Volume 44 Issue 2, February 2012

We describe the synthesis of a styrene–ethylene copolymer using a trivalent titanium-based polymerization catalyst system, tris(acetylacetonate)titanium/triisobutylaluminum-modified methylaluminoxane (MMAO). The catalyst system yielded a mixture of two different polymers. ¹³C nuclear magnetic resonance analysis of Soxhlet-extracted fractions indicated that the Soxhlet-soluble part contains the syndiotactic styrene–styrene sequence and the ethylene units adjacent to continuous styrene units. Consideration about a relation among sequence distribution, styrene content and thermal property data reasonably indicates that the block-like copolymer was produced, which contains the long syndiotactic polystyrene portions separated by the ethylene units.

Coarsening behavior—optical micrographs of poly(ɛ-caprolactone) (PCL)/ poly(styrene-co-acrylonitrile) (SAN) (70/30) blend prepared by precipitation into methanol, during static annealing at 200 °C: after 1 and 2 min, the regularly phase-separated structure was achieved; after 6 min, the structure coarsened to the particles of approximately 10 μm in size in a matrix and small domains of approximately 1--2 μm in size appeared in both the particles and the matrix regions; after 15 min, the particles grew to several tens of microns and the number of small domains increased; after 15 min, quenching to 25 °C and crystallization—the large dispersed particles can be assigned to a PCL-rich region.

Conformation changes occurring during the melting of various polyethylene (PE) materials such as HDPE, LLDPE and LDPE are investigated using near-infrared spectroscopy. The trans conformation decreases while the chain ends and/or gauche conformation increases at around melting point.

We analyzed the generation mechanism of birefringence in poly(methyl methacrylate (MMA)/styrene (St)) through measurement of infrared (IR) dichroism. Through IR measurement, the conformational changes in the St unit were suggested and found to differ between orientational and photoelastic birefringence generation. We thought that, during photoelastic birefringence generation, the α-CH3 group of the MMA unit hinders the rotation of the benzene ring of St units that are adjacent to MMA units. The influence of compositional distribution on birefringence was also investigated and the results suggested that the compositional distribution of poly(MMA/St) minimally affects the birefringence.

The melting behavior and the crystallization kinetics of poly(butylene/diethylene naphthalate) and poly(butylene/thiodiethylene naphthalate) random copolymers were investigated by means of DSC. By the Hoffman–Weeks’ method, the T_m° of α and β′-PBN phases were derived: the T_m° value of β′-form was higher, as expected, taking into account that it is thermodynamically favorite and more tightly packed. The presence of oxygen or sulphur atoms in PBN reduced its ability of crystallizing, the crystallization rate regularly decreasing with the co-unit content. α-PBN phase crystallized faster than β′-one, being the more kinetically favorite.

Gold was vacuum deposited on one side of 6-μm-diameter silica-gel particles to prepare Janus particles (JPs). Thiol-terminated pH-responsive poly(sodium 6-acrylamidohexanoate) (pAaH-SH) was immobilized onto the gold surface of JPs. pH-responsive flocculation and dispersion behavior of pAaH-grafted JPs can be observed with optical and fluorescence microscopy measurements.

Conformation of poly(γ-benzyl-L-glutamate) (PBLG) in the block copolymers in which polystyrene (PS) was attached to the N terminus (PBLG_n-N-PS_m) or the C terminus (PS_n-C-PBLG_m) of PBLG was studied in trifluoroacetic acid (TFA)–chloroform mixture at various concentrations. Contribution of the PS segment to helix–coil transformation of PBLG was obvious in PS_n-C-PBLG_m rather than in PBLG_n-N-PS_m, indicating that conformational free energy of the C terminus in the PBLG chain differs from that of the N terminus.

The rapid polymerization and the formation of blue-state polydiacetylene are accomplished by 1D alignment of diacetylene moieties assisted both with β-sheet peptide network and with 2D air–water interface.

Interpolymer complexes of microbial poly(ɛ-L-lysine) (ɛ-PL) and poly(acrylic acid) (PAA) were studied by Fourier transform infrared spectroscopy, differential scanning calorimetry and solid-state ¹³C and ¹⁵N nuclear magnetic resonance (NMR) experiments. These measurements suggested the poly-ionic complex formation between ɛ-PL and PAA, ɛ-PL-H₃N⁺···⁻OOC-PAA. By analyzing ¹³C NMR spectra of the complex, we concluded that there exist three forms of the carboxyl group of PAA, namely: (1) the ionized form, interpolymer ion-complex between ɛ-PL and PAA, (2) the dimeric form, intrapolymer hydrogen bonding among PAA molecules and (3) the free form, no particular form of hydrogen bonding.