Jinglin Shen

Manipulation the behavior of supramolecular hydrogels of α-cyclodextrin/star-like block copolymer/carbon-based nanomaterials

A new supramolecular hydrogel self-assembled between α-cyclodextrin (α-CD) and a star-like block copolymer AE73 was prepared. The cooperation effect of complexation of poly-(ethylene oxide) (PEO) segments with α-CD and the hydrophobic interaction between poly-(propylene oxide) (PPO) blocks resulted in the formation of the supramolecular hydrogel with a strong macromolecular network. Then two kinds of carbon materials (graphene and graphene oxide) were successfully incorporated into the above α-CD/AE73 hydrogel to further enhance the mechanical properties. The native hydrogel, as well as hybrid hydrogels, have been thoroughly characterized by using various microscopic techniques, including transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA). Our main purpose is to ascertain whether the properties of the obtained gels depend on these architectures. Interestingly, the phase behavior, the morphology and the mechanical strength of the native hydrogel can be successfully modulated by incorporating graphene and graphene oxide. Taking into account that both PEO/PPO copolymers and α-CD seem to be biocompatible, these gels can be promising for biomedical applications.

Studies on the gel behavior and luminescence properties of biological surfactant sodium deoxycholate/rare-earth salts mixed systems

Luminescent hydrogels were facilely designed through supramolecular self-assembly of biological surfactant (sodium deoxycholate, NaDC) and lanthanide salt (Eu(NO3)3). The microstructures of the hydrogels were characterized by transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) and field emission scanning electron microscopy (FE-SEM), from which nanofibers and tiny particles were observed. The arrangement of the deoxycholate and metal ions was proposed according to small-angle X-ray scattering (SAXS) and X-ray powder diffraction (XRD) measurements. Rheological measurements revealed that the mechanical strength of the hydrogels increased with increasing concentration of NaDC and Eu(NO3)3, while the maximum emission of the fluorescence of the gels appeared at a stoichiometry between Eu(NO3)3 and NaDC of 1:3. It is expected that the incorporation of luminescent lanthanide ions could impart versatile functionalities for practical applications to the hydrogels.

Biodegradable, multiple stimuli-responsive sodium deoxycholate–amino acids–NaCl mixed systems for dye delivery

Supramolecular hydrogels were prepared in mixtures of the biological surfactant sodium deoxycholate (NaDC) and amino acids (glycine (Gly), alanine (Ala), lysine (Lys) and arginine (Arg)) in different pH buffer solutions. We characterized their performance through phase behavior observation, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and rheological measurements. The results demonstrate that the presence of Gly and Ala can enhance the formation of the gels, whereas the addition of Lys and Arg could cause the breakage of the hydrogen bonds and weaken the formation of the gels. The formation of hydrogels with different gelling kinetics and mechanical properties or the behavior of the sol–gel transformation of the systems may be obtained by finely modulating pH. Moreover, the addition of the halide salts (NaCl) can enhance the mechanical strength of the gels. Because of their unique responsiveness to multi-stimuli environments, these biodegradable and pH-sensitive hydrogels hold great promise as versatile vehicles for dye (or drug) delivery.

Manipulation of multiple-responsive fluorescent supramolecular materials based on the inclusion complexation of cyclodextrins with Tyloxapol

A fluorescent supramolecular hydrogel was prepared by α-cyclodextrin (α-CD) and Tyloxapol, which can be considered as an oligomer of the nonionic surfactant polyoxyethylene tert-octylphenyl ether (Triton X-100, TX-100) with a polymerization degree below 7. For comparison, both Tyloxapol and TX-100 were selected to form hydrogels with α-CD to get more information about the interaction between different types of surfactants and cyclodextrin. These hydrogels have been thoroughly characterized using various techniques including phase behavior observation, transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), fluorescence spectra, fluorescence microscopy observations, Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, 2D 1H-1H ROESY NMR, small-angle X-ray scattering (SAXS), X-ray diffraction (XRD) and rheological measurements. The hydrogels of α-CD/Tyloxapol are responsive to external stimuli including temperature, pH and guest molecules, and present gelation-induced quenching fluorescence emission properties. The reason for this phenomenon may be that Tyloxapol molecules come into the cavity of α-CD and form the inclusion complexes. Due to the high electron density of the narrow cavity of α-CD, it induces the shift of the electron on the benzene ring which can weaken the π–π interaction and lead to the fluorescence quenching. Moreover, the hydrogel formed by α-CD/Tyloxapol is highly responsive to the formaldehyde (HCHO). The addition of a small amount of HCHO can induce a gel-to-sol transition. Interestingly, once the gel transforms into solution, it becomes fluorescent. This makes the α-CD/Tyloxapol hydrogel a promising candidate for HCHO detection and removal in home furnishings to reduce indoor environmental pollutants.

