End Group-Functionalization and Synthesis of Block-Copolythiophenes by Modified Nickel Initiators

Influence of the dispersity and molar mass distribution of conjugated polymers on the aggregation type and subsequent chiral expression

This study aims to determine the influence of the dispersity on the aggregation of conjugated polymers and their subsequent chiral expression. Dispersity has been thoroughly investigated for industrial polymerizations, but research on conjugated polymers is lacking. Nonetheless, knowledge thereof is crucial for controlling the aggregation type (type I versus type II) and its influence is therefore investigated. For that purpose, a series of polymers is synthesized via metered initiator addition, resulting in dispersities ranging from 1.18-1.56. The lower dispersity polymers yield type II aggregates and the resulting symmetrical electronic circular dichroism (ECD) spectra while the higher dispersity polymers are predominantly type I due to the longer chains effectively acting as a seed and therefore yield asymmetrical ECD spectra. Furthermore, a monomodal and bimodal molar mass distribution of similar dispersity are compared, demonstrating that bimodal distributions show both aggregation types and therefore more disorder, leading to a decrease in chiral expression.

The expression of chirality in linked poly(thiophene)s

Conjugated polymers have demonstrated to express chirality, for instance, by strong circular dichroism (CD). However, the shape and intensity of the spectra can be quite different and are very difficult to predict. Molecular irregularity, star-shapes, and linking polymers have demonstrated to affect the CD, often in a positive way. In this research, we design two different chiral arms, in which the molecular irregularity results in a significantly different CD. Next, the arms are coupled to a linear core in all possible combinations. In this way, we demonstrate that rather small irregularities and linking arms to a central core increases CD, whereas heterogenous combinations result in smaller CD.

Programmable Assembly of π-Conjugated Polymers

π-Conjugated polymers have numerous applications due to their advantageous optoelectronic and mechanical properties. These properties depend intrinsically on polymer ordering, including crystallinity, orientation, morphology, domain size, and π-π interactions. Programming, or deliberately controlling the composition and ordering of π-conjugated polymers by well-defined inputs, is a key facet in the development of organic electronics. Here, π-conjugated programming is described at each stage of material development, stressing the links between each programming mode. Covalent programming is performed during polymer synthesis such that complex architectures can be constructed, which direct polymer assembly by governing polymer orientation, π-π interactions, and morphological length-scales. Solution programming is performed in a solvated state as polymers dissolve, aggregate, crystallize, or react in solution. Solid-state programming occurs in the solid state and is governed by polymer crystallization, domain segregation, or gelation. Recent progress in programming across these stages is examined, highlighting order-dependent features and assembly techniques that are unique to π-conjugated polymers. This should serve as a guide for delineating the many ways of directing π-conjugated polymer assembly to control ordering, structure, and function, enabling the further development of organic electronics.

New strategy for synthesis of hydroxyl-terminated poly(3-hexylthiophene) and its block copolymer using an η3-π-allyl hydroxyl-functionalized Ni(i) initiator

A novel hydroxyl-terminated π-allyl nickel initiator [η³-Ni(CH₂CHCHCH₂OCOCH₃)][BPh^F₄] is synthesized for the first time. ¹H-NMR analysis confirms that the Ni initiator possesses a typical π-allyl structure with a protected hydroxyl group. The Ni initiator is applied to synthesize hydroxyl-terminated poly(3-hexylthiophene). It successfully initiates the homopolymerization of thiophene, and yields narrow molecular weight distribution, hydroxyl-terminated poly(3-hexylthiophene). Moreover, it is found that [η³-Ni(CH₂CHCHCH₂OCOCH₃)][BPh^F₄] has high initiating activity in the polymerization of styrene and butadiene. A hydroxyl-terminated polybutadiene-b-poly(3-hexylthiophene) block copolymer is synthesized by using [η³-Ni(CH₂CHCHCH₂OCOCH₃)][BPh^F₄] to improve the workability and brittleness of poly(3-hexylthiophene).

A novel hydroxyl-terminated π-allyl nickel initiator is synthesized for the first time. Hydroxyl-terminated PB-b-P3HT block copolymer and hydroxyl-terminated P3HT are synthesized by using the initiator to improve the workability of P3HT.

Synthesis of Structurally Defined Cationic Polythiophenes for DNA Binding and Gene Delivery

Water-soluble conjugated polymers (WCPs) have prospective applications in the field of bioimaging, disease diagnosis, and therapy. However, the use of WCPs with controllability and regioregularity for bioapplications have scarcely been reported. In this work, we synthesized polythiophenes containing ester side chains (P3ET) via Kumada catalyst-transfer polycondensation (KCTP) and confirmed a quasi-"living" chain-growth mechanism. In addition, we obtained cationic regioregular polythiophenes (cPTs) by aminolysis of P3ET with varied chain lengths, and studied DNA binding capability and gene delivery performance. Benefiting from photocontrolled generation of intracellular reactive oxygen species (ROS), the cationic polythiophenes successfully delivered DNA into tumor cells without additional polymer species.

