Solid-state nuclear magnetic kinetics

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

Kinetic gelation models [178] have been used to determine, within experimental error, the fraction of constrained and unconstrained double bonds over a wide range of conversions in the polymerization of ethylene glycol dimethacrylate. The amount of unconstrained and constrained functional groups was determined experimentally by solid state nuclear magnetic resonance spectroscopy. The rules for determining constraint in the model were that all pendant double bonds and all monomers in pools of six or less are constrained. Monomers in pools of seven or more are assumed to be unconstrained. Whether a site is constrained or not does not affect the reactivity only the analysis of the model is affected by the rules defining constraint. 

Solid-state nuclear magnetic resonance Interaction between nuclear magnetic Polymerization kinetics, time evolution of... 

The immobilization of ionic liquids (ILs) is intimately connected with spectroscopy, with the goal to characterize the support, the IL film, or the catalyst. Besides the characterization by BET surface methods and catalytic activity, the most powerful tools are nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy, which are discussed separately in the following. NMR spectroscopy is mostly performed in the solid state, where either the support itself or the IL film with the dissolved catalyst therein is characterized. For the latter case, some liquid-state NMR experiments are also applicable. Besides the characterization of the SILP system itself, solubility effects of the reactants using liquid-state NMR are well established to understand the kinetics. Those examinations are beyond the theme of this chapter and are therefore not discussed here. 

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