Diphenolic 9,9-Diarylfluorene Trimers and Derivatives Possessing Flexible Alkylene Chain Spacers: Synthesis of the Monomers, Their Polymerization, and Properties of the Resulting Polymers

Design, Synthesis and Properties of Semi-Alicyclic Colorless and Transparent Polyimide Films with High Glass Transition Temperatures and Low Retardation for Potential Applications in Flexible Electronics

Polyimide (PI) optical films with high glass transition temperatures (high-Tg), high optical transparency, and low optical retardations (low-Rth) are highly desired in advanced optoelectronic applications. However, the standard PI films usually suffer from deep colors, high optical anisotropies and limited Tg values. In the current work, a series of semi-alicyclic colorless and transparent PI (CPI) films were developed from hydrogenated pyromellitic dianhydride stereoisomers, 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride, and fluorene-containing diamines, including 9,9-bis(4-aminophenyl)fluorene and 9,9-bis(3-fluoro-4-aminophenyl)fluorene, respectively. The derived CPI films showed Tg values higher than 420 °C according to differential scanning calorimetry measurements. In addition, the fluorene-based CPI film showed optical transmittances higher than 80% at the wavelength of 400 nm, with yellow indices in the range of 0.60~1.01 and haze values below 3.0%. The CPI films showed average refractive indices from 1.5407 to 1.6309, extremely low birefringence at the level of minus fourth power of ten, and further exhibited quite low optical retardations below 10 nm.

Correlation of the Abbe Number, the Refractive Index, and Glass Transition Temperature to the Degree of Polymerization of Norbornane in Polycarbonate Polymers

The influences of the average degree of polymerization (D_p), which is derived from M_n and terminal end group, on optical and thermal properties of various refractive indexed transparent polymers were investigated. In this study, we selected the alicyclic compound, Dinorbornane dimethanol (DNDM) homo polymer, because it has been used as a representative monomer in low refractive index polymers for its unique properties. DNDM monomer has a stable amorphous phase and reacts like a polymer. Its unique reaction allows continuous investigation from monomer to polymer. For hydroxy end group and phenolic end group polymers, the refractive index (n_d) decreased with increasing D_p, and both converged to same value in the high D_p region. However, the Abbe number (ν_d) of a hydroxy end group polymer is not dependent on D_p, and the ν_d of a phenolic end group polymer is greatly dependent on D_p. As for glass transition temperatures (T_g), both end group series were increased as D_p increased, and both converged to the same value.