Abstract: Provided is an aspartic acid composition containing aspartic acid and an impurity, the impurity containing at least one selected from the group consisting of an amino acid other than aspartic acid, an organic acid, and salts of the amino acid other than aspartic acid and the organic acid, a content of the impurity being 0.02% by mass or more and 1.1% by mass or less. Also provided is a method for producing polysuccinimide, the method including performing a polymerization reaction of the aspartic acid using the aspartic acid composition. Also provided is a polysuccinimide composition produced by the method for producing polysuccinimide.

Abstract: The present invention relates to a novel iron complex having a cyclic amine compound as a ligand and a method for producing polymers by polymerizing a radical polymerizable monomer in the presence of the iron complex and a radical generator. The problem for the present invention is providing a method capable of producing a polymer or block copolymer having a chemically convertible functional group at the end from a radical polymerizable monomer and providing a method for recovering the iron complex in a solvent with a high recovery rate after the polymerization reaction. This problem is solved by providing a novel iron complex, a method for producing a polymer in the presence of a radical polymerization initiator that uses the iron complex as a polymerization catalyst and a method for simply and easily recovering the iron complex.

Abstract: The invention relates to a novel iron complex bearing a cyclic amine as ligand; and a process for the production of polymers by polymerizing a radical-polymerizable monomer in the presence of the iron complex and a radical generator. The invention aims at providing a process by which a polymer having a chemically convertible functional group at the end can be produced from a radical-polymerizable monomer and which permits the production of a block copolymer and a process for recovering, after polymerization, an iron complex into a solvent at a high recovery ratio. The aim can be solved by providing a novel iron complex, a process for producing a polymer in the presence of a radical polymerization initiator by using the iron complex as the polymerization catalyst, a process for the production of a block copolymer which is subsequent to the polymerization for producing the above polymer, and a process for recovering the iron complex easily and simply.