Remarkably high miscibility of octa-substituted POSS with commodity conjugated polymers and molecular fillers for the improvement of homogeneities of polymer matrices

Thermal Degradation of Photoluminescence Poly(9,9-dioctylfluorene) Solvent-Tuned Aggregate Films

The progression of the green emission spectrum during the decomposition of polyfluorenes (PFs) has impeded the development and commercialization of the materials. Herein, we constructed a solvent-tuned aggregated PFO film with the aim of retarding the material’s thermal degradation behavior which causes a significant decline in optical properties as a result of phase transformation. The tuning of the aggregate amount and distribution was executed by applying a poor alcohol-based solvent in chloroform. It emerges that at a lower boiling point methanol evaporates quickly, limiting the aggregate propagation in the film which gives rise to a more transparent film. Furthermore, because of the modulated β-phase conformation, the absorption spectra of PFO films were red-shifted and broadened. The increase in methanol percentage also led to a rise in β-phase percentage. As for the thermal degradation reactions, both pristine and aggregated PFO films exhibited apparent changes in the UV-Vis spectra and PL spectra. In addition, a 97:3 (chloroform:methanol) aggregated PFO film showed a more defined emission spectrum, which demonstrates that the existence of β-phase is able to suppress the unwanted green emission.

Recent Progresses on Designable Hybrids with Stimuli-Responsive Optical Properties Originating from Molecular Assembly Concerning Polyhedral Oligomeric Silsesquioxane

In this review, we describe recent progresses on the stimuli-responsive hybrid materials based on polyhedral oligomeric silsesquioxane (POSS) and their applications as a chemical sensor. In particular, we explain the unique functions originating from molecular assembly concerning POSS-containing soft materials mainly from our studies. POSS has an inorganic cubic core composed of silicon-oxygen (Si-O) bonds and organic substituents at each vertex. Owing to intrinsic properties of POSS, such as high thermal stability, rigidity, and low chemical reactivity, various robust hybrid materials have been developed. From the numerous numbers of POSS hybrids, we herein focus on the environment-sensitive optical materials in which molecular assembly of POSS itself and functional units connected to POSS should be a key factor for expressing material properties. We also explain the mechanisms of chemical sensors originating from these stimuli-responsive optical properties. Stimuli-responsive excimer emission and pollutant detectors, nanoplastic sensors with the water-dispersive POSS networks, trans fatty acid sensors, turn-on luminescent sensors for aerobic condition and fluoride anion sensors are described. We also mention the mechanochromic polyurethane hybrids and the thermally-durable mechanochromic luminescent materials. The roles of the unique optical properties from soft materials composed of rigid POSS, which doesn't have significant light-absorption and emission properties in the visible region, are surveyed.

Paintable Hybrids with Thermally Stable Dual Emission Composed of Tetraphenylethene-Integrated POSS and MEH-PPV for Heat-Resistant White-Light Luminophores

Thermally stable dual emission followed by white-light luminescence from hybrid materials is reported. Hybrid films were prepared with a spin-coating method with the mixture solution containing tetraphenylethene (TPE)-integrated polyhedral oligomeric silsesquioxane (POSS) and poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV). TPE-tethered POSS (TPE-POSS) showed high compatibility with MEH-PPV. Therefore, homogeneous films with variable concentrations of TPE-POSS were obtained. Owing to good dispersion of rigid silica cubes into matrices, POSS-containing films demonstrated high thermal stability toward molecular rearrangement by annealing as well as pyrolysis, similar to conventional polymer hybrids. Furthermore, it was found that TPE-POSS was able to enhance emission efficiencies, probably by suppressing chain aggregation. By modulating introduction ratios of TPE-POSS, dual-emission properties followed by white-light luminescence composed of cyan and orange emissions from TPE-POSS and MEH-PPV, respectively, were accomplished. It should be noted that these color balances can be preserved even in the high-temperature region (425 K). Finally, white-light luminescent materials with thermal durability were obtained.

Synthesis, characterization and use of a POSS-arylamine based push–pull octamer

This article reports on the synthesis and first use of a POSS-arylamine based push–pull octamer as molecular donor in organic solar cells.

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.

One-pot strategy for synthesis of open-cage silsesquioxane monomers

A novel synthetic strategy to access POSS monomers has been proposed; one reaction site of an open-cage POSS was capped, and the remaining two silanol groups were functionalized for polymerization. Importantly, the monomer can be obtained by one-pot synthesis without any troublesome isolation process.

Optical, Electrical and Thermal Properties of Organic⁻Inorganic Hybrids with Conjugated Polymers Based on POSS Having Heterogeneous Substituents

Preparation of organic⁻inorganic hybrids with conventional conjugated polymers such as polyfluorene (PF) and poly(3-hexylthiophene) (P3HT) were demonstrated via the facile blending in solution by employing polyhedral oligomeric silsesquioxane (POSS) having heterogeneous alkyl substituents. From the optical measurements, it was shown that the modified POSS derivatives played a critical role in facilitating amorphous state of polymer matrices. Interestingly, although inter-strand interaction decreased after POSS addition in the hybrid films, thermal stability can be enhanced in the presence of the modified POSS with long alkyl chains. Furthermore, it was demonstrated that carrier mobilities through the hybrid film was minimally reduced by POSS. These results suggest that POSS should be a versatile building block to form hybrid with various types of polymers for enhancing durability without loss of electronic properties of organic components.

Self-Assembly and Applications of Amphiphilic Hybrid POSS Copolymers

Understanding the mechanism of molecular self-assembly to form well-organized nanostructures is essential in the field of supramolecular chemistry. Particularly, amphiphilic copolymers incorporated with polyhedral oligomeric silsesquioxanes (POSSs) have been one of the most promising materials in material science, engineering, and biomedical fields. In this review, new ideas and research works which have been carried out over the last several years in this relatively new area with a main focus on their mechanism in self-assembly and applications are discussed. In addition, insights into the unique role of POSSs in synthesis, microphase separation, and confined size were encompassed. Finally, perspectives and challenges related to the further advancement of POSS-based amphiphilics are discussed, followed by the proposed design considerations to address the challenges that we may face in the future.

Rh-catalyzed direct arylation of a polyhedral oligomeric silsesquioxane

Conjugation of a polyhedral oligomeric silsesquioxane (POSS) with the π-electrons of functional organic units has recently attracted much attention. This is the first example of catalytic direct arylation of a POSS.

Heat-Resistant Mechanoluminescent Chromism of the Hybrid Molecule Based on Boron Ketoiminate Modified Octasubstituted Polyhedral Oligomeric Silsesquioxane

The development of a heat-resistant mechanoluminescent chromic (MLC) dye based on an organic-inorganic hybrid molecular scaffold is reported. Luminescent organoboron complexes were introduced into polyhedral oligomeric silsesquioxane (POSS) at each vertex through the rigid linker structure in the Suzuki-Miyaura cross-coupling reaction. From optical measurements, it was found that the crystalline state of the modified POSS showed orange emission. By adding mechanical forces to the sample, regular structures collapsed. Correspondingly, the emission color turned to yellow. Interestingly, the yellow-emissive amorphous state can be preserved during heating. By radially distributing luminescent chromophores on the rigid cube, both optical and thermal properties can be modulated to realize heat- resistant MLC behavior. POSS can contribute not only to expressing the MLC behavior, but also to improving thermal stability in the amorphous state. This is the first example, to the best of our knowledge, to offer the rational design of a heat-resistant MLC material.