Polyhedral Oligomeric Silsesquioxane (POSS)-Styrene Macromers

Four polyhedral oligomeric silsesquioxane (POSS) macromers, R7Si8O12styrene (R=isobutyl, cyclopentyl, cyclohexyl, or phenyl), containing a single polymerizable styrene unit were synthesized from the POSS-trisilanols R7Si7O9(OH)3 in a high yield and purity. The base-assisted reaction to produce these macromers appears to be general for POSS-trisilanols of this type. However, in some cases it may be necessary to control the rate at which the base is introduced during reaction to prevent unwanted side reactions that decompose the trisilanol. Cyclohexyl-, cyclopentyl-, and isobutyl-substituted POSS-stryenes (at 30 wt% or approximately 4 mol% loadings) undergo free radical bulk polymerizations with styrene to produce polymers that show variation in the modulus above the glass transition temperature. The phenylPOSS derivative is too insoluble in styrene to undergo this polymerization. The effect on the modulus is more pronounced for the copolymers containing 30 wt% cycloalkylPOSS than that seen with isobutylPOSS, which is similar to that for bulk polymerized polystyrene. The effect of the group at the POSS cage on bulk polymer properties has been noted before and is presumed to arise from differences in polymer microstructure.