Enhanced thermal properties of PS nanocomposites formed from inorganic POSS-treated montmorillonite

We have prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. The nanocomposites were exfoliated at up to a 3 wt% content of pristine clay relative to the amount of polystyrene (PS). We used two different surfactants for the montmorillonite: the aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS) and the ammonium salt of cetylpyridinium chloride (CPC). Both surfactants can intercalate into the layers of the pristine clay dispersed in water prior to polymerization. Although the d spacing of the POSS-intercalated clay is relatively smaller than that of the CPC-intercalated clay, PS more easily intercalates and exfoliates the POSS-treated clay than the CPC-treated clay. IR spectroscopic analysis further confirms the intercalation of POSS within the clay layers. We used X-ray diffraction (XRD) and transmission electron microscopy (TEM) to characterize the structures of the nanocomposites. The nanocomposite prepared from the clay treated with the POSS containing surfactant is exfoliated, while an intercalated clay was obtained from the CPC-treated surfactant. The molecular weights of polystyrene (PS) obtained from the nanocomposite is slightly lower than the virgin PS formed under similar polymerization conditions. The value of T_g of the PS component in the nanocomposite is 8 °C higher than the virgin PS and its thermal decomposition temperature (21 °C) is also higher significantly. The presence of the POSS unit in the MMT enhances the thermal stability of the polystyrene.     

Studies on thermal properties of PS nanocomposites for the effect of intercalated agent with side groups

Polystyrene-layered silicate nanocomposites were prepared from three new organically modified clays by emulsion polymerization method. These nanocomposites were exfoliated up to 3 wt% content of pristine clay relative to the amount of polystyrene (PS). The intercalated agents C₂₀, C₂₀-4VB, and C₂₀-POSS intercalated into the galleries result in improved compatibility between hydrophobic polymer and hydrophilic clay and facilitate the well dispersion of exfoliated clay in the polymer matrix. Results from X-ray diffraction, TEM and Fourier transform infrared spectroscopy indicate that these intercalated agents are indeed intercalated into the clay galleries successfully and these clay platelets are exfoliated in resultant nanocomposites. Thermal analyses of polystyrene-layered silicate nanocomposites compared with virgin PS indicate that the onset degradation temperature ca. 25 °C increased and the maximum reduction in coefficient of thermal expansion (CTE) is ca. 40% for the C₂₀-POSS/clay nanocomposite. In addition, the glass transition temperatures of all these nanocomposites are higher than the virgin PS.     

Formation of the crystalline inclusion complex between γ-cyclodextrin and poly(N-acetylethylenimine)

Poly(N-acetylethylenimine) was found to form a crystalline inclusion complex with γ-cyclodextrin (CD). It did not form crystalline inclusion complexes with α-CD or β-CD. It is a hydrophilic, nitrogen atom-containing polymer that forms a crystalline inclusion complex with CD. FT-IR spectroscopy, thermogravimetry analysis, X-ray diffraction, ¹H NMR spectra and ¹³C CP/MAS NMR spectra were used to characterize the structure and property of the crystalline inclusion complex.     

Preparation and characterization of inclusion complexes formed by biodegradable poly(ε-caprolactone)-poly(tetrahydrofuran)-poly(ε-caprolactone) triblock copolymer and cyclodextrins

Inclusion complexes (ICs) formed with cyclodextrins (CDs) and polymers have been an interesting topic over the past decade. Recently, more focus has been shifted to the ICs with biodegradable polymers or copolymers because of their potential applications as novel biomaterials. This work reports the IC formation between CDs and biodegradable poly(ε-caprolactone)-poly(tetrahydrofuran)-poly(ε-caprolactone) (PCL-PTHF-PCL) triblock copolymer and the characterization of the ICs. The PCL-PTHF-PCL triblock copolymer was found to form crystalline ICs with all α-, β-, and γ-CDs. All the three ICs were prepared in high yields from aqueous medium. The ICs were characterized by X-ray diffraction (XRD), ¹³C CP/MAS NMR, ¹H NMR, Fourier transform infrared, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The XRD studies demonstrated that all the ICs assumed a channel-type structure similar to the necklace-like ICs formed by α-CD and poly(ethylene glycol) homopolymers. Solid-state CP/MAS ¹³C NMR studies showed that the CD molecules in the ICs adopted a symmetrical conformation due to the threading onto a polymer chain. The compositions of the ICs were studied by using ¹H NMR spectroscopy. From the ¹H NMR and DSC results, it was proposed that only the two flanking PCL blocks are included and covered by α-CD in the α-CD-PCL-PTHF-PCL IC, while the two PCL blocks as well as the middle PTHF block are included and covered by β-CD in the β-CD-PCL-PTHF-PCL IC. On the other hand, it was proposed that the PCL-PTHF-PCL copolymer is probably included and covered by γ-CD in a double-stranded mode in the γ-CD-PCL-PTHF-PCL IC. Finally, The TGA analysis revealed that the ICs had better thermal stability than their free components due to the inclusion complexation, suggesting that the complexation stabilized the copolymer included in the CD channels.     

