Nonlinear optical hyperbranched polyaspartimide/montmorillonite nanocomposites based on reactive fluorine- or phosphorous-containing organoclays

A series of novel hyperbranched polyaspartimide/organoclay nanocomposites were developed for second-order nonlinear optics. The hyperbranched polyaspartimides were synthesized from an azobenzene chromophore bis(4-aminophenyl(4-(4-nitrophenyl)-diazenyl)phenyl)amine (DAC; A2 type monomer) and a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-containing trimaleimide (Dopo-trimaleimide; B3 type monomer) via Michael addition reaction. Moreover, reactive fluorine- and phosphorous-containing organoclays (F-montmorillonite, i.e. F-MMT and P-montmorillonite, i.e. P-MMT) which had been prepared by modifying the high aspect ratio silicate layers of MMTs with two different swelling agents 1,1,1-tris[4-(4-amino-2-trifluoromethylphenoxy)-phenyl]ethane (F-triamine) and (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl)tris(4-aminophenyl)methane (P-triamine) were respectively incorporated into the nonlinear optical hyperbranched polyaspartimides. The organoclays were exfoliated and dispersed in the hyperbranched polyaspartimide films. The incorporation of exfoliated organoclay F-MMT could effectively enhance the electro-optical (EO) coefficients and temporal stability of the hyperbranched polyaspartimides. The hyperbranched polyaspartimide/F-MMT nanocomposite exhibited temporal stability (r33(t)/r33(0) = 73%) at 100 °C, EO coefficient r33 of 20.9 pm/V, and optical loss of 3.0 dB/cm at 1310 nm.