Search

A bolaamphiphile contains a hydrophobic skeleton and two water-soluble groups on the both ends. Bolaamphiphile forms thermally stable associates in water under lower concentration than those of typical mono-headed amphiphiles, indicating the potential usefulness of bolaamphiphile as the component of nano-materials. However, the structural diversity of bolaamphiphiles is limited at this moment. Herein, we show the bolaamphiphilic properties of naturally occurring quercetin glycosides. In addition to natural flavonoids, quercetin (Que) and isoquercitrin (IQ), we have prepared quercetin polyglycoside (QP) via one-pot grafting polymerization using sugar-based cyclic sulfite as a monomer, which plays a crucial role to elucidate the effects of sugar chain length on the micellization. The micellization behaviors of QP are systematically investigated through the comparison with those of Que and IQ. The polyphenolic structures of quercetin derivatives exhibit unique pH-dependency of critical micelle concentration (CMC). While Que hardly forms micelles in pH 10.0 aqueous medium, the solutions of IQ and QP form micelles in the same medium, indicating that the sugar chain would endow the micelles with pH-tolerance. The effects of sugar chain length on the micellization behaviors are discussed through the time-course of UV-vis spectra and the profiles of dynamic light scattering (DLS) analyses. The morphology of the micelles bearing QP is observed by transmission electron microscopy (TEM), suggesting the formation of bolaamphiphile-specific helical ribbon-like micelles. It is indicated that the polysaccharide chains integrated on the surface of micelle would serve as a steric protecting group to afford kinetically stable micelles.

Polysaccharide is a naturally abundant material, which is regarded as an indispensable scaffold for a structural material. The properties of polysaccharides are dependent not only on the structure of repeating sugar unit but also the glycosidic position between the repeating units. Herein, we report the development of polysaccharide-based self-standing film consisting of naturally occurring (1 → 2)-glucopyranan skeleton. The self-standing film of (1 → 2)-glucopyranan derivative with hexyl carbamate groups

A series of alternating peptides with glycine-N-substituted valine dipeptide repeating units were synthesised. The N-substitution included methyl, ethyl, n-propyl, and hydroxyl groups. The performa...

Tough hydrogels with facile processability to reform into various shapes are required in many practical applications. In this work, we reported that a novel, tough, and self-healing physical hydrogel based on polyion complex (PIC) can be dissolved in 4 M NaCl solution to form a PIC solution. The PIC solution can be easily reprocessed into various shapes, such as thin films, sheets, fibers, and capsules, by using simple methods, such as casting and injection, while maintaining excellent mechanical properties comparable to, or even better than, the original hydrogel. The reprocessability and robust mechanical properties of PIC hydrogels are promising for practical applications in soft materials, especially in 3D/4D printing technology.

α-Galactosyl ceramide (GalCer) is an anticancer glycolipid consisting of d-galactose and phytosphingosine-based ceramide. Although the amphiphilic structure of GalCer is expected to form self-associates in water, the self-assembly behaviors of GalCer and its derivatives have not been systematically investigated at this moment in spite of its great importance. The evaluation of morphologies and properties of the associates should open new insights into glycolipid chemistry such as the application of GalCer derivatives to a nanocarrier and the elucidation of the detailed pharmacological mechanism of GalCer. Herein, we show the synthesis of the aglycon fragment (Aglycon) of GalCer and the self-assembly behaviors of both GalCer and Aglycon in water. The critical aggregation concentrations of Aglycon and GalCer were determined using UV-vis spectral measurements at various concentrations. The transmission electron microscopy observations of the aqueous sample solutions indicated that the solution of GalCer includes vesicles, while that of Aglycon comprises giant micelles in the absence of vesicles. The vesicle formation in the solution of GalCer was also confirmed by Triton X-100-triggered dye-release experiments. To reveal the effects of glycon on the self-assembly behaviors in detail, we performed the measurements of dynamic light scattering, temperature-dependence of turbidity, differential scanning calorimetry, and wide-angle X-ray diffraction. The results clarify that the glycon moiety of GalCer has a significant role in the formation inhibition of second associates and the plasticization of the hydrophobe. This work will shed light on the other natural glycosides to evaluate the self-assembly behaviors for supramolecular and pharmacological applications in the near future.