Preparation, characterization and novel photoregulated rheological properties of azobenzene functionalized cellulose derivatives and their α-CD complexes

Novel azobenzene functionalized hydroxypropyl methylcellulose (AZO-HPMC) polymers and their α-CD (α-Cyclodextrin) complexes have been prepared. FT-IR, ¹H NMR and FT-Raman spectroscopy confirm the existence of azobenzene chromophores in AZO-HPMC polymers. α-CD can improve the water solubility of AZO-HPMC by formation of inclusion complexes with azobenzene side groups. Rheological studies substantiate that both AZO-HPMC and its α-CD complex undergo thermoreversible sol-gel transitions in aqueous solutions. Viscometric measurements suggest that the association between azobenzene side groups can be eliminated by α-CD. The effect of photoirradiation on the rheological behavior shows that the gelation temperature of AZO-HPMC increases after UV irradiation, while the gelation temperature of AZO-HPMC/α-CD complex decreases after UV irradiation.     

Preparation and characterization of polyseudorotaxanes based on adamantane-modified polybenzoxazines and β-cyclodextrin

β-Cyclodextrin (β-CD) forms inclusion complexes (ICs) with adamantane-modified benzoxazines (2 benzoxazine and 3 benzoxazine). These benzoxazines can readily penetrate into the CD's hydrophobic cavity, causing turbidity of their solutions, from which fine crystalline powders are obtained. We characterized these complexes by powder X-ray diffraction, ¹³C and ¹³C CP/MAS NMR spectroscopies, DSC, and TGA. The X-ray diffraction and solid-state ¹³C CP/MAS NMR spectroscopy indicate that the IC domains of the polypseudorotaxanes maintain their channel-type structures after the ring-opening curing reactions have occurred. Furthermore, DSC measurements indicate that complexing the adamantane-modified benzoxazine units with β-CDs result in stiffer main chains and, thus, higher glass transition temperature. TGA also indicates that the inclusion complexes have enhanced its thermal stability.     

Structure and dynamics of a vinylidene fluoride oligomer and its cyclodextrin inclusion compounds as studied by solid-state F MAS and H → F CP/MAS NMR spectroscopy

The molecular structure and dynamics of a vinylidene fluoride oligomer telomerized by carbon tetrachloride (Cl-OVDF) and its inclusion compound (IC) with β-cyclodextrin (β-CD) have been investigated using solid-state ¹⁹F magic angle spinning (MAS) and ¹H → ¹⁹F cross-polarization (CP)/MAS NMR spectroscopy. The preferential IC formation of the lower-molecular-weight components with β-CD was used to refine as-received Cl-OVDF. The refined Cl-OVDF with larger molecular weight readily takes γ-form (tttg⁺tttg⁻) conformation, and it also forms ICs with β-CD (Cl-OVDF/β-CD IC) under a certain condition. ¹⁹F MAS NMR indicates that Cl-OVDF chains virtually isolated in the β-CD cavities take no specific conformations even at −40 °C. The temperature dependence of the magnetic relaxation times (T₁^F, T_1ρ^F) indicates that the Cl-OVDF chains in ICs undergo molecular motions similar to the amorphous phase in the bulk, although the intramolecular spin diffusion among ¹⁹F nuclei is more significant in the former because of the one-dimensional confinement.     

