Transcending the Trade-off in Refractive Index and Abbe Number for Highly Refractive Polymers: Synergistic Effect of Polarizable Skeletons and Robust Hydrogen Bonds

High-refractive-index polymers (HRIPs) are attractive materials for the development of optical devices with high performances. However, because practical components and structures for HRIPs are limited from the viewpoint of synthetic techniques, it has proved difficult using traditional strategies to enhance the refractive index (RI) of HRIPs to more than a certain degree (over 1.8) while maintaining their visible transparency. Here, we found that poly(phenylene sulfide) (PPS) derivatives featuring both methylthio and hydroxy groups can simultaneously exhibit balanced properties of an ultrahigh RI of n _D = 1.85 and Abbe number of ν_D = 20 owing to the synergistic effect of high molar refraction and dense intermolecular hydrogen bonds (H-bonds). This brand new strategy is anticipated to contribute to the development of HRIPs displaying ultrahigh RI with adequate Abbe numbers beyond the empirical n _D-ν_D threshold, which has not been achieved to date.

Development of Novel Triazine-Based Poly(phenylene sulfide)s with High Refractive Index and Low Birefringence

High-refractive-index (high-n) polymers with a high optical transparency and low birefringence (Δn) have been desired in progressive optoelectronic devices. However, the trade-off between high-n and low-Δn remains a challenge at present. Here, the development of a novel array of high-n, high-sulfur-containing, highly transparent, colorless poly(phenylene sulfide) (PPS) polymers bearing triazine units in the main chains is reported. Six new triazine monomers T1-T6 with various pendant groups via different linkers (-O- and -NH-) could be prepared for developing PPSs with high-n and low Δn values. These PPSs (P1-P6) were obtained by the polycondensation of T1-T6 with commercial aromatic dithiol, 4,4'-thiobisbenzenethiol, respectively, which showed very high-n values (n av: 1.6902-1.7169 at 633 nm), high optical transparency (T % > 90% @ 400 nm), and low birefringence (Δn = 0.0015-0.0042). All the PPSs displayed high n ∞ values (1.6340-1.6654), providing valuable information for the development of high-n triazine-based PPS materials for application not only in the visible region but also in the near-infrared region.

Excellent performance of aromatic polyguanamines induced by multiple hydrogen bondable tetraazacalix[2]arene[2]-triazine ring in their main chain

A series of poly(guanamine) (c-PG)s containing tetraazacalix[2]arene[2]-triazine (mPDA2CyC2) were successfully prepared by solution polycondensation of mPDA2CyC2 with various aromatic diamines in an aprotic organic solvent with a lithium chloride additive (5 wt%) at 150 °C for 6 hours. The number-average molecular weights (M n)s of these c-PG polymers reached up to 31 500, with a relatively broad molecular weight distribution (M w/M n) of 5.3. They showed good solubility in aprotic organic solvents, such as N-methylpyrrolidone and N,N-dimethylacetamide at a concentration of 2 mg mL-1. The glass transition temperatures (T g) of the c-PG polymers were in the range 359 °C-392 °C, approximately 160 °C higher than those of counterpart polymers (i.e., with no aza-calixarene-based PG (l-PG)). The coefficients of thermal expansion (CTEs) of the c-PG polymers were 29.7-48.1 ppm K-1 (at 100 °C-150 °C), much lower than those of l-PG samples, i.e., 59.1-85.1 ppm K-1. Transparent and almost colorless c-PG films were successfully prepared by a solution casting method, showing maximum tensile strength (σ S), modulus (E γ), and elongation at break (E b) values of 151 MPa, 6.3 GPa, and 4.4%, respectively, for the c-PG polymer from mPDA2CyC2 and 4,4'-oxydianiline monomers. The corresponding l-PG film exhibited σ S, E γ, and E b values of just 76 MPa, 5.4 GPa, and 1.6%, respectively. These outstanding thermal and mechanical properties of the c-PG polymers can be attributed to their multiple hydrogen bonding interaction between mPDA2CyC2 residues in the polymer backbone. This interaction was identified by infrared spectroscopy measurements at the broad absorption band around 3000-3400 cm-1.

In situ reduction of chloroauric acid (HAuCl4) for generation of catalytic Au nanoparticle embedded triazine based covalent organic polymer networks

A facile synthetic route was applied to generate Au@COPN-1 hybrids via in situ reduction of Au³⁺ with no additional reducing agent. Au@COPN-1 is a promising catalyst platform and good biocompatibility confirmed by dynamic real-time cell analysis.