Synthesis and supramolecular organization of chiral poly(thiophene)–magnetite hybrid nanoparticles

Fe₃O₄ nanoparticles decorated with a conjugated polymer is synthesized and the supramolecular organization of the polymer is studied.

Pentafluorobenzene end-group as a versatile handle for para fluoro "click" functionalization of polythiophenes

A convenient method of introducing pentafluorobenzene (PFB) as a single end-group in polythiophene derivatives is reported via in situ quenching of the polymerization. We demonstrate that the PFB-group is a particularly useful end-group due to its ability to undergo fast nucleophilic aromatic substitutions. Using this molecular handle, we are able to quantitatively tether a variety of common nucleophiles to the polythiophene backbone. The mild conditions required for the reaction allows sensitive functional moieties, such as biotin or a cross-linkable trimethoxysilane, to be introduced as end-groups. The high yield enabled the formation of a diblock rod-coil polymer from equimolar reactants under transition metal-free conditions at room temperature. We further demonstrate that water soluble polythiophenes end-capped with PFB can be prepared via the hydrolysis of an ester precursor, and that such polymers are amenable to functionalization under aqueous conditions.

Facile synthesis of oligo(3-hexylthiophene)s conductive wires with charge-transfer functions

A series of fully conjugated oligo(3-hexylthiophene)s bearing different starting- and end-groups have been synthesized by means of externally initiated Kumada catalyst-transfer polymerization (KCTP) and Grignard Metathesis Polymerization (GRIM).

Synthetic approaches towards structurally-defined electrochemically and (photo)redox-active polymer architectures

This review details synthetic strategies leading to structurally-defined electrochemically and (photo)redox-active polymer architectures,e.g.block, graft and end functionalized (co)polymers.

Poly(3-hexylthiophene) End-Functionalization via Quenching Resulting in Heteroatom-Bond Formation

End-functionalized poly(3-hexylthiophene) (P3HT) has contributed to continued advancements in conjugated polymer applications, especially within organic electronics. P3HT synthesized using Kumada catalyst-transfer polymerization (KCTP) has many favourable attributes such as controlled molecular weight, high regioregularity, and narrow dispersity. With the addition of reactive end-groups, P3HT plays an important role in advancing the development of hybrid materials and preparation of block copolymers. Exploring methods of end-functionalization that result in heteroatom-bond formation, giving a non-carbon atom bonded to the terminal thiophene, could help control and understand the p–n junction of hybrid materials. This research highlight focuses on the development of a novel and facile way of end-functionalizing P3HT with chalcogens.

Simple procedure for mono- and bis-end-functionalization of regioregular poly(3-hexylthiophene)s using chalcogens

The efficient synthesis of regioregular poly(3-hexylthiophene-2,5-diyl)s (rr-P3HTs) capped with chalcogens using a simple quenching method is reported. Thiol (SH) end groups are selectively installed at the terminating end (ω-end) or at both the initiating (α-) and ω-ends using sulphur powder or triisopropylsilanethiol (TIPS-SH), respectively.

Synthesis of All-Conjugated Donor-Acceptor-Donor ABA-Type Triblock Copolymers via Kumada Catalyst-Transfer Polycondensation

A novel initiator, N,N'-bis(2-decyltetradecyl)-2,6-dibromonaphthalene-1,4,5,8-bis(dicarboximide) (NDI-Br₂), was found effective in the Kumada catalyst-transfer polycondensation (KCTP) for the synthesis of regioregular poly(3-hexylthiophene) (P3HT). In addition, a two-step method of synthesizing all-conjugated triblock copolymers comprised of both n-type and p-type blocks was proposed. With a 10:9 feed molar ratio of NDI-Br₂ to 2,5-bis(trimethylstannyl)thiophene, an n-type macroinitiator (PNDITh-Br₂) was prepared via the Stille coupling reaction. Two outer P3HT blocks were then emanated via KCTP initiated by PNDITh-Br₂ to produce all-conjugated ABA-type triblock copolymers. The size exclusion chromatography (SEC) curves of all the triblock copolymers showed narrow distribution, with the lowest polydispersity index (PDI) of 1.15. Moreover, the molecular weight of the block copolymer was found to be independent of the amount of Ni catalyst, while it can be tailored by the feed molar ratio of the thiophene monomer to PNDITh-Br₂. The transmission electron microscopy (TEM) images and grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns of the block copolymer thin film revealed a well-defined lamellar structure and two distinguished crystalline domains, where the P3HT layer was in the range of 10-20 nm and presented an edge-on rich alignment.