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Deuterium NMR has been employed to determine the average orientation of chain segments in poly(butadiene) networks. It is shown that the free induction decay separates the contribution to the orientation arising from the network constraint to that from chain interactions. The NMR spectrum line shape reveals the orientational distribution of network vectors due to the cross-links, whereas the observed splitting gives information about the orientation due to segmental interactions. Both the line shape and splitting have been fitted simultaneously for a range of deformed poly(butadiene) networks. From the fitting parameters, the separate contributions to the average orientation of the chain segments arising from the network constraint and from the interactions are calculated. These in turn are used to determine the molecular weight between cross-links and the size of the segmental interactions, which we choose to express in terms of the Edwards' screening length. This work is also important to computer modeling of the stress−optical coefficient where the interchain interactions are ignored.

No abstract

Abstract. A Peclet number, Pe, for the drying of colloidal films can be used as a predictor of the uniformity of water concentration in the direction normal to the film. Uniform drying is predicted to occur when Pe < 1, whereas with Pe > 1, a layer of packed particles is expected to develop above a more dilute layer. Routh and Zimmerman have more recently proposed that the particle concentration gradient between the packed and dilute layers, dφp/dz , will scale as Pe 1/2 . Here, this scaling relation is tested experimentally with magnetic resonance profiling data obtained from waterborne colloidal films dried under conditions to yield a range of Pe. It is found that dφp/dz increases with Pe but scales as Pe 0.8 . This disagreement with the prediction can be attributed to an underestimate of Pe when there are greater non-uniformities of drying, because of an unquantified slowing down of the evaporation rate.

No abstract

Ah igh-purity methylammonium lead iodide complex with intercalated dimethylformamide (DMF) molecules, CH 3 NH 3 PbI 3 ·DMF,i si ntroduced as an effective precursor material for fabricating high-quality solution-processed perovskite layers.S pin-coated films of the solvent-intercalated complex dissolved in pure dimethyl sulfoxide (DMSO) yielded thick, dense perovskite layers after thermal annealing.The low volatility of the pure DMSO solvent extended the allowable time for low-speed spin programs and considerably relaxed the precision needed for the antisolvent addition step.A no ptimized, reliable fabrication method was devised to take advantage of this extended process windowa nd resulted in highly consistent performance of perovskite solar cell devices, with up to 19.8 %p ower-conversion efficiency (PCE). The optimizedmethod was also used to fabricate a22.0 cm 2 ,eightcell module with 14.2 %P CE (active area) and 8.64 Voutput (1.08 V/cell).Hybrid organic-inorganic lead halide perovskites are promising materials for cost-effective printable photovoltaics. As ar esult of the enhanced purity of the reagents [1,2] and careful optimization of the perovskite layer fabrication process, conversion efficiencies have increased significantly since the first report on perovskite solar cells in 2009. [26] Thehighest certified power-conversion efficiency(PCE) now exceeds 23 %. [27,28] Forl arge-area devices,h owever, the certified PCE of as ubmodule still remains under 12 %. [28]

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The adsorption of natural pigments onto TiO2nanoparticles was investigated. The pigments were extracted from the dark purple colored pulp of the berry-like capsule of Kuduk-kuduk (Melastoma malabathricumL.). The Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm models were used to analyze the equilibrium experimental data. Data correlated well with the Sips isotherm model, where the heterogeneity factor (n=0.24) indicated heterogeneous adsorption characteristics, with a maximum adsorption capacity of 0.0130 mg/g. The heterogeneous adsorption character was further supported by results obtained from zeta-potential measurements. When a dye-sensitized solar cell (DSSC) was sensitized with the extracted pigment, the photo-energy conversion efficiency was measured to be 0.83%, thus proving the suitability of Kuduk-kuduk fruit pulp as a sensitizer in DSSCs.