Volume 46 Issue 9, September 2014

The universal control of cell functions at single-cell level through artificial modulation of extracellular microenvironments by mimicking the natural extracellular matrices (ECMs) would be a key technique for biomedical fields. In the present review, fabrication of nanometer-sized artificial ECM films using various polymers and proteins on single-cell surfaces to control cell functions is described. The simple coating techniques reported here have opened a new window as a key technique for control of the extracellular microenvironments in tissue engineering, pharmaceutical and pathophysiological fields.

The interaction between synthetic particles and proteins has been studied to identify factors that govern the interaction in vitro. The composition and properties of the protein corona that forms on the surface of NPs have been studied in vivo. Recently, synthetic NPs that recognize target molecules are designed and prepared by optimizing the combination of functional groups on the particles, molecular imprinting, in combination with the affinity purification. Some particles are capable of recognizing target molecules and neutralizing their function, in the bloodstream of living animals, as ‘plastic antibodies.’

An effective synthetic method for the transformable polymer was developed by the introduction of a rotaxane structure into the polymer system. The interaction between a sec-ammonium and a dibenzo-24-crown-8-ether was the key for the synthesis of mechanically linked poly(δ-valerolactone) without desllipage of wheel component during the polymerization. After the acetylation of the ammonium moiety, the crown ether having a polymer chain was able to move along the axle polymer to reach the urethane linkage at the ω-end in a non-polar solvent.

Main chain-type liquid crystalline (LC) polyrotaxanes were synthesized via the ene-thiol copolymerization of pseudorotaxane and LC monomers. The effects of the rotaxane moiety and its content on LC properties were investigated using differential scanning calorimetry. Introduction of the rotaxane moiety on the LC polymer reduced the stabilization of the LC phase. Neutralization of the rotaxane moiety also destabilized the LC phase, probably due to the movable wheel components of the rotaxane on the axle LC polymer chain.

Chitosan phenylcarbamate (CtsPC) samples were synthesized and their lyotropic liquid crystallinity in ionic liquids was investigated. 1-Ethyl-3-methylimidazolium dicyanamide ([C2Mim][N(CN)₂]) was found to be a novel solvent for CtsPC, and the lyotropic system formed a cholesteric liquid-crystalline phase and exhibited vivid colorations owing to selective light reflection. The cholesteric helical pitch was controllable by polymer concentration, temperature or the degree of phenylcarbamoyl substitution. Although the helical sense of CtsPC/[C2Mim][N(CN)₂] cholesterics remained right-handed under the adopted measurement conditions, an inversion of cholesteric sense was achieved by using a mixed solvent of [C2Mim][N(CN)₂]/N,N-dimethylformamide.

It was discovered that a novel blend of two super-engineering plastics, poly(p-phenylene sulfide) (PPS) and poly(phenylsulfone) (PPSU), has partial miscibility. The partial miscibility and the segmental mobility of PPSU at ∼–100 °C most likely contribute to remedy brittleness of PPS effectively. SAXS measurements revealed that segregation of PPSU chains during melt crystallization of PPS results in intrusion of PPSU chains into the amorphous region between PPS lamellae. TGA measurements under a nitrogen atmosphere demonstrated that the thermal stability of PPS blends is significantly improved upon the addition of PPSU.

Poly(NDI)s are a versatile class of polymers, which have been recently utilized as cell adhesion materials, membranes, insulating materials and in various optics applications. A well-controlled and clean polymerization profile is essential for successful manipulation of important physical properties such as glass transition temperature, decomposition temperature, refractive index, trans–cis content and molecular weight. We have investigated the ROMP of N-cyclohexyl-exo-norbornene-5,6-dicarboximide using four common initiators, Grubbs 1, Grubbs 2, Hoveyda–Grubbs 1 and Hoveyda–Grubbs 2. Only Grubbs 1 was found to be able to control the polymerization successfully, leading to a fine control over the molecular weight and associated physical properties.

