Size characterisation of modified celluloses in various solvents using flow FFF-MALS and MB-MALS

The size characterisation of modified celluloses is a necessary, but also c omplex, task that often requires use of different methods. In this paper, t wo different size characterisation methods were used to obtain molar mass a nd size information of three hydroxypropyhmethyl cellulose (HPMC) samples i n four different solvents. The two methods employed were the combination of flow held-how fractionation and multi-angle light scattering (MALS) as wel l as sole utilisation of the MALS instrument itself performed in the so-cal led micro-batch mode (MB-MALS). The influence of the different solvents, on the obtained molar mass and size for the HPMC-samples was found to be pron ounced. For example, the molar mass obtained for the high molar mass HPMC 1 0000 increased from 310,000 up to 650,000 g/mol when the solvent was shifte d from a 50% methanol-salt mixture into 1 mM NaCl. Also the radius of gyrat ion was clearly affected by the change in solvent. Theses changes were comp ared with values of the second virial coefficient, A(2), obtained from MB-M ALS. Furthermore, both techniques were able to identify clear differences i n solution behaviour between the HPMC-samples, which were delivered by two different manufacturers. It was concluded that the two methods gave compara ble results and complement each other well in the size analysis of these co mplex polymers. (C) 2000 Elsevier Science Ltd. All rights reserved.