Research articles

We compared the effects of adding two salts with different carbon chain lengths––LiCF₃SO₃ (LFMS) and LiC₄F₉SO₃ (LFBS)––on the uniaxial tensile properties of poly(methyl methacrylate) (PMMA). The longer average relaxation times in the flow region of the PMMA/salts indicate that the salts have a “pinning” effect on PMMA chains. This pinning effect was more pronounced for the LFMS sample with a shorter carbon chain length. We found that the rheological behavior (pinning effects) at the compression-molding temperature affects the brittle fracture behavior in tension.

We selected a polylactide (PLA) copolymer with poly(ethylene glycol) (PEG) and a urethane capping PLA and prepared various stereocomplex (SC). Depending on the combination of L-isomers and D-isomers, the SCs were classified as Homo-SC, Co-SC, and Multi-SC: Homo-SC by the same polymer chain ends and copolymers, Co-SC by different polymer chain ends and copolymers, and Multi-SC by a mixture of various polymer chain ends and copolymers. Multi-SC showed two broad melting points at around 200 °C, suggesting the various combinations of polymer–polymer interaction in the case of Multi-SC.

Low-molecular-weight amphiphilic block copolymers with controlled architecture represent an interesting manner for safe delivery of siRNAs and hydrophobic anticancer drugs. The tailored synthesis, supramolecular assembly and morphology were investigated using triblock copolymers based on α- and ε-lysine oligomers.

In this work, Fumaric acid units containing unsaturated carbon-carbon double bonds used as comonomers to synthesis of the Poly(butylene carbonate) derived copolymers(PBCFs). The microstructure of PBCFs was random in all cases, and their thermodynamic compatibility could also be confirmed by fitting of the Fox equation. The introduction of carbon-carbon double bonds not only increased the thermal stability of the PBCFs, but also demonstrated faster degradation rates than PBC. The good biodegrability in a wide compositional range allows the selection of suitable physical properties for different applications.

We synthesized novel benzoxazine-polymers, poly(1)_230–2000 consisting of rigid phenyleneethynylene and flexible polypropylene glycol (PPG) moieties in the main chain. Resins obtained by cross-linking reaction of poly(1)_230–2000 were thermally as stable as a previously synthesized polybenzoxazine resin containing phenyleneethynylene moieties. Introduction of flexible PPG unit was effective to lower the curing temperature, and enhance mechanical toughness keeping thermal stability.

Adding rod-like low-mass molecules (LMs) increases the elastic modulus of polycarbonate (PC). The anisotropy of the rotational dynamics of rod-like LMs in PC was investigated by dielectric relaxation and dynamic mechanical analysis. Two rotations of the LM around the short and long axes were separately observed at 80 °C and −100 °C, respectively. The rotation of the LM around the short axis was cooperative with the local dynamics of PC and. In contrast, the rotational motion around the long axis was independent of PC motions.

A soluble double-chain (ladder-like) polysiloxane (DC-PS) with high thermal stability was successfully prepared by intramolecular polycondensation (template polymerization) of a polysiloxane, in which diethoxysilyl groups were introduced into the side chains, using hydrochloric acid and purified water as the catalysts. The DC-PS cast film had coexistence of relatively high water repellency and adhesion to glass.

This work studied the crosslinking of PLA/star-shaped polycaprolactone to enhance the toughness and resistance to thermal deformation of PLA. The tensile and thermal properties of the blend and crosslinked films were investigated. The simple test of resistance to thermal deformation by immersing in hot water was done. The crosslinked film shows resistance to deforming in hot water (80 °C, above its T_g).

Self-assembled smectic lamellae of comb-like polymers with pendant-like perfluorocarbon side chains have been extensively used as water-repellent, hydrophobic coating materials, which are characterized by large water contact angles (θ > 120°). By measuring off-specular neutron scattering under defined osmotic pressures, we unraveled that such “apparently hydrophobic” materials interact with water and adapt the inter-lamellar correlation. This suggested that water molecules could be used to optimize the self-assembly of hydrophobic liquid crystalline polymers.

Disiloxane-linked decathiophene and dodecathiophene polymers were prepared and their optical properties were examined. Compared with the monosilane-linked congeners reported previously, these polymers showed slightly redshifted absorption and PL bands in solution. Interestingly, the PL bands were redshifted when the spectra were measured in film, and the redshifts became pronounced as the silicon linkers were elongated from monosilane to disiloxane. This is likely due to the enhanced aggregation of the oligothiophene units, reflecting the improved flexibility of the silicon linkers.

