Alexandros Chremos

National Institute of Standards and Technology

Influence of Molecular Shape on the Properties of Polymeric Materials

Abstract

 

Molecular shape is a fundamental feature of matter and its quantification in relation to material properties is crucial for the design of new materials. While for polymers in solutions it is well established that the overall size and shape of polymer chains dictate the polymer dynamics, it is unclear how molecular shape affects polymers in melt. In the current talk, I will present and discuss how the molecular shape through the variation of polymer topology (linear chains, stars, rings, and

bottlebrushes) in melt influences the structural, dynamical, and thermodynamical behavior for these systems. In particular, we find the existence of a configurational transition point between anisotropic chains and spherically symmetric particle-like structures. Curiously, at this transition point a number of distinct molecular topologies, such as star polymers having f = 6 arms, rings, and bottlebrushes, exhibit very similar thermodynamic and dynamical behaviors, which is a feature not predicted by mean field theories. Another consequence of our findings is that the ``Flory theorem'', indicating that polymer chains in the melt are similar to ideal chains without excluded volume, does not generally extend to polymers having a non-trivial topology. These counter-intuitive findings raise fundamental questions regarding the importance of chain topology in the packing and dynamics of polymeric materials.



Date: 11/9/2017
Time:11:00 (coffee & cookies will be served at 00:00)
Place:FORTH Seminar Room 1