Antimicrobial with modified-chitosan functionalization via dopamine linkage

A composition comprising a substrate and a chitosan polymer or oligomer having a general formula

• wherein
• n ranges from 1 to about 300;
• each of R1, R2, R3 is independently selected from a thiol, an alkane, an alkene, an alkyne, a secondary amine, a nitrile, an aldehyde, an imidazole, an azide, a halide, a polyhexamethylene dithiocarbonate, a hydrogen, a hydroxyl, a carboxylic acid, an aldehyde, a carboxylic ester, a carboxamide, a urea, a catechol, a quaternary ammonium, a quaternary phosphonium, a quaternary pyridinium, or combinations thereof;
• at least one of the R1, R2, and R3 groups in the polymer or oligomer comprises the quaternary ammonium, the quaternary phosphonium, or the quaternary pyridinium;
• the chitosan polymer or oligomer has between about 1 to about 99% quaternization;
• and
• at least one of the R1 groups in the polymer or oligomer is a substituted or unsubstituted dopamine or a derivative thereof, wherein the dopamine or derivative thereof is bound to the substrate, and wherein the dopamine or derivative thereof is bound to the chitosan polymer or oligomer via a —NH—C(O)— group which forms a —NH—C(O)—NH— group in combination with the —NH— group that is bound between R1 and the chitosan pyranose ring.