Cyclocarbonate group-containing (meth)acrylate monomer and polymer

A method of producing a polymer,

• the method comprising a step of subjecting a monomer mixture to radical polymerization, said monomer mixture comprising a cyclocarbonate group-containing (meth)acrylate monomer (A) represented by the following formula (1) and di(meth)acrylate monomer (B) represented by the following formula (2),
• wherein a content of said di(meth)acrylate monomer (B) contained in said monomer mixture is 3 mass % or lower and 0.1 mass % or higher, with respect to a total of a content of said monomer (A) and said content of said monomer (B),
• wherein in the formula (1),
• R1 represents a hydrogen atom or a methyl group,
• R2 represents an alkyl group having 2 to 10 carbon atoms, and
• X is 0 or 1,
• wherein in the formula (2),
• R3 represents a hydrogen atom or a methyl group,
• R4 represents an alkyl group having 2 to 10 carbon atoms, and
• X is 0 or 1.