Preparation and solution properties of microhydrogels from poly(vinyl alcohol)

Microgels were synthesized by intramolecular crosslinking of poly(vinyl alcohol) single chains with glutaraldehyde in dilute aqueous solutions (concentration c = 0,1 g/100 mt). The degree of crosslinking was varied from X = 0 to X = 150 (Xis the number of crosslinker molecules per chain). The reaction products were characterized by static and dynamic light scattering and viscosity measurements. A clear shrinking of molecular dimensions could be observed with increasing degree of crosslinking, since the radius of gyration R(g), and with that, the rho-parameter (rho = R(g)/R(h)) decrease with the number of intramolecular crosslinks. A similar behavior is seen from viscosity measurements. The intrinsic viscosity [eta] decreases with increasing X-parameter and depends only very weakly on the temperature which is an indication of a loss in flexibility and therefore for a relatively fixed structure.