Research articles

A poly(styrene)(PS)-b-poly(methyl methacrylate)(PMMA)-b-PS triblock copolymer was successfully solubilized as single chains to form PS single-block particles at either end without aggregation of the PS blocks in poly(n-nonyl acrylate)(PNA) and PMMA Langmuir monolayers, which both form miscible monolayers with the middle PMMA block. The end-to-end distance was evaluated using the PS single-block particles at either end, and the PMMA block chain was not found to be highly segregated in either the PNA and PMMA monolayers but was rather elongated and interpenetrated with the matrix chains.

PVDF is a promising candidate material for fabricating superhydrophobic surfaces because of its intrinsic low surface free energy, chemical resistance, and thermal stability. In this work, we investigated how morphologies influenced the surface wettability of PVDF nanostructure assembly coatings. The coatings consisting of PVDF nanoparticles exhibited highly improved hydrophobicity compared with that of the flat drop-coating PVDF surface. These results provide valuable insight into PVDF surface design, especially for superhydrophobic coatings.

For bulk crystallization, the growth rate is governed by the nucleation process and depends mainly on the crystallization temperature and composition of the blends. If the crystallization process is confined in ultrathin films, then the diffusion-controlled growth process is remarkably retarded due to the thickness confinement. The longitudinal and lateral growth rates of basal and overgrown lamellar crystals shows different. This study reports the film thickness significantly retards the growth rate of basal and overgrown lamellar crystals and reduces the number of overgrowths on the basal lamellar crystals.

Sum-frequency generation (SFG) spectroscopy is a powerful tool for studying the molecular orientation in confined systems based on the second-order nonlinear optical effect. Here, we demonstrated the SFG imaging for films of uniaxially-oriented poly(vinylidene fluoride) (PVDF) and spin-coated isotactic polypropylene (iPP). The orientational difference of lamellar fibrils in the two films was identified.

The deformed BPEP/GR with a 3D structure rapidly recovered to a 2D film by remote NIR irradiation. Furthermore, because the crystal structure of the biphenyl unit can be regulated through rapid polymerization, thermal treatment is applicable. The activation and recombination of the biphenyl units and the NIR responsiveness results in the self-folding behavior of BPEP/GR under NIR laser irradiation. It is also recognized as a reconfigured permanent shape, which can be recovered under a thermal stimulus.

Herein, we synthesize a new organic-inorganic hybrid material by direct coordination of a chain-end-functionalized naphthalene diimide (NDI)-based n-type semiconducting polymer with thiol group(s), PNDI-SH, to lead sulfide quantum dots (PbS-QDs). The synthesized hybrid n-type material, PNDI-SH:PbS-QD (70:30, w-w), was found to show good dispersibility in organic solvents and excellent atmospheric stability even after storage for 8 months. The formation of PbS-QD nanoclusters is confirmed by transmission electron microscopy (TEM) for a PNDI-SH:PbS-QD (70:30, w-w) thin film, which is also supported by ultraviolet-visible-near-infrared (UV-Vis-NIR) absorption spectroscopy.

A synthetic strategy is developed towards highly amphiphilic cellulose nanocrystals (CNCs) by selectively introducing carboxylic acid groups at the reducing end and –C8 units on the surface. The resulting chloroform soluble CNCs formed an exceptionally stable monolayer at the air/water interface, and resulted in a well-defined LB isotherm, allowing their facile transfer to both hydrophilic and hydrophobic substrates. These monolayers were successfully transferred onto substrates to create monolayer or smooth multilayer films.

Molecular imprinting of methylene blue (MB), a small cationic dye, was conducted to free-standing films prepared from polyion complexes of chondroitin sulfate and chitosan. Molecular permeability of the MB-imprinted films in phosphate-buffered saline (PBS) was evaluated. MB, orange II and porphyrin derivatives were used as permeants to clarify the effects of charge and size of the permeant on the permeation behaviors. In the case of porphyrin derivatives, the inner voids of the films were not significant for the permeation behavior, but the surface charges of the films were important.

