ORDERED AND DISORDERED PNA MOLECULES IN MESOPOROUS MCM-41

Para-nitroaniline (pNA) has been incorporated into the one-dimensional channels of mesoporous MCM-41, the hexagonal member of the M41S famil y of ordered mesoporous silicate materials. The composite material sho ws a number of remarkable features, depending on the sorption procedur e for the organic component, the after treatment, and the annealing ti me of the composite. In X-ray diffraction experiments different states of one-dimensional ordering of the sorbate molecules in the channel p ores are observed. in agreement with the molecular dipole, chain-like coherent domains with the long axis of the sorbate molecule parallel a s well as perpendicular to the host channel axis show up. In aged samp les the periodic ordering of the pNA molecules is lost, and nonlinear optical properties of the composite have been measured in second harmo nic generation experiments indicating the presence of a polar directio n in the sample. (C) Elsevier Science Inc. 1997.