Visual recognition of supramolecular graft polymer formation via phenolphthalein-cyclodextrin association

Visual recognition of the formation of supramolecular graft polymers in aqueous solution driven by host-guest assembly is presented. The interaction between β-cyclodextrin (β-CD) and phenolphthalein moieties can be followed via a distinctive change of color in basic media by optical inspection. The phenolphthalein-containing lateral polymer chain was obtained via reversible addition-fragmentation chain transfer (RAFT) copolymerization of N,N-dimethylacrylamide and N-(2-hydroxy-5-(1-(4-hydroxyphenyl)-3-oxo-1,3-dihydroisobenzofuran-1-yl)benzyl)acrylamide. The RAFT polymerizations afforded statistical copolymers with molecular masses between 6900 and 8800 g mol−1 and molar mass dispersities (Đ) between 1.1 and 1.2. β-CD-functionalized building blocks were synthesized using a propargyl-functionalized chain transfer agent for the polymerization of N,N-diethylacrylamide followed by a copper(I)-catalyzed cycloaddition with β-CD-azide (Mn = 8200 g mol−1; Đ = 1.2). Self-assembly of both polymers to form supramolecular graft polymers was evidenced by 2D NOESY NMR, UV-vis spectroscopy and dynamic light scattering.

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