Crystallization kinetics study of poly(L‐lactic acid)/carbon nanotubes nanocomposites

Effects of carbon nanotubes (CNT) on the isothermal crystallization kinetics of poly(L ‐lactic acid) (PLLA) were quantitatively investigated using the Avrami equation and the secondary nucleation theory of Lauritzen and Hoffman. CNT via grafting modification with PLLA could well disperse in the PLLA matrix and give significantly enhanced crystallization rate and crystallinity of PLLA as analyzed by differential scanning calorimetry and polarized optical microscopy. Analysis of isothermal crystallization kinetics using the Avrami equation demonstrated that CNT significantly enhanced the bulk crystallization of PLLA. Analysis of spherulite growth kinetics using the secondary nucleation theory of Lauritzen and Hoffman found that CNT could expand the temperature range of the crystallization regime III of PLLA. Values of the nucleation constant (K_g) in crystallization regimes III and II of PLLA both increased with increasing CNT contents. The K_g III/K_g II ratios were found to be close to the theoretical value 2 but were not clearly found to depend on the CNT contents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 983–989, 2010     

Branched poly(1,4‐butylene carbonate‐co‐terephthalate)s: LDPE‐like semicrystalline thermoplastics

Branched poly[1,4‐butylene carbonate‐co‐terephthalate]s (PBCTs) have been synthesized by the addition of a small amount of glycerol propoxylate ( 1 ) or pentaerythritol ( 2 ) in the polycondensation of 1,4‐butanediol, dimethyl carbonate, and dimethyl terephthalate. To avoid gel formation, the feed amount of 1 or 2 was carefully controlled at below 0.5 mol % for 1 and below 0.3 mol % for 2 . When feed of 1 or 2 was used, a high‐molecular weight melt state (M_w ～180,000 g/mol) was reached in a total reaction time of 5.5 to 6.5 h with a yield higher than 90%. The generated PBCTs were a semicrystalline polymer (T_g ～5 °C and T_m ～120 °C) when the terephthalate content (F_[TPA]) was 45 to 50 mol %. The crystallization rate increased with increasing F_[TPA] and branch content (F_{[ 1 or 2 ]}); PBCT composed of F_[TPA] = 49 mol % and F_{[ 1 ]} = 0.44 mol % was crystallized completely in a short time, ～3 min, at a crystallization temperature of 50 °C. The branched PBCT exhibited more pronounced toughness in tensile test while providing the advantage of processibility at high shear rates due to the pronounced shear thinning in melt. It was also found that the branched PBCTs were biodegradable. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 914–923     

Modulation of optical and electronic properties of quinoxailine‐based conjugated polymers for organic photovoltaic cells

The synthesis of donor–acceptor type semiconducting copolymers is described. Quinoxaline (QX) or difluorinated quinoxaline (DFQX) derivatives serve as electron acceptors, while thiophene (T) or selenophene (Se) serve as electron donors. Alternating polymers are synthesized through Stille cross‐coupling, and their thermal stability, optical and electrochemical properties, field‐effect carrier mobilities, film crystallinities, and photovoltaic performances are investigated. The intramolecular charge transfer between the electron‐donating and electron‐accepting units in the backbone induces absorption from 450 to 750 nm. The optical band‐gap energies of the polymers are between 1.65 and 1.73 eV, and depend on the polymer structure. Organic photovoltaic cells fabricated using a polymer composed of DFQX and selenophene (PSe‐DFQX) exhibit a power conversion efficiency of 5.14% with an open‐circuit voltage of 0.78 V, a short‐circuit current density of 11.71 mA/cm², and fill factor of 0.57 under AM 1.5 G irradiation (100 mW cm^?2). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1904–1914     

Investigate oxoazolidine-2,4-dione based eutectic mixture via DFT calculations and SAR

In this work, DFT calculations for the designed eutectic mixtures (EMs) using oxoazolidine 2,4-dione (OZD) and zinc chloride (ZnCl2) are done. The interaction between the hydrogen bond donor and hydrogen bond acceptor at atomic level to get EMs are studied using DFT calculations. At room temperature, the stability of these various systems have been investigated using thermodynamic values or parameters such as enthalpy, free energy and others. DFT calculations is used to investigate the possibility of forming the systems (EMs). Further, the impact of varying the temperature on each system was also investigated (323K, 348K). Various other thermodynamic parameters are studied like dipole moment, hardness, chemical potential of the systems (individual molecules and EMs) at different temperatures. The results of the calculations showed that O1Z4 and O4Z1 have maximum dipole moment having values 8.1291, 9.8801 respectively, indicating maximum polarizability. Change in free energy for O1Z4 is least and was found to be ?37.2496 kcal/ mol. Further on changing the temperature, the parameters do not show much variation. Additionally, we have analyzed structure activity relationship (SAR) method to understand the physico-chemical properties of designed EMs and predict their regression and correlation to optimized energy. From the calculated values of pOE model, the value of r² is 0.9995 confirms the validity of the equation obtained. The results of this study suggest a link between the structures that have been utilized to describe the intermolecular interaction between the hydrogen bond donor and acceptor, as well as the stability of the EMs.     

Development of high ionic-conductive Li1.5Al0.5Ge1.5(PO4)3 glass-ceramic solid electrolyte sheet at low temperature using glass/powder composite

Journal of Solid State Electrochemistry - Because of some drawbacks of the organic electrolytes, such as high toxicity and flammability, inorganic electrolytes have attracted attention regarding...     

Asymmetry in electrical properties of Al‐doped TiO2 film with respect to bias voltage

The energy diagram of RuO₂/Al‐doped TiO₂/RuO₂ structures was estimated from the capacitance–voltage and leakage current density–voltage curves. The Al‐doping profile in TiO₂ film was varied by changing position of the atomic layer deposition cycle of Al₂O₃ during the atomic layer deposition of 9 nm‐thick TiO₂ film. The interface between the TiO₂ film and the RuO₂ electrode containing Al‐doping layer showed a higher Schottky barrier by 0.1 eV compared with the opposite interface without the doping layer. The evolution of various leakage current profiles upon increasing the bias with opposite polarity could be well explained by the asymmetric Schottky barrier. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Photofunctional Platinum Complexes Featuring N‐heterocyclic Carbene‐Based Pincer Ligands

Photoactive platinum complexes of stoichiometry [Pt(^RCCC^R)L]^0/+ (R=Me, nBu and L=? CN, ? C≡CPh, ? N≡CCH₃, ? Py, ? CO) featuring pincer‐type bis N‐heterocyclic carbene (NHC) ligands (^RCCC^R) were synthesized. Organometallic syntheses of these complexes are facile and achievable through standard laboratory procedures. Control of intermolecular Pt???Pt interaction, π–π stacking, and emission tuning is achieved through suitable choice of the NHC‐wingtip substituent (R) and the auxiliary ligand (L). Exposure to specific volatile organic compounds (VOCs) or mechanical grinding triggers changes in emission colors, which render these complexes photofunctional. Solid‐state structures and photoluminescence results are described herein.