| Abstract: | Summaries. By the use of continuous polymer fractionation (CPF) the initial polymer can be separated into fractions of different molar masses, which makes it possible to obtain hydroxyethyl starch (HES) fractions tailor-made for specific application. Two samples of HES (HES A and HES B) were fractionated by means of CPF. By size-exclusion chromatography-multi-angle laser light-scattering-differential refractive index (SEC/ MALLS/DRI) measurements it was shown that CPF is able to remove the low-molar-mass components and to adjust the samples to various desired molar masses with lower polydispersities than the original samples. In terms of the weight-average mean molar mass Mw, the sol fractions have smaller molar masses than the starting sample, whilst the gel fractions have higher molar masses. Furthermore the radius of gyration RG could be determined for the initial sample HES B with 19.7 and 19.4 nm and also for some of its fractions. However, no general RG-MW relationship could be established for the HES samples fractionated using CPF. This is probably due to the complex branched structure of amylopectin. Mw and Mw/Mn of the six fractions obtained from HES A with Mw = 161.000g/mol and Mw/Mn =4.7 ranged from 19,000 to 362,000 g/mol with Mw/Mn from 1.8 to 3.1. The molar masses of the four fractions obtained from HES B with Mw= 460,000 g/mol and Mw/Mn = 6.0 were between 18.000 and 680.000 g/mol with Mw/Mn from 1.7 to 4.8 or between 202,000 and 1,005,000 g/mol with Mw/Mn from 2.7 to 4.7 depending on fractionation strategy. |
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