The challenging fabrication of sub-100-nm structures with high aspect ratio by UV-nanoimprint lithography (NIL) is addressed in this work. Thermal shrinkage is induced by cooling the structures below room temperature to avoid the issues commonly arising during the release of the polymeric nanostructures from the master. The UV-NIL has been performed to obtain OrmoComp(A (R)) nanostructures using OrmoStamp(A (R)) working stamps copied from Si masters. Nanoridges and nanopillars with 45 nm width and 380 nm thickness have been fabricated with a corresponding aspect ratio of 8.5. This is, to the best of our knowledge, the highest aspect ratio achieved using organic-inorganic hybrid materials at the sub-100-nm scale.