Entropy‐Driven Selectivity for Chain Scission: Where Macromolecules Cleave. Issue 4 (10th December 2015)

• Record Type: Journal Article
• Authors: Pahnke, Kai; Brandt, Josef; Gryn'ova, Ganna; Lin, Ching Y.; Altintas, Ozcan; Schmidt, Friedrich G.; Lederer, Albena; Coote, Michelle L.; Barner‐Kowollik, Christopher
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 4(2016)
• Page Start: 1514
• Page End: 1518
• Publication Date: 2015-12-10
• Subjects: cycloadditions -- entropic effects -- polymers -- supramolecular chemistry -- thermodynamics; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201508531
• Languages: English
• ISSNs: 1433-7851

Abstract

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. Abstract : Middle versus end? When all other conditions are equal, bond cleavage in the middle of molecules is entropically much more favored than bond cleavage at the end. Experimental and theoretical approaches were used to study the selectivity of bond cleavage or dissociation of both covalent and supramolecular adducts. The findings have extensive implications for other fields of chemistry.