Umashankar Male

Graphene oxide incorporated poly(ε-caprolactone) honeycomb-patterned porous polymer films by the breath figure method

Poly(ε-caprolactone)-graphene oxide (PCL-GO) honeycomb-patterned films were successfully fabricated by breath figure method for the first time by the simple blending of individual components in a water miscible solvent, tetrahydrofuran. PCL-GO films were reduced using sodium borohydride to obtain PCL-reduced graphene oxide (PCL-rGO) films. The films were characterized by their color, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). TGA result shows the improvement of the thermal properties of PCL by the incorporation of GO. The SEM image shows the formation of monodispersed porous honeycomb-patterned PCL-GO films, and these patterns are retained after the reduction of GO to PCL-rGO without any wreckage. The reduction of GO to rGO was confirmed from the color of the films and from the XPS analysis. The present methodology is expected to widen the use of breath figure technique to achieve a wide variety of functionalized films by simple blending using water miscible solvents, which would otherwise not be possible using water immiscible solvents.

Reversible change of wettability in poly(ɛ-caprolactone/azobenzene) honeycomb-patterned films by UV and visible light illumination

A new type of photosensitive poly(ɛ-caprolactone) (PCL) composites containing 4-dimethylamino-4′-(6-hydroxy hexyloxy) azobenzene (Azo) was synthesized by in situ ring-opening polymerization of ɛ-caprolactone in the presence of different Azo amounts. The PCL-Azo composites were characterized using Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and UV–vis spectroscopy. Honeycomb-patterned porous polymer films were fabricated by casting the polymer solution under humid conditions: and for comparison, flat films were also prepared by drying the polymer solution at ambient conditions. Water contact angle was compared between porous and flat films, and was reversely changed by UV and visible light illuminations. The contact angle of PCL-Azo composite films was decreased by UV illumination and was recovered with visible light illumination both on the patterned and flat films. Reversibility in contact angles by UV and visible light can be interpreted by photo-switched isomerization of the Azo component in the polymer composite films due to isomeric structural changes between trans and cis isomers inducing the changes in dipole moment of the films.

Synthesis and characterization of polyaniline-grafted CNT as electrode materials for supercapacitors

AbstractPolyaniline (PANI) was grafted with carbon-nanotubes (CNT) via azobenzene (Azo) to increase the pseudo-capacitance of PANI. CNT was functionalized with azobenzene and used in the in-situ polymerization of aniline using emulsion polymerization. X-ray diffraction result supports the formation of composite materials. Morphology of grafted composites showed a higher uniform growth in PANI/ CNT-Azo composite than PANI/CNT composite. Electrochemical performance was evaluated by symmetric super-capacitor cells using cyclic voltammetry and chargedischarge studies. PANI/CNT-Azo showed a higher specific capacitance value than pristine PANI. The results show grafting of PANI onto CNT via Azo helps to achieve higher capacitance and thermal stability than non-grafted PANI/CNT composite materials.

Photo-Regulated Conductivity of Polycaprolactone Honeycombpatterned Porous Films Containing Azobenzene-Functionalized Reduced Graphene Oxide

Photo-regulated electrical conductive materials plays an important role in light driven applications such as photo-switching, reversible optical storage etc. Designing of such materials in flexible porous polymeric forms adds advantage in terms of light weight, less density, enhanced performance due to increased surface area. As a result we have synthesized poly(ε-caprolactone) (PCL) composite via in situ ring opening polymerization of ε-caprolactone in the presence of azobenzene-functionalized reduced graphene oxide (rGO-Azo) and studied its photo-regulated conductive properties in porous and flat films. PCL-rGO-Azo composites were characterized using Fourier transform infrared and UV-vis spectroscopy. Honeycombpatterned porous films were fabricated by breath figure method. The morphology of the films was examined by scanning electron microscopy (SEM). Photo-regulated conductivity of the PCL-rGO-Azo films depending on the UV and visible light illumination has been studied. The conductivity was increased by UV irradiation and recovered by visible light irradiation. The conductivity change is due to the trans-cis isomerization of azobenzene moieties covalent-bonded to reduced graphene oxide (rGO).