The development of new peptide-based glues has been strongly urged from the viewpoints of industrial applications and biomedical engineering. However, the large-scale synthesis of polypeptides with an ordered sequence is highly challenging, which strictly restricts materials resources for the research and development of polypeptides. In this work, the framework of adhesive alternating peptides has been designed to be glycine (Gly)-N-substituted valine (Val) as the dipeptide repeating sequence, considering the peptapeptide repeating sequence of viscoelastic natural elastin as a motif. The alternating peptides are prepared via three-component polymerization exploiting Ugi four-center three-component reaction as the elemental polymerization reaction. The adhesive strength (SAdh ) values of the polymers are evaluated by a shear adhesive test method using two glass plates. Alternating peptides with Gly-N-benzylated Val dipeptide repeating units exhibit the optimal adhesive properties such as much higher SAdh than that of conventional fibrin glue and a unique readhesion capability. It is indicated that the remarkably high SAdh would be attributed to the shear-induced structural change of single polymer chain, the slow relaxation of extended structure, and the weak interchain interactions. Due to the favorable adhesive properties of alternating peptides, these adhesives may be highly suitable for real-world applications.

A bolaamphiphile is a special member of amphiphilic molecules, which contains a hydrophobic skeleton and two water-soluble groups on both ends. Bolaamphiphiles form thermally stable associates in water under lower concentration than those of typical monoheaded amphiphiles, indicating the potential usefulness of bolaamphiphiles as the component of nanomaterials. However, the structural diversity of bolaamphiphiles is limited at this moment. We recently developed the synthesis of quercetin-3-O-polyglycoside (QP) as a new entry of bolaamphiphiles via a one-pot polymerization using sugar-based cyclic sulfite initiated by quercetin skeleton. Herein, we show the bolaamphiphilic properties of QP in detail. The micellization behaviors of QP are systematically investigated through comparison with those of quercetin (Que) and isoquercitrin (IQ) to evaluate the roles of glycone on the micellization of quercetin derivatives. The morphology of the micelles bearing QP is observed by cryo-transmission electron microscopy (cryo-TEM), suggesting the formation of bolaamphiphile-specific giant ribbon-like micelles in addition to spherical micelles. The thermoresponsive micellization behaviors are also discussed through the critical micelle concentration (CMC) values, the dynamic light scattering analyses at various temperatures, and thermal hysteresis of the micellizations. It is indicated that the polysaccharide chains integrated on the surface of micelles would serve as a steric protecting group to endow the micelles with kinetic stability. These results will shed light on natural glycoside skeletons to design a new class of micelles for advanced health applications in near future.

We have prepared benzylated glucopyranans and evaluated the structural effects on the adhesion capacity. It was found that 97%-benzylated (1→2)-glucopyranan exhibited a unique shear-induced adhesion. The effects of structural factors on the adhesion behaviors are discussed through systematic adhesion tests, differential scanning calorimetry, theoretical models, and IR spectroscopy.

Quercetin polyglycoside as a new bolaamphiphile is prepared via a one-pot grafting polymerization technique using sugar-based cyclic sulfite. Micelles comprising quercetin polyglycoside exhibit special pH-effects, in which the polyglycoside moieties on the surface of the micelle serve as a steric protecting group to endow chemical stabilization.

This paper describes the experimental elucidation for the impact of polypeptide sequence on the solution structure and the thermo-responsivity, having considered the corresponding theoretical prediction using a binary pattern of hydrophobic and hydrophilic units. We prepare diblock, random, and alternating copolymers consisting of a stoichiometric amount of valine as a hydrophobic unit and glycine as a hydrophilic unit. Through the thermo-responsivity measurements of aqueous polymer solutions, it is found that the UV spectra of diblock copolypeptide exhibit a cloud point upon heating, which indicate that the polymer adopts a random coil structure at low temperature. On the other hand, the alternating peptide shows an upper critical solution temperature (UCST) behavior indicating a globule-to-coil transition upon heating. The opposite behavior of alternating peptide to that of diblock copolypeptide is found to be dependent on not the chirality of repeating units but the alternating binary pattern of hydrophobic and hydrophilic units. The random copolypeptide exhibits not only coil-to-globule transition at low temperature but also globule-to-coil transition at high temperature owing to the presence of both segregated and alternating polymer sequences in the polymer. The thermo-responsive structures of the polymers in an aqueous media are also discussed by determining the thermodynamic parameters for the transitions.

Saccharification of a glass surface has been performed using two grafting methods: grafting-from and grafting-onto, using a sugar-based cyclic sulfite as monomer. Central to the technique is a cati...

