The Column - June 2008 - (Page 27) June 2008 www.thecolumn.eu.com The Column Clarke just for comparison). In this instance, the difference between the linear and branched samples is quite small but the amount of branching and the branching frequency can be quantified accurately. We can see that, as mentioned previously, the value of Bn increases with molecular weight [Figure 7(a)] but the value of the branching frequency, , decreases with respect to molecular weight [Figure 7(b)], showing that in this sample the lower molecular weight macromolecules have more frequent branches than the longer chains. The level of branching here is very low with ranging from 1 to 2 branches per 1000 daltons over the whole molecular weight range. Conclusion Measurement of branching is of great importance in all areas of macromolecular materials. Triple detection GPC offers a rapid and simple way to give both qualitative and quantitative information on branching whilst also giving accurate molecular weight and viscosity data. Reference 1. B.H. Zimm and W.H. Stockmayer, J. Chem. Phys., 17, 1301 (1949). Figure 6: Polycarbonates/structural comparison. Mark-Houwink-Plot 0.70 Log (Intrinsic viscosity) 0.40 0.10 0.20 Log IV PC 1 PC 2 Polysterene Expanded scale Paul Clarke has been involved with multi-detector GPC/SEC for 20 years. He has an extensive knowledge of the technology and a broad experience of applications gained from working with users in the UK and all over Europe. He is currently European business manager for Viscotek products. Viscotek is a Malvern Instruments company. 0.50 0.80 1.10 1.40 1.70 3.20 3.60 4.00 4.40 4.80 Linear Branched Log MW Supplies & Services 6.80 5.20 5.60 6.00 6.40 Log (Molecular weight) the classified directory from LC•GC Europe To advertise in this section call Laura Howell today on +44 (0)1244 393 149 or email: lhowell@advanstar.com to reserve your space Figure 7: Polycarbonates/branching quantification. 2.80 2.40 Lambda 2.00 Bn 1.60 1.20 0.80 0.40 0.70 4.20 4.60 5.00 5.40 Number of branches 2.50 2.30 2.10 1.90 1.70 1.50 1.30 1.10 0.90 0.70 0.50 4.20 Branching frequency (M) R RBn M 1000D ION CHROMATOGRAPHY Cecil Instruments the name you can trust presents Log (Molecular weight) 4.60 5.00 5.40 Log (Molecular weight) Ion Chromatographs Website: www.viscotek.com Covering your requirements now and in the future www.cecilinstruments.com email: info@cecilinstruments.com http://www.thecolumn.eu.com http://www.cecilinstruments.com http://www.viscotek.com http://www.cecilinstruments.com
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