The Effect of Stereocomplex Polylactide Particles on the Stereocomplexation of High Molecular Weight Polylactide Blends

Stereocomplexation is one of several approaches for improving polylactide (PLA) properties. The high molecular weight of poly L-lactide (PLLA) and poly D-lactide (PDLA) homopolymers are a constraint during the formation of stereocomplex PLAs (s-PLAs). The presence of s-PLA particles in PLA PLLA/PDLA blends can initiate the formation of s-PLA crystalline structures. We used the solution casting method to study the utilization of s-PLA materials from high molecular weight PLLA/PDLA blends for increasing s-PLA formation. The s-PLA particles initiated the formation of high molecular weight PLLA/PDLA blends, obtaining 49.13% s-PLA and 44.34% of the total crystalline fraction. In addition, the mechanical properties were enhanced through s-PLA crystalline formation and the increasing of total crystallinity of the PLLA/PDLA blends. The s-PLA particles supported initiation for s-PLA formation and acted as a nucleating agent for PLA homopolymers. These unique characteristics of s-PLA particles show potential to overcome the molecular weight limitation for stereocomplexation of PLLA/PDLA blends.

A NEW ALKALOID FROM DERRIS INDICA (LAM) BENNETT SEED OIL: ISOLATION AND CHARACTERIZATION

Objective: The aim of the study was to isolate alkaloid compound from seed oil of Derris indica (Lam) Bennett where relevant antimicrobial properties in traditional medicines. Methods: The plant was selected based on their usage in traditional medicines and ethnopharmacological importance. Crude extract from D. indica seeds fractioned with different solvents through column chromatography. Isolated pure fraction was identified and characterized using UV, FTIR, 1HNMR and Mass spectroscopy. Results: D. indica seeds hexane extract on fractionation with ethyl acetate and methanol through column chromatography yielded a crystalline fraction. The fraction was identified as alkaloid group and characterized as a 2-(6-methoxyphenanthridin-8-yl) propan-2-ol. The compound is a new report from D. indica seed oil. Conclusion: The usage of D. indica plant is much in traditional health care for treatment of diseases. Isolation of alkaloid compound from D. indica seeds in traditional herbal medicines may be found a good source of drug discovery.

Nucleation Heat Treatment on the Crystalline Fraction and Crystal Morphology of Lamav Cad Lithium Disilicate

The authors have withdrawn this preprint due to author disagreement.

Nucleation Heat Treatment on the Crystalline Fraction and Crystal Morphology of Lamav Cad Lithium Disilicate

Thus, this study aimed to evaluate the influence of different nucleation heat treatments on the crystalline fraction and crystal morphology of the LS2 LaMaV CAD. Discs (12 mm diameter x 1.2 mm thickness) of LS2 LaMaV CAD and IPS e.max CAD (C, control group, n=3) were made. LS2 LaMaV CAD discs were annealed at 380oC/2h followed by different nucleation heat treatments in which time and temperature were varied composing 4 groups (n=3): T1 (1h30/500oC), T2 (3h/500oC), T3 (6h/500oC) and T4 (6h/480oC). Scanning Electron Microscopy images were obtained to characterize the microstructure and to quantify the crystalline fraction using the ImageJ software. X-ray diffraction with Rietveld refinement was performed. ANOVA one-way with Tukey post-hoc test (a = 0.05) was used to analyze the ImageJ images and the Rietveld refinements for X-ray diffraction data. X-ray diffraction analysis showed peaks of approximately 86% of lithium disilicate for all groups. The morphology of crystals was in lath-shaped and homogeneous format for all groups; the group that most resembled the C group was T1. The crystalline fraction (%) was: C = 59.33 ± 0.47, T1 = 61.63 ± 0.61, T2 = 61.07 ± 1.09, T3 = 56.39 ± 0.32, and T4 = 57.48 ± 0.90, all the groups were statistically different to the C group. It was concluded that the nucleation temperature influenced the size and quantity of the crystals of lithium disilicate; treatment that showed the best result was that that received nucleation treatment for 1 hour and 30 minutes at 500ºC.

Study of nanocrystalline silicon-germanium for the development of thin film transistors

In this work, we study the effect of the deposition RF-power on the structural, optical and electrical properties of hydrogenated nanocrystalline silicon-germanium (nc-SiGe:H) thin films obtained by plasma enhanced chemical vapor deposition (PECVD) at substrate temperature of 200 °C. The objective is to produce films with high crystalline fraction in order to be used as active layers in thin film transistors (TFTs). Bottom-gate (BG) thin film transistors were fabricated with nc-SiGe:H active layers, deposited at different RF-power. Values of ON-OFF current ratio, subthreshold slope and threshold voltage of 105, 0.12 V/dec and 0.9 V, respectively, were obtained on TFTs with the nc-SiGe:H active layer deposited at 25 W.

Thermal Properties of Composite Polymer Electrolytes Poly(Ethylene Oxide)/Sodium Trifluoroacetate/Aluminum Oxide (PEO)10CF3COONa + x wt.% Al2O3

Polymeric membranes of poly(ethylene oxide) (PEO) and sodium trifluoroacetate (PEO:CF3COONa) combined with different concentrations of aluminum oxide (Al2O3) particles were analyzed by impedance spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). DSC results show changes in the crystalline fraction of PEO when the concentration of Al2O3 is increased. TGA analysis showed thermal stability up to 430 K showing small changes with the addition of alumina particles. The decrease in crystalline fraction for membranes with low Al2O3 concentration is associated with the increase in conductivity of (PEO)10CF3COONa + x wt.% Al2O3 composites.