We developed 2,5-furanylene sulfide-containing polymers bearing different spacers as repeating units and evaluated the interactions between the furanylene sulfide units in the polymers. The treatment of 2,5-dichlorofuran derivatives with dithiolates at 200 °C promotes polycondensation via nucleophilic aromatic substitution to give the corresponding furanylene sulfide-containing polymers. Tensile measurements and spectral analyses demonstrate that the furanylene sulfide moieties form remarkably stable π–π stacking structures based on the enhanced dipole moment induced by sulfur linkages. When the polymer has a long spacer between repeating furanylene sulfide units, the polymer behaves as a chemically stable network polymer comprised of π–π stacking structures as cross-linking units. We developed 2,5-furanylene sulfide-containing polymers bearing different spacers as repeating units and evaluated the interactions between the furanylene sulfide units in the polymer. Treatment of a 2,5-dichlorofuran derivative with dithiolates at 200 °C promotes polycondensation via nucleophilic aromatic substitution to give the corresponding furanylene sulfide-containing polymers. Through tensile measurements and spectral analyses, it was found that the furanylene sulfide moieties form remarkably stable π–π stacking structures based on the enhanced dipole moment induced by sulfur linkages. When the polymer has a long spacer between repeating furanylene sulfide units, the polymer behaves as a chemically stable network polymer comprised of π–π stacking structures as cross-linking units.

A new species of fluorinated polymer surfactant was developed by three component polycondensation analogous to Ugi four-component condensation. The surfactant exhibited unique surface properties, which made cellulose-based materials hydrophobic and decreased the surface tension of CHCl3. It turned out that the polymer forms micelles in CHCl3.

A series of N-substituted poly(Gly&ndash, alter&ndash, Val) peptides were successfully synthesized for the systematic evaluation of the micellization behavior of alternating peptides. Three-component polymerization employing an aldehyde, a primary ammonium chloride, and potassium isocyanoacetate afforded four alternating peptides in excellent yields. We investigated the dependence of the hydrophilic&ndash, lipophilic balance of alternating peptides on the micellization behavior. All the aqueous solutions of alternating peptides exhibited upper critical solution temperature (UCST) behaviors, strongly indicating that the alternating binary pattern would mainly contribute to the UCST behaviors. The cloud points of alternating peptides shifted to higher temperatures as the side chains became more hydrophilic, which is opposite to the trend of typical surfactants. Such unusual micellization behaviors appeared to be dependent on the quasi-stable structure of single polymer chains formed in water.

Oppositely charged homopolyelectrolytes were found to form strong, tough, and self-healing polyion-complex (PIC) hydrogels, similar to polyampholytes (PA) which have opposite charges randomly distributed on the same polymer chains. The excellent mechanical performances of these two novel hydrogels are the results of dynamic ionic bonds formation between entangled polymer chains. For the PIC system, only interchain bonding occurs, while for the PA system both inter- and intrachain bonding exist. In addition, the ion pairs are expected to form stronger bonding in the PIC system than those in the PA system. In this work, we performed a comparative study of PIC hydrogels with the PA hydrogels. The PIC hydrogels are synthesized by sequential homopolymerization of cationic and anionic monomers at varied formulation, and their swelling and mechanical properties are systematically studied in comparison to the PA hydrogels that were synthesized from random copolymerization of anionic monomers and cationic monomers of the similar formulation. Different from the PA system which only forms tough hydrogels around zero net charge composition without chemical cross-linking, the PIC system forms tough physical hydrogels even at weakly offbalanced charge composition. At the charge-balanced composition, the low entanglement concentration of homocharged polyelectrolyte chains leads to tough PIC hydrogels formation at much lower concentrations than that of PA hydrogels. As a result, the PIC hydrogels are much tougher than the PA hydrogels prepared at the same monomer composition. In similar to PA hydrogels, the PIC hydrogels also exhibit broad dynamic mechanical spectra, indicating the formation of ion complexes with widely ranged bond strength. The PIC hydrogels have strong viscoelasticity in comparison with PA hydrogels. However, the two systems show the similar activation energies of the dynamic mechanical spectra. The SEM microstructural observation shows that the PIC hydrogels have segregated structure while PA hydrogels are more homogeneous.

Developing nonspecific, fast, and strong adhesives that can glue hydrogels and biotissues substantially promotes the application of hydrogels as biomaterials. Inspired by the ubiquitous adhesiveness of bacteria, it is reported that neutral polyampholyte hydrogels, through their self-adjustable surface, can show rapid, strong, and reversible adhesion to charged hydrogels and biological tissues through the Coulombic interaction.

