title: Entropy-Driven Selectivity for Chain Scission: Where Macromolecules Cleave.
abstract: We show that, all other conditions being equal, bond cleavage in the middle of molecules is entropically much more favored than bond cleavage at the end. Multiple experimental and theoretical approaches have been used to study the selectivity for bond cleavage or dissociation in the middle versus the end of both covalent and supramolecular adducts and the extensive implications for other fields of chemistry including, e.g., chain transfer, polymer degradation, and control agent addition are discussed. The observed effects, which are a consequence of the underlying entropic factors, were predicted on the basis of simple theoretical models and demonstrated via high-temperature (HT) NMR spectroscopy of self-assembled supramolecular diblock systems as well as temperature-dependent size-exclusion chromatography (TD SEC) of covalently bonded Diels-Alder step-growth polymers.
authors.affiliation: Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 18, 76131, Karlsruhe, Germany.|Institut für Biologische Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Pahnke
authors.affiliation: Leibniz-Institut für Polymerforschung Dresden, Hohe Strasse 6, 01069, Dresden, Germany.|Technische Universität Dresden, 01062, Dresden, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Brandt
authors.affiliation: ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University (ANU), Canberra, ACT, 0200, Australia.|Ecole polytechnique fédérale de Lausanne, Switzerland.
authors.forename: Ganna
authors.initials: G
authors.lastname: Gryn'ova
authors.affiliation: ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University (ANU), Canberra, ACT, 0200, Australia.
authors.forename: Ching Y
authors.initials: CY
authors.lastname: Lin
authors.affiliation: Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 18, 76131, Karlsruhe, Germany.|Institut für Biologische Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Ozcan
authors.initials: O
authors.lastname: Altintas
authors.affiliation: Evonik Industries AG, Paul-Baumann-Strasse 1, 45764, Marl, Germany.
authors.forename: Friedrich G
authors.initials: FG
authors.lastname: Schmidt
authors.affiliation: Leibniz-Institut für Polymerforschung Dresden, Hohe Strasse 6, 01069, Dresden, Germany. lederer@ipfdd.de.|Technische Universität Dresden, 01062, Dresden, Germany. lederer@ipfdd.de.
authors.forename: Albena
authors.initials: A
authors.lastname: Lederer
authors.affiliation: ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University (ANU), Canberra, ACT, 0200, Australia. michelle.coote@anu.edu.au.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Coote
authors.affiliation: Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 18, 76131, Karlsruhe, Germany. christopher.barner-kowollik@kit.edu.|Institut für Biologische Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany. christopher.barner-kowollik@kit.edu.
authors.forename: Christopher
authors.initials: C
authors.lastname: Barner-Kowollik
keywords: cycloadditions; entropic effects; polymers; supramolecular chemistry; thermodynamics