Local and Network Structure of Thermoreversible Polyrotaxane Hydrogels Based on Poly(ethylene glycol) and Methylated α-Cyclodextrins

Graphene oxide (GO)-polyamidoamine (PAMAM) dendrimer nanocomposite hydrogels were prepared through one-step synthesis by mixing a GO suspension and a PAMAM solution at varying ratio of GO to PAMAM. The materials self-assembled into physically crosslinked networks, mainly driven by electrostatic interactions between the oppositely charged GO nanosheets and PAMAM dendrimer. The chemical structure of PAMAM dendrimer was studied by mass spectrometry, nuclear magnetic resonance spectroscopy and potentiometric titration.The structure and properties of GO-PAMAM nanocomposite hydrogels were investigated by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy and rheometry. The nanocomposite hydrogels exhibited a relatively high mechanical performance with a storage modulus of up to 284 kPa, as well as self-healing property, owing to their reversible and multiple physical cross-links. These hydrogels may be further developed for biomedical applications.2

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“…Stable hydrogels, G10D1H, G10D5H, G10D10H and G10D20H, were formed and confirmed by the tube inversion test 41 (Fig. S1).…”

Section: Characterization Of Go-pamam Nanocomposite Hydrogelsmentioning

confidence: 70%

One-Step Synthesis of Graphene Oxide–Polyamidoamine Dendrimer Nanocomposite Hydrogels by Self-Assembly

Piao

Chen

2016

Ind. Eng. Chem. Res.

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“…[8] There is now good understanding of the formation mechanisms and structures of such PPR hydrogels, but little has been explored concerning their dissociation and reassembly, though increasing temperature [9] and shearing [9b,c] could make the hydrogel turn to a sol. Herein, we demonstrate a facile photocontrollable supramolecular route to realize the disassembly and reassembly of the PPR hydrogels.…”

mentioning

confidence: 99%

Photoresponsive Pseudopolyrotaxane Hydrogels Based on Competition of Host–Guest Interactions

et al. 2010

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Reversibility is a basic and crucial feature of supramolecular systems.[1] In designing and fabricating new supramolecular materials, the realization of reversibility is particularly important as it could enable these substances to be superior to conventional materials. An excellent example is an elastomer reported recently, made of small functional molecules which form both long chains and cross-linkers through intermolecular multiple hydrogen bonding. When broken or cut, the elastomer can be simply repaired by just bringing together the fractured surfaces and allowing the recovery of the hydrogen bonding. [2] There are plenty of reports on supramolecular assemblies of polymers showing reversible responses to environmental changes; however, these are mostly based on the inherent stimuli-sensitive properties of the building blocks, such as the temperature-induced coil-globule transition of poly(N-isopropyl acrylamide) (PNIPAM) [3] and pH-induced protonation of poly(vinyl pyridine), [4] rather than the reversibility of the supramolecular interactions. Therefore, taking full advantage of the reversibility of the noncovalent interactions to construct supramolecular materials is still a big challenge. This has drawn increasing interest in recent years, and has led to a series of promising results. For example, some hydrophobically modified water-soluble polymers realized sol-gel transition as a result of the reversible interactions of cyclodextrin and alkyl chains.[5] The assembly and disassembly of polymeric vesicles can be controlled by photosensitive interactions between cyclodextrin and azobenzene compounds.[6]The self-assembly of polyethylene glycol (PEG) and a-cyclodextrins (a-CDs) to form linear pseudopolyrotaxane (PPR), with PEG as the axis and a-CDs as threaded rings, was reported by Harada et al. [7] Since the ability of PPR to form physical hydrogels was first reported in 1994, the system has been extensively studied as the hydrogels show very promising uses as biomedicine materials. [8] There is now good understanding of the formation mechanisms and structures of such PPR hydrogels, but little has been explored concerning their dissociation and reassembly, though increasing temperature [9] and shearing [9b,c] could make the hydrogel turn to a sol. Herein, we demonstrate a facile photocontrollable supramolecular route to realize the disassembly and reassembly of the PPR hydrogels. The addition of a photoresponsive compound containing an azobenzene moiety to the PPR hydrogel was found to be effective in converting the hydrogels to transparent solutions. By subsequent alternation of UV and visible irradiation, reversible sol-to-gel and gel-to-sol transitions were observed. Thus, the widely investigated PEG/a-CD PPR hydrogel is proved to be "active" in supramolecular chemistry, and the reversible nature of supramolecular materials is fully realized.In our study, the PPR hydrogel (Figure 1 a) was prepared by using PEG10K (molecular weight 10 000) and a-CD in water as described in reference [7c]. The concen...

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“…10). The peaks around 11 • and 20 • for all the α-CD/PEG gellike samples belong to the hexagonal lattice of α-CD in channel-type crystal structures [37,38] and their heights decrease with increasing the molecular weights of PEG (e, f, and g in Fig. 10).…”

Section: Thermal Properties and Crystalline Structure Of Gelmentioning

confidence: 95%

Hydrogels assembled by inclusion complexation of poly(ethylene glycol) with alpha‐cyclodextrin

Wang

Zhu

et al. 2009

Asia-Pacific J Chem Eng

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Polymeric hydrogels were prepared based on the inclusive complexation between α-cyclodextrin (α-CD) and poly(ethylene glycol) (PEG). Because the rheological property of a thermodynamic stable hydrogel should be gap-independent, it is found in this work that the uniformed hydrogel can be distinguished from gel-like aggregation by changing the plate gap during the rheological measurement. By this rheological method it is determined that suitable storage duration is necessary for the preparation of uniform hydrogels. However, the sonication technique after mixing CD and PEG solutions or increasing PEG concentration can shorten the time to form stable hydrogels. Moreover, the molecular weight of PEG should be high enough (≥8000 g/mol) for sol-gel transition. The higher the molecular weight of PEG is, the longer storage time is needed to obtain a uniform hydrogel. From the observation by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) of prepared hydrogels, we concluded that the driving force of networks should be attributed to the crystallization of complexed α-CDs in the α-CD/PEG pseudo-polyrotaxanes.

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Local and Network Structure of Thermoreversible Polyrotaxane Hydrogels Based on Poly(ethylene glycol) and Methylated α-Cyclodextrins

Cited by 87 publications

References 42 publications

One-Step Synthesis of Graphene Oxide–Polyamidoamine Dendrimer Nanocomposite Hydrogels by Self-Assembly

One-Step Synthesis of Graphene Oxide–Polyamidoamine Dendrimer Nanocomposite Hydrogels by Self-Assembly

Photoresponsive Pseudopolyrotaxane Hydrogels Based on Competition of Host–Guest Interactions

Hydrogels assembled by inclusion complexation of poly(ethylene glycol) with alpha‐cyclodextrin

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