pH-responsive diblock copolymers with two different fluorescent labels for simultaneous monitoring of micellar self-assembly and degree of protonation

Jeppe Madsen*, George Madden, Efrosyni Themistou, Nicholas J. Warren, Steven P. Armes

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

We report the synthesis of a novel amphiphilic pH-responsive diblock copolymer labeled with two different fluorophores. This copolymer comprises a water-soluble poly(glycerol monomethacrylate) [PGMA] block and a pH-responsive poly(2-(diisopropylamino)ethyl methacrylate) [PDPA] block. Pyrene methacrylate [PyMA] is statistically copolymerized with glycerolmonomethacrylate (GMA) to introduce a suitable fluorescent label. The chain-ends of the PDPA block are labelled with cresylviolet perchlorate [CV] by exploiting the spin trap properties of this dye molecule. Below pH 6, fluorescence from both dyelabels can be detected, but deprotonation of the PDPA block between pH 6 and 7 leads to strong attenuation of the CV fluorescence owing to formation of a charge transfer complex with the tertiary amine units in the PDPA block. Therefore, changes in the Cresyl Violet fluorescence intensity can be correlated to changes in PDPA protonation. Diblock copolymer self-assembly to form PDPA-core aggregates occurs under these conditions, leading to pyrene fluorescence at an excitation wavelength of 405 nm. This allows direct measurement of chain aggregation, whereas using pH-responsive dyes is simply ameasure of the degree of protonation. Here we focus on the synthesis and characterisation of dual-labeled copolymers and their spectroscopic properties in different environments. Finally, we show that using CV as a spin trap provides a convenient and versatile route to fluorescently-labeled copolymers prepared by either RAFT or ATRP. Moreover, this cost-effective dyefluoresces in the red part of the visible spectrum at both neutral and acidic pH.
Original languageEnglish
JournalPolymer Chemistry
Volume9
Pages (from-to) 2964-2976
ISSN1759-9954
DOIs
Publication statusPublished - 2018

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