Mono substituted octaphenyl POSSs: The effects of substituents on thermal properties and solubility

Four novel Polyhedral Oligomeric Silsesquioxanes (POSSs) having seven C6H5- groups linked to seven silicon atoms of cage, whilst a substituted −p (C6H4-X) group (X = -CH3, -OCH3, -F, -Cl) is linked to the eighth silicon atom, were synthesized and characterized by elemental analysis and 1H NMR. POSSs were degraded in both inert and oxidative atmosphere, and the temperatures at 5% mass loss (T5%) were determined as a measure of the resistance to thermal degradation. Differential Scanning Calorimetry (DSC) and solubility in CHCl3 and THF experiments were also performed and the results obtained were compared with those found for commercial octaphenyl POSS, which was also here studied. Mono substituted POSSs exhibited slightly lower T5% values and higher solubility than octaphenyl POSS. This behaviour was attributed to symmetry changes determined by the substitution of a hydrogen atom of a POSS phenyl group with various dimensions substituents.