Development of sulfur-containing high performance polymers for optical applications

Abstract

Recently, high refractive polymers with good thermal properties and low bi-refringence have been developed for many advanced optical applications, including anti-refraction coatings, camera lenses, and telecommunication systems. In Chapter 1, in introduction, the fields of use of high refractive materials, the general approach to prepare high refractive index polymers, and research trends of high refractive polymers will be described. The research presented in Chapter 2 is focused on the effect of sulfurated pol-ymers on the refractive index. The new sulfur-containing monomers were synthesized, and sulfurated polymers were polymerized through these monomers. In detail, this chapter is divided into two main parts depending on type of polymer: (2.1) sulfurated polyimides (PIs) and (2.2) sulfurated polybenzoxazoles (PBOs). In Chapter 2.1, a new diamine, bis(4-((4-aminophenyl)thio)phenyl)(phenyl)phosphine oxide (BATPO), con-taining phosphine oxide and thioether bonds was prepared via the Grignard reaction, followed by an aromatic substitution reaction. The polyimides (PIs) were synthesized by the conventional two-step polycondensation from several aromatic dianhydrides such as 4,4’-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4’-oxydiphthalic anhydride (ODPA), and with the BATPO. All produced PIs exhibited outstanding thermal proper-ties, including high thermal decomposition temperatures (>500 oC), glass transition tem-perature (Tg) in the range of 212-264 oC, and optical transparency higher than 80 % at 450 nm at a thickness of about ca. 10 μm. In particular, 3SDEA-BATPO exhibited not only high refractive index (1.725) but also low birefringence (0.0087) due to the heavy atom effect derived from high sulfur and phosphorous contents in the polymer main-chain. In Chapter 2.2, a series of aromatic polybenzoxazoles (PBOs) containing sulfur atom in their main chains have been developed. All of the PBOs were prepared from newly synthesized hydroxyl-diamine 4,4'-bis(4-amino-3-hydroxyphenylthio)diphenylsulfide (3SDA) and aromatic diacyl chlorides such as 4,4'-((thiobis(4,1-phenylene))bis(sulfanediyl))dibenzoyl chloride (3SDBC), trans-1,4-cyclohexanedicarbonyl dichloride (trans-CHDC), isophthaloyl dichloride (IPC), and 4,4'-oxybis(benzoyl chloride) (OBC) via a conventional two-step procedure. The PBOs exhibited high thermal stability, including a thermal decompositon temperature (>430 oC) and a glass transition temperature (204255 oC). The PBO derived from 3SDA and 3SDBC exhibits very high refractive index, i.e., 1.7862 at 637 nm due to the high sulfur content (21.79%). The research in Chapter 3 presents synergistic effect of sulfur and chalco-gen atoms on the enhanced refractive indices of polyimides in the visible and near in-frared. The new PIs containing chalcogen atoms in polymer chains with an ultrahigh refractive index was prepared. A series of PIs were successfully synthesized via con-ventional two-step polycondensation from the diamines 4,4’-oxydianiline (ODA), 4,4'-thiodianiline (TDA), 4,4'-selenodianiline (SEDA), and 4,4'-tellurodianiline (TEDA) along with 4,4’-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA). The PIs exhibited good thermal stability, including a good thermal decompositon temperature (>390 oC) and a good glass transition temperature (183-217 oC). The PIs also exhibited high refractive indices of over 1.7. In particular, the TEDA-3SDEA was 1.778, which was the highest refractive index value of a PI ever reported.