Colloidal Nanoplatelet/Conducting Polymer Hybrids: Excitonic and Material Properties

Here we present the first account of conductive polymer/colloidal nanoplatelet hybrids. For this, we developed DEH-PPV-based polymers with two different anchor groups (sulfide and amine) acting as surfactants for CdSe nanoplatelets, which are atomically flat semiconductor nanocrystals. Hybridization of the polymers with the nanoplatelets in the solution phase was observed to cause strong photoluminescence quenching in both materials. Through steady-state photoluminescence and excitation spectrum measurements, photoluminescence quenching was shown to result from dominant exciton dissociation through charge transfer at the polymer/nanoplatelet interfaces that possess a staggered (i.e., type II) band alignment. Importantly, we found out that sulfide-based anchors enable a stronger emission quenching than amine-based ones, suggesting that the sulfide anchors exhibit more efficient binding to the nanoplatelet surfaces. Also, shorter surfactants were found to be more effective for exciton dissociation as compared to the longer ones. In addition, we show that nanoplatelets are homogeneously distributed in the hybrid films owing to the functional polymers. These nanocomposites can be used as building blocks for hybrid optoelectronic devices, such as solar cells

Living Light-Induced Crystallization-Driven Self-Assembly for Rapid Preparation of Semiconducting Nanofibers

Well-defined nanostructures composed of conjugated polymers have attracted significant attention due to their intriguing electronic and optical properties. However, precise control of the size and uniformity of these semiconducting nanostructures is still rare and challenging, despite recent advances in strategies to obtain self-assembled nanostructures with narrow dispersions. Herein, we demonstrate the preparation of fluorescent conjugated block copolymers by one-shot polymerization and rapid formation of nanofibers in a few minutes via light-induced crystallization-driven self-assembly, driven by facile <i>cis</i>-to-<i>trans</i> photoisomerization of its poly­(<i>p</i>-phenylene­vinylene) blocks. Furthermore, living self-assembly was possible, allowing not only nanofibers with excellent length control and narrow size distribution but also ABA triblock comicelles and gradient comicelles, to be produced by seeded growth. Lastly, the seeded growth could be activated and deactivated repeatedly by switching the light on and off, analogous to light-induced living radical polymerization

Functionalization of P3HT with Various Mono- and Multidentate Anchor Groups

<div><p>Due to its favorable optoelectronic properties and the accessibility via Grignard metathesis (GRIM) polymerization, poly(3-hexylthiophene) (P3HT) is one of the most applied conjugated polymers. The ‘living' nature of GRIM polymerization enables the modification of the polymer and the installation of desired properties. In the present study, two versatile approaches for the synthesis of anchor group-modified P3HT have been developed, which enable the functionalization of various inorganic nanoparticles. Depending on the polymerization conditions, mono- and bifunctional ethynyl-terminated P3HT or solely monofunctionalized aldehyde-terminated P3HT was synthesized. Afterwards, the quantitative introduction of amine, mono- and multidentate disulfide and catechol anchor groups was performed by copper-catalyzed 1,3-dipolar cycloaddition or via imine formation reactions. The influence of the polymeric ligand structure on the functionalization of nanoparticles was then investigated for CdSe@ZnS quantum dots and TiO2 nanorods by transmission electron microscopy (TEM) and infrared (IR) spectroscopy.</p></div

Reactivity Studies of Alkoxy-Substituted [2.2]Paracyclophane-1,9-dienes and Specific Coordination of the Monomer Repeating Unit during ROMP

The polymerization of alkoxy-substituted [2.2]­paracyclophane-1,9-dienes via ring-opening metathesis polymerization (ROMP) to obtain soluble poly­(<i>p</i>-phenylenevinylene)­s is a versatile method due to its living nature which enables the possibility of block copolymerization and end group modification. However, detailed studies on the reactivity behavior and the polymerization process of alkoxy-substituted [2.2]­paracyclophane-1,9-dienes have not been reported so far. Herein we present a detailed study on the varying tendencies of the four isomers of dimethoxy-(2-ethyl­hexyloxy)-[2.2]­para­cyclophane-1,9-diene to undergo ROMP. Therefore, we carried out polymerization combining all individual isomers with five different metathesis catalysts and collected initiation and propagation kinetics for various combinations. Furthermore, we revealed a specific coordination of the monomer repeating unit to the catalyst during the polymerization process and succeeded to polymerize not only the pseudogeminal isomers but also one of the pseudo-<i>ortho</i> isomers

Synthesis of Functional Block Copolymers Carrying One Poly(<i>p</i>‑phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure

Block copolymers composed of a MEH–PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxy­poly­(ethylene glycol)­amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60–95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optical properties depending on the polymer composition and the micellization procedure. Furthermore, the reactive ester carrying block copolymers enabled the introduction of anchor groups which facilitated the preparation of nanocomposites with CdSe/CdZnS core–shell QDs. The obtained composites were studied using time-resolved photoluminescence measurements. The results revealed an increased interaction based on an accelerated decay of the QD emission for composites as compared to the mixture of the QDs with unfunctionalized polymers