Unusual Compatibility of N‐Reacetylated Oligochitosan with Sodium Dodecyl Sulfate in Aqueous Solution with a Wide Range of the Solution pH

N‐reacetylated oligochitosan (RA‐oligoCHI) with molecular weight ≤ 12 kDa and a random‐type distribution of acetyl groups can form soluble RA‐CHI/SDS (SDS; sodium dodecyl sulfate) complexes and transparent solutions both in acidic, where RA‐oligoCHI is soluble, and alkaline aqueous media, where RA‐oligoCHI is soluble too, at SDS concentration above its critical micellar concentration. AN antibacterial activity test shows that RA‐CHIs preserve a high bacteriostatic activity toward S. aureus and E. coli in the presence of SDS both in acidic and alkaline aqueous solutions. The discovered compatibility and preservation of antibacterial activity can make promising the application of RA‐CHIs as artificial biocides for the preparation of microbiologically stable pharmaceutical hydrocolloids and cosmetic compositions containing strong anionic surfactants designed for topical applications. Chitosan soluble in acidic media forms insoluble complexes and turbid solutions with sodium dodecyl sulfate (SDS) while N‐reacetylated chitosan having specific molecular characteristics and a random type distribution of acetyl groups soluble both in acidic and alkaline media can form soluble complexes and transparent solutions in the presence of SDS both in acidic and alkaline media