Linear rheology of diluted linear, star and model long chain branched polymer melts

We present experiments and theory on the diluted melt dynamics of monodispe rse entangled polymers of linear, star and H-shaped architecture. Frequency -dependent rheological data on a series of progressively diluted linear, st ar and H-polymers are in good agreement with a refined tube-model theory th at, for H-polymers, combines star polymer melt behaviour at high frequency, with linear polymer reptation behaviour at low frequencies. Taking into ac count the effect of dilution via some simple scaling relations, mild polydi spersity and by incorporating the high frequency Rouse modes, we are able t o model quantitatively the entire frequency range. This work suggests a nov el rheological route to analysing long chain branching in polymer melts.