Surface Modifier-Free Organic-Inorganic Hybridization To Produce Optically Transparent and Highly Refractive Bulk Materials Composed of Epoxy Resins and ZrO2 Nanoparticles

Recent Progress in Sulfur-Containing High Refractive Index Polymers for Optical Applications

The development in the field of high refractive index materials is a crucial factor for the advancement of optical devices with advanced features such as image sensors, optical data storage, antireflective coatings, light-emitting diodes, and nanoimprinting. Sulfur plays an important role in high refractive index applications owing to its high molar refraction compared to carbon. Sulfur exists in multiple oxidation states and can exhibit various stable functional groups. Over the last few decades, sulfur-containing polymers have attracted much attention owing to their wide array of applications governed by the functional group of sulfur present in the polymer repeat unit. The interplay of refractive index and various other polymer properties contributes to successfully implementing a specific polymer material in optical applications. The focus on developing optoelectronic devices induced an ever-increasing need to integrate different functional materials to achieve the devices' full potential. Several devices that see the potential use of sulfur in high refractive index materials are reviewed in the study. Like sulfur, selenium also exhibits high molar refraction and unique chemical properties, making it an essential field of study. This review covers the research and development in the field of sulfur and selenium in different forms of functionality, focusing on the chemistry of bonding and the optical properties of the polymers containing the heteroatoms mentioned above. The strategy and rationale behind incorporating heteroatoms in a polymer matrix to produce high-refractive-index materials are also described in the present review.

Superhydrophobic materials used for anti-icing Theory, application, and development

The accumulation of ice will reduce the performance of the base material and lead to all kinds of damage, even a threat to people's life safety. Recent increasing studies suggest that superhydrophobic surfaces (SHSs) originating from nature can remove impacting and condensing droplets from the surface before freezing to subzero temperatures, and it can be seen that hydrophobic/SH coating has good freezing cold resistance. But such anti-icing performances and developments in practical applications are restricted by various factors. In this paper, the mechanism and process of surface icing phenomenon are introduced, as well as how to prevent surface icing on SHS. The development of SH materials in the aspect of anti-icing in recent years is described, and the existing problems in the aspect of anti-icing are analyzed, hoping to provide new research ideas and methods for the research of anti-icing materials.

A Highly Controlled Organic-Inorganic Encapsulation Nanocomposite with Versatile Features toward Wearable Device Applications

Ultraviolet-curable polyurethane acrylate (PUA) materials can be used in a number of important applications spanning from microfluidics, surface patterning to wearable technology. For the first time, the potential of encapsulation of modified zirconia (ZrO₂ ) nanoparticles is reported in PUA-based hybrid films aimed to facilitate profoundly enhanced hardness and refractive index. By successfully manipulating the interfacial reaction conditions between ZrO₂ nanoparticles and PUA film, the PUA-based nanocomposites exhibit an ultrahigh hardness of 9 and superior refractive index of 1.64 (589.3 nm). The outcomes obtained pave the way for seamless application of nanozirconia/PUA as a potent encapsulating material that provides structurally morphable, water resistant, and optically transparent light emitting diodes toward wearables devices in healthcare.

Dispersions of Zirconia Nanoparticles Close to the Phase Boundary of Surfactant-Free Ternary Mixtures

The achievement of a homogeneous dispersion of nanoparticles is of paramount importance in supporting their technological application. In wet processing, stable dispersions were largely obtained via surfactant or surface functionalization: although effective, the use of dispersant can alter, or even impair, the functional properties of the resulting nanostructured systems. Herein, we report a novel integrated modeling and experimental approach to obtain stable ZrO₂ nanoparticle (NP) dispersions at native dimensions (about 5 nm) in homogeneous ternary mixtures of solvents (i.e., water, ethanol, and 1,2-dichlorobenzene) without any further surface functionalization. A miscibility ternary diagram was computed exploiting the universal quasi-chemical functional-group activity coefficient (UNIFAC) model, which was then experimentally validated. Dynamic light scattering (DLS) on these mixtures highlights that nanometric structures, resembling nanoemulsion droplets, form close to the mixture two-phase boundary, with a size that depends on the ternary mixture composition. ZrO₂-NPs were then synthesized following a classic sol-gel approach and characterized by XRD and Raman spectroscopy. ZrO₂-NPs were dispersed in HCl and mixed with different mixtures of ethanol and 1,2-dichlorobenzene (DCB), obtaining homogeneous and stable dispersions. These dispersions were then studied by means of DLS as a function of DCB concentration, observing that the nanoparticles can be dispersed at their native dimensions when the mass fraction of DCB was lower than 60%, whereas the increase of the hydrophobic solvent leads to the NPs' agglomeration and sedimentation. The proposed approach not only offers specific guidelines for the design of ZrO₂-NPs dispersions in a ternary solvent mixture but can also be extended to other complex solvent mixtures in order to achieve stable dispersions of nanoparticles with no functionalization.

High Refractive-Index Hybrids Consisting of Water-Soluble Matrices with Bipyridine-Modified Polyhedral Oligomeric Silsesquioxane and Lanthanoid Cations

We report high refractive-index (RI) films composed of polyhedral oligomeric silsesquioxane (SSQ) matrices and various lanthanoid cations. The SSQ matrices were constructed from octaammonium SSQ by connecting with bipyridine dicarboxylic acid, which is expected to capture cations. By modulating the feed ratio between SSQ and dicarboxylic acid, the series of the SSQ matrices were obtained with variable cross-linking ratios among the SSQ units. Thin transparent films were able to be prepared through the drop-casting method with the aqueous mixtures containing SSQ matrices and various kinds of lanthanoid salts up to 40 wt %. From RI measurements, it was revealed that the increase of the amount of the metal ion can significantly lift up the RI values. In particular, critical losses of Abbe numbers, which theoretically have the trade-off relationship toward increases in RI values, were hardly detected. This effect could be obtained by cation assembly in local spots that are assisted by SSQ.

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.