Ionic Self-Assembly of a Giant Vesicle as a Smart Microcarrier and Microreactor

Giant vesicles (1-10 μm) were constructed via a facile ionic self-assembly (ISA) strategy using an anionic dye Acid Orange II (AO) and an oppositely charged ionic-liquid-type cationic surfactant 1-tetradecyl-3-methylimidazolium bromide (C14mimBr). This is the first report about preparing giant vesicles through ISA strategy. Interestingly, the giant vesicle could keep the original morphology during the evaporation of solvent and displayed solid-like properties at low concentration. Moreover, giant vesicles with large internal capacity volume and good stability in solution could also be achieved by increasing the concentrations of AO and C14mimBr which contributed to the increase of the other noncovalent cooperative interactions. In order to facilitate comparison, a series of parallel experiments with similar materials were carried out to investigate and verify the driving forces for the formation of these kinds of giant vesicles by changing the hydrophobic moieties or the head groups of the surfactants. It is concluded that the electrostatic interaction, hydrophobic effect and π-π stacking interaction play key roles in this self-assembly process. Importantly, the giant vesicles can act as a smart microcarrier to load and release carbon quantum dot (CQD) under control. Besides, the giant vesicles could also be applied as a microrector to synthesize monodispersed Ag nanoparticles with diameter of about 5-10 nm which exhibited the ability to catalyze reduction of 4-nitroaniline. Therefore, it is indicated that our AO/C14mimBr assemblies hold promising applications in the areas of microencapsulation, catalyst support, and lightweight composites owing to their huge sizes and large microcavities.

Supramolecular Hydrogels of α-cyclodextrin/Reverse Poloxamines/Carbon-based Nanomaterials and Its Multi-functional Application

Supramolecular hydrogels were prepared using α-cyclodextrin (α-CD) and a poloxamine (reverse Tetronic 90R4, T90R4) which has four diblock arms with a poly(propylene oxide)–poly(ethylene oxide) (PPO–PEO) structure. The α-CD can slide past the PPO blocks and towards the middle PEO blocks owing to the unsuitable energy between α-CD and PPO to form α-CD/T90R4 inclusion complexes (ICs). The incorporation of graphene oxide (GO) into α-CD/T90R4 ICs changes their phase behavior and forms mechanically strong hydrogels because of the hydrogen-bonding between the GO nanosheets and the α-CD and PEO blocks of T90R4. The native hydrogel, as well as the α-CD/T90R4/GO hybrid hydrogels, have been thoroughly characterized by using various microscopy techniques. Field emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hydrogel, and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to evaluate the thermal stability of the hydrogel. Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) were used to characterize the interactions within the supramolecular assemblies and the degree of crystallinity of the xerogels, respectively. The experimental results demonstrated that α-CD/T90R4/GO hybrid hydrogels could adsorb various dyes selectively, and that it is a promising candidate for sewage treatment, while the native one cannot adsorb the dyes well. Moreover, the native α-CD/T90R4 hydrogel has excellent biocompatibility, and the results of the in vitro drug release study showed that the injectable doxorubicin (DOX)-loaded hydrogel is appropriate for the controlled release of anticancer drugs, while the α-CD/T90R4/GO hybrid hydrogels can reduce the release rate of DOX.

