Preparation and sorption studies of β‐cyclodextrin/epichlorohydrin copolymers

Abstract

b-Cyclodextrin (b-CD) copolymer materials were synthesized by reacting different mole ratios (1 : 15, 1 : 25 and 1 : 35) of b-CD with epichlorohydrin (EP). The products were characterized using N 2 porosimetry, Fourier Transform Infrared spectroscopy, 13 C CP-MAS NMR spectroscopy, thermogravimetry analysis, elemental (C and H) analysis, and scanning electron microscopy. The sorption properties in aqueous solution were studied using p-nitrophenol (PNP) with UV-Vis spectrophotometry. Sorption isotherms were obtained at pH 4.6 and three temperatures (22, 35, and 45 C) and at pH 10.3 at 22 C. The isotherms were analyzed using the BET isotherm model and the sorption parameters provided estimates of the surface area, sorption capacity, and isosteric heats of sorption for each polymeric material. The estimated surface areas are as follows: 58.2, 52.1, and 90.1 m 2 /g at pH 4.6. At pH 10.3, the estimated surface areas are 44.2, 40.5, and 58.5 m 2 /g, respectively. The removal efficiency of PNP by the polymeric materials ranged between 4.5 and 58% for the conditions investigated whereas the isosteric heats ranged between À24.5 and À13.6 kJ/mol. Removal efficiencies were concluded to strongly depend on the sorption conditions such as pH, temperature, and the relative amounts of sorbent and dye in aqueous solution.

Preparation and sorption studies of polyester microsphere copolymers containing β-Cyclodextrin

“…The shift in temperature stability of the copolymers is related to the change in heat capacity, H-bonding effects, and the amorphous character of the copolymers as the linker content increases. Similar TGA results were reported for urethane- [31], epichlorohydrin- [34], and polyester-based copolymers [19] containing b-CD.…”

Surface area and pore structure properties of urethane-based copolymers containing β-cyclodextrin

“…Scheme 2) [35]. Previous sorption studies have hypothesized the occurrence of inclusion binding and non-inclusion adsorption of dyes onto the copolymer framework [30,46]. Therefore, SA estimates of CD-based polymers using the dye-based method are subject to error when an inappropriate isotherm (e.g., Langmuir) is applied to heterogeneous sorption (i.e., multi-site binding) phenomena.…”

“…The greater SA estimates derived from the dye-based method are attributed to framework structural changes of the copolymer in aqueous solution despite the relative insolubility of the copolymers in water. In a previous study, the occurrence of swelling for CD-based copolymers was reported [6,7,30,36,37]. Quantitative estimates of the swelling were determined from water uptake measurements for a urethane-methacrylate b-CD copolymer that ranged from 34.2% to 50.2% [38].…”

“…The published results [49] do not adequately account for the presence of multiple binding sites (i.e., inclusion vs. non-inclusion) in the urethane copolymer framework (cf. Scheme 2), as outlined previously [30,35]. Based on a comprehensive sorption study [35] of related urethane copolymers with PNP, the binding affinities (K eq $ 10 1 -10 2 M À1 ) for the copolymers are similar to those for the 1:1 native b-CD/ PNP complex in aqueous solution at 295 K. We conclude that the slightly attenuated binding affinity (K eq < 10 2 M À1 ) observed for urethane copolymer materials is attributed to steric effects of the inclusion sites and contributions arising from competitive binding equilibria at the different adsorption sites (cf.…”

“…Templated silica materials generally possess SA (BET) values $10 2 -10 3 m 2 /g with substantive pore volume and good mechanical stability [12]. Framework mesopores originate from the macromolecular pores and the interstitial sites embedded within the copolymer network, as shown in Scheme 2 [30]. The framework confined micropores are comparable to the diameter of the macrocycle (b-CD $7-8 Å); [8] whereas, the interstitial mesopores can vary according to the size and the structural rigidity of the diisocyanate co-monomer and its relative mole ratio.…”