Delayed Gelation Kinetics of In-Situ Polymerized Gel Based on the Mechanism of Living/Controlled Radical Polymerization

In previous work, cross-linked water shut-off polymerized gel emerged rapid gelation within hours, which limited the in-depth migration of such gels. The concentration of active radicals generated by the thermal decomposition initiator cannot be controlled in the polymerization process, which is the fundamental reason for the fast gelation time. To delay the gelation time of in-situ polymerized gel in the process of deep profile control, a novel initiation system was developed based on the simultaneous reverse and normal initiation (SR&NI) for atom transfer radical polymerization (ATRP). The polymerization indicated features of living/controlled, such as linear first-order kinetics, linear evolution of the molecular weight with conversion, and lower molecular weight distributions. As compared with the reported conventional initiator, the current initiation system can effectively delay the gelation time of the in-situ polymerized gel by maintaining the concentration of active radicals at a low level. This pioneer work in the exploration of SR&NI ATRP initiation system to trigger hydrogel gelation offered the possibility to deploy in-situ polymerized gel with delayed gelation for in-depth conformance control.