Hyaluronic acid (HA) of different molar masses from 38 000 to 990 000 g mol⁻¹ were used as terminating agents during the cationic ring-opening polymerisation of 2-methyl-2-oxazoline. HA was first converted into a tetrabutylammonium salt to solubilize it in polar aprotic organic solvents where the termination was conducted by varying the excess of HA units to the growing poly(2-methyl-2-oxazoline) (PMeOx) chains (with various PMeOx degree of polymerisation). This led to HA derivatives with various PMeOx degrees of substitution from 4% up to 13% (determined by ¹H NMR). HA-g-PMeOx copolymers were analysed by Size Exclusion Chromatography with on-line detectors (Multi-angle light scattering, Viscometer, Refractive index) in 0.1 mol L⁻¹ LiNO₃ to study their macromolecular characteristics in dilute medium. The reaction was applied to functionalize HA with thermo-responsive poly(2-isopropyl-2-oxazoline)-co-poly(2-n-butyl-2-oxazoline) moieties, resulting in materials displaying thermally dependent hydrogel properties in aqueous solutions which could be used for biomedical applications.