Limiting viscosity number and weight average molecular weight of hyaluronate samples produced by heat degradation

Abstract Two samples of high molecular weight hyaluronate were extensively degraded by heat at 128°C for up to 190 min in an autoclave that ensured reproducible degradation conditions. The weight average molecular weight, M w , of hyaluronate in 0.15 m NaCl was determined by low angle laser light scattering and related to the limiting viscosity number, [η], determined at high shear rate (∼ 1000 s −1 ). The M w of the samples varied from 150 000 to 4.3 × 10 6 . Treatment of the data according to the Mark-Houwink equation, [η] = K × M w α , suggested two relationships with K = 3.46 × 10 −5 and 3.97 × 10 −4 , α = 0.779 and 0.601, below and above M w = 1 × 10 6 , respectively. The heat degradation was found to be in accordance with that of random scission.