Isothermal Crystallization Behavior of Poly(L-lactic acid)/Organo-Montmorillonite Nanocomposites

The isothermal crystallization behavior of poly(L-lactic acid)/organo-montmorillonite nanocomposites (PLLA/OMMT) with different content of OMMT, using a kind of twice-functionalized organoclay (TFC), prepared by melt intercalation process has been investigated by optical depolarizer. In isothermal crystallization from melt, the induction periods (t(i)) and half times for overall PLLA crystallization (100 degrees C <= T-c <= 120 degrees C) were affected by the temperature and the content of TFC in nanocomposites. The kinetic of isothermal crystallization of PLLA/TFC nanocomposites was studied by Avrami theory. Also, polarized optical photomicrographs supplied a direct way to know the role of TFC in PLLA isothermal crystallization process. Wide angle X-ray diffraction (WAXD) patterns showed the nanostructure of PLLA/TFC material, and the PLLA crystalline integrality was changed as the presence of TFC. Adding TFC led to the decrease of equilibrium melting point of nanocomposites, indicating that the layered structure of clay restricted the full formation of crystalline structure of polymer.

Functional gold nanoparticles for studying the interaction of lectin with glycosyl complex on living cellular surfaces

In this study. lectin-conjugated gold nanoparticles (GNPs) were prepared by standard biotin-streptavidin chemistry. The lectin-conjugated GNPs call be used as ail indicator for studying the interaction of lectin with glycosyl complex on living cellular Surfaces due to the high affinity of the lectin with saccharides. The interactions of two well-known lectins (Ricinus communis agglutinin and concanavalin A) and three different cell lines (HeLa, 293, and 293T) were selected here to establish this assay. Highly binding affinity of R. communis agglutinin with cells was demonstrated by conventional microscopic and UV-visible spectroscopic Studies. In addition, the binding process can be inhibited by galactose, giving further proof of the binding mechanism. (c) 2009 Elsevier Inc. All rights reserved.

Precipitates formed in a Mg-7Y-4Gd-0.5Zn-0.4Zr alloy during isothermal ageing at 250 degrees C

The ageing behavior of an extruded Mg-7Y-4Gd-0.5Zn-0.4Zr alloy during ageing at 250 degrees C has been investigated. Two types of phases have been observed during the ageing process. One is a lamellar phase with a 14H long periodic stacking structure, the other is the beta' phase with an ellipsoidal morphology. The increased mechanical properties of the peak-aged alloy are mainly ascribed to the presence of both of these phases at peak hardness.

A general route to transform normal hydrophilic cloths into superhydrophobic surfaces

Herein, we describe a simple and inexpensive method for forming superhydrophobic cloths with the highest water contact angle of close to 180 degrees, in which normal commercial cloths serving as pristine materials are modified with suitable gold micro/nanostructures.

Non-isothermal crystallisation kinetics of polyamide 6/mesoporous silica nanocomposites

Non-isothermal crystallisation kinetics of a polyamide 6/mesoporous silica nanocomposite (PA6-MS) has been investigated by differential scanning calorimetry (DSC) at different cooling rates. Mandelkern, Jeziorny-Ziabicki and Ozawa methods were applied to describe this crystallisation process. The analyses show that the mesoporous silica particles act as nucleating agents in the composite and that the Avrami exponent n varies from 3.0 to 4.6. The addition of mesoporous silica influenced the mechanism of nucleation and the growth of polyamide 6 (PA6) crystallites.

Shape-gradient composite surfaces: Water droplets move uphill

The approach of water droplets self-running horizontally and uphill without any other forces was proposed by patterning the shape-gradient hydrophilic material (i.e., mica) to the hydrophobic matrix (i.e., wax or low-density polyethylene (LDPE)). The shape-gradient composite surface is the best one to drive water droplet self-running both at the high velocity and the maximal distance among four different geometrical mica/wax composite surfaces. The driving force for the water droplets self-running includes: (1) the great difference in wettability of surface materials, (2) the low contact angle hysteresis of surface materials, and (3) the space limitation of the shape-gradient transportation area. Furthermore, the average velocity and the maximal distance of the self-running were mainly determined by the gradient angle (alpha), the droplet volume, and the difference of the contact angle hysteresis. Theoretical analysis is in agreement with the experimental results.

