<p>In this study, cotton fabric was chemically modified using sodium chloroacetate (SCA) in an ethanol/water system to produce carboxymethylated cotton. The influence of ethanol concentration (0–60% v/v) and SCA concentration (50–200&#xa0;g/L) on the properties of the modified cotton fabrics was systematically examined. Increasing ethanol content from 0 to 60% and SCA concentration from 50 to 200&#xa0;g/L significantly increased the carboxyl content (from 0.09 to 1.23&#xa0;mmol/g). At 60% (v/v) ethanol and 100&#xa0;g/L SCA, the degree of substitution reached 0.136. FTIR analysis indicates that the modification treatment introduced carbonyl groups (peak at 1735&#xa0;cm⁻¹) onto the cotton fibers. However, this treatment resulted in a reduction in the crystallinity of the cotton fibers and caused a gradual change of the crystalline structure from cellulose I to cellulose II. While the modification treatment does not change the morphology of the cotton fibers, it substantially influences their dyeing properties. Increasing ethanol content to 60% raised the negative Zeta potential (from − 28 to − 48&#xa0;mV), resulting in dyeing-resistance performance against C. I. Reactive Red 195 (decreased by 60% K/S values). Simultaneously, the breaking strength of the fabric decreased, whereas its elongation at break significantly improved by 350%. Additionally, the thermal stability of the fabric decreased (lower maximum thermal decomposition temperature), while the amount of decomposition residue at 600&#xa0;°C increased. These findings offer fundamental insights for advancing the development of carboxylation on different cellulose substrates.</p> Graphical abstract <p></p>