Supramolecular Interaction-Assisted Fluorescence and Tunable Stimuli-Responsiveness of l-Phenylalanine-Based Polymers

Langmuir. 2017 Oct 10;33(40):10588-10597. doi: 10.1021/acs.langmuir.7b02431. Epub 2017 Sep 27.

Abstract

Supramolecular host-guest interactions between randomly methylated β-cyclodextrin (RM β-CD) and side-chain phenylalanine (Phe) and Phe-Phe dipeptide-based homopolymers have been employed for the amplification of fluorescence emission of otherwise weakly fluorescent amino acid Phe. The host-guest complex has been characterized by 1H and 13C NMR spectroscopy, two-dimensional rotating-frame overhauser spectroscopy, Fourier-transform infrared spectroscopy, UV-visible spectroscopy, and fluorescence spectroscopy. To gain insights into the origin of fluorescence in homopolymers, density functional theory calculations were performed where phenyl moieties inside the less polar core of β-CD were observed to form a π-π coupled complex resulting in an enhanced emission. Furthermore, the complex-forming ability of Phe, the guest molecule, has been employed in tuning the cloud point temperature (TCP) of statistical copolymers derived from side-chain Phe/Phe-Phe-based methacrylate monomers and N-isopropylacrylamide. By varying the co-monomer feed ratios in the statistical copolymer and hence the concentration of RM β-CD throughout the polymer chain, host-guest interaction-assisted broad tunability in TCP of the supramolecular polymeric complex has been achieved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Macromolecular Substances
  • Phenylalanine / chemistry*
  • Polymers
  • Spectrometry, Fluorescence
  • Temperature

Substances

  • Macromolecular Substances
  • Polymers
  • Phenylalanine