To date, cationic polymers with high transfection efficiencies (TE) often have a high cytotoxicity. By screening an 18-membered library of cationic 2-oxazoline-based polymers, a polymer with similar TE as linear poly(ethylene imine) but no detectable cytotoxicity at the investigated concentrations could be identified. The influence of the polymer side chain hydrophobicity and the type and content of amino groups on the pDNA condensation, the TE, the cytotoxicity, the cellular membrane interaction as well as the size, charge, and stability of the polyplexes was studied. Primary amines and an amine content of at least 40% were required for an efficient TE. While polymers with short side chains were non-toxic up to an amine content of 40%, long hydrophobic side chains induced a high cytotoxicity.
The immobilization of homogeneous catalysts within nanoporous membranes gives access to catalytically active and multi-functional composite materials, e.g. for use in flow reactors.
We present the synthesis and characterization of amphiphilic terpolymers containing photoacids based on 1-naphthol using reversible addition fragmentation chain transfer radical polymerization (RAFT).
This review focuses on block copolymers featuring different photo-responsive building blocks and self-assembly of such materials in different selective solvents. We have subdivided the specific examples we selected: (1) according to the wavelength at which the irradiation has to be carried out to achieve photo-response; and (2) according to whether irradiation with light of a suitable wavelength leads to reversible or irreversible changes in material properties (e.g., solubility, charge, or polarity). Exemplarily, an irreversible change could be the photo-cleavage of a nitrobenzyl, pyrenyl or coumarinyl ester, whereas the photo-mediated transition between spiropyran and merocyanin form as well as the isomerization of azobenzenes would represent reversible response to light. The examples presented cover applications including drug delivery (controllable release rates), controlled aggregation/disaggregation, sensing, and the preparation of photochromic hybrid materials.
The implementation of photoswitches within polymers offers an exciting toolbox in the design of light‐responsive materials as irradiation can be controlled both spatially and temporally. Herein, we introduce a range of water‐soluble copolymers featuring naphthol‐based chromophores as photoacids in the side chain. With that, the resulting materials experience a drastic increase in acidity upon stimulation with UV light and we systematically studied how structure and distance of the photoacid from the copolymer backbone determines polymerizability, photo‐response, and photostability. Briefly, we used RAFT (reversible addition–fragmentation chain transfer) polymerization to prepare copolymers consisting of nona(ethylene glycol) methyl ether methacrylate (MEO9MA) as water‐soluble comonomer in combination with six different 1‐naphthol‐based (“N”) monomers. Thereby, we distinguish between methacrylates (NMA, NOeMA), methacrylamides (NMAm, NOeMAm), vinyl naphthol (VN), and post‐polymerization modification based on [(1‐hydroxynaphthalen‐2‐amido)ethyl]amine (NOeMAm, NAmeMAm). These P(MEO9MAx‐co‐“N”y) copolymers typically feature a 4:1 MEO9MA to “N” ratio and molar masses in the range of 10 kg mol−1. After synthesis and characterization by using NMR spectroscopy and size exclusion chromatography (SEC), we investigated how potential photo‐cleavage or photo‐degradation during irradiation depends on the type and distance of the linker to the copolymeric backbone and whether reversible excited state proton transfer (ESPT) occurs under these conditions. In our opinion, such materials will be strong assets as light‐mediated proton sources in nanostructured environments, for example, for the site‐specific creation of proton gradients. We therefore exemplarily incorporated NMA into an amphiphilic block copolymer and could demonstrate the light‐mediated release of Nile red from micelles formed in water as selective solvent.
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