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Progress in the development of a new class of multi-functional polyimides for use in electro-optical devices is reported. These polyimides contain hydroxymethyl-functional side-groups attached to the polymer backbone, allowing for the attachment of a wide variety of molecular species. It is shown that multiple types of organic molecules may be attached to the polymer simultaneously, with a quantitatively controllable distribution, to tailor the physical properties of the material. Methods for cross-linking the polyimides are presented, based on both modification to the backbone and the addition of difunctional additives (such as isocyanates) to solutions of the polymer during spin casting. Processing studies using spectroscopy to track the cross-linking reaction and its effects on organic nonlinear optical materials indicate that the latter method is compatible with poling processes for polymer guest/host systems with high nonlinear optical activities. Further studies using a novel thermomechanical analysis method demonstrate that the cross-linking reactions increase the glass transition temperature and inhibit physical relaxation processes in the cross-linked guest/host films.