Morphology, optical properties, and curing behavior of UV-curable acrylate-siloxane polymer blends

Abstract

UV-curable organic-inorganic blends have captured lots of attention recently due to leveraging the positive features of polymer blending and radiation curing. However, the optical properties of such blends, including transparency, which is an important attribute in many applications, have not been sufficiently explored. In this study, a series of UV-Curable acrylate-siloxanes blends were prepared using different compositions and processing variables to obtain blends with promising transparency, and acceptable stability before and after curing. The variables include speed and time of mixing, siloxane functionality (-OH versus –CH3), the monomer/oligomer ratio in the acrylate phase, and the amount of compatibilizer.The spectrophotometric results revealed that blends containing 100 wt% of acrylate monomer as the acrylate phase and 10 wt% of compatibilizer in the siloxane phase, demonstrated the highest transparency regardless of the siloxane functionality. SEM illustrated that a two-phase droplet-in-matrix morphology was formed containing dispersed siloxane particles in an acrylate matrix. The incorporation of compatibilizer significantly reduced the average size of the droplets and increased the uniformity of their distribution. Additionally, Photo-DSC, RT-ATR, AFM, and refractometry methods respectively showed that the addition of the siloxane phase to the acrylate matrix, regardless of its functionality, reduced the heat of reaction and CC conversion, while increased the surface roughness and refractive index. The developed UV-Curable acrylate-siloxane blends showed promising stability and transparency, and present a potential platform for PDLCs.