Articles in 2015

The effects of thermal curing reactivity on phase-separated structures of acrylic copolymer/epoxy thermosetting resin composites were investigated to clarify their phase separation behavior. These composites displayed a sea-island structure, for which the island size altered as the amount of accelerator. The island diameter distribution was represented as a lognormal plot. This phase separation is explained by the law of proportionate effect as observed during the last stage of phase separation via spinodal decomposition.

The laborious supercritical CO₂ drying method limits the commercial availability of polymeric aerogels. Here we demonstrate a green and scalable method for the preparation of high-performance polyimide (PI) aerogels using low-boiling-point solvent mixture of tetrahydrofuran/methanol, and especially using sublimation drying instead of supercritical CO₂ drying. Monolithic and powdery PI aerogels with nanofibrous morphology, low density and high thermal stability can be prepared facilely and thus facilitate their applications in many fields, especially high-temperature resistance, which are of essential importance.

Poly(l-3-hydroxybutanoic acid) [P(l-3HB)] and poly(d-3-hydroxybutanoic acid) [P(d-3HB)] in their equimolar blend crystallized synchronously and separately into each homo-crystallites but not stereocomplex crystallites. In the case of the blend, the orientation and periodical rotation of lamellae in the spherulites disappeared at a relatively low crystallization temperature (T_c); the nucleation for the spherulite growth was prolonged, and the size of homo-crystallites and the radial growth rate of spherulites were decreased, owing to the synchronous and separate homo-crystallization and the coexistence of P(l-3HB) and P(d-3HB) homo-crystallites in spherulites.

The impact strength of polyamide 11 (PA11) was improved by dispersing 10–30 wt% poly(butylene succinate) (PBS) without adding a compatibilizer, and no deterioration of the flexural modulus was occurred. The impact strength was controlled by the difference in shrinkage ratios between PA11 and PBS, and was three times that of neat PA11 (an increase from 13 to 40 kJ m⁻²). The mechanism of impact strength enhancement is discussed in terms of the formation of the dilational stress fields.

A facile method of preparing cyclodextrin-grafted chitosan (CyD-g-CS) by means of the carboxymethlation of cyclodextrins and the dehydration-condensation reaction to chitosan was developed. In this method, crude product containing ~10% of the carboxymethylated-cyclodextrin was subjected to the grafting reaction without further purification. The product (CyD-g-CS) was finally purified by dialysis. Furthermore, doxorubicin-capturing nanoparticles composed of CyD-g-CS and sodium triphosphate were prepared.

The incorporated star-shaped four-armed stereo diblock poly(lactide) (4-LD) with poly(l-lactide) (PLLA) core and poly(d-lactide) (PDLA) shell and equimolar l- and d-lactide units formed stereocomplex (SC) crystallites and facilitated and accelerated the homo-crystallization of linear one-armed PLLA during heating and slow cooling and of linear one-armed PDLA during heating. The accelerating effect was higher for PLLA/4-LD with the opposite configurations of one-armed PLLA and the PDLA shell of 4-LD than for PDLA/4-LD with the identical configurations of one-armed PDLA and the PDLA shell of 4-LD.

The molecular dynamics simulations of the telomeric single-stranded DNA (ssDNA) and protection of telomere 1 (POT1) in the single and biding states have been performed for 100 ns to compare the structures of those and to calculate root-mean-deviation, gyration radii, root-mean-square fluctuation and the number of hydrogen bonds. We found that the structures of the telomeric ssDNA in the single and binding states are different, and that one guanine and Gln94 are important for the binding system.

A polymer brush with exchangeable alkoxyamine side chains was prepared by surface-initiated atom transfer radical polymerization on silica nanoparticles. Fluorinated and ionic polymers were grafted to the polymer brush and the grafted side chains could be detached from the surface of the nanoparticles via radical exchange reactions of alkoxyamine moieties. The chemical composition of the polymer brushes on nanoparticles before and after the exchange reactions was investigated by X-ray photoelectron spectroscopy. The dispersibility of the nanoparticles in solution could be changed by the reversible grafting reactions.

The functionalized polystyrene microspheres containing 3-(trimethoxysilyl) propyl-methacrylate (silane bridging agent) were prepared by dispersion copolymerization, and nickel layers were successfully introduced onto the surface of the microspheres by an electroless plating method. The silane bridging agent makes the nickel layer surface of PS microspheres more compact and uniform in distribution and seems to provide a stronger bond between the metal shell and the polymer core, as well as more adsorption area for Si-O-Ni.

Homogeneously dispersed states of the modified gold nanoparticles were obtained in the hydrogel with the interaction of the imidazolium units tethered to both the nanoparticle surfaces and the side chains of the networks. Initially, by swelling and shrinking the hydrogels, it was found that the absorption properties can be changed. Next, by using the photo-responsive mono-carboxylate linker, we observed the photo-triggered modulation of the absorption properties of the hydrogels. These results can be explained by the change of the interparticle distances of the nanoparticles in the hydrogel matrices.

Three new copolymers P1, P2, P3 have been synthesized and characterized. A variety of post-treatments are employed to optimize the performance of solar cells based on these copolymers. A maximum power conversion efficiency (PCE) of 1.22% is achieved by P2 in conventional configuration cells. The PCE of P2 can be further enhanced with inverted configuration, which is ascribe to the more light absorption by TiO₂ nanoparticles and the close energy alignment between the work function of MoO₃ and the HOMO energy levels of P2.

