Novel nonlinear optical, piezoelectric, pyroelectric, waveguide, and other materials are presented together with processes for their employment and articles formed thereby. Such materials, processes and articles comprise diacetylenes and polymers formed from diacetylenic species, which polymers are amenable to close geometric, steric, structural, and electronic control. Accordingly, it is now possible to design, formulate and employ new diacetylenic species and polymers formed therefrom to provide nonlinear optic, waveguide, piezoelectric, and pyroelectric materials and devices having surprising efficiencies and degrees of effect. According to a preferred embodiment of the invention, diacetylenes which are crystallizable into crystals having a noncentrosymmetric unit cell may form single crystals or may be elaborated into a thin film upon a substrate by the Langmuir-Blodgett technique. Such films may, optionally, be polymerized either thermally or by irradiation for use in nonlinear optical and other systems. According to other preferred embodiments, diacetylenes are covalently bonded to substrates through the employment of silane species and subsequently polymerized to yield nonlinear optic and other devices having high structural integrity in addition to high efficiencies and effects.