Full Citation: Fluorescence Analysis of Thermoresponsive Polymers. A.G. Ryder and C. Morris, Reviews in Fluorescence 2015 ,
Annual Volumes, Vol. 8, pp. 97-126, (2015). ISBN: 978-3-319-24607-9 (Hardcover), 978-3-319-24609-3 (ebook) Springer.
Page 11 of 31
Emission measurements carried out above the LCST showed similar log(IN*/IT*) changes, except
that the magnitude was lower. This indicates that the PNIPAm films were still absorbing some water
in this more hydrophobic state, interrupting the polymer-probe interaction (Figure 6).
Figure 6: Plot of log(I N* /I T* ) ratio vs. increasing humidity of PNIPAm films doped with (a) FE, (b) BFE and
(c) MFE at 25C (■) and 37C (). Taken from ref [61] and reproduced with permission. Copyright © 2010
American Chemical Society, all rights reserved.
In the more hydrophobic, condensed state above the LCST one would have expected that the rate
of water adsorption should be decreased. However, fluorescence analysis of PNIPAm thin films show
clearly that in every case, the log(IN*/IT*) value increases at a similar rate (Figure 6). This method
thus provides a relatively facile, non-contact methodology for assessing the ingress of water into
thermoresponsive polymers when fabricated as thin films on solid surfaces.
5.2
PHYSICOCHEMICAL PARAMETERS BY SOLVATOCHROMISM
Measuring polarity and hydrogen bonding changes in thermoresponsive polymers is vital for
understanding how these polymers will behave in the real world. For example, we know that many
of the common thermoresponsive polymers are appreciably hygroscopic and will absorb appreciable
amounts of water below and above the LCST thus influencing polarity within thin films [61]. The
most widely based methods for assessing polarity is based on solvatochromism, and there is an
extensive literature on solvent systems. Solvatochromism describes the change in shape, location
and sometimes intensity of absorption or emission spectra, relative to the polarity of the medium. A
hypsochromic (or blue) shift corresponds to negative solvatochromism, while a bathochromic (or red)
shift corresponds to positive solvatochromism with increasing solvent polarity [85-87].
Solvatochromic methods are generally robust and reasonably easy to implement but do require the use
Annual Volumes, Vol. 8, pp. 97-126, (2015). ISBN: 978-3-319-24607-9 (Hardcover), 978-3-319-24609-3 (ebook) Springer.
Page 11 of 31
Emission measurements carried out above the LCST showed similar log(IN*/IT*) changes, except
that the magnitude was lower. This indicates that the PNIPAm films were still absorbing some water
in this more hydrophobic state, interrupting the polymer-probe interaction (Figure 6).
Figure 6: Plot of log(I N* /I T* ) ratio vs. increasing humidity of PNIPAm films doped with (a) FE, (b) BFE and
(c) MFE at 25C (■) and 37C (). Taken from ref [61] and reproduced with permission. Copyright © 2010
American Chemical Society, all rights reserved.
In the more hydrophobic, condensed state above the LCST one would have expected that the rate
of water adsorption should be decreased. However, fluorescence analysis of PNIPAm thin films show
clearly that in every case, the log(IN*/IT*) value increases at a similar rate (Figure 6). This method
thus provides a relatively facile, non-contact methodology for assessing the ingress of water into
thermoresponsive polymers when fabricated as thin films on solid surfaces.
5.2
PHYSICOCHEMICAL PARAMETERS BY SOLVATOCHROMISM
Measuring polarity and hydrogen bonding changes in thermoresponsive polymers is vital for
understanding how these polymers will behave in the real world. For example, we know that many
of the common thermoresponsive polymers are appreciably hygroscopic and will absorb appreciable
amounts of water below and above the LCST thus influencing polarity within thin films [61]. The
most widely based methods for assessing polarity is based on solvatochromism, and there is an
extensive literature on solvent systems. Solvatochromism describes the change in shape, location
and sometimes intensity of absorption or emission spectra, relative to the polarity of the medium. A
hypsochromic (or blue) shift corresponds to negative solvatochromism, while a bathochromic (or red)
shift corresponds to positive solvatochromism with increasing solvent polarity [85-87].
Solvatochromic methods are generally robust and reasonably easy to implement but do require the use