Electrospun polystyrene fibers containing high temperature stable volatile fragrance/flavor facilitated by cyclodextrin inclusion complexes

In this study, we report on electrospinning of functional polystyrene (PS) fibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-ICs). Our goal is to develop functional electrospun fibers containing fragrances/flavors with enhanced durability and stability assisted by cyclodextrin inclusion complexation. We have used menthol as a model fragrance/flavor material and CD-menthol-ICs were incorporated in electrospun PS fiber by using three types of CDs; α-CD, β-CD and γ-CD. Due to complexation of menthol with CDs, we observed that the stabilization of menthol was achieved up to 350 °C for all the PS/CD-menthol-IC webs whereas the PS fibers without the CD complex could not preserve volatile menthol molecules. In addition, γ-CD was more effective for the stabilization and release of menthol at a broad temperature range (100–350 °C) when compared to α-CD and β-CD. This study suggested that the electrospun fibers functionalized with CD-ICs are very effective for enhancing the temperature stability of volatile fragrances/flavors and therefore show potentials for the development of functional fibrous materials.     

Synthesis and characterization of polyrotaxanes comprising α-cyclodextrins and poly(ε-caprolactone) end-capped with poly(N-isopropylacrylamide)s

Biodegradable polyrotaxane (PR)-based triblock copolymers were synthesized via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) initiated with polypseudorotaxanes (PPRs) consisting of a distal 2-bromopropiomyl bromide end-capping poly(ε-caprolactone) (Br-PCL-Br) and a varying amount of α-cyclodextrins (α-CDs) in the presence of Cu(I)Br/PMDETA at 25 °C in aqueous solution. The copolymers were featured by relatively higher yields from 46.0% to 82.8% as compared with previous reports. Their structure was characterized in detail by using ¹H NMR, ¹³C CP/MAS NMR, GPC, WXRD, DSC and TGA analyses. When a feed molar ratio of NIPAAm to Br-PCL-Br was changed from 50 to 200, the degree of polymerization of PNIPAAm blocks attached to two ends of PPRs was in a range of 158–500. About one third of the added α-CDs were still entrapped on the central PCL chain after the ATRP process. Attaching PNIPAAm rendered the copolymers soluble in aqueous solution showing the thermo-responsibility as evidenced by turbidity measurements.     

Effect of clay content and clay/surfactant on the mechanical, thermal and barrier properties of polystyrene/organoclay nanocomposites

In the present paper, three ammonium salts namely, tetraethylammonium bromide (TEAB), tetrabutylammonium bromide (TBAB), and cetyltrimethylammonium bromide (CTAB) were employed to prepare organoclay by cation exchange process. Polystyrene (PS) /clay nanocomposites were prepared by melt blending using commercial nanoclay and organoclays prepared using above mentioned salts. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis indicated that the modified clays were intercalated and/or exfoliated into the polystyrene matrix to a higher extent than the commercial nanoclay. Further, amongst the modified organoclays, TBAB modified clay showed maximum intercalation of clay layers and also exfoliation to some extent into the polystyrene matrix. TEM micrograph exhibited that TBAB modified clay had the best nanoscale dispersion with clay platelet thickness of ∼6–7 nm only. The mechanical properties of the nanocomposites such as tensile, flexural and izod impact strength were measured and analyzed in relation to their morphology. We observed a significant improvement in the mechanical properties of polystyrene/clay nanocomposites prepared with modified clays as compared to commercial organoclay, which followed the order as; PS/TBAB system > PS/CTAB system > PS/TEAB system. Thermogravimetric analysis (TGA) demonstrated that T₁₀, T₅₀ and Tmax were more in case of polystyrene nanocomposites prepared using modified organoclays than nanoclay [nanolin DK4] and maximum being in the case of PS/CTAB system. The results of Differential Scanning Calorimetry (DSC) confirmed that the glass transition temperature of all the nanocomposites was higher as compared to neat polystyrene. The nanocomposites having 2% of TBAB modified clay showed better oxygen barrier performance as compared to polystyrene.     

High yield production of high molecular weight poly(ethylene glycol)/α-cyclodextrin polyrotaxanes by aqueous one-pot approach

An easy, one-pot, high-yield preparation of high molecular weight polyrotaxanes (PRs) from poly(ethylene glycol) (PEG) and α-cyclodextrin (α-CD) by click chemistry is presented with novel water soluble and clickable end-capping agents containing quaternary ammonium and propargyl groups. The threading numbers of α-CD on the PEG chain were investigated by means of ¹H NMR spectroscopy and gel permeation chromatography (GPC). When M_n of the PEG axis is 35 kDa, the yield is up to 614 mg per 100 mg PEG axis and the average number of α-CDs on each PEG axis is 193. Wide-angle X-ray diffraction (WAXD) revealed that PRs form a column-type crystalline structure. The prepared PR possesses terminal alkyne groups which can connect with functional molecules to make the PR more useful. As a typical example, fluorescent rhodamine B has been successfully installed on the PR terminals.     

