Silsesquioxanes are compounds of formula (RSiO1.5)n, in which each silicon is bound to three bridging oxygens and to one organic group [1]. The most studied member is the cubic octamer, a cage of eight silicon atoms at the corners of a cube with oxygen along the edges and the organic substituent projecting outward [1]. The rigid inorganic core and the tunable organic shell make the molecule a hybrid building block, and the corner groups set solubility and compatibility with a matrix [2]. Because the cage carries one to eight reactive groups, it enters a material as a pendant unit, as a crosslinker or as the core of a star-shaped polymer [1]. Hydrolysis and condensation of trifunctional silanes give the cage, while incomplete condensation yields open or ladder structures [3].
- poss cage
- hybrid building block
- siloxane framework
- sol-gel condensation
- polyhedral oligomer
References
- Zhang, K.; Huang, S.; Zhang, Q.; Zhu, H.; Zhu, S.; Polyhedral oligomeric silsesquioxane‐based functional coatings: A review. The Canadian Journal of Chemical Engineering 2023, 101, 4979-4991, 10.1002/cjce.24857.
- Lorenz, V.; Fischer, A.; Edelmann, F.T.; Silsesquioxane chemistry.. Journal of Organometallic Chemistry 2002, 647, 245-249, 10.1016/s0022-328x(01)01434-6.
- Li, G.; Wang, L.; Ni, H.; Pittman, C.U.; Polyhedral Oligomeric Silsesquioxane (POSS) Polymers and Copolymers: A Review. Journal of Inorganic and Organometallic Polymers 2001, 11, 123-154, 10.1023/a:1015287910502.