Articles in 2013

The polysilsesquioxanes containing tetra(ethylene glycol) chains were newly prepared and modified by several kinds of hydrophobic components. The obtained polysilsequioxane derivatives showed a reversible thermoresponsive aggregation behavior in an aqueous solution. The introduction of azobenzene structure as the hydrophobic component led to the polysilsesquixane that showed the combined photo- and thermostimuli responsive properties.

Rotating ring-shaped microtubule assemblies were successfully formed on dynein-coated surface through active self-organization process in a similar way to kinesin. However, no preferential direction of rotation was observed in contrast to the aforementioned results of previous kinesin studies. This indicates that dynein is less sensitive to the experimental condition than kinesin.

Surface texturing of catechol derivative urushiol was achieved using a thermal imprinting technique. An indented surface was obtained by thermal curing at 100 °C for 10 min while pressing an urushi film with a patterned mold. The indented surface enhanced the static water contact angle in comparison with the flat urushi film.

Biomimetic dimpled and multilayered films containing black thin layers, which had multi-angle reflectivity, were successfully prepared by embossing microlens arrays on the multilayered films.

The synthesis of amphiphilic poly(dimethylsiloxane) derivatives with quaternized imidazolium salts having alkyne group was achieved. The introduction of the alkyne group enabled coupling with azide-functionalized fluorescent dyes and green fluorescent protein by the click reaction using a copper catalyst. Fluorescence-labeled o/w emulsions were successfully formed using the labeled polymers. Therefore, these polymers would be useful for drug delivery by conjugating cell-specific targeting molecules by the click reaction.

The injection-molded isotactic polypropylene (PP) containing a specific nucleating agent exhibits unique molecular orientation. Although the skin layer has ‘woven-cloth’ structure, in which α- and β-form crystals orient perpendicular to each other, it shows positive birefringence on average because of the stronger orientation of α-form crystals. In the core, both crystals show perpendicular orientation to the flow direction. As the average orientation direction in the skin layer is perpendicular to that in the core, the anisotropy in mechanical properties and thermal expansion is greatly reduced.

Poly(vinylbenzyl chloride) (PVBC) with controlled molecular weight and polydispersity was obtained by reversible addition-fragmentation chain transfer (RAFT) polymerizations of vinylbenzyl chloride using benzyl ethyl trithiocarbonate as the RAFT agent. Furthermore, amphiphilic AB diblock copolymers PVBC-b-PNIPAMs could be successfully prepared by RAFT polymerization of N-isopropylacrylamide (NIPAM) by using PVBC macro-RAFT agent.

One step method for the fabrication of electospun nanofibrous membranes (ENMs) with hydrophilic surfaces and improved flux via in situ polymerization technique is described. The developed membranes also possess enhanced antifouling properties when compared with the virgin PVDF polymer.

Thermo-responsive liquid marbles can be prepared using poly(N-isopropylacrylamide) powder and Na₂SO₄ aqueous solution, which were transferred to the surface of bulk water containing Na₂SO₄ aqueous solution. They remained stable at room temperature. When the bulk aqueous solution was cooled, the liquid marbles disintegrated because powder wettability increased. Thus, the remote triggering of chemical reactions using liquid marbles can be achieved by cooling.

π-Conjugated polymers attract attention from showing not only an interesting electric and optical property but also workability. The random co-oligomers with N-cyclohexylmaleimide and N-substituted carbazole in the main chain were carried out by Yamamoto coupling reaction. The co-oligomers showed the fluorescence color of red from blue. Especially, when 2,7-dibromo-N-hexylcarbazole was used as the monomer, the fluorescence color of the resulting co-oligomer changed from magenta to blue by the difference of polarity of solvent.

The aim of this study is to establish the factors that affect the formation of polyion complex (PIC) vesicles. The effects of anionic segment length of PEG-PAsp_y, and chemical structure of the side chains of Homo-P(Asp-Cn)_x on the properties of PICs were carefully examined. It was found that PEG weight fraction (f_PEG) has a significant role in determining the PIC morphologies as PICs with f_PEG <10% formed submicron/nanosized polyion complex vesicles (Nano-PICsomes), whereas micelles were selectively fabricated at f_PEG >10%. In addition, Homo-P(Asp-Cn)_x containing five and six carbon atoms on the aliphatic spacers in their side chains facilitated the formation of Nano-PICsomes (compared with the shorter ones). These findings shed new light on how to control the structure and properties of PIC assemblies for diverse material applications.

