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Modification of carbon nanotubes (CNTs) and their incoporation in polymer matrix have attracted much attention of researchers. As maximum dispersion of CNTs could enhance the properties of matrix dynamically, researchers are trying to find new methodologies to obtain this target. However, maximum dispersion remains a great challenge and under the stage of progress. Here, we claimed the synthesis of composites with a highly uniform dispersion of the filler that results significantly improved electrical features. In this regard, composites of polymethylmethacrylate (PMMA) were fabricated by using pristine and zwitterionic surfactant (ZIS) modified CNTs (ZIS-CNTs). Characterization was done by using ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermo gravimetric analysis (TGA) techniques. UV-Vis and FTIR spectroscopy confirmed the synthesis of ZIS-CNTs and composites. UV-Vis spectra showed an increase in wavelength with the decrease in optical band gap for CNTs-based (CNTs/PMMA) and ZIS-CNTs-based (ZIS-CNTs/PMMA) composites. SEM and XRD studies confirmed a significant homogenoeus and uniform dispersion of CNTs in ZISCNTs/PMMA composites. An increase in conductivity of PMMA from 10-9 to 10-2 and 10-1 S/cm was observed on addition of less than 1% (mass fraction) of CNTs without and with modification by ZIS, respectively. Low values of percolation threshold at 0.5% and 0.005% for CNTs/PMMA and ZISCNTs/PMMA composites were obtained, respectively. TGA analysis showed a slow rate of decomposition for composites than that for pure PMMA. Around 600 °C, 3% CNTs/PMMA and 7% ZIS-CNTs/PMMA composites were left in the end, which depicts the increase in thermal stability of PMMA. This work depicts a better dispersion of CNTs in PMMA matrix via slight modification in synthesis as well as by using ZIS as surfactant. [ABSTRACT FROM AUTHOR]

Photochemical modification of single-walled carbon nanotubes (SWCNTs) was carried out by covalent attachment of 2-propanol-2-yl radicals on the surface of SWCNTs, which were engendered by the photolysis of 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (HPHMP) under ultraviolet (UV) light. Pristine single-walled carbon nanotubes (p-SWCNTs) were dispersed in acetone along with HPHMP photoinitiator. After that, the mixture was irradiated by UV light to generate the free radicals which were introduced onto the surface of SWCNTs. The modification of SWCNTs was supported by UV/visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermal gravimetric analysis–mass spectrometry (TGA–MS), and transmission electron microscopy (TEM). UV/visible results revealed the loss of van Hove singularities due to covalent modification. The modification was further verified by FT-IR showing the signals at 3421 and 1100 cm−1 due to stretching and bending of O–H group, respectively. Moreover, other peaks at 2927 and 2858 cm−1 indicated the asymmetric and symmetric stretching modes of aliphatic C–H bond, respectively. Raman spectra illustrated that the intensity ratio of the tangential mode to the disorder mode ( IG/ ID), for modified SWCNTs (F-SWCNTs), decreased nearly four times than p-SWCNTs. TGA–MS also evidenced the signal corresponding to m/ z 59 at 400 °C indicating the presence of 2-propanol-2-yl groups. TEM and dispersibility data demonstrated that the sidewall modification detached the bundled structure, enhanced the dispersion in common organic solvents and retained the original size of SWCNTs without hefty modification, which could cut or damage the nanotubes. [ABSTRACT FROM AUTHOR]

Summary: Acrylates are esters of acrylic acid formed by the reaction of acrylic acid with alcohols. These acrylic esters were produced by polymerization of combination with different acrylic monomers to produce the materials with enhanced characteristics for coating applications. The acrylate-based polymers were prepared by varying the nature and ratios of the monomers. Moreover, the properties of the polymeric materials were further improved by compositing with the nano-fillers i.e. carbon nanotubes. Further, the materials were coated on different surfaces to evaluate the coating characteristics by standard analytical procedures. Composition and morphology of the materials were characterized by different spectroscopic techniques. Polyacrylate based polymers were synthesized by step growth polymerization using different types of monomers moieties (5 different types of acrylic monomer along with one functional monomer and an aromatic monomers) to enhance coating properties and to enhance dispersion of carbon nanotubes. Characterization was done by FTIR (Fourier Transform Infra-Red) and UV-Vis spectroscopy. Study of polymeric coating was done on different surfaces by different techniques like Barcol Hardness, Gloss Test, Salt Spray Test, Cross Hatch Test and Mandrel Dent Measurement as given in standard ASTM methods. The results revealed better adhesion, crack resistance, and abrasion resistance. The graphical abstract is given below as Fig-1. [ABSTRACT FROM AUTHOR]

Abstract: To study the effect of carbon nanotube aspect ratio (AR) on the frequency response of the electrical properties, the alternating current (AC) electrical conductivity and dielectric permittivity of different AR multi-wall carbon nanotubes (MWCNTs)/thermoplastic elastomer (TPE) composites were studied in the AC frequency range of 100 Hz to 10 MHz. Qualitatively, the effect of frequency on the electrical properties of the composites was the same for all AR MWCNTs and shared many typical features of electrically percolative composites. Quantitatively, the frequency responses of electrical properties were found to be independent of nominal AR, concentration, percolation threshold, and the diameter of the MWCNT. Instead, frequency response of electrical properties was dependent on the MWCNT length and initial electrical conductivity of the composites. With the same initial conductivity of the MWNT composites, frequency-conductivity sensitivity varied inversely with the nominal length of the MWCNTs. Composites with MWCNTs of the same nominal length and similar electrical conductivity values, regardless of whether the MWCNT concentration was below or above the percolation threshold, exhibited quantitatively similar frequency-conductivity sensitivity. The frequency-dielectric sensitivity at the percolation threshold was a reflection of frequency-conductivity sensitivity and was also found to be dependent on the initial conductivity of the composites. [Copyright &y& Elsevier]