Muhammad Siddiq

Polymeric micelles as drug delivery vehicles

Though much progress has been made in drug delivery systems, the design of a suitable carrier for the delivery of hydrophobic drugs is still a major challenge for researchers. The use of micellar solutions of low molecular weight surfactants has been one of the popular methods for the solubilization of hydrophobic drugs; however, such surfactants suffer from high critical micelle concentration and concomitant low stabilities. In contrast to surfactants of low molecular masses, polymeric micelles are associated with general advantages like higher stability, tailorability, greater cargo capacity, non-toxicity and controlled drug release. Therefore, the current review article is focused on the engineering of the core of polymeric micelles for maximum therapeutic effect. For enhanced drug encapsulation capacity and getting useful insights into the controlled release mechanism we have reviewed the effects of temperature and pH on responsive polymeric micelles. The article also presents important research outcomes about mixed polymeric micelles as better drug carriers in comparison to single polymeric micelles.

Thermal, mechanical and electrical studies of novel shape memory polyurethane/polyaniline blends

Shape memory polymer (SMP) blends based on polyurethane (PU) and polyaniline (PANI) were prepared via chemical in situ polymerization process. The thermal, mechanical, electrical and shape memory properties were investigated. The structural characterization and morphology of the polymer blends were inspected by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), respectively. The 1 wt% of PANI loading enhanced the thermal stability of the system up to 339 °C. According to differential scanning calorimetry (DSC), the glass transition temperature (Tg) and melting temperature (Tm) of PU/PANI blends increased with the polyaniline loading (0.1 wt%–1 wt%). Improved mechanical properties such as tensile strength and Young’s modulus of PU matrix were also observed with PANI. Moreover, the electrical conductivity of PU/PANI blends was also found to be a function of PANI loading. Remarkable recoverability of thermally triggered shape memory (SM) behavior to the extent of 96% was achieved for 1 wt% PANI blend.

New supramolecular ferrocenyl amides: synthesis, characterization, and preliminary DNA-binding studies

Three ferrocenyl amides have been synthesized and characterized by analytical techniques. Based on single-crystal X-ray analysis, a supramolecular structure was attributed to 1 owing to the presence of intermolecular non-covalent interactions. UV-Visible spectroscopy, viscometry, and dynamic laser light scattering was used to assess the mode of interaction and binding of these complexes with DNA, which varied in the sequence 1 > 2 > 3. The binding is presumably due to the ability of these complexes to form secondary non-covalent interactions with DNA bases. Complex-DNA adduct formation depends on the nature of R of the amide.

Advances in thermoplastic polyurethane composites reinforced with carbon nanotubes and carbon nanofibers: A review

Carbon nanotubes (CNTs) have long been recognized as the stiffest and strongest man-made material known to date. Owing to high electrical conductivity, CNTs have also gained interest in the area of electrical appliances and communication related applications. Moreover, carbon nanofibers (CNFs) depict fine electrical and mechanical profile. Due to their miniscule size, excellent mechanical, electrical, and thermal properties, CNTs can only be beneficial if they are homogeneously dispersed and embedded into light-weight engineering polymer matrices. Adding small amounts of CNTs strongly improve the electrical, thermal, and mechanical properties of the composites. In order to enhance their chemical affinity to polymer matrices, chemically modifying the graphitic sidewalls and tips is necessary. This article reviews the processing technology and improvement of various properties of carbon nanotube-reinforced thermoplastic polyurethane (PU) composites. Initially, the structure, morphology, mechanical, thermal, and electrical properties of nanotubes are described. Then various strategies for fabricating PU/CNTs composites and their properties are discussed. To conclude, recent developments in the field of mechanical, thermal, and electrical properties of thermoplastic PU reinforced with nanotubes and nanofibers are reviewed. A brief account regarding the toxicity and environmental safety aspects of carbon nanomaterials is also included in this article.

Polymer/Nanodiamond Composites in Li-Ion Batteries: A Review

Nanodiamonds have emerged as a subject of tremendous research interest in recent years due to their unique combination of properties, such as large diameter, small and accessible surface, and excellent mechanical properties. Outstanding performance of these nanocomposites basically arises from their structure. When incorporated appropriately, this carbon nanomaterial can remarkably improve physical characteristics of polymer matrix even at extremely small loading content. Physical techniques summarizing thermal, morphological, mechanical, electrical and other properties of polymer/nanodiamond nanocomposites have been discussed. Furthermore, the review elaborates their uses in Li-ion battery, as well as current challenges associated and future prospective for this exciting class of nanocomposites.

