Per H. J. Carlsen

X-ray scattering from oriented poly(3-alkylthiophenes)

Abstract Solution-cast films of poly(3-hexylthiophene) (P3HT) and poly(3-octylthiophene) (P3OT) were oriented by stretching to obtain more detailed information about their crystalline structure. For the first time reflections associated with the stretch direction l = 1–7 were revealed using a combination of X-ray film exposures and detailed intensity mapping by various detector scans. The reflections were located at finite angles to the stretch axis indicating a monoclinic (or triclinic) unit cell. The equatorial diffraction patterns (l = 0) of P3HT and P3OT show that the two structures are equal only with one differing lattice dimension caused by the length of the alkyl side chains. The crystalline structure for the unstretched (isotropic) and the stretched sample is found to be the sa me. Existence of h00 and absence of hk0, h0l and hkl reflections, all with finite integers h, k and l, indicate layer stacking disorder between bc-planes. Intensity calculations based upon this model corroborate well with the measured diffraction pattern on the assumption of disordered alkyl side chains.

Chain configuration of poly(3-hexylthiophene) as revealed by detailed X-ray diffraction studies

Abstract Detailed diffractometer and Laue x-ray studies of streched poly (3-hexylthiophene) films enabled us to identify several 001 reflections associated with the polymer chain direction. The chain repetition distance could then be determined for the first time, giving c =2·7.4 A =14.8 A . 7.4 A is shorter than expected for a model involving “alternating updown” monomers along the chain (7.8A), whereas the observed c value is in agreement with a new “up-up-down-down” model (14.9A). Intensity calculations assuming side chain disorder corroborate well with the new model.

Synthesis and polymerization of 3,3′-dialkyl-2,2′-bithiophenes

Abstract A series of 3,3′-dialkyl-2,2′-bithiophenes (DAT2s) has been synthesized by the nickel-catalyzed Kumada coupling of 2-bromo-3-alkylthiophene with 2-(3-alkylthienyl) magnesium bromide. These monomers were analyzed by NMR and UV–Vis spectroscopies. The monomers were oxidatively polymerized with iron(III) chloride to yield the respective π-conjugated poly(3,3′-dialkyl-2,2′-bithiophene)s. The new polymers were characterized with 1 H NMR and UV–Vis spectroscopies. Conductivity was in the order of 10–10 2 S/cm, depending upon the length of the alkyl chain.

Synthesis of Novel Diammonium Gemini Surfactants

Selective synthesis of linear and gemini quaternary ammonium surfactants was accomplished by reacting the corresponding alkyl alcohols with 2-chloro-N,N-dimethyl-ethylamine under basic conditions. The amines were quaternized with methyl chloride or methyl iodide.

STUDY OF AN EFFICIENT AND SELECTIVE BROMINATION REACTION OF SUBSTITUTED THIOPHENES

Abstract Bromination in concentrated solutions of substituted thiophenes in acetic acid with NBS at room temperature was studied. Under the conditions, bromination readily took place with high regioselectivity at the 2-ring positions, > 99 %. The developed method was demonstrated to be suitable for multimolar preparations.

Conformational features of linear and cyclic enkephalins. A computational study

A theoretical conformational study using the CICADA program package (J. Mol. Struct. (Theochem), 1995, 337, 17-24) was performed for two linear enkephalins, Leu-enkephalin and Met-enkephalin, and two cyclic analogues, DLFE and DPDPE. The conformational flexibilities of whole molecules and selected torsions were calculated. The low energy conformers obtained were compared with structures obtained by spectroscopic methods. The mutual space positions of key elements for receptor recognition were analyzed. Conformations were clustered using RMS deviation computed for selected atoms. The different conformational behavior of aromatic rings in cyclic analogues of enkephalins was observed. While aromatic rings of cyclic analogues exhibit different conformational behavior, the linear enkephalins show similar behavior in these key parts. Hydrogen bonds predicted by spectroscopic measurements were confirmed by our calculations. Also very specific conformational features, like concerted conformational movement, were analyzed.

Molecular structure of stretch oriented poly(3-hexylthiophene) studied by an extended X-ray diffraction mapping

Abstract Detailed x-ray diffraction intensity mapping of the reciprocal space of stretched poly(3-hexylthiophene) films enabled us for the first time to reveal reflections associated with the stretch direction (l = 1−7). The reflections are located at finite angles to the stretch axis and can therefore only be indexed on a monoclinic (or triclinic) unit cell. The monoclinic cell parameters are a =16.90 A , b =4.85 A , c =7.84 A , α=50.6° , ( a =4.85 A , b =16.90 A , c =7.84 A and β=129.4° by crystallographic conventions) and with two monomer units per cell. The values of a and c are directly measured whereas b and α are refined from structure factor calculations. Existence of h00 but absence of hk0, h0l and hkl reflections indicate layer disorder between oblique bc planes, whereas structure factor calculations indicate side chain disorder.

Broken π-conjugated thiophene systems: 1. Synthesis and polymerization of 2,2′-di(alkylthienyl) methanes

Abstract A series of 2,2′-di(alkylthienyl)methanes has been synthesized by chloroalkylation of 3-alkylthiophenes in the presence of zinc chloride. These monomers were oxidatively polymerized with iron(III) chloride to yield the respective partially broken π-conjugated poly(2,2′-di(alkylthienyl)methane)s. Solubility and processability properties of the polymers were dependent on the alkyl groups attached to the thiophene ring. The new polymers contain quinoidal segments due to dehydrogenation of the bridge carbon during polymerization, which can be seen by UV–Vis and 1H NMR spectroscopy. Due to the quinoidal segments, these polymers show conductivity in the range from 10−6 to 10−4 S/cm.

NUCLEOPHILIC RING OPENING OF CYCLIC SULPHAMIDITES

Abstract The cyclic sulphamidites (2 S ,4 S )- and (2 R ,4 S )-3-benzyl-4-benzyloxymethyl-2-oxo-1,2,3-oxathiazolidine 1 were prepared from S -glycidol in 60–66 % overall yield. Nucleophilic ring opening of 1 by cyanide, azide and benzyloxy anions have been studied with respect to regio and stereospecificity. A mild procedure for benzylation of alcohols was introduced.

Structural and thermochromic properties of mixtures of poly(3-hexylthiophene) and poly(3-octylthiophene)

Abstract For the first time, the structural and thermochromic properties of mixtures of poly(3-hexylthiophene) (PHT) and poly(3-octylthiophene) (POT) have been studied. X-ray diffraction and optical absorption spectroscopy were employed, the latter on spin-cast films in the temperature range 20–210 °C. The results show that the mixtures are single-phase materials that are structurally intermediate between PHT and POT. It was found that the longest interchain distance a in the crystalline part of the polymer and the thermochromic transition temperature Tt both vary nonlinearly with composition in such a way that Tt and a are approximately linear to each other. This indicates that the side chains act primarily as spacers between main chains, rather than being directly involved indicates that the side chains act primarily as spacers between main chains, rather than being directly involved in the thermochromic transition. This transition may instead be induced by a melting of the polymer backbone.