Solid-State Complexation of Poly(Ethylene Glycol) with α−Cyclodextrin

Abstract

Low-molecular-weight liquid poly(ethylene glycol) (PEG) spontaneously forms an inclusion compound (IC) when combined with R-cyclodextrin (R-CD) powder at room temperature. This process can be followed with wide-angle X-ray diffraction (WAXD). The WAXD data shows that the R-CD crystals undergo a solid-state crystal-crystal transformation from the cage to the channel crystal structure upon IC formation over a period of about 8 h. The time dependence of the 2θ ) 20°R-CD channel structure X-ray peak can be described by a simple first-order kinetic model. The effects of changing the temperature, PEG:R-CD molar ratio, PEG molecular weight, and vacuum-drying the CD have been studied. The barrier opposing the PEG inclusion-induced solid-state transformation of R-CD from the cage to the channel crystal structure appears to be dominated by changes in the packing/interactions of R-CDs, rather than the loss in the conformational entropy experienced by the PEG chains during the inclusion process.

Electrospinning of Cyclodextrin–Pseudopolyrotaxane Nanofibers

“…The diffraction patterns of these nanowebs containing various weight ratios of a-CD-PEG-IC are shown in Figure 2 d-f. PEO is a semicrystalline polymer with diffraction peaks at 2q = 198 and 238 (Figure 2 c). The characteristic peaks of the a-CD channel structure [24,25] at 2q values of approximately 208 and 138 were observed for all a-CD-PEG-IC/PEO nanowebs. In addition, an increased peak intensity was observed for the nanowebs containing a high proportion of a-CD-PEG-IC in the matrix.…”

“…The powder diffractogram of a-CD-PEG-IC has characteristic strong reflections at 2q values of approximately 208 and 138, arising from the channel packing and not the cage structure of unmodified a-CD (Figure 2 a). [24,25] The electrospinning of a-CD-PEG-IC nanofibers is not possible because of their crystalline nature and the low molecular weight of the PEG. Therefore the PEO polymer matrix was chosen to be used as a carrier for three reasons: 1) it is easy to electrospin PEO nanofibers, and PEO has been shown to be a good carrier matrix for both inorganic compounds and polymers that cannot be electrospun by themselves, [26][27][28][29][30] 2) it has the same chemical structure as PEG, and 3) PEO nanofibers may have many uses in various applications.…”

Stereoselective Complex Formation between Polybutadiene and Cyclodextrins in Bulk

“…Recently, the complex formation of CDs with some polymers in bulk have been reported by some groups. [26,27] It has been reported that the complex formation of CD in bulk was also selectively adjusted to the cross-sectional area of the polymers. Previously, we reported that CDs form inclusion complexes with polybutadiene (PB) to give inclusion compounds in aqueous media.…”

Solid Crystal Network of Self-Assembled Cyclodextrin and Nonionic Surfactant Pseudorotaxanes

“…The use of this amphiphile is very suitable because its structure presents well-defined regions that show differential bindings with -CD in aqueous solution. 39 Herein we report a combined X-ray powder diffraction (XRPD), high resolution electron transmission microscopy (HRTEM), and 13 C CP/MAS NMR study of the solid supramolecular polyrotaxane formed between Igepal CO-520 and -CD, supported by single crystal structural analysis. Moreover, we confirm the obtained structure and stoichiometry by comparison of the 1 H NMR spectra of several -CD pseudorotaxanes prepared from Igepals with different numbers of oligo(oxyethylene) groups (n ) 5, 9, and 40) in solution.…”