Organic nanotubes (ONTs) were functionalized and hybridized with poly(ethylene glycol) (PEG) to generate mechanically enhanced nanocomposite hydrogels with improved drug delivery in an easy, efficient and tunable manner. These nanoengineered hydrogels have 4-fold greater mechanical stiffness than unreinforced hydrogels and show a more stable network. The incorporation of ONTs enabled simple and effective post-loading of the model drug, as well as a sustained drug release profile from the hydrogels.

We investigated the functions that reproduce the configurational heat capacity (C_config) that occurs above the glass transition temperature for polystyrene (PS), polyisobutylene (PIB), and their oligomers. The results show that C_config could be well reproduced using the power and logarithmic functions based on the Landau theory. The power and logarithmic functions had four and three fitting parameters, respectively. The error ranges were approximately ±2% for PS and ±5% for PIB. At this stage, the two functions are not functions with the clear physical meanings but the practical functions that were evaluated using regression analysis and simply reproduce the configurational heat capacity.

Poly(2,5-dimethyl-1,4-phenylenesulfide) (PMPS) was prepared as a highly crystalline and thermostable polymer via oxygen oxidative polymerization of bis(2,5-dimethylphenyl) disulfide (2,5-DPS) with a VO(acac)₂-strong acid catalyst under bulk conditions. The thermal property of PMPS was enhanced after subsequent heat curing through the exchange reaction of a reactive disulfide bond, which reached a higher melting temperature of T_m = 286 °C. The copolymerization of 2,5-DPS with diphenyl disulfide (DPS) was also conducted, affording polymers with much higher melting temperatures and crystallinities (T_m = 309 °C, X_c = 58% in maximum).

Polytetrafluoroethylene (PTFE) has a weak boundary layer (WBL) on the surface. A cross-section of PTFE was observed using a scanning electron microscope for investigating the difference in morphology between WBL and bulk layer. Large voids of 0.5–2.0 µm in diameter were observed on the surface side of PTFE but not on the bulk side. These voids existed up to approximately 5 µm from the outermost surface of the PTFE. This result indicated that the thickness of WBL of PTFE was in the order of single µm.

Three different silk sources were explore for sericin (SS) extraction and film formation. Features of each raw material, especially the degree of processing, have remarkable effects on the primary structure and the presence of nonprotein compounds in the sericin extract. As a result, sericin films exhibited distinctive properties that seemed to be correlated with the amount of natural impurities and the molecular properties of the SS extract obtained from each raw material.

Time-resolved small-angle X-ray scattering measurements were made for a mixed solution of silica nanoparticles (SiNPs) and atelocollagen (AC) in aqueous media. The scattering intensity from the SiNPs gradually changed and reached asymptotic values approximately 5–20 min after rapid mixing of the two solutions. The obtained time scale to form the complex can be important information to control the aggregating structure of SiNPs with the aid of collagen molecules.

We developed lanoconazole (LCZ)-loaded emulsions stabilized with cellulose nanocrystals grafted with polyphosphoesters (LCZ-loaded CP-PEs). The sustained release of LCZ and superior skin permeation of the LCZ-loaded CP-PEs, likely due to the excellent stability and rigidity of oil droplets, assured prolonged local action. The anti-inflammatory efficacy of the LCZ-loaded CP-PEs was confirmed using a mouse ear model of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation.

Proton exchange membranes (PEMs) based on trifluoromethanesulfonylimide-grafted polybenzimidazole (PBI-TFSI) were prepared, and their physical and chemical properties were studied. PBI-TFSI showed higher proton conductivity than Nafion and propanesulfonic acid-grafted polybenzimidazole (PBI-PS) at a 40% relative humidity due to its high acidity of side chain. PBI-TFSI membranes are promising materials for next-generation PEM fuel cells.

An optically active acylhydrazine-functionalized biphenyl (AHB) carrying L-alanine-derived oligoamide side chains supramolecularly coassembled with the corresponding achiral AHB to form a one-dimensional helical nanofiber, in which intermolecular hydrogen bonding between the chiral/achiral oligoamide pendant units resulted in modest chiral amplification (the sergeants-and-soldiers effect). The chiral/achiral AHB-based covalent copolymers folded into a preferred-handed helical structure with amplification of the helical sense excess driven by intramolecular hydrogen bonds and further polymerized into a higher molar mass supramolecular helical polymer stabilized by end-to-end intermolecular hydrogen bonding.

Surface oxidation method using chlorine dioxide radical (ClO₂^•) for poly(phenylene sulfide) (PPS) was developed. During the oxidation reaction, sulfonyl groups and sulfite groups were successfully introduced to the surface of the PPS films. The water contact angle of the surface of the PPS film decreased dramatically after the oxidation, indicating that the surface hydrophilicity was improved. Electroless plating demonstrates that typical metals could be tightly deposited on the surface of oxidized PPS film and cannot be removed. This method provides an effective, clean, energy-saving treatment for super engineering plastics.