Various flame-retardant epoxy (EP) composites were prepared in combination with phenolic resin (PF), DOPO derivative (DD) and nanoclay (NC). The flame-retardancy of epoxy composites was studied by LOI, UL-94 and cone calorimeter analyses. The EP-DD2.0 (2.0% phosphorus) and EP-DD2.0-NC2.0 (2.0% phosphorus and 2.0% NC) composites gave best V-0 rating without dripping and LOI values of 29.0-29.2%. In cone calorimeter analysis, the peak heat release rate and total heat release were decreased by 63.6 and 59.1% for EP-DD2.0-NC2.0 nanocomposite. The epoxy composites on heating exhibited higher char yield at the cost of volatile products as noted in thermogravimetric and cone calorimetry analyses. The DSC and DMA were carried to measure the glass transition temperature (T g ). The results indicated a significant drop in T g from 213 degrees C of EP to 146 degrees C of EP-DD2.0-NC2.0, while an improvement in storage modulus was observed of the sample by decreasing the cross-link density as a result of plasticization effect of flame-retardant.
In this study, we report the design and synthesis of two novel diamine monomers: hydroxyl-containing 4-(bis(4-amino-3,5-dimethylphenyl) methyl) phenol (HGDT) and pyridine-functionalized 4,4'-(pyridin-4-ylmethylene) bis(2,6-dimethylaniline) (PYDT). These monomers were copolymerized with three dianhydrides-4,4'-(hexafluoroi-sopropylidene) diphthalic anhydride (6FDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) via a one-step polymerization method to fabricate seven colorless polyimide films (PI-2-1 to PI-2-7). Theoretical calculations using density functional theory (DFT) and time-dependent DFT (TD-DFT) were performed to predict the optical properties of the polymers. Among binary systems, PI-2-2 exhibits the lowest values for four characteristic parameters (D = 8.603 & Aring;, TSE = 0.99 e, t = 6.279 & Aring;, lambda max = 295.65 nm), indicating its excellent colorless transparency. Experimental results further confirm that all seven PI films exhibit high optical transmittance, ranging from 53.85%similar to 82.61% at 450 nm and 71.46%similar to 89.42% at 500 nm. Notably, PI-2-2 achieves the highest transmittance (82.61% at 450 nm, 89.42% at 500 nm), and the film exhibited the best overall performance: (i) it exhibits a 5% weight-loss temperature (T5%) as high as 493.12 degrees C, T10% of 520.72 degrees C, and Tg of 351.0 degrees C, indicating exceptional thermal stability; (ii) remarkable optical transparency (82.61% transmittance at 450 nm, 89.42% at 500 nm) with low haze (1.89); and (iii) superior colorlessness (CIE coordinates: L* = 94.72, a* = -0.56, b* = 0.41). The incorporation of bulky pyridine side groups was found to significantly enhance both thermal stability and optical transparency, positioning these advanced PIs films as promising candidates for next-generation flexible display technologies.
For effective fabrication of organic complementary circuits, separate optimization of p- and n-channel semiconductors and contacts is generally required; however, this necessity increases the material and process complexity. In this study, we investigated whether the operating polarity of organic field-effect transistors (OFETs) can be controlled via carrier-injection engineering while the semiconductor layer remains unchanged. OFETs were fabricated on CYTOP-coated n-type Si/SiO2 substrates using a common device platform comprising Al source/drain electrodes with diindeno[1,2,3-cd:1’,2’,3’-lm]perylene (DIP) as the organic semiconductor. Molybdenum trioxide (MoO3) and 2,6-bis(1,3,4,6,7,8-tetrahydro-2H-pyrimido[1,2-a]pyrimidin-1-yl)pyridine (Py-hpp2) were employed as hole- and electron-injection interlayers, respectively; their thicknesses were systematically varied. MoO3 was deposited on the electrodes only, whereas two Py-hpp2 configurations were examined: deposition on the electrodes only and deposition on both the electrodes and channel region. The MoO3-modified devices exhibited p-channel operation, whereas the Py-hpp2-modified devices, for which the interlayer was deposited on both the electrodes and the channel region, exhibited n-channel operation within the same semiconductor/electrode framework. In both systems, the drain current was strongly affected by the interlayer thickness. These results demonstrate that the polarity of a DIP-based OFET can be controlled through interfacial carrier-injection engineering and can be rationally designed by adjusting the selected material, thickness, and spatial configuration of the injection layer. Rather than demonstrating a circuit-ready technology, these results provide a proof of concept for interface-engineered polarity assignment within a common semiconductor platform.
The growing demand for lightweight, sustainable gamma radiation shielding necessitates alternatives to traditional empirical design. This study employs a density functional theory (DFT)-guided strategy to develop a bio-based benzoxazine monomer synthesized from renewable eugenol and p-tert-butylaniline. DFT thermochemical calculations confirmed thermodynamic spontaneity (Delta G = -8.14 kcal/mol) and the exothermic nature (Delta H = -31.03 kcal/mol) of the monomer formation. Theoretical molecular geometries and predicted 1H NMR chemical shifts showed excellent agreement with experimental FT-IR and 1H NMR spectra, validating the predictive model. The monomer was thermally polymerized and reinforced with erbium oxide (Er2O3) at various loadings (5-20 wt%). Gamma radiation shielding measurements revealed that attenuation properties improved progressively with filler content. At 20 wt% Er2O3 loading, the composite achieved a superior mass attenuation coefficient of approximately 92.64 cm2/g, along with significantly enhanced linear attenuation and radiation protection efficiency compared to the neat polymer. These results demonstrate that combining DFT-assisted molecular design with high-Z rare-earth oxide reinforcement provides a highly effective route for engineering next-generation, sustainable radiation shielding materials.
In this work, four biphenyl diamine monomers bearing gradient steric hindrance from methyl and tert-butyl substituents were synthesized and copolymerized with 6FDA and CHDA dianhydrides to fabricate a series of colorless and transparent polyimide (CPI) films. The regulating mechanisms of substituent steric hindrance and dianhydride backbone on the optical, thermal, surface wetting and water absorption performances of the resulting CPIs were systematically investigated. The alkyl steric hindrance was proven to effectively suppress intermolecular charge-transfer complex (CTC) formation and improve the optical transmittance of films. Methyl-modified CPIs delivered superior comprehensive optical performance, while tert-butyl-incorporated systems exhibited enhanced thermal stability and hydrophobicity. Notably, asymmetric tert-butyl substituents introduced excessive molecular torsional distortion and aggravated yellowing of the films. Combined with time-dependent density functional theory (TD-DFT) calculations, the steric hindrance-induced anti-yellowing mechanism was clarified at the electronic level. Among all samples, the Y-2TB@6FDA film achieved a balanced performance of high transparency, outstanding thermal resistance and low water absorption (L* = 95.79, Td5% = 539 degrees C). This work offers a reliable molecular design strategy for developing high-performance CPI optoelectronic materials.
