All issues / Volume 15 (2021) / Issue 1 (January)
This is an editorial article. It has no abstract.
In the present work, polyaniline-titanium (IV) oxide (PANI-TiO2) nanocomposites have been synthesized by solidstate (solvent-free) oxidative polymerization method of aniline as a monomer under green condition using both iron (III) chloride hexahydrate (FeCl3·6H2O) and ammonium peroxydisulfate (APS) as two different type of the oxidants as well as various modes and increasing of the ratios of monomer to oxidant. The structural and morphological of the nanocomposites have been characterized using kinetic and microscopic analysis. The electrical conductivities, cyclic voltammetry, bandgap energy (Eg), and morphology of the nanocomposites are mainly dependent on the type of oxidants and reaction conditions. Also, the nanocomposites were shown electro-active and functional properties. The I–V characteristics of PANI-TiO2 in an Al/(PANI-TiO2)/TiO2/FTO solar cell are achieved by drawing the plot of the I–V curves. It is noted that nanocomposites with different conditions were shown similar FT-IR and UV-Vis spectra with different morphologies. The TEM images in different conditions showed a thin layer of TiO2 nanoparticles in the outer wall of the nanotube when the APS was used as the oxidant, while when the FeCl3 was used as the oxidant, the TiO2 nanoparticles have been distributed on a plantain leaf of PANI matrix. The XRD results confirm completely results obtained from TEM. As a result, the nanocomposites with both methods showed a good P–N junction between TiO2 and PANI.
It is well known that high-temperature curing of natural rubber (NR) with a conventional accelerated-sulfur (CV) system is limited because of reversion. This paper describes the curing behavior and the reversion resistance characteristics of unfilled NR with a CV system in the presence of two different bismaleimides: Perkalink 900 (PL) and Maleide F (MF). Rheometer studies reveal that MF can directly interact with the NR during accelerated-sulfur curing and forms some thermally stable bismaleimide type crosslinks in the beginning via Alder-ene reaction. However, even with the use of 4 phr of MF, a considerable reversion was noticed during the curing of NR with CV at 180 °C for 1 hr. A high dosage (5 phr) of MF was therefore required for a complete reversion free plateau type cure pattern. On the other hand, PL has no direct interaction with the NR at the beginning of the curing reaction. Moreover, even 1 phr PL exhibits a marching modulus curing behavior via Diels-Alder reaction. Therefore, to solve the individual issues of these chemicals, a synergistic combination of MF and PL has been identified and applied to facilitate the high-temperature curing of NR/CV devoid of reversion with a plateau type cure pattern.
Shape memory polymer (SMP) based on thermoplastic natural rubber (TPNR) for soft-touch splint application has been successfully developed. The main aim was to investigate the proper phase combination between thermoplastic (i.e., polycaprolactone (PCL)) and rubbers materials. Different types of rubbers, namely natural rubber (NR) and epoxidized natural rubber (ENR), were used as the rubber phases in the SMP-TPNR. Mechanical properties, shape memorial efficiency, swelling, and morphologies of the resulting material were examined. The tensile strength and hardness of the SMP-TPNR were found to be increased by using polar ENR as the rubber phase. Better compatibility between ENR and PCL molecular chains lead the material to achieve significant improvement in the shape memory behavior compared to the one with unmodified NR. The main advantage of polar rubber is its great opportunity to apply the material for splint fixing applications. On comparing with various commercially available materials (i.e., plaster, fiberglass, aluminum with foam and commercial thermoplastic splint), the developed SMP-TPNR material exhibited better performances in terms of ease of processing, costeffectiveness, comfortability (soft-touch), water resistance and impact resistance.
In this study, a PVDF/PVDF-g-(PSSS-co-PAA) graft copolymerization-blending cation exchange material was synthesized with polyvinylidene fluoride (PVDF), sodium p-styrene sulfonate (SSS) and acrylic acid (AA) by the methods of solution polymerization and suspension polymerization, based on the preparation of cation exchange materials. Experimental results indicated that the exchange capacity was well designed, and that water absorption and water swelling could be effectively controlled. The morphology of the modified material was analyzed by SEM, which showed that the material had a uniform particle size. Thermal analysis of the material demonstrated that the material synthesized in N,N-dimethylformamide (DMF) had excellent thermostability and good compatibility with PVDF.
