Expression of Chirality in a Conjugated Polymer without Any Excess of Chiral Centers

© 2015 American Chemical Society. Chirality is typically expressed in chiral molecules, including polymers. In this work, we demonstrate that chirality can also be expressed in a polymer molecule that does not contain any excess of chiral centers; in this specific material the chirality is evoked by a specific order of manipulations ("events"). The polymer studied is an all-conjugated block copoly(3-alkylthiophene), in which the first block contains exactly the same amount of (S)-enantiomers as the second block (R)-enantiomers. Moreover, to introduce a distinct difference in solubility - required to have multiple consecutive events - the S-block is composed of S-monomers copolymerized with octyl-functionalized thiophene monomers, while the R-block is composed of R-monomers in combination with amine-functionalized thiophene monomers. By making use of the difference in solubility of both blocks, a chiral response can be evoked from this polymer without the need of a chiral trigger.status: publishe

Expression of Chirality in Tailor-Made Conjugated Polymers

Copyright © 2018 American Chemical Society. The supramolecular organization and chiral expression in tailor-made conjugated polymers (CP) are investigated. The polymers were synthesized in a controlled way, providing (almost) perfect control over the molecular structure. This allowed to understand the effect of different parameters in the molecular structure. The polymers were analyzed by gel permeation chromatography (GPC) and 1H NMR. Solvatochromism experiments were performed on all polymers, using UV-vis spectroscopy and circular dichroism (CD). Two new parameters influencing the supramolecular organization and chiral expression were found. First, in block copolymers consisting of an (S)-chiral and (R)-chiral block of equal length, end-groups are required to break the symmetry. If no end-group is present, the polymer chains do not aggregate. Second, if one single (head-to-head) HH-coupling is present in regioregular poly(thiophene), the supramolecular aggregation is completely disrupted, which is in contrast to the presence of one (tail-to-tail) TT-defect. The obtained results were confirmed by differential scanning calorimetry (DSC).status: publishe

Controlled Polymerization of a Cyclopentadithiophene-Phenylene Alternating Copolymer

© 2018 American Chemical Society. The new conjugated poly(4,4-bis(2-ethylhexyl)cyclopentadithiophene-alt-p-phenylene) (PCPDTPP) has been synthesized in a controlled way via catalyst transfer condensative polymerization (CTCP) of the corresponding biaryl monomer. Therefore, a series of Ni catalysts as well as (new) Pd-PEPPSI catalysts were employed in different Kumada CTCPs (KCTCPs) and Negishi CTCPs (NCTCPs). A series of tests confirmed the absence of undesired transfer and termination reactions and, hence, the controlled character of the chain-growth polymerization with Ni(dppe)Cl2 as catalyst. This resulted in polymers with low dispersities (D = 1.2), Mn of 33 kDa, and relatively good end-group control. Furthermore, formation of PCPDTPP-b-poly(3-octylthiophene) (P3OT) block copolymers was possible. Via optical analysis and DSC measurements, we demonstrated that the conjugated alternating PCPDTPP copolymer is an amorphous, strongly fluorescent polymer with a fluorescence quantum yield (ψf) of 58% in chloroform.status: publishe

Expression of Chirality in a Conjugated Polymer without Any Excess of Chiral Centers

Chirality is typically expressed in chiral molecules, including polymers. In this work, we demonstrate that chirality can also be expressed in a polymer molecule that does not contain any excess of chiral centers; in this specific material the chirality is evoked by a specific order of manipulations (“events”). The polymer studied is an all-conjugated block copoly­(3-alkylthiophene), in which the first block contains exactly the same amount of (<i>S</i>)-enantiomers as the second block (<i>R</i>)-enantiomers. Moreover, to introduce a distinct difference in solubilityrequired to have multiple consecutive eventsthe S-block is composed of <i><b>S</b></i>-monomers copolymerized with octyl-functionalized thiophene monomers, while the R-block is composed of <i><b>R</b></i>-monomers in combination with amine-functionalized thiophene monomers. By making use of the difference in solubility of both blocks, a chiral response can be evoked from this polymer without the need of a chiral trigger

Direct observation of the influence of chirality on the microstructure of regioregular poly- (3-alkylthiophene)s at the liquid/solid interface

The degree of order of poly(3-alkylthiophene)s on atomically flat surfaces is strongly influenced by interchain interactions. Regularly ordered, disordered and amorphous microstructures are observed for achiral, homochiral and meso poly(3-alkylthiophene)s, respectively, as revealed by scanning tunneling microscopy.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Steven De Feyter (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 6 October 2016; Accepted 31 October 2016; Advance Article published 14 November 2016; Version of Record published 20 December 2016status: publishe

Advances in the controlled polymerization of conjugated polymers

This article features recent advances in the synthesis of conjugated polymers via a controlled polymerization. These polymerizations typically rely on transition metal catalyzed cross coupling reactions. The mechanisms of the polymerization protocols are discussed in detail. An overview of all possible protocols and all homopolymers that have been investigated is given. Next, the synthesis of copolymers - random, gradient and block copolymers - is reviewed. Another advantage of a controlled polymerization is the possibility to introduce specific functional groups, either at the beginning of each polymer chain by the use of an external initiator, or at the end of the polymer chain using an endcapper. Finally, topologies different from simple linear polymer chains are discussed. This feature article is complementary to other recent review articles on this topic.publisher: Elsevier articletitle: Advances in the controlled polymerization of conjugated polymers journaltitle: Polymer articlelink: http://dx.doi.org/10.1016/j.polymer.2016.09.085 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.status: publishe

Harmonic light scattering study reveals structured clusters upon the supramolecular aggregation of regioregular poly(3-alkylthiophene)

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Controlled Synthesis and Supramolecular Organization of Conjugated Star-Shaped Polymers

© 2018 American Chemical Society. Through the incorporation of chiral and achiral poly(3-alkylthiophenes) (P3ATs) into a star-shaped system, a well-defined supramolecular organization is obtained lacking the unfavorable linear lamellar structure typically obtained for P3AT. Through the combination of a controlled chain-growth polymerization and efficient postpolymerization and click reactions, well-defined star-shaped P3ATs with a low dispersity of 1.1 were obtained. The combination of UV-vis, circular dichroism (CD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) measurements showed the formation of a strong (chiral) supramolecular organization into fibers, different and stronger than those obtained with the linear P3ATs. The fact that the width of the fibers is in good agreement with the width of a single star-shaped P3AT excludes the formation of a linear lamellar structure. Furthermore, the particular supramolecular organization of the star-shaped polymers, which appears thanks to the precision polymer synthesis, triggers properties of the arms of the star-shaped molecule that are not present in the individual arms.status: publishe