Cellulosic bottlebrush regioselectively possessing poly(ethylene glycol) (PEG) and polystyrene (PS) side chains (PEG-PS-cellulose) was synthesized, and its secondary structure in dilute solution was investigated with SAXS and SEC-MALS. The relationship between the cross-sectional mean squared radius of gyration (〈S_c²〉) and molecular weight of PS chain (MW_PS) showed that PEG-PS-cellulose has a core-shell-corona structure in cross section. The dependency of main-chain stiffness (λ⁻¹) on MW_PS was discussed on the basis of the interactions of the PS and PEG side chains as well as the restricted rotation of the cellulosic main chain.

A cell-cultivable gel based on a polysaccharide “sacran” has been developed. Although the conventionally produced sacran gel does not show cell adhesion, it achieved compositing with collagen, which has cell adhesion, and showed its potential as a cell scaffold. The feature of this study is that the gelation of sacran was controlled by the addition of salt, and the composite with collagen was achieved for the first time.

The addition of a fibrous nucleating agent (MDBS) significantly enhanced the crystallization temperature of PP with the accelerated crystallization rate, which was barely affected by the applied shear flow. In the case of pure PP, rapid crystallization was detected only after the history at a high shear rate. Furthermore, the shear history enhanced the chain orientation of PP greatly especially for the sample with MDBS, which resulted in a good transparency.

We developed pDNA/polysaccharide complexes suitable for reverse transfection (RTF) and investigated their transfection mechanisms. The pDNA/chitosan/hyaluronic acid ternary complexes showed excellent transfection efficiency in RTF compared with the conventional forward transfection (FTF). The ternary complexes were taken up via macropinocytosis in RTF. Furthermore, the ternary complexes in RTF were transported to late endosomes via microtubules, and were remarkably accumulated in the nucleus. These results suggest that the cell transfection efficiency of the ternary complexes in RTF was enhanced by their efficient delivery to the nucleus via late endosomes.

Molecular dynamics simulation of chitosan and anionic oligosaccharides was conduced to elucidate the formation mechanism and structure of polyion complex (PIC) of polysaccharides. The association of oligosaccharides with scrambled structure indicated that PIC of polysaccharides takes on the structure of “Scrambled egg model”. The formation of hydrogen bond between deprotonated chitosan and anionic oligosaccharides suggested that hydrogen bonds contribute to the stabilization of PIC under neutral condition.

The surface glass transition temperature (T_g) of polymer materials is believed to be significantly lower than the bulk value. We prepared a molecularly flat substrate of poly(methyl methacrylate) (PMMA) by thermally imprinting a PMMA plate with mica, on which polystyrene-b-PMMA was deposited by the Langmuir-Blodgett technique in a dilute state, and the thermal stability of the surface was evaluated by in situ high-temperature atomic force microscopy. Both the PMMA chains deposited on the plate and of the surface of the plate started to move close to the bulk PMMA T_g.

Photoisomerization of doped azobenzene (AB) caused “photoinduced plasticization” effects such as reductions in the glass transition temperature (T_g) and Young’s modulus of the matrix polymer. The mechanism of the reduction in T_g and Young’s modulus of polycarbonate (PC) was investigated by comparing the two values with the characteristic times of the isomerization reactions. The sum of the characteristic times of trans→cis and cis→trans conversion is related to the repeating isomerization rate. The faster repeating isomerization enhanced the free volume of PC, resulting in the reduction in T_g and Young’s modulus.

We visualized the spatial inhomogeneity of chain orientation on the submicron scale in high-density polyethylene associated with strain-induced density fluctuations using STXM and USAXS/SAXS/WAXD. Real-space images of the density fluctuations were obtained with STXM at the strain where a butterfly pattern was observed with USAXS. STXM observation also revealed that the chains in the low-density region were more often oriented parallel to the stretching direction than those in the high-density region.