Nanocomposites based on ethylene-acrylic acid copolymer (EAA) and polyhedral oligomeric silsesquioxanes (POSS) molecules were prepared by melt mixing: partial cage POSS with different pendent organic groups were used to investigate the interaction between the –OH POSS’s groups and the acrylic functionalities of the matrix. All measured properties of EAA/POSS nanocomposites are the result of two contrasting phenomena, particularly, the plasticizer and reinforcement effect. Moreover, the properties of up generation nanocomposites depend significantly on the presence of some functionalities in the components and on possible interaction between them.

Two polystyrene-based amphiphilic diblock copolymers, PS(x)-PV(y) and PS(x)-PA(y) (where PS(x)-PV(y) and PS(x)-PA(y) possess poly[(ar-vinylbenzyl)trimethylammonium chloride] and poly(2-acrylamido-2-methylpropanesulfonic acid) blocks, respectively, and x and y are the degrees of polymerization), were prepared by reversible addition-fragmentation chain transfer radical polymerization to investigate their formation of reverse micelles in less polar organic media. Theoretical analysis using light scattering data indicated that PS(x)-PV(y) formed star-like micelles at x/y>6 and brush-like micelle micelles at x/y<6 in DCE.

We prepared imidazolium-containing silica hybrid films by sol–gel reactions of 1-(trimethoxysilylpropyl)-3-methylimidazolium chloride under microwave irradiation. Furthermore, we incorporated hydrophobic dyes such as pyrene and 1-pyrenecarboxaldehyde into the silica hybrids, and we investigated dispersion behaviors of these dyes in the matrices. It was suggested that the local heating of the imidazolium groups caused under microwave irradiation contributed to the enhancement to reaction rates in the sol–gel process. Finally, we established to incorporate higher concentration of the dyes into the silica hybrids as compared with the conventional heating.

In this paper, we have studied the effects of increasing poly(methyl methacrylate) (PMMA) concentration on the triboluminescent properties of europium dibenzoylmethide triethylammonium (EuD₄TEA). The research shows that the amount of PMMA could be increased such that the EuD₄TEA PMMA polymer could be sensitive to selective minimum energies. Thus, a functional triboluminescent polymer was successfully obtained for the first time.

Mean-square radii of gyration <S²> for two polystyrene samples in toluene and 2-butanone and a cyclic amylose tris(phenylcarbamate) (cATPC) sample in tetrahydrofuran were determined by SAXS between −77 and 70 °C. Whereas <S²> of cATPC does not depend on temperature over the range investigated, those for polystyrene depend to a significant degree. The characteristic ratio for polystyrene in toluene monotonically decreases with increasing temperature. However, that in 2-butanone has a minimum ∼10 °C, suggesting that the RIS energy parameters are affected by the intermolecular interactions between the polymer and solvent.

The solvent evaporation rate in the production of three types of poly(vinylidene fluoride) (PVDF) crystalline structures by using the solvent casting method was quantified. The PVDF crystalline structures were predominantly determined by solvent evaporation rate. PVDF (form I) was obtained when the solvent evaporation rate was <0.0001 g min⁻¹, PVDF (form II) was obtained when the solvent evaporation rate >0.2 g min⁻¹ and PVDF (form III) was obtained when the solvent evaporation rate was from 0.03 to 0.00058 g min⁻¹.

We report the preparation of novel functional microparticles by self-assembly of amphiphilic copolymer composed of poly(γ-glutamic acid) (γ-PGA) as a hydrophilic backbone and dodecylamine (DOA) as a hydrophobic side chain (γ-PGA-DOA). γ-PGA-DOA with a grafting degree of 55% self-assembled by hydrophobic interaction, and formed microparticles (diameter 13±3 μm) in aqueous solution. These microparticles possess functional carboxylic groups, and could be further modified with active compounds such as drugs, proteins and peptides, and thus have great potential as vaccine carriers.

Dynamic birefringence and viscoelasticity for cellulose acetate butyrate, CAB, were measured simultaneously at various temperatures covering a wide frequency region from the rubbery plateau to the glassy zone in order to discuss the viscoelastic segment size of cellulose. The segment sizes for cellulose derivatives are larger than vinyl polymers, reflecting the stiff chain structure of β-linked D-glucose units (about 10 glucose units per segment).

The combined effect of cytotoxic T-lymphocyte antigen-4-Ig (CTLA4Ig) and interleukin-1 receptor antagonist (IL1ra) on the survival of subcutaneous mouse islet grafts with temperature-sensitive hydrogel, pNIPAAm-chitosan-hyaluronic acid (CPNHA), and gelatin microspheres in an allogeneic mouse model is examined. The survival of the allogeneic islets was prolonged when the grafts were transplanted into a subcutaneous matrix composed of CPN-CTLA4Ig-HA (CPNCHA) and gelatin microspheres containing IL1ra relative to those implanted in CPNHA containing gelatin microspheres without an immunomodulator.