Effects of Dielectric Material, HMDS Layer, and Channel Length on the Performance of the Perylenediimide-Based Organic Field-Effect Transistors

Shellac as a multifunctional biopolymer: A review on properties, applications and future potential

Shellac is a physically refined form of lac resin, a natural biopolymer of animal origin obtained from tiny insects feeding on the sap of specific host trees. Shellac, in its basic form, is a polyester macromolecule composed of inter and intra esters of polyhydroxy aliphatic and sesquiterpene acids. It has been used in several industries for ages due to its exceptional properties such as film-forming, adhering, bonding, thermoplasticity, water-resistance and easy solubility in spirit and aqueous alkali solvents. From the beginning of the 21^st century, due to increasing demand for natural products, a paradigm shift in the scope and applications of shellac has been witnessed, especially in green electronics, 3D printing, stealth technology, intelligent sensors, food and pharmaceutical industries. Shellac offers enormous potential for greener technologies as a natural and environmentally friendly material. This review provides an insight into the lac in detail, covering various forms of the lac, structure, properties, different applications of shellac and its future potential. This article would benefit the researchers involved in shellac research and others looking for natural and greener alternatives to synthetic polymers in various applications.

Superhydrophobic Coating Derived from Geothermal Silica to Enhance Material Durability of Bamboo Using Hexadimethylsilazane (HMDS) and Trimethylchlorosilane (TMCS)

Bamboo, a fast-growing plant from Asia, is used as building material with unique properties, while exhibiting fast degradation due to its hydrophobicity. Therefore, many attempts have been implemented using several technologies for bamboo modification to alter the hydrophobicity. Most previous studies producing superhydrophobic properties are conducted by using tetraethoxysilane (TEOS) as a precursor agent. However, this method, using TEOS with harmful properties and unaffordable compounds, requires many steps to accomplish the experimental method. Therefore, this paper employed geothermal solid waste as a silica source of the precursor. Thus, an effective and efficient method was applied to prepare superhydrophobic coating by using a precursor of geothermal silica and further modification using hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS). The research was executed by the full factorial statistical method using two numerical variables (HMDS/TMCS concentration and silica concentration) and one categorical variable (solvent types). The uncoated material revealed higher weight gain in mass and moisture content than that of the coated bamboo after the soil burial test to assess the durability of the bamboo. However, the durability of superhydrophobic coating realized hydrophobic performance for both agents during sand abrasion for a total of 120 s at an angle of 45°. Statistical results showed the optimum contact angle (CA) achieved in superhydrophobic performance with lower silica concentration for HMDS concentration and the appropriate solvent of n-hexane for HMDS and iso-octane for TMCS. All results were supported using many instruments of analysis to confirm the step-by-step alteration of geothermal silica to be used as a superhydrophobic coating, such as XRF, XRD, FTIR, SEM, and SEM EDX.

Improving Thin-Film Properties of Poly(vinyl alcohol) by the Addition of Low-Weight Percentages of Cellulose Nanocrystals

The increased demand for electronic devices, combined with a desire to minimize the environmental impact, necessitates the development of new eco-friendly materials. One promising approach is the incorporation of renewable and green materials that possess the desired mechanical and electrical properties while allowing for more ecologically friendly disposal of these devices. The addition of low-weight percentages (0.25-0.75 wt %) of cellulose nanocrystals (CNCs) was investigated as an environmentally friendly additive in aqueous dispersions of poly(vinyl alcohol) (PVA). It was found that these low CNC loadings were sufficient to induce a favorable increase in viscosity, which in turn dramatically enhanced the film quality of the PVA blends through an improvement in the critical radius of the spun film, overall film thickness, and homogeneity of the thin film. This corresponded to an increase in the number of functioning organic electronic devices that could be fabricated by spin coating, including metal-insulator-metal (MIM) capacitors and organic thin-film transistors (OTFTs). Most importantly, the incorporation of CNCs into PVA did not significantly alter the native dielectric properties of the polymer thin films when incorporated into both MIM capacitors and OTFTs.

Reversible Polymorphic Transition and Hysteresis-Driven Phase Selectivity in Single-Crystalline C8-BTBT Rods

Organic semiconductors (OSCs) are highly susceptible to the formation of metastable polymorphs that are often transformed by external stimuli. However, thermally reversible transformations in OSCs with stability have not been achieved due to weak van der Waals forces, and poor phase homogeneity and crystallinity. Here, a polymorph of a single crystalline 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothio-phene rod on a low molecular weight poly(methyl methacrylate) (≈120k) that limits crystal coarsening during solvent vapor annealing is fabricated. Molecules in the polymorph lie down slightly toward the substrate compared to the equilibrium state, inducing an order of greater resistivity. During thermal cycling, the polymorph exhibits a reversible change in resistivity by 5.5 orders with hysteresis; this transition is stable toward bias and thermal cycling. Remarkably, varying cycling temperatures leads to diverse resistivities near room temperature, important for nonvolatile multivalue memories. These trends persist in the carrier mobility and on/off ratio of the polymorph field-effect transistor. A combination of in situ grazing incident wide angle X-ray scattering analyses, visualization for electronic and structural analysis simulations, and density functional theory calculations reveals that molecular tilt governs the charge transport characteristics; the polymorph transforms as molecules tilt, and thereby, only a homogeneous single-crystalline phase appears at each temperature.

Direct amination and N-heteroarylation of perylenediimides

A mild, fluoride-mediated reaction for the direct introduction of amines and N-heterocycles.

Design and synthesis of N-substituted perylene diimide based low band gap polymers for organic solar cell applications

In this study, we report on the synthesis and device studies of a series of new copolymers containing N-substituted perylene dimide and dioctylfluorene units as part of the main backbone. A facile synthetic approach avoiding non-selective bromination was used to synthesize the monomer M1 by the reaction of perylene-3,4,9,10-tetracarboxylic dianhydride with 2-amino-7-bromo-9,9-dioctylfluorene. The copolymers P1 and P2 were synthesized by Suzuki polycondensation of M1 with 2,2′-(9,9-dioctyl-9H-fluoren-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) M2 and 9-(heptadecan-9-yl)-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole M3, respectively. The copolymer P3 was synthesized by direct arylation polymerization of M1 with 4,7-bis(4-octylthiophen-2-yl)benzo[c]-1,2,5-thiadiazole M4. All the copolymers showed thermal stability greater than 380 °C as evidenced from thermogravimetric analysis. The copolymers exhibited a narrow optical band gap (1.80–2.08 eV) with their UV-visible absorption spectra extending up to the NIR region and they are found to be suitable for use in OSC applications. The molecular weights of the polymers P1–P3 were found to be in the range of 10.68 to 16.02 kg mol⁻¹ as measured from GPC analysis. The surface morphology of the active layers based on P1/P2/P3:P3HT blend films was investigated by AFM and the rms values from height images range from 0.65 to 2.90 nm. The polymers were blended with P3HT to fabricate BHJ solar cells in three different weight ratios i.e. 1 : 1, 1.5 : 1 and 2 : 1 and the best power conversion efficiency was observed for the binary film of P3:P3HT blend device in a 1 : 1 weight ratio which reached up to 1.96% with a V_oc of 0.55 V, J_sc of 10.12 mA cm⁻² and FF of 34.63% which is among the highest reported for BHJ solar cells with N-substituted PDI based acceptors.

Newly designed N-substituted perylene diimide based acceptor copolymers have been characterized and tested for organic solar cells with P3HT in different weight ratios.