Patent ID: 8546487

Claim:
A cationic poly(amino acid) of formula (1): wherein: R 1 is a hydroxyl group, an unsubstituted or substituted linear or branched alkyloxy group having 1 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkenyloxy group having 2 to 12 carbon atoms, an unsubstituted or substituted linear or branched alkynyloxy group having 1 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkyl-substituted imino group having 1 to 12 carbon atoms; R 2 is a hydrogen atom, an unsubstituted or substituted linear or branched alkyl group having 1 to 12 carbon atoms, or an unsubstituted or substituted linear or branched alkylcarbonyl group having 1 to 24 carbon atoms; R 3a and R 3b are each independently a methylene group or an ethylene group; R 4a and R 4b are each independently selected from the group consisting of: —NH—(CH 2 ) p1 —[NH—(CH 2 ) q1 —] r1 NH 2 (i); —NH—(CH 2 ) p2 —N[—(CH 2 ) q2 —NH 2 ] 2 (ii); —NH—(CH 2 ) p3 —N{[—(CH 2 ) q3 —NH 2 ][—(CH 2 ) q4 —NH] r2 H} (iii); and —NH—(CH 2 ) p4 —N{—(CH 2 ) q5 —N[—(CH 2 ) q6 —NH 2 ] 2 } 2 (iv), wherein: p1 to p4, q1 to q6, and r1 and r2 are each independently an integer of 1 to 5; in 5 to 40% of all of the R 4a and R 4b groups, one hydrogen atom of at least one amino group is substituted with (i) an acyl group having a saturated or unsaturated linear or branched aliphatic hydrocarbon residue having 6 to 27 carbon atoms, or (ii) a steroloxycarbonyl group; n is an integer of 30 to 5,000; and y is an integer of 0 to 5,000, provided that, when R 3a and R 3b are each a methylene group, y is less than n, when n is less than y, n−y is set equal to zero, and when n does not equal y and when y does not equal zero, the units having a number of repetitions n−y and the units having a number of repetitions y may be arranged in any order.