Study of the inclusion compounds formed between α-cyclodextrin and high molecular weight poly(ethylene oxide) and poly(ϵ-caprolactone)

• Published in: Polymer (Guilford) 1998-09, Vol.39 (20), p.4857-4865
• Main Authors: Huang, Lei, Allen, Emily, Tonelli, Alan E.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Ftir; Organic polymers; Physicochemistry of polymers; polymer inclusion compounds; Properties and characterization; Structure, morphology and analysis; X-ray diffraction
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(97)00568-5

We report the formation of high molecular weight polymer inclusion compounds (ICs) between α-cyclodextrin and poly(ethylene oxide) (PEO) ( M n = 100 kg mol −1), and poly(ϵ-caprolactone) (PCL) ( M n = 40 kg mol −1). Both high molecular weight polymer ICs were successfully made by ultrasonic and heating techniques. Dsc, tga, X-ray diffraction, FT i.r. and solid state 13C n.m.r. were utilized to observe the PCL and PEO polymer chains included inside the channels formed by α-cyclodextrin. Dsc and tga scans showed that the high temperature stable polymer-CD-IC samples contain no free crystalline polymer. The much higher decomposition temperatures observed for these polymer-CD-ICs may imply that polymer chains included inside the polymer CD-IC channels can greatly improve cyclodextrin's stability. The polymer-CD-IC's X-ray diffraction patterns were very similar to that of valeric acid-CD-IC, which is confirmed to be a channel crystal structure, and the strong peak for both polymer-CD-ICs at approximately 20.0° (2θ) may confirm their IC formation. New bands appeared at 1729 cm −1 for PEO-CD-IC and at 1739 cm −1 for PCL-CD-IC in their FTi.r. spectra. Both bands were absent from the α-cyclodextrin spectrum. In CP/MAS/DD 13C n.m.r. spectra, single resonances for PEO-CD-IC, which compared with the multiple resonances observed for each carbon type in α-cyclodextrin, may indicate that α-cyclodextrin adopts a more symmetrical cyclic conformation in the PEO-CD-IC sample, while pure α-cyclodextrin assumes a less symmetrical conformation in the crystal when it does not include a guest polymer PEO inside its cavity. A one-pulse 13C n.m.r. spectrum was observed to identify the resonance peak for PEO inside the PEO-CD-IC.