Clarifying the relationship between structure and viscoelastic properties of novolac resins, having different molar mass and different methylene linkage pattern content, by GPC, NMR, rheology and dynamic birefringence analysis.

We tried to prepare a gel material enclosed in many compartments, inspired by plant body framework. According to this concept, hydrogels reinforced by polymer foam were fabricated, and their mechanical properties were investigated. We prepared sodium acrylate hydrogels reinforced by open-cell polyurethane foams. After the gelation, the mechanical properties were assayed by the compression test. The compression strength of the composite gel was ∼2 MPa, which was much higher than that of poly(sodium acrylate) hydrogel alone; and the compression modulus was also considerably higher than that of each constituent material alone.

Ring-opening copolymerization of caprolactone and glycidyl methacrylate can generate cyclic and linear double-bond-functionalized copolymers. These polymers can be cross-linked by thiol–ene click reaction, and/or radical copolymerized with 2-hydroxyethyl methacrylate. Networks having interesting and variable damping properties were obtained.

Fluorescent poly(boron enaminoketonate)s (PBEKs) were synthesized via polycycloaddition of homoditopic nitrile N-oxide to diynes and subsequent polymer reactions. Click polycycloaddition of the nitrile N-oxide to various diynes effectively produced polyisoxazoles in high yields. Transformation of the polyisoxazoles afforded the corresponding fluorescent PBEKs via intermediary formation of poly(β-aminoenone) followed by the reaction with (C₆F₅)₂BF·OEt₂. The optical properties of PBEKs were evaluated by the UV–vis and fluorescent spectra obtained under solution and solid states.

Small-angle X-ray scattering (SAXS) was measured from the aqueous solutions of polyion complexes (PICs), prepared with isoelectrical mixing oppositely charged two block copolymers MAPTAC-b-PMPC and AMPS-b-PMPC. The ratio (R_p) of the polymerization degree of the cationic to the neutral chains was changed from 0.27 to 9.5. When R_p is 0.27, 4.7 and 9.5, PICs took a star-like spherical, a cylindrical and vesicle-like shape, respectively. We found how tethered PMPC chains are crowded on the shell, and this parameter was much smaller than those of PEG in spherical core-shell polymeric micelles.

Dispersion of C₆₀/silica nano-composite, prepared by inclusion of C₆₀ into grafted polymer chains on silica, in organic solvent and poly(methyl methacrylate) (PMMA) matrix was investigated. The polymer-grafted SiO₂ particles were prepared by grafting of poly(methyl methacrylate-co-2-naphthyl methacrylate) onto colloidal silica of 9.1 nm in diameter. Inclusion of C₆₀ into the grafted polymer chains was significantly dependent on molecular weight of the polymer and independent on amounts of grafted polymer. The C₆₀/SiO₂-PMMA hybrid film, composed of 0.21% C₆₀ and 10% SiO₂, showed high transparency in visible light region.

Dithienogermole-dithienylbenzothiadiazole alternating polymers with high molecular weights were synthesized. Optical properties of the polymers were investigated with respect to UV-Vis absorption spectroscopy, indicating that the polymer electronic states are highly dependent on the molecular weight, and the nature and position of substituents on the dithienylbenzothiadiazole units. Photovoltaic properties of the polymers in bulk heterojunction-type polymer solar cells were also examined as blend films with PC₇₀BM, affording the power conversion efficiencies of 1.04-3.83%.

We developed a very quick and convenient preparative method for an injectable polymer (IP) formulation to overcome solubility problems of IPs. We investigated the effects of various additives on the dispersion time and gelation behavior for triblock polymers composed of poly(ɛ-caprolactone-co-glycolic acid) (PCGA) and PEG, and found that the addition of PEG with appropriate molecular weight was the best for quick preparation of IP suspension exhibiting temperature-responsive sol–gel transition. This method should be very convenient for usage at clinical scene.