Influence of chain length on the alpha-beta bifurcation in oligomeric glass formers.
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.
Mattsson
J
J
Department of Physics and DEAS, Harvard University, Cambridge, Massachusetts 02138, USA.
Bergman
R
R
Jacobsson
P
P
Börjesson
L
L