A polymer for imparting functions such as ultraviolet absorbing property and flame retardancy to a condensation system, particularly a synthetic resin comprising an aromatic ester-based polymer and vinyl-based polymer, and a production method thereof are provided, and a modifier using such a functional polymer like that is consequently provided.
There is provided a copolymer to which functions are imparted by block-copolymerizing a radical polymerizing function imparting monomer to a polyazo compound comprising a condensation-type or vinyl-based polymer segment and an azo group at a repeating unit using said azo group as a radical polymerization initiator, and this copolymer is used as a modifier for the other synthetic resin.