Project 1. Synthesis of PIB-silsesquioxane stars via the sol-gel process. Project 2. Solution and aqueous suspension/emulsion polymerization of isobutylene coinitiated by bis(bispentafluorophenylboryl)tetrafluorobenzene.

摘要

Project 1. The objective of this research was to investigate the use of sol-gel chemistry for the joining of well-defined polyisobutylene (PIB) prearms to form PIB-silsesquioxane stars. The synthetic strategy for star formation involved the living polymerization of isobutylene (IB) followed by quantitative allylic end functionalization to yield PIB-CH2-CH = CH2 (o-allyl-PIB) prearms. Hydrosilation of the resultant prearms with trifunctional silanes bearing hydrolysable groups (e.g. triethoxysilane) was then conducted to afford reactive o-SiR3-PIB (R = OEt, OMe, Cl) prearms and star formation was effected by subsequent hydrolysis/condensation of these prearms. Although many variables were investigated including: prearm concentration, solvent identity, catalyst identity, catalyst concentration, reaction time, reaction temperature, and added tetraalkoxysilanes; only the chemical identity of the silyl terminus and prearm molecular weight had a significant bearing on star formation.; Project 2. A great deal of interest exists in the development of initiating systems for isobutylene polymerization that produce high molecular weight polymers in high yields at high temperatures in the absence of chlorinated solvents. Use of initiating systems containing weakly coordinating anions (WCAs) is one strategy for meeting these goals and it was realized that such initiating systems could be derived from 1,2-C6F4[B(C 6F5)2]2 (1). This research began with the initial synthesis of 1 and led to the development of an improved synthetic procedure for this compound. Modeling experiments carried out on the ionization of cumyl-based cationogens by 1 showed it to be as effective as SbF5 and led to the synthesis of a previously unknown compound, [Ph3C][1,2-C6F4 [B(C6F5)2]2], which served as a model ion pair.; Moreover, 1 readily coinitiated isobutylene polymerization under anhydrous conditions in conjunction with various cationogens in the presence of a proton trap. Although these polymerizations were well behaved, the proton trap was shown to degrade initiating carbocations. Alkylaluminum scrubbing agents were also shown to be detrimental to polymerization as coinitiated by 1. 1 was found to be highly effective as a coinitiator for protically-induced polymerization of isobutylene. This research ultimately led to the discovery/development of the first aqueous suspension/emulsion polymerizations of isobutylene and copolymerizations with isoprene.