A mild and straightforward one-pot hyaluronic acid functionalization through termination of poly-(2-alkyl-2-oxazoline)

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 H-1 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 thermoresponsive 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.

Automated summary

Hyaluronic acid of different molar masses was used as terminating agents in the cationic ring-opening polymerization of 2-methyl-2-oxazoline, resulting in HA-g-PMeOx copolymers with varying degrees of substitution. These copolymers showed thermally dependent hydrogel properties in aqueous solutions, making them potentially valuable for biomedical applications.