Interfacial supramolecular self-assembled monolayers of C-60 by thiolated beta-cyclodextrin on gold surfaces via monoanionic C-60

The supramolecular self-assembled monolayers (SAMs) of C-60 by thiolated beta-cyclodextrin (CD) on gold surfaces were constructed for the first time using C-60 monoanion. The results indicate that monoanionic C-60 plays a crucial role in the formation of the C-60-containing self-assembled monolayers. The generation of C-60 monoanion and the formation process of C-60 SAMs were monitored in-situ by UV-visible and near-IR spectroscopy. The resulting C-60 SAMs were fully characterized by spectroscopic ellipsometry (SE), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. After the immobilization of C-60 by the SAMs of thiolated beta-CD, the film thickness increased by approximately 1 nm from 0.8 to 1.8 nm as determined by SE, demonstrating the formation of the supramolecular self-assembled monolayers of thiolated beta-CD/C-60. The new C-60 SAMs exhibited one quasi-reversible redox couple at half wave potential of -0.57 V vs SCE in aqueous solution containing 0.1 M KCl. The surface coverage of C-60 on the gold surfaces was estimated to be 1.1 x 10(-10) mol cm(-2). The XPS showed the assembly of C-60 over the thiolated beta-CD SAMs.

Isothermal crystallization kinetics of iPP during self-nucleation process

In this paper, the isothermal crystallization kinetics of polypropylene (iPP) during self-nucleation was studied by means of differential scanning calorimetry(DSC). The iPP was melted at 438 K and then isothermally crystallized in the range of temperature between 421 and 425 K. The mechanism of nucleation and growth of iPP was discussed. The Avrami equation was applied to analyzing the process of isothermal crystallization of iPP from the melt. The average value of Avrami exponent is n=3.01, suggesting that the primary crystallization maybe corresponds to three-dimensional spherulitic growth. The K-g value obtained from Lauritzen-Hoffman equation is 1.128 X 10(5) K-2, which suggests that crystallization species should be regime I. The decrease of crystallization active energy and chain folding work indicates that the self-nucleation can greatly promote the overall crystallization of iPP.

Micropatterning of metal films coated on polymer surfaces with epoxy mold and its application to organic field effect transistor fabrication

In this letter, a simple and versatile approach to micropatterning a metal film, which is evaporated on a Si substrate coated with polymer, is demonstrated by the use of a prepatterned epoxy mold. The polymer interlayer between the metal and the Si substrate is found important for the high quality pattern. When the metal-polymer-Si sandwich structure is heated with the temperature below T-m but above T-g of the polymer, the plastic deformation of the polymer film occurs under sufficiently high pressure applied. It causes the metal to crack locally or weaken along the pattern edges. Further heating while applying a lower pressure results in the formation of an intimate junction between the epoxy stamp and the metal film. Under these conditions the epoxy cures further, ensuring adhesion between the stamp and the film. The lift-off process works because the adhesion between the epoxy and the metal film is stronger than that between the metal film and the polymer. A polymer field effect transistor is fabricated in order to demonstrate potential applications of this micropatterning approach.

Superhydrophobic PTFE surfaces by extension

A rather simple but yet effective way to achieve a superhydrophobic film by extending a Teflon film is proposed. The water contact angle can be increased from 118 to 165degrees by extending to ca. 190%. The fibrous crystals and the increasing distance between the fibrous crystals are believed responsible for the high water-contact angle. It indicates that the density of the aligned microstructures is very important for the superhydrophobicity.

Pt nanoparticles: Heat treatment-based preparation and Ru(bpy)(3)(2+)-mediated formation of aggregates that can form stable films on bare solid electrode surfaces for solid-state electrochemiluminescence detection

A simple thermal process for the preparation of small Pt nanoparticles is presented, carried out by heating a H-2-PtCl6/3- thiophenemalonic acid aqueous solution. The following treatment of such colloidal Pt solution with Ru( bpy)(3)(2+) causes the assembly of Pt nanoparticles into aggregates. Most importantly, directly placing such aggregates on bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.

Wettability of zinc oxide surfaces with controllable structures

Zinc oxide (ZnO) surfaces with controllable structures (i.e, microstructure, nanostructure, and micronanobinary structure) have been created by controlling pH at < 4 or > 10.5 in the Zn(gray) + H2O2 reaction. The resulting surface shows superhydrophobicity. It is found that the water contact angle (CA) of the surface with micronanobinary structure is greater than that of nanostructure and that of nanostructure is greater than that of the microstructure. Theoretical analysis is completely in agreement with the experimental results.

Macroporous fluoropolymeric films templated by silica colloidal assembly: A possible route to super-hydrophobic surfaces

A super-hydrophobic surface was obtained on a three-dimensional (313) polyvinylidene fluoride (PVDF) macroporous film. The porous films were fabricated through self-assembled silica colloidal templates. The apparent water contact angle of the surface can be tuned from 106 degrees to 153 degrees through altering the sintering temperature and the diameter of the colloidal templates. A composite structure of micro-cavities and nanoholes on the PVDF surface was responsible for the super-hydrophobicity. The wettability of the porous surfaces was described by the use of the Cassie-Baxter model and Wenzel's equation.