Two cross-linkable parylene polymers, tert-butylethynyl and phenylethynyl, were deposited via the well-known Gorham method from a unique synthesis route to their respective cyclophane precursors. Unlike the bulky substituent group-functionalized parylenes which exhibit low melting points (parylene E), these polymers are stable to 350 °C under vacuum because of the cross-linking reaction which eliminates their respective melting points. This is the conversion of ethynyl groups to the diene moieties. tert-Butylethynyl-parylene exhibits an isotropic index of refraction, whereas phenylethynyl-parylene is optically birefringent and has an index of refraction, much like parylene N, of 1.6595 after a 350 °C vacuum anneal. The development of cross-linkable parylene polymers allows the improvement of both the thermo-mechanical and optical properties of parylene. It is also very positive that the precursors can be made in a high-yield scalable process, for example, a 60% 3-step route for 4-(tert-butylethynyl)[2.2]paracyclophane.