Date of Award

Fall 12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

Committee Chair

Robson F. Storey

Committee Chair Department

Polymers and High Performance Materials

Committee Member 2

Jeffrey S. Wiggins

Committee Member 2 Department

Polymers and High Performance Materials

Committee Member 3

William L. Jarrett

Committee Member 3 Department

Polymers and High Performance Materials

Committee Member 4

Derek L. Patton

Committee Member 4 Department

Polymers and High Performance Materials

Committee Member 5

James W. Rawlins

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

In the first project, we demonstrated a new reaction, which is a subset of the Friedel‑Crafts alkylation reaction, in which the alkylating carbocation undergoes a cleavage reaction prior to reaction with the aromatic substrate. This reaction was discovered by the observation that when a PIB containing a large amount of coupled fraction was subjected to a mixture of protic and Lewis acids (HCl/TiCl4) in the presence of an alkoxybenzene compound, the coupled fraction was quantitatively converted to its constituent monofunctional chains, which became functionalized by the alkoxybenzene.

In the second project, a commercial polymer, poly(isobutylene-co-isoprene) (butyl rubber) was used as a substrate upon which the aforementioned electrophilic cleavage and functionalization reaction was performed. The goal of this project was to degrade a high molecular weight, main-chain olefin-containing copolymer of isobutylene into low molecular weight difunctional telechelic polyisobutylenes. This general process, though not necessarily proceeding by the aforementioned novel chemical reaction, has been described in the literature as “constructive degradation.” Though we were unable to synthesize truly telechelic polyisobutylenes by this method, we were able to demonstrate this method as a viable route to low molecular weight multifunctional PIBs.

In the third project, we attempted to synthesize a random copolymer, previously reported by Kennedy et al., of isobutylene and 2,4-dimethyl-1,3-pentadiene (DMPD). The interest in this copolymer was based on its structural similarity to the coupled PIB mentioned in the first project. However, we found that these two monomers are not well suited to the creation of random copolymers due to a large difference in reactivity ratios. The project presented in this chapter was then redirected toward the structural characterization of the products of attempted copolymerization and of the homo-polymerization of DMPD.

In the fourth project, we investigated the copolymer of isobutylene and β-pinene as a substrate for the aforementioned cleavage/functionalization reaction. We were able to synthesize high molecular weight copolymers of these two monomers via slurry polymerization catalyzed by either TiCl4 or ethylaluminum dichloride (EADC), and though the degradation and functionalization kinetics were much slower than for butyl rubber, we did observe a drastic decrease in molecular weight accompanied by functionalization of the polymer, thus proving this chemistry is applicable to copolymers of isobutylene other than butyl rubber.

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