This review summarizes the most widely used mechanisms in high-performance polymeric resistive memory devices, such as charge transfer, space charge trapping and filament conduction. In addition, recent studies of functional high-performance polymers for memory device applications are reviewed, compared and differentiated based on the mechanisms and structural design methods used. The reported memory properties show extremely high endurance during long-term operation, making high-performance polymers very suitable materials for memory applications.

Thiol-ene photopolymerizations of isocyanurate-based trithiol (S3I) / mercaptopropyl-substituted random-type polysilsesquioxane (SQ) and allyl-etherified trehalose (AxT) with a degree of allylation, x = 6 or 8, which was prepared by the reaction of α,α-D-trehalose and allyl bromide, produced trehalose-incorporated organic-inorganic hybrid nanocomposites (AxT-S3I/SQy) with a SQ content, y =10 or 20 (wt%). All of the photo-cured hybrid films exhibited high transparency to visible light. FT-IR spectral analysis revealed the progress of thiol-ene photopolymerization. The thermal properties (glass transition and 5% weight loss temperatures) and mechanical properties (tensile strength and modulus) of the hybrids were much improved by the incorporation of SQ.

Procedures for implementing molecular dynamic simulations in preproduction evaluation and optimization of miniemulsion systems in polymeric material design has been investigated and evaluated in the production of ligand-selective synthetic receptor mimic-containing polymeric particles targeting the ligand bisphenol A. The graphical abstract, from left to right, presents the ligand bisphenol A, snapshot from simulation overlaid with molecular density distribution plot for components, indicating the stability of simulated emulsions, and finally a graphical representation of a theoretical binding site extracted from simulated systems presenting a cavity with bisphenol A and two interacting polymer monomers.

Recent developments on bipolar electrochemistry as an effective tool for the fabrication of gradient polymer surfaces were reviewed. The electrochemical doping and reactions of conducting polymers under an applied potential distribution using bipolar electrodes have been carried out to prepare conducting polymers with composition gradients. Indirect electrolysis using an electrogenerated metal catalyst on bipolar electrodes successfully afforded gradually modified polymer surfaces and gradient polymer brushes. The newly designed cylinder bipolar electrode system is available for site-selective applications of electric potentials, which produced electrochemical patterning of conducting polymer films.

Boron-moiety-containing aluminoxanes (BMAOs) were prepared from the partial protonolysis of Me₃Al using various arylboronic acids. Compared with methylaluminoxane (MAO) generated from the hydrolysis of Me₃Al, BMAO prepared from C₆F₅B(OH)₂ and Me₃Al induced a higher activity at the same Al/Ti ratio in the propylene polymerization using ansa-Me₂Si(Flu)(N^tBu)TiMe₂ catalyst. The time course of propylene consumption when using BMAO showed the deactivation of the catalyst. Among the BMAOs, only those derived from arylboronic acids with electron-withdrawing groups were observed to act as efficient cocatalysts.

The lithography process simulations modeled by coarse-grained polymer techniques are reviewed. As a case of top-down process, development and rinse processes were simulated. From these simulations, line edge structure can be obtained to discuss the line edge roughness. As a case of bottom-up process, the directed self-assembly (DSA) process was simulated, and the polymer chain dynamics in the defect annihilation process can be analyzed.

Microbial fermentation system is designed to convert glucose to 4-hydroxyphenyllactic acid (DHPA), an aromatic-containing derivatives of lactic acid. By a methylation, DHPA was transformed to a diol monomer to synthesize bio-based polyesters with benzene rings in their backbone. The polycondensation of DHPA diol was performed with a series of aliphatic diacid chlorides to produce semi-aromatic polyesters with glass-transition temperatures <45 °C. By polycondensation with aromatic diacylchlorides such as terephthaloyl chloride and isophthaloyl chloride, thermally stable DHPA-based polyesters with glass-transition temperatures as high as 130 °C were obtained.

Hg(II)-imprinted polymers were analyzed by Fourier transform infrared spectroscopy. The spectrum of IIP2, prepared using diphenylcarbazone, showed two additional peaks attributed to the stretching of nitrogen bonded to the aromatic carbon of diphenylcarbazone, not found in IIP1. Comparing leached and unleached IIP2, the peak shape of C=N (1636.3 cm⁻¹) in unleached IIP2 was drastically changed emphasizing the interaction of mercury with nitrogen on 4VP. Moreover, a slight shift of the additional peaks was observed. These results show the possible interaction of mercury ions both with the nitrogen bonded to the aromatic carbon of diphenylcarbazone and the nitrogen of the monomer.

In this review, we show that using two-dimensional (2D) samples suitable for atomic force microscopy (AFM) observation, especially Langmuir–Blodgett films, molecular images of various polymer structures could be obtained by tapping-mode AFM. The molecular-level observations included isolated polymer chains and their movements on substrates, 2D folded-chain crystals and their melting behavior, crystallization behavior of single isolated chains, supramolecular multistranded stereocomplex and chain packing in monolayers. The molecular-level information obtained by the direct observations should greatly improve our understanding of polymer science.