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Structural and motional heterogeneity in .alpha.,.omega.-dicarboxylatopolybutadiene: an NMR study

NMR relaxation data for α,η1-dicarboxylatopolybutadiene (M n = 4600 and 1900), in the acid and Zr-neutralized forms, illustrate graphically the qualitative features of thermoreversible structural crosslink formation, due to end-group interactions and the concomitant effect on molecular motion. These crosslinks are in the form of aggregates in the neutralized telechelic. The precise nature of end-group associations in the acid is less certain, but one can reasonably speculate that dimers or higher multiplets are formed. The ability to resolve end-group carboxyl and proton resonances gives more detailed, though, as yet, incomplete, insight into chain dynamics at the cross-link itself