| High molecular weight, soluble polybenzoxazoles (PBO) were synthesized by a non-traditional synthetic route. First, soluble polyhydroxyamides (PHA) were synthesized from various bis(o-aminophenol)s and diacid chlorides via solution polyamidation attempts at temperatures below 0{dollar}spcirc{dollar}C, then solution cyclized at 160-170{dollar}spcirc{dollar}C for a period of 6 hours or less. In contrast to typical PBOs synthesized via polyphosphoric acid, the resulting polymers were soluble in amide solvents at concentrations of up to 15 percent (wt/vol.) at 25{dollar}spcirc{dollar}C.; Of particular interest was the synthesis and characterization of the PBO based on terephthaloyl chloride, 2,2-Bis(3-amino-4-hydroxyphenyl)-1,1,1-3,3,3-hexafluoropropane (6F-TC), which was extensively studied. Block and graft copolymers were generated from 6F-TC PBO and oligomers of polypropylene oxide (PPO). The copolymers were fully characterized and used in order to determine whether foamed material with pore sizes on the submicron scale would be generated. The resulting foamed polymer matrix was then characterized using thermal and microscopic techniques. The density of the foamed material was determined and compared to that of the homopolymer. While the block copolymer produced foamed material with pore sizes in the desired submicron scale, the graft copolymers collapsed during the foaming process, resulting in a non foamed system.; Polycyanurate resins are known to have several attractive characteristics, such as low dielectric constants and low moisture absorption. A drawback to these resins, however, is their high degree of brittleness. The cyanate esters proposed for this study are based on the bisphenols with electron withdrawing characteristics, such as the phenylphosphine oxide structure. These monomers were synthesized by reacting the various novel bisphenols with cyanogen bromide, then characterized by proton and carbon NMR. The polymerization or "curing" of the resins was monitored for the disappearance of the carbon-nitrogen triple bond using FTIR. The cured polycyanurate resins were further investigated by DSC and TGA. In some cases, the adhesive bond strength of several resins was also measured. |
