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 7 of 31
composition [54,55]. In contrast, by increasing the amount of a hydrophilic monomer AAm in the
NIPAm/AAm copolymers (from a molar ratio of 100:0 to 75:25), the LCST is increased (from 33 to
47 °C) [56].
4 POLYMER CHARACTERISATION BY FLUORESCENCE
The use of fluorescence spectroscopy for the evaluation of thermoresponsive polymers can
provide useful insights into both the gross physical-dynamic processes and the more subtle
physicochemical changes that occur in these polymer systems. Fluorescence spectroscopy offers
high sensitivity for low probe loading and fast response times, thus minimizing perturbation of the
polymer system. In thermoresponsive polymers like PNIPAm, the most common application of
fluorescence measurements are for the study of micelle formation, aggregation dynamics, and the
major phase changes that occur at the LCST. However, fluorophore choice needs to be very carefully
considered because multiple factors (Figure 4) are at play and the environment is considerably more
complex than that encountered in solvents. This potential multi-factor environmental sensitivity may
mean that the observed changes in absorption / fluorescence intensity, shifts in absorption /
fluorescence spectra, anisotropy, or fluorescence lifetimes originate from a combination of effects [5759]. For example, when studying the phase change behavior of thermoresponsive polymers one
needs to ensure that the selected fluorophore does not have a significant intrinsic temperature
dependence, which may be convoluted with the responses due to the temperature, induced changes in
polymer conformation.
Figure 4: Some of the environmental factors which may affect impact on emission properties of fluorophores
in polymers [60].
Annual Volumes, Vol. 8, pp. 97-126, (2015). ISBN: 978-3-319-24607-9 (Hardcover), 978-3-319-24609-3 (ebook) Springer.
Page 7 of 31
composition [54,55]. In contrast, by increasing the amount of a hydrophilic monomer AAm in the
NIPAm/AAm copolymers (from a molar ratio of 100:0 to 75:25), the LCST is increased (from 33 to
47 °C) [56].
4 POLYMER CHARACTERISATION BY FLUORESCENCE
The use of fluorescence spectroscopy for the evaluation of thermoresponsive polymers can
provide useful insights into both the gross physical-dynamic processes and the more subtle
physicochemical changes that occur in these polymer systems. Fluorescence spectroscopy offers
high sensitivity for low probe loading and fast response times, thus minimizing perturbation of the
polymer system. In thermoresponsive polymers like PNIPAm, the most common application of
fluorescence measurements are for the study of micelle formation, aggregation dynamics, and the
major phase changes that occur at the LCST. However, fluorophore choice needs to be very carefully
considered because multiple factors (Figure 4) are at play and the environment is considerably more
complex than that encountered in solvents. This potential multi-factor environmental sensitivity may
mean that the observed changes in absorption / fluorescence intensity, shifts in absorption /
fluorescence spectra, anisotropy, or fluorescence lifetimes originate from a combination of effects [5759]. For example, when studying the phase change behavior of thermoresponsive polymers one
needs to ensure that the selected fluorophore does not have a significant intrinsic temperature
dependence, which may be convoluted with the responses due to the temperature, induced changes in
polymer conformation.
Figure 4: Some of the environmental factors which may affect impact on emission properties of fluorophores
in polymers [60].