], that is, to the relaxation of surface tension and adsorption after a small initial perturbation. The perturbations in the basic parameters of the micellar solution are defined in the following way ... 

Fig. 11. Effects of non-electrostatic electrode adsorption. The top differential capacitance curve illustrates effects from ion specific adsorption. In this case, neutral monomers adsorb weakly (a = 0.5), while anions (simple) and cations (charged monomers) display a strong...

---