Methyl chloride, molecular association

Further complications in the interpretation of the variation in coupling constants arise from solvent effects. The existence of molecular association in both methyl chloride and triethylamine in the liquid phase has been demonstrated by observation of directly bonded coupling constants increased coupling is ob-... 

These 2D spectra can also provide detailed structural information about the solution structure of polymers. Figure 3.26 shows the 2D NOESY spectra of a 50 50 mixture of poly(vinyl chloride) and poly(methyl methacrylate) at 38 wt% concentration [29], a polymer pair reported to form a compatible blend in films cast from tetrahydrofuran (THF). Most polymer mixtures do not form such miscible blends because of the unfavourable entropy associated with molecular-level mixing, and for those pairs that do form compatible blends there is usually some specific interaction (ionic, hydrogen bonding, etc.) between the groups on the different chains [30]. From examination of the chemical structure of the two polymers, however, it is not obvious which interchain interactions lead to the formation of a compatible blend. It has been suggested that hydrogen-bond formation between the poly(methyl methacrylate) carbonyl and the poly(vinyl chloride) electron-deficient methine proton is responsible for this interaction [31]. The top spectrum shows several intra-... 

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