Molecular materials that are built with πconjugated moieties which self-assemble to form organic semiconductors have gained greater recognition for their applications in organic electronics. By judicious molecular design, liquid crystallinity can be incorporated into them to realize π-conjugated liquid crystals. In this work, we report 3hexyl thiophene-based π-conjugated liquid crystals in which alkoxy biphenyls are introduced into the core by palladium acetate-catalyzed direct arylation. The π-conjugated molecules exhibit self-assembly in solution and enantiotropic nematic phase upon melting. Therefore, the morphological studies of molecules in solution by atomic force microscopy and scanning electron microscopy, mesophase properties by hot-stage optical polarizing microsocpe and differential scanning calorimetry, as well as molecular order by solid-state 13 C NMR is performed. The morphological studies indicate the formation of supramolecular fibers due to the self-assembly of molecules through assisted π−π stacking and van der Waals interactions. The static one-dimensional and 13 C NMR studies reveal the molecular organization and orientational order in the nematic phase. Because of the asymmetry of the thiophene ring due to the 3-hexyl chain, the orientational order in the nematic phase is characterized by three values, i.e., S zz , S xx −S yy , and S xz . The important feature of the 13 C NMR investigations is the contrasting orientational constraints for terminal octyloxy and lateral hexyl chains. The large difference in 13 C− 1 H dipolar couplings of the individual carbons of the terminal and lateral chains reveal that the mean orientation of the former is in fully trans conformation, while the lateral hexyl chain carbons prefer cis conformation to align with the core unit. A plot of alignment-induced chemical shifts versus temperature follows a decreasing trend with rise in temperature. The optical absorption and emission in solution indicate that the absorption band is structureless while the fluorescence spectrum is structured with two maxima, located at 422 and 445 nm, which are independent of terminal chain length. The investigations point out that the 3-hexylthiophene in combination with alkoxy biphenyls can result in π-conjugated low melting mesogens which undergo self-assembly in solution in addition to displaying fluorescence emission.

The usage of natural fibre as reinforcement in polymer composites has increased in the recent years with rising concerns of environmental pollution and the heavy dependence on synthetic fibres from petroleum products of the middle east and the amount of material available in the tropical countries for such low prices. These materials can decrease our dependency on conventional materials like plastics, thereby decreasing the amount of pollution we cause on disposal and manufacturing of those. In general, the impact strength of the natural fibre composites is considered to be low and this experiment quantifies these results. This research describes the fabrication of a polymer composite, using banana fibre as the reinforcement and epoxy as the polymer matrix. A sequence of samples was prepared by varying various parameters like length, volume fraction and treatment of the fibre. The parameters were optimized using Taguchi’s DOE and the combination of parameters which yields us the best result and the contribution of each parameter. The impact strength has been studied using IZOD impact tester. The work has quantified that the impact strength of the composite depends mostly on the volume fraction and also only up to a certain range and then decreases as we increase the quantity of fibre. The same goes with both alkali treatment and length of the fibre which also contribute respectively. The optimum length, volume fraction and chemical are 1mm, 25 wt% and 2% NaOH treatment shows better result.

This study provides insight into the influence of alkyl chains and linking units on the mesophase properties of thiophene-based mesogens and on the orientational constraints of the core and terminal alkyl chain.

No abstract

The advancement of composites mixed with natural fibers and with fillers has become the most supportable alternative material for engineering applications, especially in industries such as automotive and aerospace. Natural fibers are renewable, cheap, biodegradable, and ecological materials. In the present work, already used woven jute fibers, which are extracted from gunny bags with the same grams per square meter (GSM), were used, and then, woven jute fibers were chemically treated to improve their characteristics. Graphite powder-filled used jute fiber reinforced epoxy composite (UJF) are prepared by using the hand-layup technique. Tests such as tensile, flexure, impact, and thermo-gravimetric analysis (TGA) were conducted. These tests were according to ASTM standards to evaluate the effect of graphite filler content on hybrid epoxy jute composites. The composite material is prepared by changing the content by weight of the filler by 3%, 6%, 9%, and 12%. The experimental results reveal that 6% of the graphite composites showed the maximum tensile strength and modulus. With the increase in the filler content, there is a decrease in the flexural properties. The impact resistance increases slightly up to 6% of the filler content. The study of thermal decomposition showed that the lowest mass loss was found at 9% by weight of the filler content. Morphological analysis performed by FE-SEM showed that the addition of filler content improved the binding of the fiber and matrix up to 6% by weight of the filler content. It should be noted that these hybrid composites are a promising material at low cost for lightweight structural applications.