Mechanism of Formation of Partially Crosslinked Polyacrylamide Complexes

A new type of partially crosslinked polyacrylamide (PCPAM) which displays promising application in enhanced oil recovery (EOR) has been synthesized via aqueous solution polymerization under adiabatic conditions. Based on methods of real-time infrared monitoring, two-dimensional infrared correlation spectroscopy, and dynamic rheology measurement, an unusual complex formation mechanism of the PCPAM with the multifunctional initiator system is clearly disclosed. A process forming branched structures from three functional dimethylaminoethyl methacrylate (DMAEMA) was exhibited, which was supported by high-resolution Fourier transform infrared (FTIR) information. Furthermore, an interesting reaction process, dominated by reaction dynamics, is proposed. By viscosity matching, a great number of coupling terminations will be generated from the branched end chains which will result in the formation of partially crosslinked structures, whereas lots of branched structures were retained under quick gelling conditions. Consequently, the relative number of branched and crosslinked structures in PCPAM was not only mainly determined by the viscosity of the system but also by the content of DMAEMA.