Polymorphism behavior of poly(ethylene naphthalate)/clay nanocomposites: role of clay surface modification

Pluronic F-68 Montmorillonite As A Drug Delivery Vehicle For Extended Release Of Venlafaxine Hydrochloride

Short half-life and low bioavailability of Venlafaxine hydrochloride (VF), an antidepressant drug, necessitates the frequent administration of VF tablets in a day in order to maintain adequate drug concentration in blood plasma. This generates the need for the development of formulations which could prolong the release of VF and reduce the multiple dosages. The present work explores the combination of Montmorillonite (Mt) with Pluronic F-68 (PF-68) (OrganoMT) for oral delivery of VF. The effect of various parameters including pH of aqueous drug solution, contact time and initial drug concentration on drug loading capacity of OrganoMT has been studied. The synthesized OrganoMT-VF complexes were characterized by various suitable techniques. XRD studies indicated that the VF molecules were intercalated within the OrganoMT layers. In vitro release behavior of VF from OrganoMT-VF complexes shows an extended-release pattern for a period of 30 h and reaches upto 70% and 60% compared to pure VF having complete release time of 5.5 h and 3.5 h in simulated gastric and intestinal fluid respectively. Various kinetic models were employed to elucidate the drug release mechanism where the best fitting was obtained with Korsmeyer Peppas model. The results suggest the possibility of designing an oral extended controlled release formulation for VF to minimize its administration frequency thereby increasing the effectiveness of drug. This improves patient compliance by reducing the dose from 4 times in 24 h to once in 24 h.

Highly exfoliated montmorillonite clay reinforced thermoplastic polyurethane elastomer:in situpreparation and efficient strengthening

Highly exfoliated montmorillonite (MMT) clay reinforced thermoplastic polyurethane elastomers (TPUs) were prepared by an in situ solution polymerization method. By using small amount of 4,4′-methylenediphenyl diisocyanate (MDI) modified pristine clay (MDI-MMT) as fillers, the mechanical properties of TPUs were greatly improved. For example, with the addition of only 1.0 wt% of MDI-MMT, the resultant TPU/MDI-MMT nanocomposites showed approximately 36% increase in initial Young's modulus, 70% increase in tensile strength and 46% increase in ultimate elongation at break as compared with those of neat TPU. Detailed study showed that, owing to the strong covalent bonding between the MMT sheets and TPU matrix, MMT sheets were highly exfoliated during the polymerization process, and the highly exfoliated MMT sheets gave rise to the greatly improved mechanical properties and thermomechanical properties of TPU/MDI-MMT nanocomposites. The present work demonstrates that the in situ preparation of TPU/MDI-MMT nanocomposites by using MDI-MMT as fillers is a highly efficient method for reinforcing TPU.

Highly exfoliated montmorillonite (MMT) clay reinforced thermoplastic polyurethane elastomers (TPUs) were prepared by an in situ solution polymerization method.

Optical Humidity Sensing Using Transparent Hybrid Film Composed of Cationic Magnesium Porphyrin and Clay Mineral

A transparent hybrid film composed of cationic magnesium porphyrin and clay mineral was developed, and its chromic behavior depending on relative humidity (RH) was investigated. The hybrid film was obtained via intercalation of magnesium porphyrin into clay film; magnesium porphyrin was intercalated into the interlayer spaces of the clay mineral without aggregation. The absorption spectra of the hybrid film showed red shifts compared to the aqueous solution of magnesium porphyrin because of the π-conjugated system extension with coplanarization of the meso-substituted pyridinium group and porphyrin ring. The absorption maximum of the hybrid film was gradually shifted to a shorter wavelength, and the color of the hybrid film was changed with increasing RH. The X-ray diffraction measurement suggested that the basal space of clay was expanded with increasing RH, indicating that the interlayer space of clay was expanded by water adsorption, and the spectral shift was induced by the change in coplanarization degree between the porphyrin ring and meso-substituted pyridinium groups.

