A promising methodology for fabricating highly thermally stable organic second-order nonlinear optical (NLO) thin films containing low molecular weight chromophoric (LMWC) molecules was sustained by electric-field-induced layer-by-layer assembly. The new LMWC molecule but-2-enedioic acid mono- [2-({4-[4-(2-carboxy-2-cyano-vinyl)-phenylazo]-phenyl}-methyl-amino)-ethyl] ester (BCPE) was first designed and synthesized successfully, which possesses two negative groups at both ends and still retains the molecular polarity after ionization. Under a dc electric field, the density of the oriented chromophores BCPE deposited on the substrate is increased largely, and upon UV irradiation, accompanied with the transition of the ionic bonds between the layers to covalent bonds, the resulting NLO films possess excellent environmental stability and high thermal stability (the resulting films can retain 92% of the polar order up to 200°C), which may rival the properties of the latest poled polymer films for electro-optic devices.Recently, various novel and high-performance secondorder nonlinear optical (NLO) organic materials, owing to their wide application in electro-optical (E-O) modulated devices and advantages over inorganic materials, have been prepared and investigated by numerous research groups. 1 Compared with poled polymer materials which have been developed widely and remarkably in the past 20 years, 2 organic NLO film materials fabricated using low molecular weight chromophoric (LMWC) molecules have attracted less attention. Using LMWC molecules, we can design and prepare more kinds of NLO films purposely and further explore the relationship between the structures and the properties. 3 As we know, highly ordered arrangements of LMWC molecules can be obtained by Langmuir-Blodgett (LB) techniques and LMWC molecules can be ordered by self-assembly, through selective ionic interaction, hydrogen bonds, complexation, and so forth, with the layer-by-layer (LbL) technique. 4 However, LB film materials are restricted in the application of nonlinear optics because of their poor mechanical stability. In turn, when the LbL technique is used for LMWC molecule organization, the self-ordered degree, density, and stability of LMWC molecules in LbL films still need to be improved effectively due to the weak driving force for assembly and instable molecular interaction between layers. 5 Accordingly, it is hitherto still considered to be a challenge for researchers to find a constructive combination of LMWC molecules and polyelectrolytes that could be used to improve the deposition density of LMWC molecules and construct stable NLO films with high performance for E-O devices. 6 In this study, the authors clarify a new strategy that first introduces the electric-field-induced LbL assembly technique to the preparation of stable NLO multilayer films. Using this method, a new LMWC molecule (see the Supporting Information) and the polyelectrolyte diazoresin Koetse, M.; Laschewsky, A.; Wischerhoff, E.; Jullien, L.; Persoons, A.; Verbiest, ...

The SHG active nontraditional LB architectures of monolayers and multilayers were fabricated based on molecular interactions of hydrogen bonding. After photopolymerization of the diacetylene groups, the SHG thermal stability of the obtained LB films could be improved substantially and all the polymerized films exhibited unique SHG thermal rebounding phenomena.

Two crosslinkable second‐order nonlinear optical polymers were prepared by copolymerization of 2,3,4,5,6‐pentafluorostyrene, styrene (St), glycidyl methacrylate (GMA) and 1‐(4‐nitrophenyl)‐2‐(4‐{[2‐(methacryloyloxy) ethyl] ethylamino}‐phenyl) diazene (DR1M) via the sealed‐tube reaction technique. These polymers were characterized using 1H, 13C and 19F NMR spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The crosslinkable polymers have high molecular weights, good organosolubility, excellent film‐forming properties and high glass transition (106–110 °C) and thermal decomposition temperatures (290–350 °C) after being crosslinked. Furthermore, the polymer films possess not only high values (12–16 pm V−1) of electro‐optical coefficient (r33) at 1.3 µm wavelength but also low optical loss (1.7 dB cm−1) at 1.55 µm wavelength, which is of interest for applications in electro‐optical devices. Copyright © 2004 Society of Chemical Industry