Residing states of β-cyclodextrins in solid-state polyrotaxanes comprising pluronic F127 and PNIPAAm

It was reported that polyrotaxanes (PRs) comprising β-cyclodextrins (β-CDs) and Pluronic F127 end-capped with poly(N-isopropylacrylamide) blocks show a β-CD aggregated state in which the threaded β-CDs are self-aggregated into a typical channel-type crystal structure after water incubation. At the same time, they converse into a β-CD dispersed state in which the entrapped β-CDs are randomly dispersed along the backbone after DMF treatment. Herein the effects of solvent variations on the residing states of β-CDs on the polymeric backbone in a selected PR sample were investigated in detail. Treating the sample using solvents, such as water, THF, chloroform, methanol, ethanol, acetone, methylene dichloride, anhydrous ether and n-hexane, produces the β-CD aggregated state PRs. Meanwhile, treatments using DMF, DMSO and NaOH aqueous solution yield the β-CD dispersed state PRs. The self-aggregated structures of β-CDs threaded onto the Pluronic F127 chain were evidenced by using XRD, ¹³C CP/MAS NMR and FTIR techniques. Additionally, the mechanism for the solvent effects on the residing states of β-CDs in the PR sample was discussed. These findings would not only contribute to a comprehensive understanding of the self-aggregated structure of CD-based PRs, but also promote to exploit solvent-responsive PRs as smart materials.     

Polymerization of styrene in γ-cyclodextrin channels: Lightly rotaxanated polystyrenes with altered stereosequences

Modeling of polystyrene (PS) with various stereosequences in γ-cyclodextrin (γ-CD) channels has been conducted and it was found that only isotactic PS stereoisomers can fit into the γ-CD cavity. Thus, based on the modeling of stereoisomeric polystyrenes in narrow γ-CD channels, it was suggested that PSs with unusual microstructures might be produced via constrained polymerization of styrene monomer in its γ-CD-IC crystals. The in situ polymerization of styrene inside the narrow channels of its γ-CD-IC crystals suspended in aqueous media was performed. Alternatively, the solid-state polymerization of styrene/γ-CD-IC has also been conducted by exposure to γ-radiation. It was found that most host γ-CD molecules slip off during polymerization and the channel structure was not preserved. Consequently, much of the guest styrene monomer polymerizes outside of the host γ-CD channels, where the constrained environment is absent. Yet, a lightly rotaxanated structure has been obtained, where some threaded γ-CD molecules ∼15 wt% (∼1 γ-CD per 70 PS repeat units) are permanently entrapped along the PS chains after polymerization. ¹³C NMR spectra of PSs synthesized from styrene/γ-CD-IC and homogeneously in toluene show some differences, which are presumably due to variations in the stereosequences of PSs obtained from the partially constrained polymerization of styrene/γ-CD-IC.     

Polystyrene/attapulgite nanocomposites prepared via in situ suspension polymerization with redox initiation system

A series of polymer–clay nanocomposites consisting of polystyrene (PS) and attapuglite (ATP) were prepared successfully. First, silane coupling agent containing aromatic tertiary amine groups was synthesized to functionalize ATP (M‐ATP). Then, PS nanocomposites with varied clay loadings were prepared via in situ suspension polymerization process with a redox initiation system consisting of aromatic tertiary amine and benzoyl peroxide. The synthesis of silane coupling agent and functionalization of ATP were confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectra, and X‐ray photoelectron spectroscopy. Mechanical properties, morphology, thermal stability, and rheological behavior of nanocomposites were investigated to illuminate the effects of M‐ATP on the structure and properties of nanocomposites. Field‐emission scanning electron microscope images revealed an ideal dispersion of M‐ATP and an enhanced toughness of nanocomposites. The improved interface interaction between M‐ATP and PS matrix endowed the nanocomposites with outstanding mechanical properties and thermal stability. The formation of hybrid network in the nanocomposites containing 3 wt % M‐ATP resulted in higher complex viscosity (η*), storage modulus (G′), and lower loss factor (tanδ) compared with the pristine PS and PS/ATP nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41567.     

