Preparation of high-refractive-index trimethoxybenzene novolac-titania hybrid

Abstract

Recently, hybrid materials have received considerable attention owing to the fact that they particularly exhibit enhanced mechanical, thermal, and optical properties. Among these materials, optical materials, in particular, with a high refractive index have attracted considerable attention as advanced materials that can be applied to display devices, organic light-emitting diodes (OLEDs), and antireflective coatings. A sol-gel reaction was extensively used for the synthesis of inorganic moiety in order to cap on the functionalized organic structure. The possibility of developing hybrid materials with an improved refractive index using common polymers such as poly(methyl methacrylate) (PMMA) and polyimide (PI) has been investigated. It should be noted that large molecular volume fractions of an inorganic unit have an effect on the refractive index of a hybrid material. However, the morphology of the inorganic unit of a common polymer can have an adverse effect on the aggregated inorganic domain size between the inorganic sites and the organic matrixes. In order to develop a hybrid polymer with an improved refractive index, it is essential to control the inorganic domain size to less than 40 nm to avoid light scattering. A welldispersed inorganic moiety on a nanoscale, without aggregation units, is important from the viewpoint of many optical applications owing to the fact that the transparency of hybrid polymers has an impact on their advanced optical property. The possibility of controlling the aggregation size and achieving phase separation between a polymer matrix and inorganic materials, which are used to fabricate hybrid films, by a sol-gel reaction has been investigated by many researchers. Phenolic resins have been widely studied for their applications in many fields owing to the fact that they exhibit high thermal and chemical resistances and high mechanical strength and that they are inexpensive. However, the disadvantages of phenolic resins are that it is difficult to control their molecular weight, molecular structure, and reactivity. Therefore, we have been conducting studies to investigate the manner in which the solubility of phenolic resins can be improved; we have also been conducting studies to develop phenolic derivatives such as alkoxybezene, monoor multisubstituted phenol, and naphthalene derivatives. Functionalized common polymers have received considerable interest owing to the fact that they comprise improved reactive sites that serve as functional units for the attached pendent groups. In this communication, we report a simple method for synthesizing poly(phenylenemethylene):alkoxylated novolac (hybrid PPM) as an optical material. This research focused on improving the refractive index of functionalized PPM by the sol-gel reaction. An attempt was made to synthesize this hybrid phenolic resin with an improved refractive index by a simple synthetic route. Hybrid PPM comprising titania was synthesized by using a novel functionalized PPM. The synthesized PPM comprises a carboxylic acid group as the functional group.