EFFECT OF PERCOLATION ON FREE-RADICAL POLYMERIZATION OF ACRYLAMIDE ININVERSE MICROEMULSION

The kinetics of free-radical polymerization of acrylamide initiated by dibenzoyl peroxide in non-percolating and percolating inverse microem ulsions (toluene/sodium bis(2-ethylhexyl) sulfosuccinate/water/acrylam ide) and the properties of polyacrylamide particles formed from these inverse microemulsions were investigated. The acrylamide polymerizatio n rate and polyacrylamide number-average molecular mass depend on the acrylamide concentration in the dispersed phase of the inverse microem ulsion. For non-percolating inverse microemulsions these dependencies are described by the equation R(p)( or M(n)BAR) is-proportional-to [AA m]x(or y) where x and y have the values of 1.8 and 1.4 respectively, w hile for percolating inverse microemulsions the respective values of x and y are 1.1 and 0.4. Data on polymer particle size and number-avera ge molecular mass of polyacrylamide in polymer particles were used for calculation of the average number of polymer chains in polymer partic les for non-percolating (approximately one chain per particle) and for percolating (more than two chains per particle) inverse microemulsion s. The spin probe (potassium nitrosodisulfonate, Fremy's salt) correla tion time T(c) expressing the spin probe mobility in water-swollen pol ymer particles and in polyacrylamide water solution pointed to the 'co llapsed' state of polyacrylamide chains in polymer particles in both k inds of inverse microemulsions. Besides the dependencies of polyacryla mide polymerization rate and of number-average molecular mass of polya crylamide on the acrylamide concentration in inverse microemulsions, t he dependence of T50G, values, characterizing the spin probe mobility in polymer particles of inverse microemulsions as a function of polyac rylamide concentration in the polymer particles, is different for non- percolating and percolating inverse microemulsions.