Sasidhar Kantheti

The impact of 1,2,3-triazoles in the design of functional coatings

In recent times 1,2,3-triazole rich molecules have gained much importance in the field of polymer and material science because of their excellent properties like strong anti-microbial and anti fouling nature of the triazole ring along with easy synthetic procedures and exceptionally high yield of end product. Generally these molecules are synthesized by azide–alkyne click reaction and this chemistry has potential application in the functionalization of a wide range of inorganic moieties like metal oxide nanoparticles, carbon nanotubes etc. to develop hybrid nanocomposites for high performance materials. Based on the previous reports, this particular review article provides a comprehensive overview of the application of 1,2,3-triazoles in the design of various high performance organic coatings such as anti-corrosive, anti-microbial, self-healing, hybrid nanocomposite, bio degradable etc.

Development of moisture cure polyurethane–urea coatings using 1,2,3-triazole core hyperbranched polyesters

This article reports the development of moisture cure polyurethane–urea coatings. The coating has been developed using different generations of novel 1,2,3-triazole core containing hyperbranched polyester polyols (THBP). For the synthesis of THBP, the core molecule, tetra hydroxyl-terminated di-triazole (THTD), has been synthesized by click reaction involving ethylene diazide and 2-butyne-1,4-diol. The polycondensation reaction between the core THTD and 2,2-bis (hydroxymethyl) propionic acid (Bis-MPA) at different mole ratios has been used to get first (THBPG-1), second (THBPG-2), and third (THBPG-3) generations of triazole core hyperbranched polyesters. The structural investigations of these THBPs have been carried out by 1H NMR, 13C NMR, and FTIR spectroscopy. The different generations of THBPs were further reacted with 1-isocyanato-4-[(4-isocyanatocyclohexyl) methyl] cyclohexane (H12-MDI) at OH:NCO ratio of 1:1.2 to get –NCO terminated triazole core hyperbranched polyurethanes. They were cured under atmospheric moisture to get hyperbranched polyurethane–urea coatings and were named as THBPUG-1, THBPUG-2, and THBPUG-3. FTIR has been used to confirm the formation of polyurethane coatings. The TGA and DMTA have been used to determine the thermal stability and dynamic mechanical properties of the coatings, respectively. The corrosion resistance properties of the coatings have been studied by salt spray and electrochemical test. The coatings were also evaluated for microbial resistance. The results indicate that the thermal stability, glass transition temperature, and corrosion resistance properties increase with an increase in generation number of THBPs used for coating development. All three generations of coating films show excellent antimicrobial activity. Based on overall combined structure–property relationship study, these types of coatings will be useful as multifunctional applications in marine and moist environments.

Graphitic nanoparticles from thermal dissociation of camphor as an effective filler in polymeric coatings

We report an easy synthesis of uniformly-sized water soluble graphitic-carbon nanoparticles (CNP) from the soot obtained by the incineration of camphor. The soot was characterized by X-ray diffraction (XRD) and Raman spectroscopy which reveal the presence of graphitic domains in the obtained nanoparticles. Scanning electron microscope (SEM) images display uniformly sized CNPs of about ∼50 nm. The camphoric soot was then oxidized with a piranha solution to decorate the CNP surface with a carboxyl group. This presence of carboxyl groups was confirmed by the CO stretching at 1720.17 cm−1 in the Fourier transform-infrared spectroscopy. Following the surface treatment, CNPs were reacted with diisocyanate to form amide linkages, which were exploited in the fabrication of CNP–polyurethane hybrid composite material (CNP–PU). Minuscule incorporation (0.1, 0.5 wt%) of CNP into polyurethanes showed a magnificent improvement in the overall thermo-mechanical properties of the CNP–PU as compared to neat polyurethane films. From the XRD analysis of CNP–PU it is evident that incorporation of CNPs enhances the crystallinity of the resultant composite. Proper dispersion of CNPs into the polyurethane matrix was noticeable in the SEM images of the composite.

Hyperbranched polyol decorated carbon nanotube by click chemistry for functional polyurethane urea hybrid composites

In the present work we report a facile decoration of multi-walled carbon nanotubes with hyperbranched polyether polyol using copper(I) catalyzed azide–alkyne click reaction in order to create hydroxy terminal groups. This decoration has been designed to improve the dispersibility of CNTs in the polymer matrix. These hydroxy functional decorated CNTs were then dispersed into poly(tetramethylene ether) glycol (PTMG) at different weight percentages to get the hybrid pre-polymers. These pre-polymers were reacted with 1-isocyanato-4-[(4-isocyanatocyclohexyl) methyl] cyclohexane (H12-MDI) at a NCO : OH ratio of 1.2 : 1 and cured under atmospheric moisture to get the functional polyurethane–urea–CNT hybrid composites. There has been substantial improvement in the thermal stability, mechanical strength, corrosion resistance and antimicrobial activity of the polyurethane hybrid composites with the increase in carbon nanotube loading in pre-polymers. For example, with 2 wt% loading of carbon nanotubes, the tensile strength of the polyurethane hybrid composite improved from 1.25 N mm−2 to 6.25 N mm−2; the water contact angle improved from 54° to 108° and also the rate of corrosion reduced from 0.047 mm per year to 0.0019 mm per year. We also observed that these hybrids possess remarkable shape recovery properties. These results demonstrate that the decorated CNTs can be used as high performance additives for improving various properties of polyurethane hybrids in cost effective and eco-friendly ways.