Patent ID: 7550512

Claim:
A copolymer, or a salt thereof, with a molecular weight of 1,000-200,000 comprising structural units represented by the following formulas (I), (II), and (III): where R 1 in formula (I) is a group represented by the following formula (C) or (D), and R 2 in formula (II) is a group represented by the following formula (B), (D) or (E): *—(CH 2 ) n —S—(CH 2 ) p —(CO) t —NH—X u — (B) where X is hydrocarbon group, n is an integer from 2 to 8; p is an integer from 1 to 8; t is an integer 0 or 1; u is an integer 0 or 1; and * may be positioned on the ethylene oxide side or on the opposite side *—(CH 2 ) m —S—(CH 2 ) p — (C) where m is an integer from 2 to 8; p is an integer from 1 to 8; and * may be positioned on the ethylene oxide side or on the opposite side where m is an integer from 2 to 8; r is an integer from 0 to 7; s is an integer from 0 to 7; t is an integer from 0 to 4; R S an amino group, carboxyl group or sugar residue; and * may be positioned on the ethylene oxide side or on the opposite side where m is an integer from 2 to 8; r is an integer from 0 to 7; s is an integer from 0 to 7; and * may be positioned on the ethylene oxide side or on the opposite side; R 3 in general formula (II) is a sugar residue; and the respective mole percents of units (I), (II) and (III) are (I)=1-98, (II)=1-98 and (III)=1-98.