Tuning the physicochemical properties of β-cyclodextrin based polyurethanes via cross-linking conditions. Microporous Mesoporous Mater
- M. H. Mohamed, L. D. Wilson, J. V. Headley
Wilson et al. raisea number of issues that, according to their opinion, require explanation. They support their comment on their estimation of the accessibility of β-cyclodextrin (β-CD) sites of four polymers prepared by cross-linking β-CD with divinylsulfone (DVS) at four stoichiometries. In particular, they focus their attentions on our conclusion that for our system (i.e., seven polymers and six sorbates) the degree of cross-linking “plays a minor role on the formation of the inclusion complexes” [sic] and extend their criticism to the isotherms, the content of cross-linker and the limited molecular characterization. Before addressing each specific issue, it is important to remark that the polymers reported by Wilson et al. in their comments are neither characterized nor the degree of cross-linking is estimated experimentally. Singularly, they report the β-CD:DVS ratio used for the synthesis as the only estimation of cross-linking degree and the statement “the materials were synthesized according to the verbatim reported method” (i.e., our paper) as the description of the synthesis. Providing that Wilson et al. performed the synthesis correctly, and that their polymers have a different degree of cross-linking, it is important to recall the warning recently published by these authors in Microporous Mesoporous Mater. , where the comparison of the effect of the mode of addition of the cross-linker led them to conclude: “Therefore, precautions should be taken when comparing materials from independent studies since synthetic conditions under thermodynamic vs. kinetic control may result in products with variable structure and textural properties” [sic]. Wilson’s data are incomplete and difficult to evaluate and the comparison with our results is not straightforward. Their data seem to be a particular case since they particularize their analysis on the inclusion complexes of a single model compound (i.e., phenolphthalein) with four homopolymers of β-CD, whereas our conclusion was based on six different compounds (i.e., phenol, 4-nitrophenol, β-naphthol, bisphenol A, progesterone and curcumin) and seven different polymers, comprising homopolymers and heteropolymers, but only a single case of β-CD homopolymer as those synthesized by Wilson et al. No less important is the fact that three of the four polymers studied by Wilson et al. were prepared with “cross-linking ratios at much lower levels” (i.e., DVS:β-CD stoichiometries at the synthesis step) and that “heteropolymers containing starch were not examined since such materials are less amenable to the phenolphthalein dye based method” [sic]. Despite the limitations of Wilson’s study, it arises a number of points that we would like to clarify in this reply.