Dispersion of carbon nanocapsules (CNC) in a liquid aromatic dicyanate, 4,4'-ethylidenediphenyldicyanate (LECy), and in the polycyanate (PCn) resin, derived from the subsequent cure of LECy, was attempted in this study. CNC was primarily oxidized to introduce carboxylic acid groups to yield carboxylated CNC (CNC-COOHs), which can then be dispersed in the monomeric LECy through hydrogen bond (H-bond) interactions between --COOHs in CNC-COOHs and cyanate (-O-C equivalent to N) groups in LECy. Upon heating, the constituent LECy proceeds to polycyclotrimerization to generate a PCn resin, with s-triazine rings as the crosslinking points. Here, the inherent s-triazine rings serve as H-bond sites to -COOHs in CNC-COOHs and effectively promote the homogeneity in the resulting CNC-COOHs/PCn composites; further, the H-bond interactions were confirmed by infrared spectroscopy. The CNC-COOHs clusters in the liquid LECy were characterized using light scattering, to reveal a wide-range of size distribution with a mean diameter of 278 +/- 25 nm. Transmission electron microscopy (TEM) was further applied to show the well dispersion of CNC-COOHs clusters in the PCn matrix phase of the resulting composite. The absorption and emission spectra of the resulting CNC-COOHs/PCn blend were also determined to show their characteristic properties of the photoluminescence (PL) of CNC-COOHs and PCn components. The emission spectrum of the resulting CNC-COOHs/PCn blend was bathochromically shifted compared with the pure PCn. This energy-transfer process is due to pi-pi electron overlapping of aromatic ring between the PCn matrix and the CNC-COOHs, resulting in the extended conjugated lengths. (c) 2006 Wiley Periodicals, Inc.