The invention discloses by being linked together by urethane bond and via the citrate a variety of biodegradable polymers being crosslinked or the biodegradable block polyurethane copolymer of the crosslinking of oligomer preparation. Such copolymer may include folic acid, and the medical facilities of such as nerve growth conduit etc are made, and by folic acid local delivery to the damage location of such as PNS damage locations etc.