A series of tough polyion complex hydrogels is synthesized by sequential homopolymerization of cationic and anionic monomers. Owing to the reversible interpolymer ionic bonding, the materials are self-healable under ambient conditions with the aid of saline solution. Furthermore, self-glued bulk hydrogels can be built from their microgels, which is promising for 3D/4D printing and the additive manufacturing of hydrogels.

Recently, we have reported that polyampholytes, synthesized from free radical copolymerization of anionic monomer and cationic monomer, form physical hydrogels of high toughness and self-healing. The random distribution of the opposite charges forms ionic bonds of a wide distribution of strength. The strong bonds serve as permanent cross-links, imparting elasticity, whereas the weak bonds serves as reversible sacrificial bonds by breaking and reforming to dissipate energy. In this work, we focus on the rupture behaviors of the polyampholyte physical hydrogel, P(NaSS-co-MPTC), copolymerized from sodium p-styrenesulfonate (NaSS) and 3-(methacryloylamino)propyltrimethylammonium chloride (MPTC). Tensile test and pure shear test were performed at various stretch rates in the viscoelastic responses region of the material. Tensile test showed yielding, strain softening, and strain hardening, revealing the dually cross-linked feature of the gel. Pure shear test showed crack blunting at the notched tip and a large yielding zone with butterfly shaped birefringence pattern ahead of the crack tip. After blunting, crack advanced at steady-state velocity with a constant angle. The conditions for the occurrence of crack blunting and variables governing the crack advancing angle are discussed. We found that even for these highly stretchable samples, significant blunting only occurs when the tensile fracture stress σf is larger than modulus E by a factor of about 2, in consistent with Hui’s theoretical prediction for elastic materials. The crack advancing angle θ was found to be proportional to σy/E over a wide stretch rate range, where σy is the yielding stress. In addition, the fracture energy was correlated to small strain modulus by a power law in the viscoelastic response region. This systematic study will merit revealing the fracture mechanism of tough viscoelastic materials including biological tissues and recently developed tough and highly stretchable hydrogels.

Hydrogels attract great attention as biomaterials as a result of their soft and wet nature, similar to that of biological tissues. Recent inventions of several tough hydrogels show their potential as structural biomaterials, such as cartilage. Any given application, however, requires a combination of mechanical properties including stiffness, strength, toughness, damping, fatigue resistance and self-healing, along with biocompatibility. This combination is rarely realized. Here, we report that polyampholytes, polymers bearing randomly dispersed cationic and anionic repeat groups, form tough and viscoelastic hydrogels with multiple mechanical properties. The randomness makes ionic bonds of a wide distribution of strength. The strong bonds serve as permanent crosslinks, imparting elasticity, whereas the weak bonds reversibly break and re-form, dissipating energy. These physical hydrogels of supramolecular structure can be tuned to change multiple mechanical properties over wide ranges by using diverse ionic combinations. This polyampholyte approach is synthetically simple and dramatically increases the choice of tough hydrogels for applications.

Our recent study has revealed that neutral polyampholytes form tough physical hydrogels above a critical concentration Cm,c by forming ionic bonds of wide strength distribution. In this work, we systematically investigate the behavior of a polyampholyte system, poly(NaSS-co-DMAEA-Q), randomly copolymerized from oppositely charged monomers, sodium p-styrenesulfonate (NaSS) and acryloyloxethyltrimethylammonium chloride (DMAEA-Q) without and with a slight chemical cross-linking. A phase diagram of formulation has been constructed in the space of monomer concentration Cm and cross-linker density CMBAA. Three phases are observed for the as-synthesized samples: homogeneous solution at dilute Cm, phase separation at semi-dilute Cm, and homogenous gel at concentrated Cm. Above a critical Cm,c, the polyampholyte forms a supramolecular hydrogel with high toughness by dialysis of the mobile counter-ions, which substantially stabilizes both the intra- and inter chain ionic bonds. The presence of the chemical cross-linker (CMBAA > 0) brings about a shift of the tough gel phase to lower Cm,c. The tough polyampholyte gel, containing [similar]50 wt% water, is highly stretchable and tough, exhibits fracture stress of σb [similar] 0.4 MPa, fracture strain of εb [similar] 30, and the work of extension at fracture Wext [similar] 4 MJ m−3. These values are at the level of most tough soft materials. Owing to the reversible ion bonds, the poly(NaSS-co-DMAEA-Q) gels also exhibit complete self-recovery (100%) and high fatigue resistance upon repeated large deformation.