Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 5: Polymer Networks and Elastomers I
CPP 5.6: Vortrag
Montag, 12. März 2018, 11:15–11:30, PC 203
Network formation and dynamics in H-bonding telechelic polymers: competition between association time and structural relaxation — •Martin Tress1, Kunyue Xing1, Pengfei Cao2, Shiwang Cheng1, Tomonori Saito2, Vladimir Novikov1, and Alexei Sokolov1,2 — 1University of Tennessee Knoxville, Department of Chemistry, Knoxville, Tennessee, USA — 2Oak Ridge National Lab, Chemical Sciences Division, Oak Ridge, Tennessee, USA
Reversible bonds between polymer chains can form supra-molecular networks which exhibit extraordinary mechanical properties. In fact, reversible bonds are a promising route to functional materials with self-healing properties. We study short telechelic polymers with H-bonding end-groups of different interaction strength and backbone flexibility. The glass transition temperature of flexible polydimethyl siloxanes (PDMS) does not vary with H-bond strength, but differs strongly from methyl-terminated PDMS. At the same time, Tg of the much stiffer telechelic polypropylene glycol (PPG) depends significantly on the H-bond strength. In contrast, viscosity strongly depends on the H-bond strength in the PDMS series while it remains almost the same in PPG with different end groups. Complementary measurements of shear modulus and dielectric relaxation indicate that these observations can be explained by competing lifetimes of supra-molecular associations and structural relaxations. Only if the association lifetime exceeds the characteristic segmental or chain relaxation time, the glass transition or viscosity will be affected by chain associations. Otherwise the chain end associations do not influence significantly Tg or viscosity.