Provided are a copolymer of diallylamines and sulfur dioxide having a high molecular weight and a low content amount of impurities such as halogens, and a production method with which it is possible to produce such a copolymer relatively simply and at low cost. This problem is solved by: a copolymer having a weight-average molecular weight of 150,000 or higher obtained by GPC measurement and a degree of polymerization of 1000 or higher, the copolymer being obtained by copolymerizing sulfur dioxide and a sulfonate or alkyl sulfate salt of diallylamines having a specific structure; and a method for producing a copolymer, the method having a step for copolymerizing sulfur dioxide and a sulfonate or alkyl sulfate salt of diallylamines having a specific structure in ethylene glycol or in propylene glycol monomethyl ether.

Provided are a copolymer of diallylamines and sulfur dioxide having a high molecular weight and a low content amount of impurities such as halogens, and a production method with which it is possible to produce such a copolymer relatively simply and at low cost. This problem is solved by: a copolymer having a weight-average molecular weight of 150,000 or higher obtained by GPC measurement and a degree of polymerization of 1000 or higher, the copolymer being obtained by copolymerizing sulfur dioxide and a sulfonate or alkyl sulfate salt of diallylamines having a specific structure; and a method for producing a copolymer, the method having a step for copolymerizing sulfur dioxide and a sulfonate or alkyl sulfate salt of diallylamines having a specific structure in ethylene glycol or in propylene glycol monomethyl ether.

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).

A zwitterionic monomer and corresponding cyclopolymerized polyzwitterion () (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid () (PZA). The PZA under pH-induced transformation was converted into polyzwitterion/anion () (PZAN) and polyzwitterion/dianion (=) (PZDAN).