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The allylic bromide functionality in brominated poly(isoprene-co-isobutylene) rubber (BIIR) reacted readily to nucleophilic substitution by imidazole-derivatives. When reacted with the rubber, alkylimidazoles formed a stable non-thermoset ionomeric elastomer that has dynamic mechanical properties similar to those of vulcanizates; however, the strength is in its ion-pair aggregation. Structural characterization of the polymeric products was accomplished by spectroscopy with comparisons to the model compound prepared from brominated 2,2,4,8,8-pentamethyl-4-nonene (BPMN). Physical properties tests on the elastomers of varying ionic content (0-1 mol%) were done using solution viscosity and rheology, and demonstrated that small amounts of ionic functionality noticeably improved properties with a plateau of properties being attained as full conversion to ionic content was reached. The reaction of imidazole with BIIR created a thermoset elastomer that formed an ionomer and thermoset after its second alkylation. These materials provided excellent scorch protection and delayed curing at high temperatures, while still reaching good storage modulus. Formation of an elastomer with a pendant imidazole group was also achieved; however, it did not perform as well as the free imidazole. / Thesis (Master, Chemical Engineering) -- Queen's University, 2010-10-27 11:52:54.442

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Polystyrene-co-4-hydroxystyrene ionomers (3.0-22 mol %) were synthesized via neutralization of demethylated polystyrene-co-4-methoxystyrene. The polystyrene-co-4-hydroxymethylstyrene ionomers (2.5-19.4 mol %) were prepared from the partial chloromethylation of polystyrene, followed by esterification, saponification, and finally neutralization. The physical properties of the ionomers as well as their nonionic precursors were studied by calorimetry, torsion pendulum and small-angle X-ray scattering (SAXS). Stress relaxation studies of the ionomers were also done. While evidence for ion aggregation was obtained for the styrene-4-hydroxystyrene ionomers from SAXS and torsion pendulum studies, no firm evidence was obtained for the styrene-4-hydroxymethylstyrene ionomers. Stress relaxation studies on both systems, however, showed failure of time-temperature superposition at high ion contents, indicating that these systems are both thermorheologically complex. The glass transition temperature of the matrix, the size of the ionic aggregates and the strengths of the ionic interactions within these large aggregates were related to the type and position of the ionic group.

Several systems, containing up to 10 mol % ionic co-units, were investigated by dynamic mechanical techniques, primarily above the glass transition. The ionic units in quaternized poly(styrene-co-4-vinylpyridine) mildly retard chain diffusion. In contrast, the rubbery plateau of blends of poly(styrene-co-styrene-sulfonic acid) and poly(ethyl acrylate-co-4-vinylpyridine), compatible above ca. 4 mol % co-unit content, is greatly extended, independent of co-unit content. It is postulated that the kinetics of ion dissociation and reassociation in the blends are faster than chain diffusion, effectively trapping chain entanglements for comparatively long times. Time-temperature reducibility applies to both the cationic ionomers and the blends. It fails at high plasticizer contents for poly(styrene-co-sodium methacrylate), of 5 mol % ion content, plasticized by a styrene oligomer. Two relaxation processes are evident in this system. Nonpolar diluents plasticize the ionic regions of carboxylated more than sulfonated ionomers. Polar diluents destroy the effect of ionic associations in the transition and rubbery zones.

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