Polyacrylamide gels. Process of network formation

Abstract

This paper refers to the crosslinking copolymerization of acrylamide (AA or monomer-1) and N,N′-methylene-bisacrylamide (BA or monomer-2) in aqueous solution at 22°, covering a broad range of comonomer concentrations. The extent of reaction, pT, the composition of the remaining comonomer mixture, f₂, and the copolymer composition, F₂, have been determined by high resolution 1H-NMR with polymerization in situ. The non-linear regression fit of f₂ as a function of pT yields almost the same values for the reactivity ratios for any of the studied comonomers feeds. The instant copolymer composition changes with the copolymerization time due to a shift in the residual comonomer composition and, to a smaller extent, to changes in the comonomer relative reactivities. This effect contributes to the heterogeneity of the final network.