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

Surface modifier-free hybridization of ZrO₂ nanoparticles (NPs) with epoxy-based polymers is demonstrated for the first time to afford highly transparent and refractive bulk materials. This is achieved by a unique and versatile hybridization via the one-pot direct phase transfer of ZrO₂ NPs from water to epoxy monomers without any aggregation followed by curing with anhydride. Three types of representative epoxy monomers, bisphenol A diglycidyl ether (BADGE), 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (CEL), and 1,3,5-tris­(3-(oxiran-2-yl)­propyl)-1,3,5-triazinane-2,4,6-trione (TEPIC), are used to produce transparent viscous dispersions. The resulting ZrO₂ NPs are thoroughly characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and solid-state ¹³C CP/MAS NMR measurements. The results from DLS and TEM analyses indicate nanodispersion of ZrO₂ into epoxy monomers as a continuous medium. A surface modification mechanism and the binding fashion during phase transfer are proposed based on the FT-IR and solid-state ¹³C CP/MAS NMR measurements. Epoxy-based hybrid materials with high transparency and refractive index are successfully fabricated by heat curing or polymerizing a mixture of monomers containing epoxy-functionalized ZrO₂ NPs and methylhexahydrophthalic anhydride in the presence of a phosphoric catalyst. The TEM and small-angle X-ray scattering measurements of the hybrids show a nanodispersion of ZrO₂ in the epoxy networks. The refractive index at 594 nm (<i>n</i>₅₉₄) increases up to 1.765 for BADGE-based hybrids, 1.667 for CEL-based hybrids, and 1.693 for TEPIC-based hybrids. Their refractive indices and Abbe’s numbers are quantitatively described by the Lorentz–Lorenz effective medium expansion theory. Their transmissivity is also reasonably explained using Fresnel refraction, Rayleigh scattering, and the Lambert–Beer theories. This surface modifier-free hybridization provides a versatile, fascinating, and promising method for synthesizing a variety of epoxy-based hybrid materials

Impact of the Heteroatoms on Mobility–Stretchability Properties of <i>n</i>‑Type Semiconducting Polymers with Conjugation Break Spacers

The development of stretchable semiconducting polymers through statistical terpolymerization with conjugation break spacers (CBSs) has gained much attention. In this study, we systematically investigated the effects of incorporating CBSs with thioether units into naphthalenediimide (NDI)-based n-type semiconducting polymers on their semiconductivity and stretchability compared to polymers with the corresponding alkyl- and ether-based CBSs. Indeed, six NDI-based semiconducting polymers with CBSs composed of di(ethylene sulfide), tetra(ethylene sulfide), di(ethylene oxide), tetra(ethylene oxide), octylene, and tetradecylene units were synthesized by statistical terpolymerization based on Migita–Kosugi–Stille cross-coupling reactions of 5,5′-bis(trimethylstannyl)-2,2′-bithiophene (2T), 4,9-dibromo-2,7-bis(2-decyl­tetradecyl)­benzo[lmn][3,8]phenanthroline-1,3,6,8-tetraone (Br-NDI-Br), and CBSs. The experimental results indicate that heteroatom-based CBSs would sufficiently affect solid-state packing, intrinsic stretchability, and mobility retentions of the corresponding polymers. Although all of the polymers demonstrated strong edge-on orientations, those with ether-based CBSs displayed the lowest crystallinity among them. This result was attributed to the phase separation induced by highly polar ethylene oxide moieties, leading to inferior charge transport performances and low crack onset strain. In contrast, the thin film of the polymer with thioether-based CBSs showed delayed crack onset strain and a high dichroic ratio. The narrower bond angle of C–S–C (98.9°) than C–O–C (113.3°) calculated by the DFT method led to a more bent conformation along the polymer backbone, which provided a strain-releasing capability to realign the polymer chains. Consequently, the polymers with thioether-based CBSs displayed higher mobility–stretchability properties than those comprising ether-based CBSs. This is the first report on the design, synthesis, and application to organic field-effect transistors (OFETs) of stretchable n-type semiconducting polymer materials, clarifying the impact of heteroatoms on the mobility–stretchability properties of n-type semiconducting polymers with new CBSs having ethylene oxide and ethylene sulfide units

Maltopentaose-Conjugated CTA for RAFT Polymerization Generating Nanostructured Bioresource-Block Copolymer

We now describe the synthesis of a new family of oligosaccharide-conjugated functional molecules, which act as chain transfer agents (CTAs) for the reversible addition–fragmentation chain transfer (RAFT) polymerization. The synthesis was started from the catalyst-free direct <i>N</i>-glycosyl reaction of 5-azidopentylamine onto maltopentaose (Mal₅) in dry methanol at room temperature and subsequent <i>N</i>-protected reaction with acetic anhydride, producing a stable oligosaccharide-building block, such as Mal₅ with an azidopentyl group (Mal₅-N₃). The azido group was hydrogenated using platinum dioxide (PtO₂) as a catalyst to give Mal₅ with aminopentyl group (Mal₅-NH₂), which was then reacted with CTA molecules bearing activated ester moieties. These reactions produced Mal₅-modified macro-CTAs (Mal₅-CTAs, <b>1</b>), which were used for the RAFT polymerizations of styrene (St) and methyl methacrylate (MMA) in DMF. The polymerizations were performed using the [M]₀/[<b>1</b>]₀ values ranging from 50 to 600, affording the Mal₅-hybrid amphiphilic block copolymers (BCPs), such as Mal₅-polystyrene (<b>2</b>) and Mal₅-poly­(methyl methacrylate) (<b>3</b>), with a quantitative end-functionality and the controlled molecular weights between 4310 and 20 300 g mol^–1. The small-angle X-ray scattering (SAXS) measurements were accomplished for <b>2</b> and <b>3</b> to ensure their abilities to form phase separated structures in their bulk states with the increasing temperatures from 30 to 190 °C. The featured results were observed for <b>2</b> (ϕ_Mal5 = 0.14) and <b>3</b> (ϕ_Mal5 = 0.16) at temperatures above 100 °C, where ϕ_Mal5 denotes the volume fraction of the Mal₅ unit in the BCP sample. For both BCP samples, the primary scattering peaks <i>q</i>* were clearly observed together with the higher-ordered scattering peaks √2<i>q</i>* and √3<i>q</i>*. Thus, these Mal₅-hybrid amphiphilic BCP samples have a body centered cubic (BCC) phase morphology. The domain spacing (<i>d</i>) values of the BCC morphology for <b>2</b> (ϕ_Mal5 = 0.14) and <b>3</b> (ϕ_Mal5 = 0.16) were 10.4 and 9.55 nm, respectively, which were determined using Bragg’s relation (<i>d</i> = 2π/<i>q</i>*). The present RAFT agents were shown to eventually provide the phase separated structural polymeric materials in which 5.4 nm bioresource-spherical domains were periodically arrayed at the interval of about 10 nm