title: Influence of chain length on the alpha-beta bifurcation in oligomeric glass formers.
abstract: A series of oligo(propylene glycol) dimethyl ethers has been investigated using dielectric spectroscopy in order to relate features of the glass transition dynamics to the number of monomer units N in the chain. The results show that (i) when scaled with the glass transition temperature, the beta relaxations systematically become faster for larger N whereas the alpha relaxations display nearly identical temperature evolutions, i.e., the alpha-beta bifurcation shifts towards shorter times for larger N, (ii) the bifurcation scenario displays a crossover in behavior at N approximately 10 monomer units, signaling the transition from oligomeric to polymeric behavior, and (iii) the beta relaxation has a cooperative nature.
authors.affiliation: Department of Physics and DEAS, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: J
authors.initials: J
authors.lastname: Mattsson
authors.forename: R
authors.initials: R
authors.lastname: Bergman
authors.forename: P
authors.initials: P
authors.lastname: Jacobsson
authors.forename: L
authors.initials: L
authors.lastname: Börjesson