Chain-length dependent rheology and relaxation dynamics in glass-forming oligomers and polymers*

Understanding how a glass is formed on a microscopic level remains an outstanding problem in condensed matter physics; both the approach towards the glassy state and the molecular behavior within the glass remain to be fully understood. Moreover, how chain connectivity in oligomers and polymers affect the relevant molecular behavior is not presently clear. The work presented here addresses these questions through a systematic experimental study ranging from small molecules to oligomers and polymers, including molecular systems of different characteristics (flexibility, fragility, etc). The effects of molecular chain-length on the rheology and chain, structural and secondary relaxations are explored using a range of experimental techniques combined with computer simulations. Results attained from rheology, broadband dielectric spectroscopy, calorimetry, field cycling NMR, and computer simulations will be discussed, outlining their role in determining the material response for molecules of different chain-length and chemistries. The experimental and computational work will be presented in the context of established models and behaviour previously reported in the literature.