Patent ID: 7780957

Claim:
A polyethylene glycol/polycation block copolymer represented by formula (I) or a salt thereof, wherein m is an integer of 5-20,000, n is an integer of 2-5,000, x is an integer of 0-5,000, with the proviso that x is not greater than n, R 1 stands for hydrogen, or a substituted or unsubstituted, straight or branched chain C 1-12 alkyl, L 1 stands for a linker, R 2 stands for methylene or ethylene, R 3 stands for hydrogen, a protective group, a hydrophobic group, or a polymerizable group, and R 5 s each independently stand for hydroxyl, oxybenzyl, or —NH—(CH 2 ) a —X, with the proviso that at least 85% of R 5 s are —NH—(CH 2 ) a —X, wherein X independently stands for one of the following: wherein a is an integer of 1-5, X 2 stands for hydrogen or C 1-6 alkyl, X 3 stands for amino C 1-6 alkyl, R 7 stands for hydrogen or methyl, d stands for an integer of 1-5, e stands for an integer of 1-5, f stands for an integer of 0-15, and R 8 stands for Boc, acetyl, or trifluoroacetyl.