Article

Single molecule lifetime fluctuations reveal segmental dynamics in polymers.

Applied Optics Group, and Materials Science and Technology of Polymers, MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Physical Review Letters (Impact Factor: 7.73). 08/2003; 91(3):038301. DOI: 10.1103/PhysRevLett.91.038301
Source: PubMed

ABSTRACT We present a single molecule fluorescence study that allows one to probe the nanoscale segmental dynamics in amorphous polymer matrices. By recording single molecular lifetime trajectories of embedded fluorophores, peculiar excursions towards longer lifetimes are observed. The asymmetric response is shown to reflect variations in the photonic mode density as a result of the local density fluctuations of the surrounding polymer. We determine the number of polymer segments involved in a local segmental rearrangement volume around the probe. A common decrease of the number of segments with temperature is found for both investigated polymers, poly(styrene) and poly(isobutylmethacrylate). Our novel approach will prove powerful for the understanding of the nanoscale rearrangements in functional polymers.

0 Bookmarks
 · 
83 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Product releasing is an essential step of an enzymatic reaction, and a mechanistic understanding primarily depends on the active-site conformational changes and molecular interactions that involve in this step of an enzymatic reaction. Here we report our work on the enzymatic product releasing dynamics and mechanism of an enzyme, horseradish peroxidase (HRP), using combined single-molecule time-resolved fluorescence intensity, anisotropy, and lifetime measurements. Our results have shown a wide distribution of the multiple conformational states involving in active-site interacting with the product molecules during the product releasing. We have identified that there is a significant pathway that the product molecules are spilled out from the enzymatic active-site, driven by a squeezing effect from a tight active-site conformational state; although, the conventional pathway of releasing a product molecule from an open active-site conformational state is still a primary pathway. Our study provides a new insight of the enzymatic reaction dynamics and mechanism, and the information is uniquely obtainable from our combined single-molecule time-resolved single-molecule spectroscopic measurements and analyses.
    The Journal of Physical Chemistry B 07/2014; · 3.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rotational motion of fluorophores chemically attached to polystyrene chain-ends in ultra-thin films on solid substrates was studied by single-molecule fluorescence de-focus microscopy. The collective feature of the rotational motion was found and evidenced by the sharp change of the population of fluorophores undergoing rotational motion within a very narrow temperature range (named as the changing temperature, T c). The T c value was found to depend on film thickness and interfacial chemistry and the variation of the T c value is also dependent on the molecular weight of the polymer. The results demonstrate that the spatial confinement effect enhances the segmental mobility near the polymer chain-ends while the interfacial attraction restricts the segmental motion inside the thin film.
    Science China-Chemistry 03/2014; 57(3):389-396. · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A molecular rotor with a fluorescence lifetime depending on the local viscosity of its surroundings has been successfully used as a probe to monitor local viscosity changes during the bulk radical polymerization of methyl methacrylate.
    Polym. Chem. 03/2014; 5(8).

Full-text (2 Sources)

Download
50 Downloads
Available from
May 16, 2014