Glass-like dynamics of new cross-linked polymeric systems: Behavior of the Boson peak

Cyclodextrin nanosponges (CDNS) provide a very promising class of cross-linked polymers consisting of cyclo-dextrins as building blocks and showing a characteristic nanoporous structure capable of effectively encapsulat-ing and carrying a variety of both lipophilic and hydrophilic compounds. Hereafter, we investigate the vibrational dynamics of CDNS in the low-wave number region, with the aim to provide physical descriptors correlated to the elastic properties of this innovative glass-forming material. By means of Raman scattering measurements, we explore the modifications occurring to the boson peak (BP) as a function of the cavity size of the cyclodextrin and the relative amount of the cross-linking agent with respect to the monomer cyclodextrin, which can be varied during the synthesis of the polymer. The shift and intensity variations of the BP are discussed in terms of the modification of the elastic properties of CDNS, and a master curve for the boson peak can therefore be obtained. The experimental approach adopted here is a useful tool for investigating the structural and physico-chemical properties of novel nanoporous soft materials of interest for biolife applications.