A Thermodynamic Polymer Cross-Linking System Based on Radically Exchangeable Covalent Bonds

Abstract

A thermodynamic covalent cross-linking system utilizing alkoxyamine units as thermally reversible covalent bonds was demonstrated. By heating the poly(methacrylic ester)s containing alkoxyamine units on the side chain, the cross-linking reaction was achieved as a result of a radical exchange reaction of alkoxyamine moieties. Kinetic studies have revealed that the cross-linking behavior depends remarkably on concentration and reaches equilibrium at a given reaction time, and characteristic reaction behaviors for thermodynamic reactions have been observed. The de-cross-linking reaction was carried out by heating the cross-linked polymer in the presence of an excess amount of alkoxyamine. It was found that the cross-linked points thermally dissociate and that the reaction system is reversible under stoichiometric control.

Development of materials and technologies for control of polymer recycling

“…Otsuka et al 73,74 demonstrated a thermodynamic covalent crosslinking-decrosslinking system utilizing alkoxyamine units (Scheme 19). By heating the poly(methacrylic ester)s having alkoxyamine unit side chains, the crosslinking reaction was achieved under stoichiometric control as a result of radical exchange reactions of alkoxyamine moieties.…”

Arm-replaceable star-like nanogels: arm detachment and arm exchange reactions by dynamic covalent exchanges of alkoxyamine units

“…Recently, 'reorganizable chemical gels' in which the crosslinking structures change in response to specific external stimuli have been developed. 3 Several functionalities, such as sol-gel transitions [3][4][5] and controlled insertion of monomer units into crosslinking points, 3 have been reported. Note that the concept of 'dynamic covalent (bond) chemistry' , 6,7 which deals with equilibrium states of compounds based on covalently bonded systems, has contributed to the development of reorganizable chemical gels.…”

“Substitutable” Polymer Brushes: Reactive Poly(methacrylate) Brushes with Exchangeable Alkoxyamine Units in the Side Chain

“…These systems are based on the principle of reversibility of CON bonds in alkoxyamine derivatives as dynamic covalent bonds. 18 Our group has reported that the reorganization of polymers by using alkoxyamine units is useful in reversibly synthesizing graft polymers, 19 crosslinked polymers, 20,21 cyclic polymers, 22 linear polymers with desired molecular weights and compositions, 2325 and star polymers.…”