S. Radhakrishnan

Bio: S. Radhakrishnan is an academic researcher from High Energy Materials Research Laboratory. The author has contributed to research in topics: Thiophene & Side chain. The author has an hindex of 12, co-authored 30 publications receiving 442 citations. Previous affiliations of S. Radhakrishnan include Defence Research and Development Organisation & Central Leather Research Institute.

Quantum-chemical studies on hexaazaisowurtzitanes.

Abstract: Highly nitrated cage molecules constitute a new class of energetic materials that have received a substantial amount of interest. Among them 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a powerful explosive with poor impact and friction characteristics. In the present study we aim to design novel energetic materials by tailoring the molecular structure of CL-20. Important characteristics such as the heat of formation and density have been predicted using density functional theory and packing calculations, respectively. Sensitivity correlations have been established for model compounds by analyzing the charge on the nitro groups. Molecules IDX1, IDX4, and IDX7 have been found to have comparable performance with better insensitivity characteristics and may be explored as CL-20 substitutes in defense applications.

Quantum chemical studies on polythiophenes containing heterocyclic substituents: Effect of structure on the band gap

Abstract: Color tuning by the tailoring of substituents at the 3-position of thiophene is very encouraging, and comparative experimental and theoretical studies proved to be powerful in the search for a suitable design for the above. Since the novel polythiophene-based materials substituted with five-membered/six-membered ring containing sulphur and nitrogen at different positions are proven to be potential candidates for electron-transporting hole blocking functions, the structure-property relationship of these systems have been focused in the present study. Molecular-orbital calculations are applied to obtain the optimized geometries and band gaps of the thiophene oligomers. An oligomeric approach has been implemented for calculating the band gaps, and the theoretically obtained band gaps for the different model compounds are compared. Density-functional theory B3LYP∕6-31G* predicted band-gap values are compared with the experimental band gaps obtained from optical-absorption edge. The predicted values show littl...

Optical properties of functionalized polythiophenes

Abstract: This review focuses on the interrelation between the influences of polymeric structure on the optical properties of polythiophene — a versatile polymer for opto-electronic applications. From the application's point of view, the polymer should either be melt- or solution-processible. Functionalization of polythiophenes really helps for the above. On the other hand, the functionalization at the 3 and/or 4 position of the thiophene ring modifies the band gap of the polymer, which in turn, modifies photo absorption, photo- and electro-emission characteristics of polythiophenes. The present work reviews the influence of the optical properties of polythiophene on the different functional groups present in the thiophene ring.

Polythiophene: From Fundamental Perspectives to Applications

Abstract: The field of organic electronics has been heavily impacted by the discovery and development of π-conjugated conducting polymers. These polymers show great potential for integration into future optical and electronic devices due to their capacity to transition between semiconducting and conducting states as well as the ability to alter mechanical properties by controlled doping, chemical modification, and stacking or creating composites with other materials. Among π-conjugated polymers, polythiophene and its derivatives has been one of the most extensively studied and is widely investigated computationally and experimentally for use in electronic devices such as light-emitting diodes, water purification devices, hydrogen storage, and biosensors. Various theoretical modeling studies of polythiophene ranging from an oligothiophene approach to infinite chain lengths (periodic boundary conditions) have been undertaken to study a variety of electronic and structural properties of these polymers. In this review,...

Visible-induced photocatalytic reactivity of polymer-sensitized titania nanotube films

Abstract: In this study, polythiophene–TiO 2 nanotube films (PTh/TNT) were successfully prepared by a two-step electrochemical process of anodization and electropolymerization, in which a highly ordered TiO 2 nanotube (TNT) film was anodized at a low-voltage with post calcination first and then the prepared TNT film was deposited with a polythiophene layer by electropolymerization in the BFEE electrolyte. The morphology and structures of PTh/TNT composites were examined by FESEM, EDX, XRD and XPS methods. XPS spectra of PTh/TNT composites indicate the strong interaction between S sites of polymer backbone and TiO 2 nanotubes, in which electron transfer from polythiophene to titania takes place. UV–vis DRS analysis shows that these composites have a strong photoresponse in the visible region at 500 nm. The prepared PTh/TNT films revealed significant activity for 2,3-dichlorophenols (2,3-DCP) degradation under visible light irradiation and also sunlight irradiation, in which the PTh3/TNT film achieved the best performance. On the other hand, this study also confirmed that the side-chains of polythiophene could influence its photocatalytic activity significantly in an order from high to low as poly3-methylthiophene ≈ polythiophene > polythiophenecarboxylic acid > poly3-hexylthiophene. The results may provide useful information to further develop some effective polymer-semiconductor catalysts for pollutant degradation under sunlight irradiation for water and wastewater treatment.

Sensitivity and Performance of Energetic Materials

Abstract: This paper provides an overview of the main developments over the past nine years in the study of the sensitivity of energetic materials (EM) to impact, shock, friction, electric spark, laser beams, and heat. Attention is also paid to performance and to its calculation methods. Summaries are provided of the relationships between sensitivity and performance, the best representations for the calculation methods of performance being the volume heat of explosion or the product of crystal density and the square of detonation velocity. On the basis of current knowledge, it is possible to state that a single universal relationship between molecular structure and initiation reactivity does not yet exist. It is confirmed that increasing the explosive strength is usually accompanied by an increase in the sensitivity. In the case of nitramines this rule is totally valid for friction sensitivity, but for impact sensitivity there are exceptions to the rule, and with 1,3,5-trinitro-1,3,5-triazepane, 1,3,5-trinitro-1,3,5-triazinane, β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane, and the α-, β- and e-polymorphs of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane the relationship works in the opposite direction. With respect to the QSPR approach there might be reasonably good predictions but it provides little insight into the physics and chemistry involved in the process of initiation.