Characterization of long-chain branching effects in linear rheology

This is the last part of a series of five articles published in Journal of Rheology (Maier et al. (1998), Thimm et al. (1999a), Thimm et al. (2000a), Thimm et al. (2000c)) in which progress on the determination of binary molecular weight distributions from rheological data has been reported. In this article is discussed in how far the developed methods can also be used to characterize long-chain branching effects. Monomodal samples which contain long-chain branches will show two relaxation processes in the rheological examination, which are converted to two peaks in a corresponding molecular weight distribution. But these samples will show only one peak in a molecular weight distribution determined by a size-exclusion chromatography examination. This difference can be used to characterize long-chain branched materials as will be explained in this article. The usefulness of this method is demonstrated by examining polymers, which contain definite long-chain branches specified from the way, they were made.