Abstract: A polymer gel includes a structure derived from a main monomer M1, a crosslinking agent monomer M2, and a radical polymerization initiator I as a constituent element. A monomer reactivity ratio r1 of the main monomer M1 and the monomer reactivity ratio r2 of the crosslinking agent monomer M2 satisfy a condition of r1>r2, a molar ratio of an addition amount of the crosslinking agent monomer M2 to an addition amount of the main monomer M1 is 12% or less, an addition molar ratio CM of the crosslinking agent monomer M2 to an addition amount of the main monomer M1, and an addition molar ratio IM of the initiator to an addition amount of the main monomer M1 satisfy a condition of IM?0.66CM+0.0017, and the radical polymerization initiator I is a compound having a chemical structure of a general formula (I).

Abstract: There is disclosed a polymer gel including a structure derived from a main monomer M1, a crosslinking agent monomer M2, and a radical polymerization initiator I as a constituent element. In this polymer gel, a monomer reactivity ratio r1 of the main monomer M1 and a monomer reactivity ratio r2 of the crosslinking agent monomer M2 satisfy a condition of r1>r2, a molar ratio of an addition amount of the crosslinking agent monomer to an addition amount of the main monomer M1 is 1% or less, and a decomposition rate (10?7/s) of the radical polymerization initiator I at 25° C. is 25 or more. This polymer gel has properties of high strength and high viscosity.