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Three semiconducting polymers containing benzodithiophene with decylphenylethynyl substituents have been synthesized for which the spacing between alkyl substituents has been systematically increased by introduction of thiophene and bithiophene units in the backbone of the polymer. As the spacing between the side chains increased, an increase of the weight ratio of polymer to fullerene acceptor was required for achieving the highest power conversion efficiency of bulk heterojunction solar cells. The spacing between the side chains of the polymers was estimated from DFT calculations. The TMAFM analysis of polymer PCBM blends showed that the smooth films exhibited the highest solar cell performance.

Three alternating donor–acceptor copolymers have been synthesized by Stille coupling polymerization of 2,6‐(trimethyltin)−4,8‐bis(5‐dodecylthiophene‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene with 1,3‐dibromo‐5‐hexylthieno[3,4‐c]pyrrole‐4,6‐dione, 4,7‐dibromo‐1,3‐benzothiadiazole, and 5,7‐dibromo‐2,3‐didodecylthieno[3,4‐b]pyrazine, respectively. The synthesized polymers were tested in bulk heterojunction solar cells as blends with the acceptor [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM). The thienopyrroledione copolymer displayed a power conversion efficiency of 3.00% which was increased to 3.86% by application of the additive 1,8‐diiodooctane (DIO). Tapping mode atomic force microscopy analysis indicated that there was an increase in the phase separation between polymer and PCBM, leading to an improvement in the performance upon the addition of DIO. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2622–2630

An experimental technique is described for accurately measuring the steady-state fuel consumption rates in small-scale pool fires, less than 7 cm diameter. The technique is applied to studying ethanol fires burning in cylindrical vessels constructed from various materials. The results indicate that the distance between the top of a vessel and the fuel surface profoundly influences the properties of liquid pool fires, including their structure and their burning rates. For combustion in glass cylinders, the burning rates decrease exponentially with increasing freeboard until a critical ullage is attained. At this ullage, the fuel begins to bum on the inside of the vessel, and the burning rate tends to increase slightly, With a further increase of the I@ height, frame instabilities develop leading ultimately to flame self-extinction. The exponential decline in fuel consumption with the lip height depends strongly on the vessel material of construction. For fires in cylinders constructed from better conducting materials (copper and mild steel), the ethanol starts to boil beyond a certain ullage. The appearance of this phenomenon redefines the fuel consumption curve. Finally, free convection leads to non-negligible heat losses, especially from the more conducting copper and steel vessels, with the burning rates becoming dependent on the outside surface area of the cylinders.The first version of this paper was presented at the 2*