3D welan gum–graphene oxide composite hydrogels with efficient dye adsorption capacity

As a renewable material, welan gum is a kind of both biocompatible and biodegradable microbial polysaccharide and can be used to form polysaccharide/inorganic material composites. In this article, welan gum–graphene oxide (GO) composite hydrogels were prepared by simple self-assembly of both components in aqueous media and the effects of GO on the gelation of welan gum were systematically studied. The welan gum–GO hybrid hydrogels have been thoroughly characterized using transmission electron microscopy (TEM), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and rheological measurements. It can be observed that GO is dispersed on a molecular scale in the welan gum matrix and the interactions such as hydrophobic interaction, electrostatic interaction and hydrogen bonding occur between the welan gum matrix and graphene oxide sheets. The addition of GO which can act as a physical cross-linker in the hydrogel and effectively promote the gelation of welan gum, can be reflected by a decrease of the critical gelation concentration (CGC). Additionally, the welan gum–GO hybrid hydrogels exhibited good adsorption properties for water-soluble dyes such as methylene blue (MB), methyl violet (MV), amido black 10B (AB10B), rhodamine 6G (R6G) and chrome azurol S (CAS). Thus, it is expected that the GO-based composite hydrogels can act as adsorbents and have promising applications in the field of waste water treatment.

Ordered carbon nanotubes-n-dodecyl tetraethylene monoether liquid crystal composites through phase separation induced by poly(ethylene glycol).

Carbon nanotubes (CNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix at room temperature through spontaneous phase separation. The phase separation process occurred in n-dodecyl tetraethylene monoether (C12E4) solutions induced by the hydrophilic polymer, poly(ethylene glycol) (PEG). It was found that the molecular weight of PEG has a significant effect on the CNTs-C12E4 system, which not only influences the phase behavior of the system but also changes the properties of the CNTs-LLC composites. Polarized optical microscopy (POM) images, combined with small-angle X-ray scattering (SAXS) results, indicate that CNTs incorporate within the layers of the lamellar LLCs without destroying the structure of LLCs. Moreover, UV-vis absorption, Raman spectra and rheological measurements were performed to investigate the characteristic properties of the CNTs-LLC composites. This study not only gives a more comprehensive understanding of polymer-induced phase separation, but also expands the potential uses of CNTs-LLC composites in nanotechnology.

Manipulation the properties of supramolecular hydrogels of α-cyclodextrin/Tyloxapol/carbon-based nanomaterials.

Supermolecular hydrogels were prepared by α-cyclodeatrin (α-CD) and Tyloxapol, which can be considered as an oligomer of the nonionic surfactant polyoxyethylene tert-octylphenyl ether (TX-100) with a polymerization degree below 7. Two carbon materials, graphene oxide (GO) and graphene, were mixed into the α-CD/Tyloxapol hydrogel to adjust the physicochemical properties of hydrogel. In order to get stable graphene dispersion and then mix it with α-CD/Tyloxapol hydrogel, both TX-100 and Tyloxapol were used to disperse graphene for comparison. Interestingly, it can be found that TX-100 could disperse graphene better than Tyloxapol owing to smaller molecular size of TX-100 compared with Tyloxapol. Then, both the α-CD/Tyloxapol/GO and α-CD/Tyloxapol/graphene hydrogels were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, small angle X-ray scattering (SAXS), X-ray diffraction (XRD) and rheological measurements. The results revealed that the addition of carbon materials into α-CD/Tyloxapol hydrogel can change their microstructures and the rheological properties. Furthermore, it can be confirmed that a little amount of carbon materials could induce fluorescence quenching sharply which could be a promising candidate for optical sensor.

Modulating self-assembly behavior of a salt-free peptide amphiphile (PA) and zwitterionic surfactant mixed system

A salt-free surfactant system formed by a peptide amphiphile with short headgroup (PA,C16-GK-3) and a zwitterionic surfactant (dodecyldimethylamine oxide, C12DMAO) in water has been systematically investigated. The microstructures and properties of C16-GK-3/C12DMAO mixed system were characterized using a combination of microscopic, scattering and spectroscopic techniques, including transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), circular dichroism (CD) and rheological measurements. Rich phase transitions have been observed by adjusting the concentration of C16-GK-3. Investigation of the hydrogels of C16-GK-3/C12DMAO with TEM, SEM and AFM showed that all of these hydrogels form nanobelts. The nanobelt formation is performed in a hierarchical manner: β-sheet peptides and C12DMAO first interact each other to form small aggregates, which then arrange themselves to form one dimensional (1D) left-handed ribbons. The ribbons further aggregated into flat and rigid nanobelts. We proposed a mechanism to interpret the self-assembly process according to the specific peptide structure as well as multiple equilibria between the hydrogen bonding interactions between the headgroups of C16-GK-3, between C12DMAO molecules and the headgroups of C16-GK-3, chirality of the amino acid residues and hydrophobic interactions of the alkyl chains.