Non-equilibrium Properties of Thin Polymer Films
Sivasurender Chandran, Günter Reiter. In Matyjaszewski et al. (Eds.): Macromolecular Engineering: From Precise Synthesis to Macroscopic Materials and Applications, 4 Volumes, 2nd ed. Edition, Wiley-VCH Verlag GmbH, 2022. ISBN 9783527344550
Rapid industrial processes often freeze polymers in nonequilibrium conformations, which, in turn, cause material properties that are significantly different from the predictions of equilibrium theories. Such deviations in properties may introduce enhanced material performance. Thus, by choosing appropriate processing pathways, we potentially can control macroscopic properties and performance of polymers. However, due to our current lack of fundamental understanding of the behavior of nonequilibrated polymers, we have to rely on empirical knowledge, imposing trial-and-error approaches for achieving desired properties. Considering these aspects, we discuss recent studies on polymer films revealing that quantitative relations exist between properties and processing pathways, suggesting possible relations for processing-induced deviations in chain conformations. These relations propose that long-living and long-ranged correlations between polymers have been induced by processing, as indicated by the observation of relaxation times much longer than known for equilibrated polymers. We present an example where control of processing conditions for thin films allowed to translate the molecular relaxations during equilibration into a predictable lifting of macroscopic loads. Motivated by the presented results, we conclude that a comprehensive understanding of polymers with nonequilibrium conformations may not only expand the available spectrum of polymer properties but will also widen the scope of polymer science.