The allylic bromide functionality within brominated poly(isobutylene-co-isoprene), or BIIR, is amenable to substitution by a wide range of nucleophiles. The objective of this work was to gain insight into the dynamics of these substitution reactions, and to develop methods for accelerating these processes. Of particular interest was the reactivity of exomethylene (Exo-Br) and bromomethyl (BrMe) isomers found within BIIR toward various nucleophiles, and catalytic techniques for affecting the proportion of these isomers. BIIR isomerization can be catalyzed through ionic chemistry involving soluble Lewis acids such as zinc stearate and through a nucleophilic SN2’ rearrangement with soluble bromide salts such as tetrabuylammonium bromide (TBAB). The compatibility of TBAB with other nucleophiles makes it a preferable choice, but further rate enhancements can be realized using the corresponding iodide salt (TBAI). TBAI serves not only as nucleophilic isomerization catalyst, but also accelerates halide displacement from BIIR by an in-situ formation of an allylic iodide intermediate. Studies of BIIR isomerization and substitution reactions involved solvent-borne reactions of tetrabutylammonium acetate (TBAAc) and solvent-free reactions with PPh3 and 2-[2-(dimethylaminoethoxy)ethanol]. In all cases, the BrMe isomers were more reactive to nucleophilic substitution than Exo-Br. Since the esterification of BIIR with TBAAc generates TBAB as a reaction by-product, displaced bromide catalyzes the isomerization of Exo-Br to the more reactive BrMe isomers. As a result, these esterifications exhibit auto-accelerating dynamics. Similar behaviour is observed for solvent-fee alkylations of PPh3 and tertiary amines, since the resulting onium bromide salts are effective isomerization catalysts. All reactions show some increase in rate with the addition of TBAI, supporting the concept of nucleophilic catalysis. / Thesis (Master, Chemical Engineering) -- Queen's University, 2009-09-28 09:50:26.649

The allylic bromide functionality within brominated poly(isobutylene-co-isoprene), or BIIR, alkylates primary amines repeatedly to generate thermoset products at reaction rates that are too fast to support commercial rubber processing operations. The objective of this work was to assess the utility of latent N-nucleophiles as curatives and modification reagents for BIIR. Ideally, BIIR formulations containing these latent amines would not cure at standard compound mixing temperatures, but support high crosslinking rates and yields upon heating to conventional vulcanization temperatures. Carbon dioxide-derived salts of ammonia, including (NH4)2CO3, (NH4)HCO3 and (NH4)H2NCO2, can be mixed with BIIR without incurring crosslinking at temperatures below 100oC, but they generate adequate crosslink yields upon heating to 160oC. The corresponding CO2-derived salts of primary amines decompose below 100oC and, therefore, do not provide adequate scorch protection when mixed with BIIR. Latency was conferred on primary amines using imine derivatives, in particular N-alkylbenzaldimine and its substituted analogues. These latent curatives are activated by hydrolysis, thereby providing a means of controlling active nucleophile concentrations, and minimizing crosslinking activity at 100oC without impacting negatively on cure rates at 160oC. The scorch problems generated by primary amines extend to BIIR cure formulations employing conventional sulfur and ZnO curatives. In contrast, imine analogues are shown to provide low temperature scorch stability without impacting negatively on high temperature cure rates and extents. / Thesis (Master, Chemical Engineering) -- Queen's University, 2010-02-01 15:18:16.004