Abstract
We present the synthesis and characterization of well-defined polycationic copolymers containing thiazole dyes in the side chain. Atom transfer radical polymerization (ATRP) was used for the copolymerization of 3-azidopropyl methacrylate (AzPMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA) of different composition. Thiazole-based alkyne-functionalized dyes (e.g., 5-methyl-4-(prop-2-yn-1-yloxy)-2-(pyridin-2-yl)thiazole, (MPPT)) were afterwards covalently attached using copper catalyzed azide alkyne cycloadditions (CuAAC) reaching contents of up to 9 mol % dye. Subsequent quaternization of the tertiary nitrogen of DMAEMA with strong methylation agents (e.g., methyl iodide) led to permanently charged polyelectrolytes. The materials were characterized by size exclusion chromatography, as well as NMR- and UV/VIS-spectroscopy. Particular attention is paid to the spectroscopic properties of the dyes in the side chain upon environmental changes such as pH and salinity. We anticipate the application of such precisely functionalized polyelectrolytes as temperature- and pH-responsive sensors in biomedical applications, e.g., within interpolyelectrolyte complexes. Concerning the latter, first complex formation results are demonstrated.
Highlights
Complex and well-defined macromolecular architectures can nowadays be realized by various living and controlled polymerization techniques [1,2]
Common techniques are nitroxide mediated polymerization (NMP) [5,6,7], reversible addition fragmentation chain transfer polymerization (RAFT) [5,8,9], and atom transfer radical polymerization (ATRP) [3,5,10,11,12]
FT-Infrared Spectroscopy (IR) showed the presence of the azide moiety (Figure S5) for azidopropyl methacrylate (AzPMA) contents of 5% and 9%, whereas in case of P(AzPMA0.01-co- DMAEMA0.99) this absorption band is merely visible
Summary
Complex and well-defined macromolecular architectures can nowadays be realized by various living and controlled polymerization techniques [1,2]. Owing to increased tolerance of controlled radical polymerizations, a great variety of functional groups can be directly incorporated into materials with narrow molecular weight distributions, predetermined molecular weight, and the possibility of quantitative chain end modification [3,4]. The first ATRP of N,N-dimethylaminoethyl methacrylate (DMAEMA) was reported by Zhang et al using copper bromide (CuBr) with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) and 2,21-bipyridine (Bpy) as ligands [15,16]. Different architectures including star shaped materials were obtained [23,24], and DMAEMA has been used as building block for the preparation of polyampholytes and polyzwitterions [25,26]. Resulting from the pH- and thermo-responsive properties widespread applications such as grafts on films [27] (e.g., polypropylene), the formation of unimolecular micelles [28], or biomedical applications [25] (e.g., shape memory copolymers, or serum-resistant gene delivery and bioimaging) [29] were realized
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