Modulation of reversible self-assembling of dumbbell-shaped poly(ethylene glycol)s and β-cyclodextrins: precipitation and heat-induced supramolecular crosslinking

Abstract

A series of dumbbell-shaped poly(ethylene glycol) (PEG) chains 1 attached to bulky end groups were prepared, and some of the chains formed supramolecular assemblies with b-cyclodextrin (b-CD) and its multiple, ditopic and tetratopic, derivatives. The chains with proper end groups successfully allowed b-CD to be trapped onto PEG through formation of hydrogen bonds at room temperature and higher. Mixing of the PEG chain and the ditopic supramolecular crosslinker in water at 40 1C led to a change in solution property from viscous to elastic, accompanied by a significant increase in viscosity, whereas this change was not induced at room temperature. A supramolecular network formed only when the PEG chain was mixed with the tetratopic supramolecular crosslinker at 40 1C. Once formed, the supramolecular crosslinking was maintained even after the system cooled down. Instead, dilution and shaking at room temperature resulted in a return to a solution with low viscosity. These assemblies and dissociations were affected by the end groups of 1.

Formation of Polyrotaxane Particles via Template Assembly

“…To reduce the rate of CD dethreading, a semiblocking strategy can be utilized, where bulky end groups with varying molecular dimensions can be covalently attached to the ends of the PEG chain. , This concept has been shown for βCD/PEG complexes where PEG chain ends were coupled with bulky end groups of varying sizes . The solid state cavity diameter of αCD is 0.57 nm; therefore, by functionalizing PEG ends with bulky groups only slightly larger than the cavity of αCD, the rate of PPRX particle formation and degradation can be controlled.…”

“…52,53 This concept has been shown for βCD/ PEG complexes where PEG chain ends were coupled with bulky end groups of varying sizes. 54 The solid state cavity diameter of αCD is 0.57 nm; 55 therefore, by functionalizing PEG ends with bulky groups only slightly larger than the cavity of αCD, the rate of PPRX particle formation and degradation can be controlled. To explore this, a set of PEGs functionalized with different semiblocking groups was synthesized (see Supporting Information for synthetic protocol) and preliminary studies on PPRXs formation and degradation kinetics were carried out in the absence of SiO 2 templates.…”

Highly Stretchable and Elastic Polymer Electrolytes with High Ionic Conductivity and Li‐Ion Transference Number for High‐Rate Lithium Batteries

“…Due to the size match between the PEG chains and the cavity diameter of the α‐CD, the PEG chains are anticipated to enter into the cavity of α‐CD to form PEG/α‐CD inclusions. [ 69 ] The molecular weight ( M w ) of the model molecule before and after complexing with α‐CD was measured to be ca . 4055 and 6523 g·mol –1 .…”

Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils

“…The direct comparison of the linkers in A and B strongly suggests that the Thorpe-Ingold effect induced by the gemdimethyl unit is crucial for the supramolecular polymerization, thus indicating that indeed a ring-chain transformation is occurring. Next to the system described by Sijbesma and Meijer, other compounds have been described that influence the viscosity by dynamic supramolecular interactions, also leading to a viscosity increase at elevated temperatures [16][17][18].…”