Thermostable and flame retardant Mesua ferrea L. seed oil based non-halogenated epoxy resin/clay nanocomposites

Bio-based polymer nanocomposites have a unique niche of their own in the domain of green technology. A bio-based sulfone epoxy resin (BPSE) has been synthesized from the monoglyceride of Mesua ferrea L. seed oil, bis(4-hydroxyphenyl) sulfone, bisphenol-A and epichlorohydrin. The formation of resin was confirmed by the determination of viscosity, epoxy equivalent, etc. and the structure was elucidated from FTIR and ¹H NMR spectroscopies. This resin was used as the matrix for the preparation of epoxy/clay nanocomposites by ex situ technique using different doses of organo nano-clay (1, 2.5 and 5%, w/w). XRD, TEM, SEM, FTIR and rheological studies confirmed the formation of nanocomposites with partial exfoliated structure of the nano-clay. The study demonstrated that the tensile strength enhanced from 4 to 11.4 MPa, scratch hardness improved by two-fold, gloss value increased by 20 units, adhesive strength improved by two-fold and thermal stability improved by 19 °C on incorporation of 5 wt% of nano-clay with respect to the pristine polymer. The limiting oxygen index value and UL94 test indicated improvement of flame retardancy of the nanocomposites. The results exhibit the potentiality of these bio-based epoxy/clay nanocomposites for multifaceted advanced applications.     

Nanostructure and dynamic mechanical properties of silane-functionalized montmorillonite/epoxy nanocomposites

In this work sodium montmorillonite (Na-MMT) was functionalized with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane and the corresponding silylated clay was used to modify epoxy matrix cured with triethylenetetramine. The grafting/intercalation of the aminosilane inside the clay galleries were followed by infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and ²⁹Si cross-polarization magic-angle-spinning nuclear magnetic-resonance (CP/MAS NMR) spectroscopy. Epoxy-based nanocomposites were prepared with different amounts of silylated clay or commercial organoclay, Cloisite 30B, whose intercalating agent consists of a methyl, tallow, bis-2-hydroxyethyl quaternary ammonium salt. The degree of intercalation/exfoliation was estimated by X-ray diffraction experiments and confirmed by small angle X-ray scattering. Nanocomposites prepared with silylated clay displayed no peak in both XRD and SAXS curves whereas those prepared with Cloisite 30B exhibited a clear interference peak corresponding to an interlayer spacing d₀₀₁ of 4.1 nm. The former also presented a better dispersion, with a high proportion of tactoids smaller than 2 nm, as estimated by SAXS. From the results of dynamic mechanical analysis it was observed that most of the nanocomposites display higher storage modulus mainly at temperatures above the glass transition temperature. The glass transition temperature is similar or higher than the neat epoxy network for nanocomposites containing 1 wt.% of silylated clay or higher.     

Macromolecular recognition by cyclodextrins. Interaction of cyclodextrins with polymethacrylamides bearing hydrophobic amino acid residues

The interaction of cyclodextrins (CDs) with poly(N-methacryloyltryptophan) (pMTrp) and with poly(N-methacryloylphenylalanine) (pMPhe) was investigated as a simple model system of macromolecular recognition of proteins. The association constants (K) for the model compounds, sodium salts of tryptophan and phenylalanine, are not so different (i.e. 43 and 16 M⁻¹ for α-CD, 59 and 69 M⁻¹ for β-CD, and 12 and 3 M⁻¹ for γ-CD, respectively). On the other hand, there is a significant difference in the apparent K values for pMTrp and pMPhe (i.e. the K values for pMPhe are considerably smaller than ca. 10 M⁻¹, whereas those for pMTrp are 30, 83, and 11 M⁻¹ for α-, β-, and γ-CDs, respectively). These observations indicate that a subtle difference in polymer side chains can be critical in macromolecular recognition.     

The effect of water and guest hydrophobicity on the complexation of oligomers with solid α-cyclodextrin

α-Cyclodextrin (α-CD), a cyclic oligosaccharide, can form inclusion complexes (ICs) with polymer molecules in which α-CD molecules stack in the columnar crystal to form a molecular tube. Physical mixtures of α-CD powder and oligomeric liquids such as poly(ethylene glycol) (PEG) have been shown to spontaneously form an IC, which is accompanied by a solid-state α-CD phase transformation from the cage to the columnar crystal structure. In this paper, the phase transformation is tracked with wide-angle X-ray diffraction as a function of temperature, atmospheric water vapor content and the type of guest molecule. A first-order kinetic model is used to describe the kinetics of complexation. The time required to completely complex PEG200 (200 g/mol) at low water activities is greater than 300 h, whereas only a few hours are necessary at high water activities. Solid-state complexation of α-CD with a hydrophobic guest molecule (hexatriacontane, HTC), is also reported here for the first time. Slower complexation kinetics are observed for α-CD with HTC compared to PEG600 (600 g/mol).     

