Lecturer: Prof. Dr. Günter Reiter
Time: 2 + 1 st., Wed 10-12
Room: SR HH 3OG
5 ECTS
Start: 14.10.2024
Tutorials: n.V.
Program:
Many properties of long, chain-like polymers are determined by their enormous conformational entropy. However, various ways allow to increase or to reduce their conformational entropy, yielding a dramatic change in properties.
Entropy versus enthalpy: The “winner” depends on how many different conformations can be realized by polymer chains. For example, for the interaction between chemically identical polymers in a medium, a reduction in conformational entropy may lead to observations of opposite behavior (antagonistic properties). Accordingly, some experiments with polymers yield observations which appear counter to intuition. However, using basic concepts of polymer physics, these observations can be explained in a predictable manner.
Threshold value Sthreshold of the conformational entropy: Below Sthreshold one type of behavior is observed, while above Sthreshold the behavior may turn into its opposite (e.g., miscible ⇔ immiscible). Polymers which are soluble in a given solvent may become insoluble in the same solvent once their conformational entropy drops below Sthreshold, for example, due to shear-induced deformations.
Some further phenomena discussed in this course:
Breaking the symmetry by anchoring polymers at one end - “polymer brushes”
Adsorption of short versus long chain-like polymers follows the “law of the jungle” - the “big ones” always win.
Interfacial tension between chemically identical polymers ⇒ Autophobicity and its (antagonistic) temperature dependence.
Spreading ⇔ dewetting and adhesion ⇔ anti-adhesion of polymers on surfaces of identical polymers.
Competition of time scales: Viscoelasticity (segmental motion and motion of the whole chain), coil stretch transition …
Interplay of time and energy scales within a single molecule: Tuning adhesion or friction
Polymer crystallization: Cloning – self-seeding – stacking – generating “banded spherulites”