THERMODYNAMIC CHARACTERIZATION OF DEXAMETHASONE SODIUM PHOSPHATE AND ITS COMPLEX WITH DNA AS STUDIED BY CONDUCTOMETRIC AND SPECTROSCOPIC TECHNIQUES

Electrical conductivities were measured to calculate critical aggregation concentration (cac) of dexamethasone sodium phosphate (DSP) at various temperature from 298-313K with an increment of 5 K and in this way its thermodynamic parameters like Gibbs energy of aggregation ( ° ∆ agg G ) , enthalpy of aggregation ( ° ∆ agg H ) and entropy of aggregation ( ° ∆ agg S ) were estimated. The results demonstrate that DSP forms enthalpy driven aggregates through open association process. Furthermore, its interaction with DNA was studied by UV-Vis spectroscopy. The binding constant of DSP-DNA interaction was evaluated at 298 K and

Comparative Review on Structure, Properties, Fabrication Techniques, and Relevance of Polymer Nanocomposites Reinforced with Carbon Nanotube and Graphite Fillers

ABSTRACT Owing to their remarkable electrical, mechanical, thermal, catalytic, and optical properties as well as their unique structure, carbon nanotubes and graphite have been exploited to produce high performance and multifunctional composites. The resultant composites are differentiated on the basis of their properties to meet various applications. In the framework of this review article, we have mainly focused on the preparation, structure, and properties of two families of composite materials with an emphasis on the differences between them. Moreover, the current challenges, future prospectives, and applications of carbon nanotubes- and graphite-based materials in sensors and in photovoltaic and energy storage devices (Li-ion battery) have been discussed. GRAPHICAL ABSTRACT

Reinforcing Effects of Modified Nanodiamonds on the Physical Properties of Polymer-Based Nanocomposites: A Review

Exceptional mechanical and other physical properties of nanodiamond (ND) have recently attracted much attention. For thermosetting polymers, the reinforcing effects of as-received and amine-functionalized nanodiamonds on the mechanical and tribological properties have been examined and demonstrated the advantages of covalent incorporation of ND into epoxy structure resulting in strong nanofiller-matrix interface. In epoxy matrix composites, the ultimate mechanical reinforcement was achieved using high loadings level of ND powder along with improved thermal conductivity and reduced friction coefficients. In this regard, several complementary mechanical characterization techniques including pin-on-disk, nanoindentation, vickers, tensile, and compression were used to study the reinforcing mechanisms. GRAPHICAL ABSTRACT

Cobalt and sulfur co-doped nano-size TiO2 for photodegradation of various dyes and phenol

Various compositions of cobalt and sulfur co-doped titania nano-photocatalyst are synthesized via sol-gel method. A number of techniques including X-ray diffraction (XRD), ultraviolet-visible (UV-Vis), Rutherford backscattering spectrometry (RBS), thermal gravimetric analysis (TGA), Raman, N2 sorption, electron microscopy are used to examine composition, crystalline phase, morphology, distribution of dopants, surface area and optical properties of synthesized materials. The synthesized materials consisted of quasispherical nanoparticles of anatase phase exhibiting a high surface area and homogeneous distribution of dopants. Cobalt and sulfur co-doped titania demonstrated remarkable structural and optical properties leading to an efficient photocatalytic activity for degradation of dyes and phenol under visible light irradiations. Moreover, the effect of dye concentration, catalyst dose and pH on photodegradation behavior of environmental pollutants and recyclability of the catalyst is also examined to optimize the activity of nano-photocatalyst and gain a better understanding of the process.

Advances in Polymer-based Nanostructured Membranes for Water Treatment

Water pollution has become the most severe dilemma in the entire world. In this review, we have discussed the advancement in preparation and properties, plus background and challenges regarding polymer-based nanocomposite membranes. Nanofiltration thin film composite membranes have been given tremendous attention over last two decades relative to conventional systems in desalination of sea water, waste water from industries and ultra pure water production etc. In recent years, significant research efforts have been devoted towards the development of high-performance membranes through surface modification of polymers and nanoparticles, nanotubes, etc. to achieve appreciable salt rejection, water flux and antifouling properties.