Multiresponsive behavior of functional poly(p-phenylene vinylene)s in water

The multiresponsive behavior of functionalized water-soluble conjugated polymers (CPs) is presented with potential applications for sensors. In this study, we investigated the aqueous solubility behavior of water-soluble CPs with high photoluminescence and with a particular focus on their pH and temperature responsiveness. For this purpose, two poly(phenylene vinylene)s (PPVs)-namely 2,5-substituted PPVs bearing both carboxylic acid and methoxyoligoethylene glycol units-were investigated, with different amount of carboxylic acid units. Changes in the pH and temperature of polymer solutions led to a response in the fluorescence intensity in a pH range from 3 to 10 and for temperatures ranging from 10 to 85 degrees C. Additionally, it is demonstrated that the polymer with the largest number of carboxylic acid groups displays upper critical solution temperature (UCST)-like thermoresponsive behavior in the presence of a divalent ion like Ca2+. The sensing capability of these water-soluble PPVs could be utilized to design smart materials with multiresponsive behavior in biomedicine and soft materials

Effect of host-guest complexation on the thermoresponsive behavior of poly(oligo ethylene glycol acrylate)s functionalized with dialkoxynapththalene guest side chains

The combination of thermoresponsive polymers with supramolecular host-guest interactions enables accurate tuning of the phase transition temperature, while also providing additional response mechanisms based on host-guest complexation. Most studies focused on a single thermoresponsive polymer to demonstrate the effect of host-guest complexation on the responsive behavior. In this work, the effect of the polymer structure on the host-guest complexation and thermoresponsive behavior is reported. Therefore, different poly(oligoethylene glycol acrylate)s, namely, poly(2-hydroxyethylacrylate) (PHEA), poly(methoxy diethylene glycol acrylate), poly(methoxy triethylene glycol acrylate), and poly(methoxy tetraethylene glycol acrylate), are synthesized functionalized with 1,5-dialkoxynaphthalene guest molecules in the side chain. Their complexation with the cyclobis(paraquat-p-phenylene) tetrachloride host is studied to understand the effect of polymer structure on the supramolecular association and the polymer phase transition, revealing that the oligoethylene glycol side chains lead to weaker host-guest complexation and also have a smaller increase in the cloud point temperature compared to PHEA

Complexation of thermoresponsive dialkoxynaphthalene end-functionalized poly(oligoethylene glycol acrylate)s with CBPQT4+in water

Four different oligoethylene glycol acrylates (OEGA), namely hydroxypropylacrylate (HPA), methoxy diethylene glycol acrylate (mDEGA), methoxy triethylene glycol acrylate (mTEGA) and 2-hydroxyethylacrylate (HEA) were homopolymerized via RAFT polymerization employing a naphthalene functionalized chain transfer agent resulting in thermoresponsive naphthalene-functionalized POEGAs with different hydrophilicities. Supramolecular inclusion complexes of these POEGAs with electron-deficient cyclophane cyclobis(paraquat-p-phenylene) tetrachloride (CBPQT4+) in water were studied. The association constants (Ka) were determined to study the effect that polymer hydrophilicity has on the Ka and results indicated that the nature of the polymer did not significantly influence the complexation strength and the association is mostly enthalpy driven. The impact of temperature on the host–guest complexes was also investigated. A continuous partial thermally induced dissociation of complexes was observed upon raising the temperature with a more distinct decrease in complexation around the cloud point temperature (TCP) of the POEGA employed, indicating the importance of the polymer phase transition for tuning the recognition properties of dialkoxynaphthalene end-decorated poly(oligoethylene glycol acrylate)s in water

Solvent-free mechanochemical synthesis of a bicyclononyne tosylate: a fast route towards bioorthogonal clickable poly(2-oxazoline)s

The mechanochemical synthesis of a bicyclononyne tosylate (BCN-OTs) is presented. BCN-OTs is demonstrated to be a good initiator for the cationic ring-opening polymerization of 2-ethyl-2-oxazoline directly yielding BCN functional poly(2-ethyl-2-oxazoline) (PEtOx-BCN) with high chain end fidelity. Subsequent strain-promoted cycloadditions of the resulting PEtOx-BCN enable efficient additive-free conjugation reactions as demonstrated for the formation of a block copolymer and a PEtOx-protein conjugate

[2 x 2] metallo-supramolecular grids based on 4,6-bis((1H-1,2,3-triazol-4-yl)-pyridin-2-yl)-2-phenylpyrimidine ligands : from discrete [2 x 2] grid structures to star-shaped supramolecular polymeric architectures

The self-assembly of bis-tridentate ligands leads to the spontaneous formation of [2 x 2] grid-like metal complexes. However, the synthesis of such ligands is rather cumbersome. In the work, we demonstrate a straightforward synthesis route to prepare bis-tridentate 4,6-bis((1H-1,2,3-triazol-4-yl)-pyridin-2-yl)-2-phenylpyrimidine ligands through double CuAAC click chemistry with 4,6-bis(6-ethynylpyridin-2-yl)-2-phenylpyrimidine as well as their self-assembly into [2 x 2] grid-like metal complexes. In addition, four macromolecular ligands were synthesized starting from azido-end-functionalized poly(2-ethyl-2-oxazoline) (PEtOx) or poly(ethylene glycol) (PEG). These macromolecular ligands were used in the construction of star-shaped supramolecular polymers through complexation with transition metal ions (e.g., Fe2+ or Zn2+). The successful fabrication of complexes and star-shaped polymers was confirmed by UV-vis titration measurements and MALDI-TOF mass spectrometry. However, the chemical structure of the polymer was found to have a strong influence on the [2 x 2] grid formation, which was successful with the PEG-ligands but not with the PEtOx-ligands, while the molecular weight of the PEG did not interfere with grid formation