Rheological characterization of polystyrene-clay nanocomposites to compare the degree of exfoliation and dispersion

Polymer-clay nanocomposites are of great interest due to their improvement in certain material properties relative to virgin polymer or conventional composites. For example, compared to conventional materials, Nylon 6/montmorillonite nanocomposites demonstrated significant improvements, including high strength, high modulus and high heat distortion temperature. Because viscoelastic measurements are highly sensitive to the nanoscale and mesoscale structure of polymeric materials, when combined with X-ray scattering, electron microscopy, thermal analysis, and mechanical property measurements, they will provide fundamental understanding of the state and mechanism of exfoliation of the layered silicate (clay) in a polymer matrix. In addition, understanding rheological properties of polymer nanocomposites is crucial for application development and understanding polymer processability.The objective of this research is to develop a rheological technique to analyze the clay morphology in nanocomposite. Previous work has demonstrated the utility of the rheological technique to differentiate (qualify) the degree of exfoliation/dispersion. This report utilizes findings from the earlier work to further map out the structure-rheological response of polystyrene nanocomposites with various composition, clay types, and dispersion; and to quantify the key parameter that dominates the characteristic rheological response. This report explored a series of polystyrene (PS)-clay nanocomposites with 1,2-dimethyl-3-n-hexadecyl imidazolium (DMHDI) organically modified clays. These PS nanocomposites investigated here demonstrated a change of pattern in dynamic mechanical spectrum, as a function of the degree of exfoliation, from typical polymer response to a terminal response of [G′∼ω, G″∼ω], then to a pattern with double crossover frequencies, and finally to a solid-like response with G′>G″ in all frequency ranges. We showed that the number of particles per unit volume is a key factor determining the characteristic response of nanocomposites.In addition, the rheological response of PS-clays nanocomposite made from DMHDI modified clay combined with high-energy sonication (characterized as exfoliated by XRD and TEM) was compared with that of nanocomposites made by dimethyl, benzyl hydrogenated tallow (2MBHT) modified clay. We found that PS nanocomposites made by DMHDI-modified clay with high-energy sonication are better dispersed than the nanocomposites made previously using 2MBHT-modified clay. We also showed that the glass transition temperatures were not very sensitive to the degree of dispersion.The key finding of this research is that rheological measurements are complimentary to traditional polymer nanocomposite analysis techniques, and they may also serve as an analytical tool by itself (under appropriate conditions), now that some fundamental behavior has been identified.     

Suprarmolecular hydrogels driven by the dual host–guest interactions between α-cyclodextrin and ferrocene-modified poly(ethylene glycol) with low-molecular-weight

In general, α-cyclodextrin (α-CD) and low-molecular weight poly(ethylene glycol) (low-MW PEG) (M_w = 400–10,000) cannot construct supramolecular hydrogels but easily form crystalline precipitates. In this study, low-MW PEG (M_n = 2000, PEG-2000) was functionalized by ferrocene as mono-end-group. The obtained ferrocene-modified PEG-2000 (FcPEG-2000) further self-assembled into supramolecular hydrogel with α-CD even at low concentration (C_FcPEG-2000 = 17 mg/ml), driven by dual host–guest interaction between α-CD and FcPEG-2000. Interestingly, the hydrogel was still observed even when hydrophobic Fc group was oxidized to hydrophilic ferrocenium (Fc⁺) or included into the cavity of β-CD. In the former case, the existence of Fc⁺ end groups is considered to decrease the probability of PEG de-penetration from α-CD cavity, so that α-CDs have more location and opportunities to aggregate into more channel-type crystalline domains as physical cross-linking points. While in the later case, the synergistic effect of host–guest interaction between β-CD and ferrocenyl groups and host–guest interaction between α-CD and PEG chains are considered to be the main reason. The resultant FcPEG-2000 based hydrogels showed the property of shear-thinning.