Morphology and dynamics of the poly(ε-caprolactone)-b-poly(L-lactide) diblock copolymer and its inclusion compound with α-cyclodextrin: A solid-state13C NMR study

Solvent-polymer guest exchange in a carbamazepine inclusion complex: structure, kinetics and implication for guest selection

Solvent–polymer guest exchange in a carbamazepine inclusion complex in a stirred solution was studied and a mechanism was proposed.

Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes

The fabrication of nanofibers by electrospinning has gained popularity in the past two decades; however, only in this decade, have polymeric nanofibers been functionalized using cyclodextrins (CDs) or their inclusion complexes (ICs). By combining electrospinning of polymers with free CDs, nanofibers can be fabricated that are capable of capturing small molecules, such as wound odors or environmental toxins in water and air. Likewise, combining polymers with cyclodextrin-inclusion complexes (CD-ICs), has shown promise in enhancing or controlling the delivery of small molecule guests, by minor tweaking in the technique utilized in fabricating these nanofibers, for example, by forming core⁻shell or multilayered structures and conventional electrospinning, for controlled and rapid delivery, respectively. In addition to small molecule delivery, the thermomechanical properties of the polymers can be significantly improved, as our group has shown recently, by adding non-stoichiometric inclusion complexes to the polymeric nanofibers. We recently reported and thoroughly characterized the fabrication of polypseudorotaxane (PpR) nanofibers without a polymeric carrier. These PpR nanofibers show unusual rheological and thermomechanical properties, even when the coverage of those polymer chains is relatively sparse (~3%). A key advantage of these PpR nanofibers is the presence of relatively stable hydroxyl groups on the outer surface of the nanofibers, which can subsequently be taken advantage of for bioconjugation, making them suitable for biomedical applications. Although the number of studies in this area is limited, initial results suggest significant potential for bone tissue engineering, and with additional bioconjugation in other areas of tissue engineering. In addition, the behaviors and uses of aliphatic polyester nanofibers functionalized with CDs and CD-ICs are briefly described and summarized. Based on these observations, we attempt to draw conclusions for each of these combinations, and the relationships that exist between their presence and the functional behaviors of their nanofibers.

Effect of Guest Hydrophobicity on Water Sorption Behavior of Oligomer/α-Cyclodextrin Inclusion Complexes

Cyclomaltohexaose (alpha-cyclodextrin, alpha-CD) can form inclusion complexes (ICs) with polymer molecules in the columnar crystal structure in which alpha-CD molecules stack to form a molecular tube. Complementary water vapor sorption and wide-angle X-ray diffractomery (WAXD) were performed on oligomer/alpha-CD ICs to determine their structures and stabilities. To discern the effect of guest molecule hydrophobicity on water adsorption isotherms, polyethylene glycol (PEG, MW = 600 g/mol) and hexatriacontane (HTC) guests were used. Sorption isotherms for PEG/alpha-CD IC are similar to those obtained for pure alpha-CD and PEG, suggesting the presence of dethreaded PEG in the sample. WAXD collected before and after water vapor sorption of PEG/alpha-CD IC indicated a partial conversion from columnar to cage crystal structure, the thermodynamically preferred structure for pure alpha-CD, due to dethreading of PEG. This behavior does not occur for HTC/alpha-CD IC. Sorption isotherms collected at 20, 30, 40, and 50 degrees C allowed the calculation of the isosteric heats of adsorption and the integral entropies of adsorbed water which are characterized by minima that indicate the monolayer concentration of water in the ICs.