Influence of the substituent on the chiroptical and magnetic properties of conjugated polymers

In this dissertation, the influence of theside chain on the chiroptical and magnetic properties of conjugated polymers isinvestigated.In the first part regioregularpoly(thiophene)s, substituted with electron rich, conjugated aminostyryl sidechains, are synthesized in order to combine magnetism with conjugated polymers.The formation of magnetic moments (spins), necessary for a material s magneticproperties, is accomplished by selective oxidation of the electron richaminostyryl side chain. The regioregular, head-to-tail substitution patternaligns these magnetic moments within one polymer chain. As the supramolecularorder in the material is also of great importance for the creation of a purelyorganic (ferro)magnetic material (intermolecular spin alignment). Theaggregation behaviour is examined and it is shown via UV-vis and CD experimentsthat, depending on the bulkiness of the side chain, both side and main chainaggregate under the same conditions, but selective oxidation leads tode-aggregation. In order to overcome this de-aggregation upon oxidation,another class of conjugated polymers, poly-para-(phenylene ethynylene), knownfor their tendency to aggregate, is exploited. Unfortunately, after thoroughinvestigation, it was shown that the synthesis of these PPEs with aminofunctionalized, conjugated side chains could not be accomplished and thereforethis path for the creation of (ferro)magnetic materials was abandoned.The next chapter focuses on the ability tosteer the conformational behaviour of conjugated polymers, by synthesizingdifferent meta coupled arylenes, substituted with oligo(phenylene vinylene)s.By performing UV-vis, CD and DSC experiments it was proven that altering theconformation seems very difficult, as almost all the synthetical changes leadto the formation of supramolecular aggregates. These changes include the use ofdifferent polymer backbones (containing thienothiophene or bithiophene units)and altering the bulkiness and distance to the polymer backbone of the chiralmoieties.In the following chapters the aggregationbehaviour of poly(thiophene)s is studied. First the influence of the degree ofregioregularity is investigated by synthesizing a series of chiralpoly(3-alkylsulfanylthiophene)s with different degree of regioregularity. Insolution and film there is a clear trend that the amount of aggregation dependson the degree of regioregularity in a non-linear way as the strongest aggregationand chiral expression is found in those materials with a small amount ofregioirregularity. This indicates that a small amount of disorder facilitatesthe aggregation and chiral expression.In the last chapter a series ofpoly(3-alkylthiophene)s with a substituent of varying degree of bulkiness issynthesized. It is shown that in solution as well as in film the relativecontribution of the planar and aggregated chains depends on the bulkiness ofthe alkyl chains. This series of polymers also contributes to the investigationof (ferro)magnetism in neutral conjugated polymers and confirms earlierobtained results for poly(thiophene) and strengthens the hypothesis that the&#61552;-interactions and the fraction of planar polymer chains influence the coercivityand saturation magnetization, respectively.<w:latentstyles deflockedstate="false" defunhidewhenused="true" <w:lsdexception locked="false" priority="0" semihidden="false" <w:lsdexception locked="false" priority="9" semihidden="false" <w:lsdexception locked="false" priority="10" semihidden="false" <w:lsdexception locked="false" priority="11" semihidden="false" <w:lsdexception locked="false" priority="22" semihidden="false" <w:lsdexception locked="false" priority="20" semihidden="false" <w:lsdexception locked="false" priority="59" semihidden="false" <w:lsdexception locked="false" priority="1" semihidden="false" <w:lsdexception locked="false" priority="60" semihidden="false" <w:lsdexception 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Conformational Behavior of Conjugated Polymers With Oligo(phenylene vinylene) Side Chains

The synthesis and chiroptical properties of a series of meta-arylenes, equipped with chiral oligo(phenylene vinylene) (OPV) side chains, are presented. How the OPV side chain contributes to the optical properties of the polymer is investigated. Secondly, the influence of the distance of the chiral moieties, placed on the OPV side chain, to the polymer main chain is investigated, which shows that, in order to induce any chiral effects, these chiral moieties need to be placed in the ß-position near the polymer main chain. Finally, it is shown that long (a)chiral, lateral alkoxy chains on the OPV side chain prevent the polymers from adopting a helical conformation and result in the formation of lateral (a)chiral stacks of different polymer chains. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.status: publishe

A chiroptical study of chiral Lambda- and X- type oligothiophenes toward modelling the interchain interactions of chiral conjugated polymers

A variety of chiral Lambda-type and X-type oligothiophenes (MDC 1-10) was synthesized and studied by means of UV-vis and CD spectroscopy in order to model the chiral interchain interactions of conjugated polymers with optically Active side chains in both neutral and oxidized state. It was found that, within the class of chiral Lambda-type oligothiophenes, the interchain chiral exciton coupling was only present when using an electronwithdrawing imine linkage between the oligothiophene and the chiral unit (MDC 7-9). Together with the observed decrease in g-value (dissymmetry factor for absorption) by extending the oligothiophene moiety, these linkage and elongation restrictions impose crucial drawbacks on chiral Lambda-type oligothiophenes as study model in both neutral and oxidized state. Therefore, a new chiral X-type oligothiophene (MDC 10) was developed that combines chiral exciton coupling in neutral state with the additional ability of oxidation.status: publishe

Influence of the regioregularity on the chiral supramolecular organization of poly(3-alkylsulfanylthiophene)s

The manuscript investigates the influence of the regioregularity (RR) of poly(3-alkylsulfanylthiophene)s (P3AST) on their properties. Therefore, a series of P3ASTs (P1-P5) with different RR were synthesized using a combination of a "reversed McCullough method" and the GRIM method. The degree of RR was determined by 1H NMR spectroscopy. A detailed chiroptical study in good solvent, poor solvent and film was performed, which revealed that the tendency to form chiral supramolecular aggregates clearly depends on the RR, but that the relation is not simply continuously increasing. Instead, the strongest effects were observed in P3ASTs with high, but not 100% RR. As a consequence, a similar behaviour can be expected for a regioregular and a particular irregular P3AST. This hypothesis was tested on a regioregular and an irregular P3AST that proved to have similar chiroptical properties in a previous study. Their properties in the solid state were investigated in detail using STM and AFM. © 2013 The Royal Society of Chemistry.status: publishe