Physically crosslinked elastomers prepared from oligomeric polyolefins with mesogenic units

Two ABA‐type liquid crystalline oligomers were newly synthesized, where A was a mesogenic group and B was polyolefin whose molecular mass was 2470. The A segment was prepared from p‐hydroxyl benzoic acid and terephalic acid. The elastomeric films, whose moduli at 20% elongation were 0.4–1.0 MPa, were obtained by solution casting of the ABA‐type oligomers. Dynamic mechanical analysis and differential scanning calorimetry measurement showed the glass transition of amorphous polyolefin segments, the melting of mesogenic groups, and the meso‐to‐isotropic transition of liquid crystalline phase. The formation of microphase‐separated structures was confirmed by a small‐angle X‐ray scattering (SAXS) measurement. The presence of hexagonal cylinder domains, which were attributed to the aggregation of mesogenic groups in the polyolefin matrix, was also detected by SAXS. These liquid crystalline oligomers showed anisotropy under the crossed Nicoles, and the textures were observed to be nematic. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2247–2253, 2000     

Preparation of hybrid hollow capsules formed with Fe3O4 and polyelectrolytes via the layer-by-layer assembly and the aqueous solution process

Well-defined magnetic hybrid hollow capsules formed with magnetite (Fe₃O₄) and polyelectrolyte-multilayer films were successfully prepared through colloidal templating with layer-by-layer assembly of polyelectrolytes, followed by aqueous solution deposition of Fe₃O₄. Pd catalyst nanoparticles played an important role in the deposition of Fe₃O₄. Pd nanoparticles favorably adsorbed onto the polyelectrolyte layer with positively charged amino groups. Hollow capsules were obtained by the removal of the melamine–formaldehyde core particles. Although the processes were performed in aqueous solutions at temperatures less than 60 °C, X-ray diffraction patterns revealed that the deposited Fe₃O₄ was highly crystallized. The hollow capsules were stably dispersed in water; however, the capsules rapidly congregated around a locally applied magnet.     

X-ray irradiation effect of double walled carbon nanotube

We have studied double-walled carbon nanotube (DWNT) irradiated by soft X-ray by Raman scattering spectroscopy and the spectral characteristics are compared to single-walled carbon nanotube (SWNT) irradiated under the same condition. We proved that DWNT is more stable for the X-ray induced defect formation than SWNT. Moreover, we found that the outer tube of DWNT was more sensitive on X-ray irradiation than the inner tube. The defect was recovered by annealing in Ar at lower temperature than that of SWNT. Based on these results, we inferred that X-ray irradiation leads to formation of interstitial-vacancy pairs, Frenkel defects, in carbon nanotube. The interstitial-vacancy separation on the inner tube of DWNT is conceivably shorter than that of the outer tube.     

Micropatterning of copper on a poly(ethylene terephthalate) substrate modified with a self-assembled monolayer

We have developed a technique for the site-selective electroless deposition of Cu on poly(ethylene terephthalate) (PET) substrate modified with an organic self-assembled monolayer (SAM). The PET substrate was first modified with a silica-like layer by being dip-coated in an acetone solution of 3-aminopropyltrimethoxysilane and treated with UV light. The PET substrate was further modified with thiol groups using a 3-mercaptopropyltrimethoxysilane-SAM and then irradiated by UV light through a photomask to prepare thiol-group regions and OH-group regions. Cu was then deposited on only the thiol-group regions of the substrate by electroless deposition in a neutral solution with no catalysts by using dimethylamineborane as a reducing reagent. This site-selective deposition process can control the deposition conditions by an organic thin film fabricated on a surface-modified PET substrate, and thus can be applied to other low heat-resistant substrates.     

Functional monomers and polymers. XCVII. Synthesis of oligomer models of polyethyleneimine derivatives containing pendant thymine bases

A series of oligomer models of polyethyleneimine derivatives having pendant thymine bases were prepared by the reaction of carboxyethyl derivatives of thymine with oligomer amines using an activated-ester method. It was found that the hypochromicity values obtained from UV spectra and pKa values obtained from spectrophotometric titrations depend on the chain length of the oligomers and the thymine content of the polymers.     

Vinyl polymerization by metal complexes. III. Vinyl polymerization initiated by oligoamide and cupric ion system

Polymerization of methyl methacrylate and other vinyl monomers was studied in the presence of oligoamide (?-aminocaproic acid, its dimer, trimer, tetramer, and pentamer) and cupric ion in aqueous media. The polymerization was found to be of free-radical character and selective for the type of vinyl monomer. Carbon tetrachloride can accelerate the polymerization. The initiation mechanism of the polymerization is discussed. Spectroscopic measurements were indicative of formation of 1:1 complex between oligoamides and cupric ion in aqueous NaClO₄ solution. Some chemical and physical properties of the resulting polymers were measured.     

Functional monomers and polymers. CXXXII. Template polymerization of methacrylamide derivatives containing nucleic acid bases

Free-radical polymerizations of methacrylamide derivatives containing nucleic acid bases were studied in the presence of the polymethacrylamide having complementary nucleic acid bases as template polymers. The rate of the polymerization did not show remarkable difference in the presence or the absence of the template polymer. A stable polymer complex, however, was precipitated from the polymerization system, and was found to be different in a thermal analysis from the polymer complex which was obtained by mixing of the complementary polymers in solution. Free-radical copolymerizations in the presence of the template polymers also supported the template polymerization.     

Functional monomers and polymers. XXXXI. Template polymerization of methacryloyl-type monomers containing nucleic acid bases

In due consideration of the specific base–base interaction that exists between nucleic acid molecules, the free radical polymerization of N-β-methacryloyloxyethyl derivatives of adenine, thymine, and theophylline initiated by azobisisobutyronitrile (AIBN) was studied in the presence of N-β-methacryloyloxyethyl-type polymers which have complementary nucleic acid bases as template polymers. The rate of polymerization of N-β-methacryloyloxyethyladenine was accelerated when poly(N-β-methacryloyloxyethyluracil) or -thymine was present in the polymerization system. The effect of the stereoregularity of the template polymers, as well as polymerization temperature and the sort of solvents used on the rate of polymerization, was studied and discussed in some detail. The results suggest that the interaction between complementary bases plays a role in template polymerization behavior.     

Functional monomers and polymers. XCVI. Photochemical reactions on oligo- and polyethyleneimines which contain pendant thymine bases

The photodimerization reaction of oligo- and polyethyleneimine derivatives which contain pendant thymine bases in various amounts was studied in aqueous solution in a wide pH range and in N, N-dimethylformamide solution. The photodimerization reaction of these derivatives in poly(methyl methacrylate) was also studied. It was found that its quantum efficiency tended to increase as thymine units were added to the oligomers and copolymers. This result is discussed in terms of the effect of the nearest neighboring thymine units and singlet energy migration, particularly in the polymers.     

Functional monomers and polymers. XXXXVII. Complex formation of stereoregular methacryloyl-type polymers containing nucleic acid bases

The complex formation between a poly(N-β-methacryloyloxyethyl) derivative of adenine with one of thymine or uracil was studied in dimethyl sulfoxide and ethylene glycol mixture by ultraviolet (UV) spectroscopy. For the polymer pairs containing complementary nucleic acid bases both hypochromicity and hyperchromicity were found. Stereoregularity of the polymers, as well as the conditions for measurement of, for example, solvent, temperature, and time, affected the complex formation. Both inter- and intramolecular interaction of polymers in solution were discussed in some detail.