Polyrotaxane derivatives. II. Preparation and characterization of ionic polyrotaxanes and ionic slide‐ring gels

Abstract

Four types of ionic polyrotaxane (PR) derivatives, that is, carboxymethylated, sulfoethylated, diethylaminoethylated, and trimethylammoniohydroxypropylated PRs, were successfully prepared starting from the same PR consisting of poly(ethylene glycol) as an axis and a-cyclodextrins as ring molecules. The structures of the ionic PR derivatives were analyzed by 1 H and 13 C nuclear magnetic resonance (NMR), attenuated-total reflection Fourier transform-infrared, and colloidal titration. Degrees of substitution of the ionic PRs were calculated from results of 1 H NMR and colloidal titrations; both sets of results satisfactorily agreed. Cross-linking of sulfoethylated and quaternized PRs yielded ionic slide-ring gels carrying sulfoethyl and quaternary ammonium groups on the mobile cross-links, respectively. The former gel showed intriguing phenomena, including a large degree of swelling of up to 1147, drastic change in its swelling ratio by the presence of electrolyte and bending under a moderate applied electric field (7 V/cm).

Amino acid-derivatized slide-ring gels: Chemical crosslinking of polyrotaxane conjugates with different amino acid pendant groups

“…The Q values summarized in Table 6 appear to be relatively lower than previously reported values for slide-ring gels, which exceeded several hundreds [13,24]. Numerous factors may be responsible for this phenomenon, including the consumption of the primary amino groups of Phe-AA during crosslinking.…”

“…The used crosslinker HDMI reacts with primary amino groups to form urea linkages, leading to a decrease in the amino group content. Therefore, the formation of the Phe-PR slide-ring gels using HDMI as the crosslinker results in a lower degree of swelling than has been reported for other ionic slide-ring gels [13] (note that the first reported slide-ring gels [24] were also ionic gels because cyanuric chloride was employed as the crosslinker, and cyanuric acid moieties were generated after crosslinking via hydrolysis under alkaline conditions [32]). The swelling of slide-ring gels prepared from nonionic PRs and a nonionic crosslinker The swelling ratio of the AA-PR gels was also expected to change as the pH of the surrounding medium changed because the pK a value for the amino groups in the pendant AA moieties was found to be 6.3, above and below which the Q value changed dramatically.…”

“…For instance, the poor solubility of PRs in water and general organic solvents was recently overcome with the discovery of solvent systems possessing hydrogen-bond-breaking abilities [9][10][11], and the synthesis of various PR derivatives [12,13] has enhanced the utility of PRs in materials chemistry. Such PR derivatives have nonionic [12], ionic [13], polymeric [14][15][16], and liquid crystalline [17,18] functional groups. In addition to their outstanding properties attributable to the free movement of ring moieties and/or crosslinks [1][2][3][4], these functionalized PRs have additional interesting properties that have extended their use to all aspects of materials science.…”

Chitin-chitosan nanocomposite gels: reinforcement of chitosan hydrogels with rod-like chitin nanowhiskers

“…Although divinyl sulfone is known to effectively cross-link hydroxyl groups in alkaline conditions, 35,36 it does not seem to be used for cross-linking chitosan/chitin nanowhisker systems. The reason is that amino groups in chitosan and on the surface of chitin nanowhiskers are not protonated in 0.1 M NaOH, as the pK a values for both are around 6.3, resulting in insolubility of chitosan and strong aggregation of chitin nanowhiskers owing to the absence of electrostatic repulsion.…”

Star-Pseudopolyrotaxane Organized in Nanoplatelets for Poly(ε-caprolactone)-Based Nanofibrous Scaffolds with Enhanced Surface Reactivity

“…[2][3][4][5] As an example, it was demonstrated that poly(ε-caprolactone) (PCL) can form pPRs with α-cyclodextrins (CDs) [6][7][8] paving thus the way for biomedical applications. Indeed, PCL has been depicted these last decades as a key material for biomedical applications [ 9 ] because it is a biocompatible, biodegradable, and FDA-approved polyester.…”