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A sequential self-repetitive reaction (SSRR) based on carbodiimide (CDI) chemistry was utilized for preparing a high-yield wholly aromatic polyimide. The polyimide was synthesized with 4,4'-methylene-diphenylisocyanate (MDI) and a di(acid-ester) compound which was derived from the ring-opening reaction of 3,3',4,4'-oxydiphthalic dianhydride (ODPA) at room temperature by the addition of equimolar methanol. Poly-CDI was first synthesized from MDI. The di(acid-ester) compound was then reacted with poly-CDI to form poly(N-acylurea). After curing process, N-acylurea moiety was converted to di(ester-amide) structure via SSRR and further subjected to a ring-closure reaction to form the wholly aromatic polyimide with a T-g of 247 degrees C. This approach was further taken to prepare thermally stable nonlinear optical (NLO) materials. Similarly a diimide-diacid containing chromophore was reacted with poly-CDI to obtain an intermediate, poly(N-acylurea). The poly(N-acylurea) with the ester side groups would exhibit excellent organosolubility, which enabled the fabrication of high quality optical thin films. After in situ poling and curing processes, N-acylurea moiety was converted to di(ester-amide) structure via SSRR and further subjected to a ring-closure reaction to form the wholly aromatic NLO polyimide with an electro-optical coefficient, r(33) of 25 pm/V (830 nm). Excellent temporal stability at elevated temperatures (200 degrees C) and a waveguide optical loss of 2.5 dB cm(-1) at 1310 nm were also obtained

A series of thermally stable organic/inorganic second-order nonlinear optical (NLO) composites via sequential self-repetitive reaction (SSRR) and sol-gel process has been developed. This SSRR is based on carbodiimide (CDI) chemistry. The difunctional azo chromophores (2,4-diamino-4'-(4-nitrophenyl-diazenyl)azobenzene (DNDA)) was reacted with excessive amount of 4, 4'-methylenediphenylisocyanate (MDI) to form poly-CDI, and subsequently trimellitic anhydride (TMA) was added to obtain poly(N-acylurea). The organic/inorganic composites containing prepolymer of phenyltriethoxysilane (PTEOS) and poly(N-acylurea) in different weight ratios (10:90, 30:70, 50:50, 70:30, 90:10 wt%) were prepared, respectively. The moderate glass transition temperature (T-g) characteristic of the poly(N-acylurea) allows the NLO-active polymer to achieve high poling efficiency. After in situ poling and curing process, the T(g)s of the composites were elevated, and higher than that of the pristine poly(amide-imide) sample. Electro-optical (EO) coefficients (r(33)) Of about 5.5 similar to 18.0 pm/V at 830 nm were obtained. Excellent temporal stability at 100 degrees C, and waveguide characteristics (3.1-4.2 dB/cm at 830 nm) were also obtained for these composites. Copyright (C) 2008 John Wiley & Sons, Ltd

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