Identifying structure formation in semicrystalline conjugated polymers is the fundamental basis to understand electronic processes in these materials. Although correlations between physical properties, structure formation, and device parameters of regioregular, semicrystalline poly(3-hexylthiophene) (P3HT) have been established, it has remained difficult to disentangle the influence of regioregularity, polydispersity, and molecular weight. Here we show that the most commonly used synthetic protocol for the synthesis of P3HT, the living Kumada catalyst transfer polycondensation (KCTP) with Ni(dppp)Cl(2) as the catalyst, leads to regioregular chains with one single tail-to-tail (TT) defect distributed over the whole chain, in contrast to the hitherto assumed exclusive location at the chain end. NMR end-group analysis and simulations are used to quantify this effect. A series of entirely defect-free P3HT materials with different molecular weights is synthesized via new, soluble nickel initiators. Data on structure formation in defect-free P3HT, as elucidated by various calorimetric and scattering experiments, allow the development of a simple model for estimating the degree of crystallinity. We find very good agreement for predicted and experimentally determined degrees of crystallinities as high as ∼70%. For Ni(dppp)Cl(2)-initiated chains comprising one distributed TT unit, the comparison of simulated crystallinities with calorimetric and optical measurements strongly suggests incorporation of the TT unit into the crystal lattice, which is accompanied by an increase in backbone torsion. Polydispersity is identified as a major parameter determining crystallinity within the molecular weight range investigated. We believe that the presented approach and results not only contribute to understanding structure formation in P3HT but are generally applicable to other semicrystalline conjugated polymers as well.

The miscibility and aggregation of PCBM ([6,6]-phenyl-C 61 -butyric acid methyl ester) in a polymer matrix is of great importance for the development of fullerene-based organic photovoltaic cells (OPVs). In this study we have systematically investigated the loading of PCBM in regioregular and regiorandom P3HT (poly(3-hexylthiophene-2,5-diyl). Using optical microscopy, we demonstrate the partial miscibility of PCBM in thermally annealed P3HT films and relate it to the relative crystallinity of P3HT. The low polydispersity and the nearly 100% regioregularity of a self-synthesized P3HT allowed a detailed X-ray characterization as a function of PCBM content, revealing a superstructure of periodic amorphous and crystalline lamellar domains of fully chain extended polymer chains. PCBM dissolves in the amorphous interlamellar P3HT regions (partially indexmatching the X-ray scattering contrast) up to a threshold, above which PCBM aggregates start to form. These results show that crystallization of P3HT into 10-nm-wide lamellar domains sets the main length scale in P3HT/PCBM structure formation. PCBM is displaced into the amorphous intralamellar regions, swelling the lamellar stack. This structure formation by crystallization, which is intrinsic to most semicrystalline polymers, followed by the enrichment, segregation, and crystallization of PCBM provides an interdigitated structure, which is conceptually ideal for excitonic solar cells.

Low-cost antireflection coatings (ARCs) on large optical surfaces are an ingredient-technology for high-performance solar cells. While nanoporous thin films that meet the zero-reflectance conditions on transparent substrates can be cheaply manufactured, their suitability for outdoor applications is limited by the lack of robustness and cleanability.Here, we present a simple method for the manufacture of robust selfcleaning ARCs. Our strategy relies on the self-assembly of a blockcopolymer in combination with silica-based sol−gel chemistry and preformed TiO 2 nanocrystals. The spontaneous dense packing of copolymer micelles followed by a condensation reaction results in an inverse opal-type silica morphology that is loaded with TiO 2 photocatalytic hot-spots. The very low volume fraction of the inorganic network allows the optimization of the antireflecting properties of the porous ARC despite the high refractive index of the embedded photocatalytic TiO 2 nanocrystals. The resulting ARCs combine high optical and self-cleaning performance and can be deposited onto flexible plastic substrates.

SUMMARY1. The action of insulin on the transport and the distribution of Na and K has been studied in rat soleus muscles incubated at 300 C in glucose-free Krebs-Ringer bicarbonate buffer.2. Measurements of the uptake and the wash-out of 22Na indicate that the muscles contain an intracellular pool of Na available for transport which is confined to the water space not available to sucrose. Ouabain (10-4-10-3M) inhibited 22Na efflux by 69 % (0.287 #tmole/g tissue wet weight per minute) and 42K-influx by 40 % (0.196 gmole/g tissue wet weight per minute). When all extracellular Na was replaced by Li, both 22Na-efflux and 42K-influx were inhibited to about the same extent and ouabain produced very little further inhibition. 2,4-dinitrophenol decreased the ouabain-resistant component of 22Na-efflux by 39 %, 3. Insulin (from 0.1 to 100 mu./ml.) increased the rate coefficient of 22Na-efflux by from 11 to 46 % within 15 min. In the presence of ouabain (10-3M), the same relative increase was obtained, indicating that the hormone stimulates the glycoside-sensitive and the glycoside-insensitive Na transport to a similar extent. The effect of insulin on 22Na-efflux was not abolished by tetracaine (0 5 x 10-3M), phlorizin (0.5 x 10-2M) or by the substitution of Na, K, Mg or Ca. In the presence of 2,4-dinitrophenol (0.5 X 10-4M) or at temperatures below 150 C, the hormone produced no detectable change in 22Na-efflux.4. Insulin increased 42K-influx from 0*525 to 0 664 ,umole/g tissue wet weight per minute. This effect was entirely blocked by ouabain but not by tetracaine. Insulin produced a 14 % transient decrease in 42K-efflux.5. The continued exposure to insulin led to a new steady state, in which the intracellular Na pool was decreased from around 10 to around 5,almole/g tissue wet weight and the K content increased by an equivalent amount.In the presence of ouabain or at low extracellular concentrations of K, T. CLAUSEN AND P. G. KOHN insulin increased the rate of 22Na-influx by around 35 %. This effect was blocked by 2,4-dinitrophenol but not by tetracaine. 6. It is concluded that insulin stimulates the active coupled transport of Na and K, possibly by increasing the relative Na-affinity of the system mediating this process.

We present a new fully conjugated diblock copolymer, P3HT-b-PFTBTT, containing donor and acceptor blocks with suitably positioned energy levels for use in a solar cell. This is the first block copolymer to be based on an existing high-performance polymer:polymer blend. We observe phase separation of the blocks and self-assembly behavior. In ternary blends with the respective homopolymers the diblock copolymer introduces lateral nanostructure without restricting P3HT crystallization in the charge transport direction, resulting in standing lamellae. By adding the diblock to the homopolymer blend as a compatibilizer, we prevent phase separation at elevated temperatures and benefit from a dramatic increase in P3HT ordering, allowing us to demonstrate polymer blend photovoltaics where the nanostructure is thermodynamically, rather than kinetically, controlled.