Research articles

The PEDOT: PSS/PNIPAM hydrogel was simply prepared by ultrasound-enhanced free radical polymerization in an ice bath, in open air rather than spending hours under an N₂ purged environment. The resulting conductive hydrogel had a uniform texture and good flexibility for rapid resistance responses and color changes when it was exposed to temperature stimulations. The dual actions of hydrogen bonding and hydrophobic aggregation weaken the Coulomb interaction between PEDOT⁺ and PSS⁻ for better conductivity that is suitable for breathing monitoring and other wearable sensing applications.

Using LV-STEM, we found that there were previously unseen nanoscale structures inside the blends of PMMA/PVDF. These structures were formed on the same scale that did not deviate from the size of a single molecular chain, regardless of the solution casting, melt mixing, mixing ratios, and even amorphous or crystalline state of PVDF. The characteristics of these structures were discussed in accordance with thermophysical properties and intermolecular interaction properties, which provides some new findings for the first time.

In the polypropylene (PP)/carbon fiber (CF) composite, it has been well known that maleic acid modified PP (MAPP) improves the interfacial adhesion with CF. However, the effect of maleic acid modification on the PP crystals around CF, and that of the PP crystals on the interfacial adhesion have not been clarified well. In this study, the local crystal structure of PP near CF was investigated using micro-Raman spectroscopy, and it was demonstrated that the crystal growth of PP near CF contributes significantly to the interfacial adhesion.

In this study, we examined the efficiency of q1-complex and L-SPG complex in translocation to the cytoplasm. The results showed that the q1 complex can deliver YB-1-AS into the cytoplasm about three times more efficiently than the L-SPG complex.

Multivariate analysis of ¹H NMR spectra of copolymers of methyl methacrylate and benzyl methacrylate successfully extracted information on the chemical composition and the monomer sequence. Then, the fractions of diad monomer sequences in an unknown sample were predicted to calculate the monomer reactivity ratios. Thus, the monomer reactivity ratios were successfully determined from a single sample.

The pH-responsive behavior of a core-crosslinked multiarm star polymer with an ionic poly(acrylic acid) (PAA) block segment in the arm was greatly affected by the arm chain sequence. Two types of star polymers with opposite block sequences was shown to differ sharply in the balance of hydrogen bonding and ionic repulsion between arm polymers, resulting in the different pH-responsive aggregation behaviors. The fundamental understanding gained by the present study deepens the insight into the solution properties of branched polyelectrolytes, which would expand the possibility for various applications.

Polymer and composite synthesis and structures. Formation of Graphene Matrix in Natural Rubber Dispersoid. In this study, the preparation of and characterization of a composite of natural rubber (NR) discontinuous phase (dispersoid) and graphene continuous phase (matrix) were carried out. Graphene (G) was prepared and grafted on rubber particle in latex stage in the presence of initiator tert-butylhydroperoxide and tetraethylene pentaamine with optimal amount of surfactant. The structure, the morphology, the mechanical properties, and the electromagnetic shielding of the resulting materials were superior compared to that of NR/graphene blend.

The anionic polymerization behavior of phenyl-substituted [3]dendralene derivatives, 2-phenyl[3]dendralene (2-P3D) and (Z)-1-phenyl[3]dendralene (1Z-P3D), was theoretically investigated using DFT calculation. The kinetic analysis based on the activation Gibbs free energy of the chain propagation showed that the anionic polymerization of 1Z-P3D proceeded with highly regioselective character; however, that of 2-P3D did not. By conformational and molecular orbital analyses, it was suggested that an effective conjugation of phenyl substituent with the chain end carbanion had a significant effect in the regioselectivity of the anionic polymerization of phenyl-substituted [3]dendralene derivatives.

Our work studied the effect of proteins on the graft copolymerization of vinyltriethoxysilane (VTES) on natural rubber (NR) latex. Stress at break of the graft copolymers was substantially higher when proteins were present; that is, the stress at break of fresh NR-graft-PVTES was higher than that of protein-free NR-graft-PVTES. Silica nanomatrix was formed more visibly in the presence of proteins, as observed by transmission electron microscopy. Furthermore, proteins were found to accelerate the formation of silica particles by forming hydrogen bonds with VTES molecules and enhancing hydrolysis with water molecules.

Poly(ether sulfone)-based functional ultrafiltration membranes were developed by employing chitosan (CS) and ammonium chloride (NH₄Cl) as antibacterial agents. A PES membrane was prepared and immersed in CS/NH₄Cl solutions at different NH₄Cl concentrations. The composite membranes show enhancement in the antibiofouling properties, where maximum bacteria-killing ratio (%BKR) values of 99.2 and 83.3% were observed against Staphylococcus aureus and Escherichia coli, respectively. The addition of CS/NH₄Cl not only modified the morphological structure of the PES membrane but also increased its hydrophilicity, porosity, and mechanical strength, suitable for ultrafiltration applications.

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.

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.