Research on Preparation, Structure and Properties of TiO₂/Polythiourethane Hybrid Optical Films with High Refractive Index

Abstract

Hybrid optical films of TiO2‐triethoxysilane‐capped polythiourethane (TCPTU) with high refractive indices have been prepared via an in situ sol‐gel method. The high refractive index triethoxysilane‐capped polythiourethane (TCPTU) was synthesized by polyaddition of the triethoxysilane‐modified trimercaptothioethylamine (TMTEA) and 2,2′‐dimercaptoethylsulfide (MES) with 2,4‐tolylene diisocyanate (TDI). The titania content in the hybrid films can be adjusted from 0 to 80 wt.‐% by the feed ratio of titania precursor [Ti(OBu)4] to polymer (TCPTU). Both FTIR and DSC analyses indicate that there is chemical bonding between the titania domain and the polymer chain. TGA results suggest that the titania of high content was successfully incorporated into polymer matrices and this series of hybrid films have good thermal properties. AFM measurements indicate that in the hybrid films the titania domains are of nanosize scale and the domain size averagely decreases from 60–80 nm to 5–20 nm with increasing content of titania, and the variation of surface roughness for the hybrid films has the same trend. These may be relative to the content of TCPTU and the interaction between titania and polymer (TCPTU). The refractive indices of the hybrid films at 632.8 nm increased from 1 632 to 1 879 as the titania content varied from 0 to 80 wt.‐%.AFM image of the hybrid film.magnified imageAFM image of the hybrid film.

Synthesis and Optical Properties of Soluble Polyimide/Titania Hybrid Thin Films

“…The volume fractions were calculated from the weight fraction using the densities of polyimide BTDA-DMMDA and amorphous TiO 2 . [9,34] The refractive indices of the prepared hybrid thin films at 633 nm increase from 1.66 of PI0 to 1.82 of PI40. This suggests that increasing the volume fraction of the TiO 2 segment results in a linear increase in the refractive index, [35] thus suggesting the tuning of the refractive index with the TiO 2 content.…”

“…Controlling of morphology and domain size of the hybrid materials can produce high performance films or membranes. Applications of hybrid materials in optics and optoelectronics have been studied recently including waveguide materials, [1][2][3][4][5][6] high refractive index films, [7][8][9][10] UV-shielding films, [11,12] nonlinear optical materials, [13][14][15] light-emitting materials, [16,17] low dielectric constant materials, [18][19][20][21][22] and protective layer materials. [23,24] Polyimides have been recognized as suitable polymers for electronics, optoelectronics, and packing materials due to their excellent dielectric properties, thermal stability, Full Paper DOI: 10.1002/mame.200600244 Summary: In this study high-refractive-index polyimide/ titania hybrid optical thin films were successfully prepared using a sol-gel process combined with spin coating and multistep baking.…”

In situ preparation of nanoparticles/polymer composites

“…With the change of TiO 2 content in the hybrid films from 0 to 80 wt%, the refractive index of the hybrid films at 632.8 nm increases from 1.632 to 1.879. These hybrid materials can be potentially used as high refractive index optical films in the design of optics [76,77] .…”

Hyperbranched Polymer/TiO2 Hybrid Nanoparticles Synthesized via an In Situ Sol‐Gel Process

“…This can be explained taking into account that, if the dispersion of the inorganic particles inside the matrix is particularly good and the formation of covalent bonds between the two phases occurs, some organic chains may remain trapped inside the inorganic network giving a higher residue at a higher temperature than expected. [7,34] Hardness Table 2 also summarizes the hardness values for the coatings according to the standard ASTM pencil test. As expected, the presence of the TiO 2 in the coating enhances the hardness properties.…”

“…In particular, polymers combined with metal oxides nanoparticles can, as reported in the literature, lead to composites characterized by improved chemical, thermal, optical, electronic, and mechanical properties. [2][3][4][5][6][7] The incorporation of titanium oxide nanoparticles in thin films and coatings is especially encouraging since by this surface hardness can be significantly improved and, on the other hand, self-cleaning and antimicrobial properties can be introduced based on the photocatalytic effect induced by some titanium oxide modification.…”