Effect of modified α, β, and γ-cyclodextrins on the thermo-responsive behavior of the elastin-like polymer, poly(VPGVG)

Abstract The influence of modified α, β and γ-cyclodextrins (mCDs) on water solutions of the elastin-like thermo-responsive poly(VPGVG) has been studied in this work. The studied mCDs are hydroxypropyl-α-CD MS=0.6, hydroxypropyl-β-CD MS=0.6, hydroxypropyl-β-CD MS=0.8, hydroxypropyl-β-CD MS=1.0, hydroxypropyl-γ-CD MS=0.6, hydroxyethyl-β-CD MS=5.0 and methyl-β-CD MS=1.8. All mCDs were able to increase the temperature at which the inverse temperature transition of this polymer takes place ( T t ). This shift was dose-dependent and was interpreted as the consequence of specific interactions between mCDs and the polymer chains. The ability showed by mCDs to cause T t shifts was lower than that previously reported for unmodified CDs. However, due to the higher solubility of mCDs, some of the mCDs leaded to higher values of T t than those found for the unmodified CDs at saturating concentration. A continuous drop in the latent heat of the transition was also observed. This, in combination with the T t shift to higher values, has been interpreted in terms of the reduction in the number of hydrophobic hydration ordered structures as the interaction between mCDs and the polymer chain takes place.