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Cyclodextrins readily react with suitable activated polyacids derivatives to afford highly cross­linked, nanoporous polymers referred to as cyclodextrins nanosponges (CDNS). CDNS are a new class of nonoporous materials with interesting adsorption, absorption and entrapment properties. CDNS are employed for several applications, including drug delivery, thermal stabilization of enzymes, controlled release of PAC and agrochemical, environmental control. Fundamental information on the structure at atomic level and the state of some molecules encapsulated into the polymeric network can be achieved by different techniques, such as solid state NMR. HRMAS NMR. Raman and FTIR spectroscopies Some representative examples of CDNS will be illustrated from the viewpoint of the synthesis. the applications and the physico-chemical charactenzation.

The reaction between cyclodextrins and suitable carboxylic acids derivatived to afford cross­linked polymers (cyclodextrins nanosponges. CDNS) is described. Different types of CDNS have been synthesized, and the properties of the materials modulated as a function of the type or CD. the chemical nature or the cross-linker and the reaction conditions. The structural characterization of CDNS has been carried out by elemental analysis, DSC. powder X-ray diffraction. scanning electron microscopy, solid state NMR FTIR and Raman spectroscopy.

The response to pH variation of polymeric cyclodextrin-based hydrogels has been investigated by a multi-technique approach based on UV Raman and Brillouin light scattering (BLS) together with Small Angle Neutron Scattering (SANS). By exploiting the complementary information of these three investigation methods, the structural, viscoelastic and molecular modifications of the polymer brought about by the pH changes have been examined, over a spatial range going from mesoscopic to nanoscopic length-scale. The data provide a picture where an increase of pH promotes the change of the characteristic size of the hydrophilic pores when the cross-linker has the suitable structural and acid-base properties, and leads to the reinforcement of the polymer domains interconnections, providing a stiffer gel network on the length-scale probed by BLS. Raman signals are sensitive both to structural changes of the polymer network and to changes of the intermolecular ordering of water due to solvent-polymer interactions. The destructuring effect on the tetrahedral ice-like configurations of water is especially evident at high pH, and might be ascribed to an increased exposition to the solvent of the ionic portions of the polymer surface.

UV Raman and Brillouin light scattering (BLS) experiments have been used in this study to explore the complex phase change behavior occurring in pH-responsive polysaccharide hydrogels as a function of temperature. Due to the different physical quantities measured by the two techniques, the joint analysis of Raman and BLS spectra has provided an unprecedented large-scale characterization of the molecular rearrangements and of the different kinds of hydrophilic and hydrophobic interactions that cooperate to determine the phase transformation observed in these hydrogels during the heating of the gel. As the main result, the analysis of the Raman and BLS spectra showed the existence of a correlation between the local (molecular) and collective properties of the gels during the phase transformation undergone by the system, which is markedly triggered by pH. The joint set of experimental results suggests a model according to which the mechanism of pH dependence in the hydrogels under investigation is dominated by the interactions involving the hydrophobic parts of the polymer skeleton, whereas the solvation process observed under heating of the gels is driven by the progressive distancing of the polymer domains among them, as monitored by the Brillouin sound velocity.

Nitroxides have great potential as contrast agents for Magnetic Resonance Imaging (MRI). Two β-cyclodextrin (βCD) derivatives bearing one or seven (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) units on the small rim of βCD (CD3 and CD6 respectively) were synthesized. Their effective magnetic moments were measured by DC-SQUID magnetometry obtaining the values μeff/μB ≈ 1.7 and μeff/μB ≈ 4.2 for CD3 and CD6 respectively. Interestingly, while isothermal magnetization data of CD3 were well described by a Brillouin function for a S = 1/2 single spin system, those associated with CD6 could not be explained in the framework of a non-interacting spins model. For this reason, four different configurations for the seven interacting nitroxides were considered and modeled. The numerical results evidenced that only the configurations with a privileged central spin could take into account the experimental observations, thus justifying the reduced effective magnetic moment of CD6. The water relaxivity (r1) in DMSO-d6–water (9 : 1 v : v) solutions was also measured for both the derivatives obtaining the values r1 = 0.323 mM−1 s−1 and r1 = 1.596 mM−1 s−1 for CD3 and CD6 respectively.