Aminophenyl double decker silsesquioxanes: Spectroscopic elucidation, physical and thermal characterization, and their applications

The incorporation of cage-like silsesquioxanes (SQ) to form polymers has demonstrated property enhancements in areas such as: thermal and mechanical characteristics, flame retardance, dielectric properties, and oxidative resistance. However, with most hybrid polymers investigated, the attached SQs are pendant with respect to the polymer backbone. A recently developed class of these nano-structured, cage-like silsesquioxanes, formally known as double decker silsesquioxanes (DDSQ), offers the opportunity to form hybrid polymers with SQ cages as a part of the polymer backbone. However, during the capping reaction, these functionalized DDSQs generate cis and trans isomers with respect to the 3D Si-O core. Therefore, it is logical to characterize properties, which will allow for optimization of capping reaction parameters, particularly if one isomer is favored over the other. Moreover, these characteristics are also relevant when reacting or incorporating these isomers, or mixtures thereof, with other molecules to form novel materials.;In this dissertation, three aminophenyl DDSQs were synthesized. More specifically, two meta- aminophenyl DDSQs, which were differentiated according to the moiety attached to the D-Si (methyl or cyclohexyl), and one para-aminophenyl DDSQ with a methyl moiety were used. Chemical, physical, and thermal characteristics were evaluated for individual isomers as well as binary mixtures of different cis/trans ratios.;The 1H NMR spectra of the cis and trans isomers of these DDSQ had not previously been assigned to a degree that allowed for quantification, which was necessary for these studies. Thus, 1H-29Si HMBC correlations were applied to facilitate 1H spectral assignments and also to confirm previous 29Si assignments. Using 1H NMR not only saves time and material over 29Si NMR, but also provides a more accurate quantification, thus allowing for the ratio of cis and trans isomers present in each compound to be determined.;Solubility behavior was investigated for the individual isomers, such that separation techniques could be developed. It was found that cis isomers were 33 times more soluble than trans isomers for para-aminophenyl (R = methyl), and 22 times more soluble for the analogous meta-aminophenyl in a solution of THF and hexanes. For a more sterically hindered meta-aminophenyl (R = cyclohexyl), cis isomers were only 3.5 times more soluble, and the overall solubility was also the lowest.;Phase diagrams representing solid-liquid melt equilibria of the binary cis/trans mixtures were developed. Single crystal x-ray diffraction data of isolated isomers helped to interpret the phase behavior. Both compounds with a methyl moiety exhibited eutectic phase diagrams. Their trans isomers were higher melting and exhibited larger packing density. Changing from para- to meta-aminophenyl shifted the solid-liquid equilibrium further from ideal, with decreased activity coefficients. Cyclohexyl DDSQ exhibited an isomorphic phase diagram (a complete solid-solution), attributed to cyclohexyl being more similar in size to the phenyl moieties.;A specific application that was chosen for these DDSQ was high performance thermosetting oligoimides. They displayed advantages over their organic counterparts in areas such as the liquid to solid transition and viscosity, which improves the processing window. Additionally, they increased the overall degree of cross-linking leading to improved oxidative stability at elevated temperatures.