Thermal analyses of dye Disperse Red 1 grafted onto silica nanoparticles

Abstract

Dye-grafted silica nanoparticles (GSiO 2 ) were synthesized via a dual-step process involving, first, attachment of the organic dye Disperse Red 1 (DR1) to the coupling agent, 3-isocyanatopropyltriethoxysilane, by means of urethane bonds, and then grafting of the silylated-DR1 onto silica nanoparticles ($6 nm) prepared by hydrolysis and condensation of tetraethoxysilane in a sol-gel process. Dye-adsorbed silica nanoparticles (DSiO 2 ) were also prepared for comparison, for which DR1 was bound only physically to silica instead of covalent bonds. The thermal behaviors of the formed GSiO 2 and DSiO 2 were examined by means of differential scanning calorimetry and thermal gravimetric analysis. The results showed that both the particle size and silica content have significant effects on the thermal behaviors of the dye-adsorbed and dye-grafted silica. Moreover, crystalline DR1 lost significantly its crystallinity after being adsorbed on silica, and became virtually amorphous after being grafted onto silica. The formed particles were UV-cured with a multifunctional acrylic monomer to yield color coatings on glass substrates. UVvisible spectra indicated that brightness and color saturation of the coating comprising GSiO 2 could be maintained better than that comprising DSiO 2 after heat treatment at 280°C.

Preparation of dye-grafted-silica/poly(acrylate) color coatings with enhanced color stability at elevated temperatures

“…Figure 2(a) shows the FTIR (Fourier transform infrared) spectra of MR (ICPTE-DR1) formed at 50°C at different times after reaction of ICPTES with DR1. Similar to those reported previously (Chang et al , 2015), the absorption bands at 2,272 cm −1 corresponds to the vibrations of −NCO, while 1,103 and 1,079 cm −1 correspond to the −SiOC group of ICPTES. The −OH of DR1 appears as a broad hump around 3,500 cm −1 .…”

“…DR1 was linked to ICPTES through an urethanation reaction, as depicted in Scheme 1(a). The detailed synthetic procedure can be found in our previous publication (Chang et al , 2015). Briefly, DR1 was dissolved in deaerated/dehydrated MEK at 50°C.…”

“…The stability, particularly the thermal and UV resistance, can further be enhanced if the dye molecules were covalently connected to the silica nanoparticles. This was made possible by incorporation of a dual functional coupling agent, which is able to react at one site to the reactive groups of the dye, while at the other to the −OH groups on the surface of silica particles (Bringley et al , 2008; Chang et al , 2015; Kim et al , 2017; Li et al , 2008; Liang et al , 2013; Nicolescu et al , 2010; Mao et al , 2017; Marino et al , 2001; Seckin and Gultek, 2003; Seckin et al , 2003).…”

“…In a previous work, based on the approach proposed by Cui et al (2004, 2007), we synthesized the Disperse Red 1 (DR1)-grafted silica nanoparticles with incorporation of the coupling agent, 3-isocyanatopropyltriethoxysilane (ICPTES) (Chang et al , 2015). The reaction pathway is demonstrated in Scheme 1.…”