Jitendra S. Rathore

Facile chemical rearrangement for photopatterning of POSS derivatives

We report a useful acid-catalyzed crosslinking reaction which enables the direct photopatterning of POSS derivatives to form robust nanoporous matrices. Octakis(dimethylacetoxyethyl siloxy) POSS and octakis(dimethylacetoxypropyl siloxy) POSS were synthesized from commercially available octahydrido-POSS. Both the acetoxyethyl- and acetoxypropyl functionalities were observed to undergo thermal rearrangement at temperatures above 300 °C to form Si–O–Si bonds, thus forming a crosslinked POSS network. Interestingly, the same functionalities were also acid sensitive, and the chemical rearrangement occurred at much lower temperatures. Thus, patterned nanoporous features were lithographically generated when a photoacid generator (PAG) was used as a photosensitive agent to initiate the crosslinking of the POSS derivatives. The dielectric properties were evaluated for the crosslinked POSS films, which had a dielectric constant ∼2.3 and an elastic modulus of ∼2.0 GPa. These materials hold great promise for developing a photopatternable low-k material which eliminates the need for sacrificial layers when patterning low-k dielectric films.

Homogeneous catalysis: Catalysts feel the force

Latent catalysts require activation, and this is often achieved with either heat, light or an additional chemical agent. By attaching polymer chains to known classes of metal–carbene complexes, it has now been shown that mechanical force can also be used to induce catalytic activity.