Studying nanostructure gradients in injection-molded polypropylene/montmorillonite composites by microbeam small-angle x-ray scattering

The core-shell structure in oriented cylindrical rods of polypropylene (PP) and nanoclay composites (NCs) from PP and montmorillonite (MMT) is studied by microbeam small-angle x-ray scattering (SAXS). The structure of neat PP is almost homogeneous across the rod showing regular semicrystalline stacks. In the NCs the discrete SAXS of arranged crystalline PP domains is limited to a skin zone of 300 μm thickness. Even there only frozen-in primary lamellae are detected. The core of the NCs is dominated by diffuse scattering from crystalline domains placed at random. The SAXS of the MMT flakes exhibits a complex skin-core gradient. Both the direction of the symmetry axis and the apparent perfection of flake-orientation are varying. Thus there is no local fiber symmetry, and the structure gradient cannot be reconstructed from a scan across the full rod. To overcome the problem the rods are machined. Scans across the residual webs are performed. For the first time webs have been carved out in two principal directions. Comparison of the corresponding two sets of SAXS patterns demonstrates the complexity of the MMT orientation. Close to the surface (< 1 mm) the flakes cling to the wall. The variation of the orientation distribution widths indicates the presence of both MMT flakes and grains. The grains have not been oriented in the flowing melt. An empirical equation is presented which describes the variation from skin to core of one component of the inclination angle of flake-shaped phyllosilicate filler particles.

Simultaneous enhancements of UV resistance and mechanical properties of polypropylene by incorporation of dopamine-modified clay

Inspired by the radical scavenging function of melanin-like materials and versatile adhesive ability of mussel-adhesion proteins, dopamine-modified clay (D-clay) was successfully incorporated into polypropylene (PP) using an amine-terminated PP oligomer as the compatibilizer. Although the PP/D-clay nanocomposites exhibit intercalated morphology, the incorporation of D-clay greatly improves the thermo-oxidative stability and UV resistance of PP owing to the strong radical scavenging ability of polydopamine (PDA) and large contact area between PP and the PDA coating on clay mineral. Moreover, the reinforcement effect brought by D-clay is fairly significant at very low clay loadings probably owing to the strong interfacial interactions between the layered silicates and the compatibilizer as well as that between the compatibilizer and the PP matrix. The work demonstrates that D-clay is a type of promising nanofiller for thermoplastics used for outdoor applications since it stabilizes and reinforces the polymers simultaneously.

IR spectroscopy of clay minerals and clay nanocomposites

Recent applications of infrared (IR) spectroscopy in research of clays and clay minerals are reviewed. After a brief description of the structures of clay minerals and basic principles of IR spectroscopy, the selected most interesting papers published in this area in 2007–2009 are discussed. The potential of both middle-IR and near-IR spectroscopy and different sampling techniques used in the investigation of clay minerals occurring on Earth and Mars is presented, including the utilisation of clay materials in the industry and in protection of the environment. Finally, the theoretical studies of the vibrational properties of the clay minerals are considered.

Electrospinning of polyvinylidene difluoride with carbon nanotubes: synergistic effects of extensional force and interfacial interaction on crystalline structures

Polyvinylidene difluoride (PVDF) solutions containing a very low concentration of single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) of similar surface chemistry, respectively, were electrospun, and the nanofibers formed were collected using a modified rotating disk collector. The polymorphic behavior and crystal orientation of the nanofibers were studied using wide-angle X-ray diffraction and infrared spectroscopy, while the nanotube alignment and interfacial interactions in the nanofibers were probed by transmission electron microscopy and Raman spectroscopy. It is shown that the interfacial interaction between the SWCNTs and PVDF and the extensional force experienced by the nanofibers in the electrospinning and collection processes can work synergistically to induce highly oriented beta-form crystallites extensively. In contrast, the MWCNTs could not be well aligned along the nanofiber axis, which leads to a lower degree of crystal orientation.