Enhanced Clay Dispersion in Polypropylene by the Modification of Clay with Poly(Oxypropylene) Diamine

Polypropylene (PP) is a highly non-polar polymer. Where as the clay is a polar material. Hence generally we get poor dispersion out of it. In this work, effort has been taken to improve the dispersion of clay in to polypropylene matrix. Clay was modified with Poly (oxypropylene) ammonium chloride. Composites were prepared by melt blending method in a twin screw extruder. Three different ratios namely 1.5, 3.0, and 4.5 weight % loadings of clay were adopted to prepare these composites by this technique. Their structures were characterized by FTIR, x-ray diffraction (XRD). Notable change in the crystallization and melting temperatures were observed by differential scanning calorimetry (DSC). The distribution of clay in the matrix was also studied through optical microscope (OM) and scanning electron microscope (SEM). The effect of clay modification on the performance of the composites was studied.     

Drug encapsulation within self-assembled microglobules formed by thermoresponsive supramolecules

An 8-(phenyl)-2'-deoxyguanosine derivative self-assembles in aqueous media into discrete hexadecamers that further self-assemble above 32 °C into microglobules that encapsulate the drug doxorubicin.     

Non-Wieferich primes in number fields and <Emphasis Type="Italic">abc</Emphasis>-conjecture

Let K/Q be an algebraic number field of class number one and let O _K be its ring of integers. We show that there are infinitely many non-Wieferich primes with respect to certain units in O _K under the assumption of the abc-conjecture for number fields.     

Space-time tradeoffs in negative cycle detection - An empirical analysis of the Stressing Algorithm

This paper discusses space-time tradeoffs associated with algorithms for the problem of detecting negative cost cycles in networks (NCCD). NCCD is one of the more ubiquitous problems in computer science and operations research, with applications ranging from program verification and real-time scheduling to image segmentation and shortest path identification. Typical algorithmic analysis, whether theoretical or empirical, focuses almost exclusively on the running time of the algorithm. However, there exist applications in which space is just as important a parameter as time is. This is especially true when the problem instances are very large, as is the case in program verification. Consequently, an algorithm that minimizes running time while ignoring the space overhead may be impractical. In this paper, we analyze a number of the more common algorithms for NCCD from the perspectives of both time and space, with a view towards providing a space-time tradeoff for the practitioner. All the algorithms discussed in this paper (with the exception of Network Simplex) run in O(m·n) time on a network with m arcs and n vertices; however, their space requirements range from O(1) (Stressing Algorithm) to Ω(n) (all the Bellman-Ford and Network Simplex variants). Our empirical results demonstrate that in the cases where space is paramount, the Stressing Algorithm is a useful alternative to the Bellman-Ford variants.     

Effect of emulsifiers on surface properties of sucrose by inverse gas chromatography

Inverse gas chromatography (IGC) was employed to characterize the changes in surface properties of sucrose particles coated with either lecithin or polyglycerol polyricinoleate. IGC was performed using polar and non-polar adsorbates at infinite dilution with the sucrose particles as the solid stationary phase. Coating the sugar surface with emulsifiers induced an increase in the lipophilicity of the sugar particles, i.e. a sharp decrease in the acidity of the surface. Yet the two emulsifiers induced a slightly different increase in the surface basicity. It was hypothesized that this observation was due to a difference in the molecular structure of the emulsifiers.     

Chiral Phosphoric Acid Catalyzed Kinetic Resolution of 2-Amido Benzyl Alcohols: Asymmetric Synthesis of 4H-3,1-Benzoxazines

An efficient method for the asymmetric synthesis of 4H-3,1-benzoxazines was developed by kinetic resolution of 2-amido benzyl alcohols using chiral phosphoric acid catalyzed intramolecular cyclizations. A broad range of benzyl alcohols (both secondary and tertiary alcohols) were kinetically resolved with high selectivities, with an s factor of up to 94. Mechanistic studies were performed to elucidate the mechanism of these reactions, wherein the amide moieties reacted as the electrophiles. Gram-scale reaction and facile transformations of the chiral products demonstrate the potential of this method in asymmetric synthesis of biologically active chiral heterocycles.     

Novel Tailored Polymeric Surfactant for Dispersing Clay into the Non Polar Polymer

Polymers have entropy nearly zero which cause mixing of different polymers or with the fillers become very difficult. There is generally a third component necessary which is called surfactant to enhance the miscibility. The surfactant reduces interfacial tension and improves the interfacial adhesion. In this work, tailored polymeric surfactant is designed and utilized for dispersing the clay in nano scale in to the polymer matrix Polypropylene (PP). These were prepared directly from Na⁺ Bentonite by reactive processing in which melt intercalation technique was carried. They are Polypropylene-g-acrylic amido Poly(oxypropylene) ammonium chloride (POPA). This ammonium salt was prepared from diamine and Polypropylene-g-acrylic acid by the formation of amido amine and sequentially neutralized it with the hydrochloric acid solution. The amido amine formation was verified by the FTIR technique. Clay loading was kept at 5 weight % by this new technique. Their structures were characterized by x-ray diffraction (XRD). The distribution of clay in the matrix was also studied through optical microscope (OM) and scanning electron microscope (SEM). These techniques revealed that the polymeric surfactant enhances the dispersion and the dispersed clay is hardly found in the SEM images.