Connection between the vibrational dynamics and the cross‐linking properties in cyclodextrins‐based polymers

Abstract

The vibrational dynamics of a new class of cross‐linked polymers obtained from both native and modified cyclodextrin, referred to as cyclodextrin nanosponges, is here investigated. The main purpose is to spot the structure of these materials at molecular level unlikely to be characterized by diffraction methods due to the low or null degree of crystallinity. The analysis of the spectral features of the vibrational bands observed between 1650 and 1800 cm−1 in both Raman and infrared spectra, and assigned to the carbonyl stretching modes of the polymeric network, is performed by using band deconvolution procedures. At the same time, a detailed inspection of the low‐wavenumber vibrational dynamics of these polymers is carried out, focusing on the modifications occurring on the so‐called boson peak. The simultaneous analysis of different wavenumber ranges in Raman and infrared spectra of cyclodextrin nanosponges allows us to develop a reliable strategy for exploring both the cross‐linking degree and the elastic properties of these innovative materials. The overall results give a complete characterization of the structural and dynamical properties of the system, in turn strictly connected to the entrapment/transport ability of these polymeric matrices. Copyright © 2013 John Wiley & Sons, Ltd.

Water and polymer dynamics in a model polysaccharide hydrogel: the role of hydrophobic/hydrophilic balance

“…This behaviour is fully consistent with previous results obtained by the analysis of Raman and IR spectra of the CDNS hydrogel 25,[33][34][35] in the high-frequency regime 2700-3700 cm À1 . Consequently, the electrostatic environment experienced by the CQO groups causes a shift toward higher wavenumbers of the CO oscillators.…”

“…This occurrence reflects the changes in the polarizability (i.e. As widely discussed in previous studies, [29][30][31][32][33] the molar ratio n strongly affects the degree of reticulation of the CDNS polymer during its synthesis and modulates the elastic properties of the resulting material over the mesoscopic and macroscopic length scale. 6, the isotropic Raman profiles of different types of b-CDPMA1n hydrogels (with n = 4, 6, 8 and 10) are compared at the same hydration level h = 5.…”

“…38 Additional details can be found in ref. Recent results 31,33,39 demonstrated that the calculated vibrational profiles of 1,2,4,5-tetracarboxybenzoic acid dimethyl ester well reproduce the experimental Raman and IR spectra of nanosponges in the wavenumber range 1500-1800 cm À1 where no interfering vibrational bands 40,41 of cyclodextrins are present. 31 The latter model mimics the molecular environment of the cross-linking agent PMA after the condensation with the OH groups of cyclodextrins to form the ester bridges of b-CDPMA nanosponges.…”

“…31 The latter model mimics the molecular environment of the cross-linking agent PMA after the condensation with the OH groups of cyclodextrins to form the ester bridges of b-CDPMA nanosponges. As widely discussed in previous studies, 30,31,33,39,44 this asymmetric band in both Raman and IR spectra can be decomposed into two different components, n (CQO) ester and n (CQO) carbox , assigned to the stretching vibrations of the CQO belonging to the ester groups and to the carboxylic groups of PMA, respectively. The Raman and IR spectra reported in Fig.…”

“…[23][24][25] Nanosponges have been shown to be promising nanoporous materials with interesting properties of sorption of both organic and inorganic molecular species. [29][30][31][32][33] In addition, the controlled ability to undergo modifications from the state of a rigid gel to liquid suspension has been recently evidenced in CDNS-based hydrogels by changing the hydration level of polymers in water. 21,22,28 Besides their potential practical applications, nanosponges are interesting model systems for the study of water-swollen cross-linked polymers.…”