Patent ID: 8318205

Claim:
A polyethylene glycol/polycation block copolymer represented by formula (II) or a salt thereof, in which R 1 stands for hydrogen, or a substituted or unsubstituted, straight or branched chain C 1-12 alkyl, L 2 stands for a linker, R 2 stands for methylene or ethylene, R 4 is either the same as R 5 or the formula —NH—R 9 , wherein R 9 is unsubstituted or substituted straight or branched chain C 1-20 alkyl, R 5 s each independently stands for hydroxyl, oxybenzyl or —NH—(CH 2 ) a —X group, wherein X each independently stands for an amine containing one, two or more members of the group consisting of primary, secondary and tertiary amines and quaternary ammonium salt, with the proviso that at least 85% of R 5 s are —NH—(CH 2 ) a —X, a is an integer of 1-5, m is an integer of 5-20,000, n is an integer of 2-5,000 and x is an integer of 0-5,000, with a proviso that x is not greater than n.