Supramolecular Cross-Linking of Thiophenylene Polymers via Multiple Hydrogen Bonds toward High Refractive Index

Abstract

Dihydroxy-substituted poly(phenylene sulfide) (DOHPPS) was synthesized via oxidative polymerization of bis(2,6-dimethoxyphenyl) disulfide and subsequent deprotection. The synergistic effect of multiple-hydrogen-bond cross-links and the rigidity of the thiophenylene backbone afforded dense yet amorphous supramolecular networks, resulting in a polymer with visible transparency and an ultrahigh refractive index (n D = 1.85).

Molecular Structure and Properties of Sulfur‐Containing High Refractive Index Polymer Optical Materials

“…[ 8 ] Polyphenylene sulfide (PPS) with high refractive index is usually obtained by condensation of aromatic monomers containing thiol groups with halogen‐containing monomers. [ 7,10,22–25 ] In addition, Oyaizu and his coworkers [ 26,27 ] obtained ultrahigh refractive index polymers with n D > 1.80 by introducing hydroxyl groups into the PPS backbone and using intermolecular hydrogen bonding interactions. As an engineering plastic, PPS has good mechanical and thermal properties, but more benzene rings will lead to an increase in dispersion and a relatively large density.…”

“…[ 10 ] Oyaizu and his coworkers are committed to introducing hydroxyl groups on the PPS chain, and improving the refractive index by reducing the polymer volume through intermolecular interactions. [ 26,27 ] The π–π interactions in the rigid and zig‐zag PPS main chain form a well‐balance with the intermolecular hydrogen bonds formed by –OH, as shown in Figure 5b,c. [ 26 ] It not only inhibits the π–π interaction between aromatic rings, but also prevents the excessive interaction between hydroxyl groups, resulting in high solubility and transparency of bulk materials while maintaining amorphous properties.…”

“…[ 26 ] It not only inhibits the π–π interaction between aromatic rings, but also prevents the excessive interaction between hydroxyl groups, resulting in high solubility and transparency of bulk materials while maintaining amorphous properties. [ 26 ] The hydroxyl monosubstituted OHPPS and disubstituted DOHPPS exhibit refractive indices of 1.80 and 1.85 at 633 nm, [ 26,27 ] respectively. In addition, the method of reducing the molecular volume should pay attention to prevent the occurrence of material crystallization and opacity caused by excessive internal interaction.…”

“…At the same time, sulfur is easy to be introduced into the polymer chain, so the element sulfur is the most commonly used atom for preparing high refractive index materials. [ 10 ] Nowadays, there are many studies on sulfur‐containing HRIPs, such as low dispersion and high transparency of episulfide resins, [ 20,21 ] polyphenylene sulfide with good mechanical properties, [ 7,10,22–27 ] and sulfur‐containing polyimide with high chemical resistance, [ 17,28–35 ] etc. When designing and synthesizing sulfur‐containing HRIPs for practical production applications, researchers should not only consider how to improve the refractive index of the polymer, but also make the polymer have low dispersion, low birefringence, high transparency, and good mechanical properties.…”

High Refractive Index Copolymers from Aromatic Heterocycle‐Based Vinyl Sulfides and Phthalimide/Maleimide Derivatives

“…Various synthetic methodologies that produce high refractive index polymers and hybrids also rely on the incorporation of phosphorus units, [16] highly polarizable atoms (Si, Ge, Sn), [17] zinc, [18] zirconium, [19] and selenium units, [9,[20][21][22] and employments of charge-transfer complexation [23] and hydrogen bonds. [24] In addition, heteroaromatic rings are attractive building blocks for high-refractiveindex polymers because ─C═N─C─ bonds exhibit higher molar refraction (4.10) than ─C═C─C─ bonds (1.73). [25] Therefore, triazines, [26][27][28] pyridazines, [29] and pyrimidines, [29][30][31] which contain ─C═N─C─ bonds, have been employed as efficient units in main-chain-type polymers to enhance their refractive indices.…”