DAST nanocrystal dispersion having fixed anisotropy may be enhanced by orientational factors.
Experimental
DAST, lauryl acrylate, and tricyclo[5.2.1.0 2,6 ]decane-4,8-dimethanol diacrylate (TD) were purchased from Aldrich Co. Inc. n-Dodecyltrimethylammonium chloride (DTMAC) and benzoin isopropyl ether (BIPE) were purchased from Tokyo Kasei Co., Ltd. DAST and BIPE were recrystallized twice from methanol and toluene, respectively. The other reagents were used without further purification. An ethanol solution (50 lL) containing DAST (5 mM) and DTMAC (5 mM) was injected into lauryl acrylate (5 mL) containing BIPE (0.1 M) and TD (1 wt.-%) according to the reprecipitation method [2]. The average nanocrystal size was obtained using a DLS-7000 dynamic light scattering analyzer (Otsuka Electronics); the viscosity and refractive index of the dispersion were 4.0 mPa s at 25 C and 1.444 at 20 C, respectively. A sample was positioned between the two poles of an electromagnet (Fluxdial precision electromagnet control system, Applied Magnetics Laboratory Inc.), which can operate at magnetic flux densities of up to 2.5 T, and the absorption spectra of the DAST nanocrystals dispersed in lauryl acrylate solution were measured in both the Faraday and Voigt configurations using a personal computer, the electromagnet, the detectable light from a Xe lamp light source (passed through a polarizer), a JASCO CT-25C monochromator, and a 2023 photodiode detector (New Forcus Inc.). After nitrogen gas had been bubbled through the DAST nanocrystal acrylate dispersion for 20 min, photocuring was performed in the magnetic field by irradiating the sample with UV light from a 500 W high-pressure mercury lamp (UI-501C, USHIO). To fix the anisotropic orientation of the DAST nanocrystal dispersion, we used a superconducting magnet (S15/17/40RT/13 horizontal magnet system, Oxford) having an output of up to 17 T. The optical rotatory dispersion spectra were measured using a JASCO J-820 spectropolarimeter.