Volume 42 Issue 1, January 2010

The recent remarkable progress in structural investigations of helical polymers by high-resolution atomic force microscopy provides their exact helical structures including helical pitch and handedness. Seeing is believing!

Two neutral ligands, carbonyl and phosphine, were cooperatively incorporated into half-metallocene iron(II) complexes [CpFeBr(CO)(PR₃)] for more active and versatile systems in transition metal-catalyzed living radical polymerization. Among the CpFeBr(CO)(PR₃) complexes examined, CpFeBr(CO)(PMePh₂) showed the highest activity and the best controllability, and the ‘living’ character of the polymerizations therewith was proved by sequential monomer-addition experiments. In spite of the high activity, the Fe(II) complex is stable and robust enough to be handled under air, rendering it suitable for practical use.

The molecular dynamics and orientation of vulcanized natural rubber stretched at low extension ratio were studied by solid-state ¹³C NMR and density functional theory (DFT) calculations. Isoprene units of the oriented rubber chains in stretched NR rotate rapidly around an axis that almost aligned with C=C bond direction of polyisoprene.

Novel amylose ester derivatives were synthesized and their chiral recognition abilities as chiral stationary phases for high-performance liquid chromatography were evaluated. Among the prepared derivatives, the nonsubstituted cinnamate derivative showed a relatively high chiral recognition, and interestingly, its ability was influenced by the preparation conditions of packing materials using silica gel as a support.

Chiral rod-coil type-organoboron polymers, S-poly and R-poly, have been prepared from Sonogashira coupling reaction of BODIPY-based monomer bearing bis-iodophenyl and decyl groups with S- or R-binaphthyl derivatives. The SEM analysis of each chiral polymer revealed μm-sized fiber-like structures formed by aggregation of each particle, however, the mixed polymer (S-poly/R-poly = 30/70) showed complete particle structures from nm to μm sizes, and the Φ_F of the mixed polymer was significantly high (0.98).

Well-defined aniline-chain-end-functionalized regioregular poly(3–hexylthiophene)s (P3HT-NH₂) have been synthesized on the basis of Grignard metathesis polymerization. The selectivity of monofunctionalization and the high degree of amine functionality (85–92%) were confirmed by MALDI-TOF mass spectroscopy. A block copolymer through ionic interaction was successfully synthesized simply by blending P3HT-NH₂ with carboxy chain-end-functionalized polystyrene. Thermal and optical properties of the block copolymer are investigated by DSC, TGA and UV-vis spectroscopy. The self-assembly behavior of the polymer was observed by AFM showing nanofibril structures with 12–15 nm width.

Three C₂₁-based reactive polyamides with various amine values as epoxy-curing agents were synthesized from tung oil and different polyamines. It was found that the cured materials were superior to those cured by widely used C₃₆-based polyamides with regard to mechanical properties. The glass transition temperatures of three cured C₂₁-based polyamides were found to be higher than that of C₃₆-based polyamides. The curing kinetics were studied and nonisothermal DSC curves show a good agreement with theoretically calculated ones.

Transparent and homogeneous hybrids were synthesized from poly(methyl methacrylate) (PMMA) and aqueous dispersed zirconium oxide nanocrystals (ZrO₂-NCs) with a coupling agent, 3-(methacryloxy)propyltrimethoxysilane (MPTS). The covalent bonding between PMMA- and MPTS-modified ZrO₂ nanocrystals is crucial to obtain nanoscale dispersed hybrid materials. The hybrid films retained good optical transparency compared with that of PMMA/ZrO₂ blend composites and will be promisingly applied for optical functional materials and coatings.

Micrometer-sized, monodisperse polystyrene (PS)/poly(styrene-cosodium styrene sulfonate) (P(S-NaSS))/poly(n-butyl methacrylate)(Pn-BMA) composite particles having a ‘golf ball-like’ shape were prepared by seeded dispersion polymerization of n-BMA with PS-core/P(S-NaSS)-shell seed particles in the presence of dodecane droplets. The effect of the P(S-NaSS)-shell properties of seed particles on the formation of golf ball-like particles was investigated. We clarified that golf ball-like particles could be obtained by proper selection of the hydrophilicity and molecular weight of the shell moiety.

Direct condensation polymerization of N-alkylated aminobenzoic acid was carried out using hexachloroethane, triphenylphosphine and pyridine as condensation reagents. Pale-yellow, fibrous polymers (PABA_n, where n is the number of carbon atoms of the side chain) were obtained in 46–87% yields with an inherent viscosity of 0.30–1.18 per 100ml g⁻¹ (sulfuric acid, 30 °C). DSC analysis and powder X-ray scattering of polymer samples indicated that PABA_n with Me, Pr, Bu, Pe and Ste as side chains were crystalline polymers. X-ray scattering profiles indicated that PABA_n with n=0, 3, 4 and 5 crystallized in an orthorhombic lattice, whereas PABA₁ crystallized in a monoclinic lattice. PABA₁₇ crystallized with hexagonal packing at the long side chain with an interplanar spacing of 4.2Å.

Conformational changes of sPP during melting and isothermal crystallization process were studied by IR and 2D-correlation analysis. The absorption intensity of the band at 963 cm⁻¹ (amorphous) increases earlier than that of the band at 978 cm⁻¹ (shorter helix), and that of the band at 867 and 812cm⁻¹ (crystalline helix). We found that partial sPP chains in amorphous component change their conformation first and then adjust their local conformations into short helix, and then crystallization occurs.

Aromatic sulfonate esters as acid amplifiers were introduced into a photosensitive polyetherimide system on the basis of reaction development patterning (RDP), composed of polyetherimide and a diazonaphthoquinone (DNQ) as a photosensitive agent. The resulting chemically amplified RDP (CARDP) system enabled positive-tone pattern formation with a reduced amount of the photosensitive agent and exposure dose. In particular, the use of 2SCE resulted in the formation of clear patterns with 5wt% of the photosensitive agent with a sensitivity of 125mJ/cm². The patterns prepared by CARDP showed good thermal properties.

LbL multilayer properties such as thickness, conformation of the peptide component, homogeneity and periodicity of nanoparticle layers were significantly affected by the kind of polycations. The combination of anionic PLGA-coated gold nanoparticle and cationic PLL induced a β-sheet formation, which enables the fabrication of a homogeneously well-packed gold nanoparticle multilayer without aggregation.

As one of the newest additions to the NPG portfolio, Polymer Journalis proud to present the Editor's Choice - a collection of articles spanning the scope of the journal and featuring topics including: Polymer synthesis and reactions, Polymer structures, Physical properties of polymers, Polymer surface and interfaces, Functional polymers, Supramolecular polymers, Self-assembled materials and Biopolymers.