Complex Formation of Poly(ε-caprolactone) with Cyclodextrins

Abstract

Cyclodextrins (CDs) have been found to form inclusion complexes with poly(ε-caprolactone) (PEC) to give crystalline compounds. α- and γ-CD formed complexes with these polyesters in high yields, although β-CD gave complexes in moderate yields. The yields of the complexes decreased with increasing molecular weight of the polymer. α-CD−PEC complexes are stoichiometric one-to-one (cyclodextrin:monomer unit) compounds, and γ-CD−PEC complexes are one-to-two compounds when the molecular weights of PEC are low. The complexes were isolated and characterized by 1H NMR, 13C CP/MAS NMR, and X-ray diffraction studies. The inclusion modes are discussed.

Preparation and Characterization of Inclusion Complexes of β‐Cyclodextrin with Ionic Liquid

“…The b-CD and the IL can promote the solubility of each other due to the soluble nature of the ICs formed. XRD, 13 C CP/MAS NMR, and TGA studies illustrated that the ICs are isomorphous, with a channel-type structure, with the b-CD molecules adopting a symmetrical conformation, and with each glucose unit of b-CD being in a similar environment. The thermal stability of the ICs is lower than the two precursors.…”

“…The solubility and conductivity results indicated that inclusion complexes (ICs) of 1:1 stoichiometry were formed. The inclusion compounds were further characterized by using powder X-ray diffraction (XRD) analysis, 13 C CP/MAS (cross-polarization magicangle spinning) NMR and 1 H NMR spectroscopy, and thermogravimetric analysis (TGA). The results showed that the ICs were a fine crystalline powder.…”

“…[9,15,20] Small resonance peaks in the solid-state 13 C NMR spectrum of 1 at about 20, 40, 120, and 130 ppm are presumably due to the bmimPF 6 guest, which indicates its presence in the channel structure of crystalline 1. Therefore, the formation of channel structures of ICs in the present study is further supported by these 13 C CP/MAS NMR measurements. 1 H NMR spectra: The solution structure of the inclusion complexes of b-CD and bmimPF 6 was further investigated by using 1 H NMR at room temperature.…”

“…[11] Solid-state 13 C CP/MAS (cross-polarization magic-angle spinning) NMR spectroscopy: High-resolution NMR spectroscopy is another technique used to analyze the structure and molecular dynamics of ICs either in aqueous solution or in the solid state. It is known that the formation of the ICs should change the conformation and the electromagnetic environment of both the host CD and the guest molecules, which should be reflected in the 13 C CP/MAS NMR spectra of the host and the guest molecules in the ICs. [11,17,20,21] Figure 4 shows the 13 C CP/MAS NMR spectra of the uncomplexed b-CD and 1.…”

“…It is known that the formation of the ICs should change the conformation and the electromagnetic environment of both the host CD and the guest molecules, which should be reflected in the 13 C CP/MAS NMR spectra of the host and the guest molecules in the ICs. [11,17,20,21] Figure 4 shows the 13 C CP/MAS NMR spectra of the uncomplexed b-CD and 1. The b-CD molecules are known to have a less symmetrical conformation in the crystalline state.…”