In the present work, nano-rods of mixed semiconductors were reinforced to conducting polymers to get their composites. CdSe semiconductor nanoparticles were reinforced into the conducting polymer polythiophene (PTh) at room temperature following an oxidation polymerization method. This method was rapid, cost effective and produced larger yield of polymer. X-ray diffraction (XRD) data of composites revealed that the crystallite size was of the order of 45–47 nm. Field emission scanning electron microscopic (FESEM) analysis showed horizontal cross section of CdSe nanoparticles after they were embedded into the PTh matrix. In the composites phase, the nano-rods of CdSe were seen lying over the PTh matrix. UV-Vis spectral studies showed reduction in the energy band gap from 3.05 eV of native PTh to 2.26 eV of PTh/CdSe nanocomposites I-V plots of nanocomposites comprising of p-type PTh and n-type CdSe showed similar characteristics as those of the junction diode. The DC conductivity and short circuit current (Jsc) of PTh/CdSe nanocomposites indicated drastic changes as compared to those of the pure PTh. Since, I-V plot of nanocomposites phase resembled well with that of a junction diode, the as-synthesized materials has potential to be used in diode applications.
In this work, new shape-memory thermosets have been developed using a thiol-acrylate-epoxy dual-curing system. A previously studied system has been successfully modified, introducing different amounts of tri(2,3-epoxypropyl)isocyanurate (ISO) and bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BAGA) in order to enhance the thermomechanical properties and the glass transition temperature of the final materials. Preliminary studies on the curing process proved that the curing process is not affected, and the critical ratio remains unchanged. Glass transition temperatures and thermomechanical properties were successfully improved, extending the applicability of these thermosets to the field of soft-actuator. Shape-memory behavior was comprehensively investigated in unconstrained, fully and partially constrained conditions. Unconstrained experiment results showed excellent shape fixation and recovery, coupled with a fast recovery process. On the other hand, fully and partially constrained recovery experiments evidenced optimal performances obtained by the combination of both high crosslinking density and high deformability in the programming stage. Considerably high values of recovery stress (up to 7 MPa) and work output (up to 1300 kJ/m3) were found confirming the high potentiality of these dual-cured thermosets in the field of soft-actuation.
Highly solvent-stable polyimide ultrafine fibrous membranes fabricated by a novel ultraviolet-assisted electrospinning technique via organo-soluble intrinsically negative photosensitive varnishes
L. Qi, C. Y. Guo, M. G. Huangfu, Y. Zhang, L. Wu, X. X. Zhi, J. G. Liu, X. M. Zhang
Vol. 15., No.1., Pages 72-87, 2021
Vol. 15., No.1., Pages 72-87, 2021
A novel fabrication methodology for polyimide (PI) UFMs based on soluble PIs with high solvent durability was developed. As fiber-forming agents, a series of intrinsically negative photosensitive polyimides (PSPIs) with solubility in organic solvents were synthesized by the one-step thermal polymerization of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with three ortho-alkyl-substituted diamine monomers, namely, 3,3′,5,5′-tetramethyl-4,4′-diaminodiphenylmethane (TMMDA, for PI-1), 3,3′-dimethyl-5,5′-diethyl-4,4′-diaminodiphenylmethane (DMDEDA, for PI-2), and 3,3′,5,5′-tetraethyl-4,4′-diaminodiphenylmethane (TEMDA, for PI-3), respectively. Electrospun UFMs were prepared by both traditional electrospinning (PI UFMs) and the novel ultraviolet-assisted electrospinning (UVAES) method (PI-UV UFMs). The effects of the fabrication method on the physical and chemical properties of the electrospun UFMs were investigated systematically. High-efficiency photoinduced crosslinking reactions under ultraviolet (UV) radiation provided the PI-UV UFMs with considerable thermal dimensional stability with the 5% weight loss temperature over 440 °C. Meanwhile, the derived PI-UV UFMs showed excellent resistance against a polar aprotic solvent, N,N-dimethylacetamide (DMAc).