A solution including an antimicrobial polymer having the structure of Formula (I): in which R1 is a C2-C7 alkyl; R2 is a C8-C15 alkyl; R3 is an oxygen atom forming a maleic anhydride residue which optionally converts to a vicinal monoesterified dicarboxylic acid group in alcoholic solution; R4 and R5 are each independently a C1-C4 alkyl; Hal- is a halide anion selected from the group consisting of bromide (Br-), chloride (Cl-) and iodide (I-); i, j, k and i are each independently an integer from 1 to 100; and the ratio of j:1 is from 1:1 to 19:1 in a polar solvent. The quaternary ammonium salt moieties in the polymer provides it with antimicrobial activity. A method of producing the solution comprises reacting poly(styrene-co-maleic anhydride) copolymer with N,N-dimethyl-3-amino(C2-C7)alkyl-1-amine, then reacting the resulting product with a C8-C15 alkyl bromide, chloride or iodide to produce the polymer of Formula (I). The antimicrobial solution may be coated onto a substrate and cured to provide an antimicr
