Podgorski, Maciej published the artcileMixed mechanisms of bond exchange in covalent adaptable networks: monitoring the contribution of reversible exchange and reversible addition in thiol-succinic anhydride dynamic networks, HPLC of Formula: 7575-23-7, the main research area is thiol succinic anhydride dynamic network bond exchange mechanism property.
Dynamic photopolymer networks that take advantage of the thermodynamically controlled reversibility of thiol-succinic anhydride adducts were synthesized from com. substrates and investigated as a new class of covalent adaptable networks (CANs). Through systematic studies of the catalyst and stoichiometry effects on the exchange dynamics two distinctive exchange mechanisms were found, and then demonstrated to contribute to the overall dynamic characteristics. By varying the catalyst activity, i.e. basicity and/or nucleophilicity, control over the dynamic responsiveness through changes in the type of dynamic covalent chem. mode (reversible addition vs. reversible exchange) was achieved in otherwise compositionally analogous materials. More specifically, the participation of the associative mechanism (thiol-thioester exchange) in the otherwise dissociative networks, and its relevance on materials properties was demonstrated by dielec. anal. (DEA) and dynamic mech. anal. (DMA). The activation energies (Ea) for viscous flow obtained from DMA stress relaxation experiments and from dielec. modulus and loss crossover points were shown to match well between the two techniques. The Ea in stoichiometric systems was found to be 110-120 kJ mol-1, whereas 50% excess thiol systems were characterized by Ea ranging 95-105 kJ mol-1. The thermodn. equilibrium conversion, estimated in the temperature controlled FTIR, for a stoichiometric 3-mercaptopropionate-succinic anhydride combination was determined at 92 ± 1% at ambient temperature, and decreased to 67 ± 1% at 120°C within one hour of equilibration time (ΔH° = -46 ± 5 kJ mol-1). Such high potential for reversibility of the thioester anhydride linkages resembles maleimide-furan diels-alder networks but has many other attributes that make these CANs of unprecedented value in fundamental research on dynamic materials.
Polymer Chemistry published new progress about Activation energy. 7575-23-7 belongs to class alcohols-buliding-blocks, name is Pentaerythritol tetra(3-mercaptopropionate), and the molecular formula is C17H28O8S4, HPLC of Formula: 7575-23-7.
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