What Factors Determine Hierarchical Structure of Microbial Cellulose – Interplay among Physics,Chemistry and Biology –

A microbial cellulose film (pellicle), prepared by Acetorbactor xylinum, is a supramolecule system, absorbing a huge amount of water (99% by weight). To elucidate the affinity to water, we investigated the hierarchical structure in a pellicle by using ultra-small-angle and small-angle neutron scattering, observing a wide range of length scales from nm to µm. We successfully determined mass fractal dimensions for the amorphous structure, which hierarchically varies local concentration fluctuations, bundle and network, appeared as the length scale increases. On a basis of these findings, we discuss to address a question what factors determine the hierarchy in the microbial cellulose. This is a new topic of soft matter science, regarded as reaction-induced self-assembly in a non-equilibrium open system, therein soft matter physics, biochemistry and cell biology crucially interplay.     

Phase transition and self‐assembly in block copolymers

We focussed on the following two topics on block copolymers; (i) the Brazovskii effects, effects of thermal fluctuations on phase transition of systems having a short characteristic length L, and (ii) nanofabrication and nanohybrids based on block copolymer nanostructures. We highlight the following two aspects: Block copolymers provide good model systems for studies of basic physical science and are useful for advanced functional materials and devices.     

Structure factors of dispersible units of carbon black filler in rubbers

We report the structures of dispersible units, a most fundamental but minimal dispersible structural unit of a carbon black (CB) filler that is formed in two kinds of rubber (polyisoprene and styrene-butadiene random copolymer) matrices under a given processing condition. The results obtained from various small-angle scattering techniques showed that the CB aggregates, as observed after the sonification of a CB/toluene solution, were a spherical shape composed of approximately nine primary CB particles fused together. In the rubber matrices, the aggregates clustered into higher order structures defined in this work as the dispersible units, which are the fundamental structural elements (or the "lower cutoff structures") that build up a higher order mass-fractal structure. Furthermore, we found that the morphology of the dispersible units strongly depended on the rubber matrix, although the mass-fractal dimensions remained unchanged.     

Preparation of polystyrene/poly(methyl methacrylate) composite particles having a dent

Nonspherical polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles having a dent were prepared by releasing toluene from PS/PMMA/toluene droplets dispersed in a poly(vinyl alcohol) aqueous medium. An ex-centered PS-core/PMMA-shell morphology, in which a part of the PS core contacted with the aqueous medium and toluene partitioned more in the PS core than in the PMMA shell, was formed in the polymers/toluene droplet in the process of phase separation therein with releasing toluene. The volume of the dent became bigger with an increase in the PS content and in the toluene content partitioned in the PS core.Part CCLXI of the series Studies on Suspension and Emulsion.     

Curve-structured phenalenyl chemistry: synthesis, electronic structure, and bowl-inversion barrier of a phenalenyl-fused corannulene anion

We have demonstrated the features of curve-structured phenalenyl chemistry, for the first time. A phenalenyl-fused corannulene anion has been designed by the annelation of a six-memberd ring across peri-positions of corannulene and generated as a stable species in a degassed solution. The 1H and 13C NMR spectra have shown the highly symmetrical structure and high-field shifts of protons and carbons at the asterisked positions in the chemical structure, indicating the occurrence of large negative charge densities at these positions. These results well agree with the HOMO picture and the electrostatic potential surface, demonstrating the phenalenyl anion-type electronic structure is retained in the curved-surface pi-system. The calculated bowl-inversion barrier of the anion (11.3 kcal/mol) is larger than that of corannulene (9.2 kcal/mol) because of peri-annelation of the corannulene skeleton. The calculations of the barriers of the neutral radical (12.6 kcal/mol), radical dianion (8.1 kcal/mol), and trianion (5.4 kcal/mol) of the phenalenyl-fused corannulene have exhibited a stepwise flattening of the curvature with increase in negative charge. Therefore, we have revealed that the bowl-inversion barrier of the anion is governed by the setoff of the peri-annelation and negative charge effects.     

Self-assembly and morphology of gel networks in l,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol/n-dibutylphthalate

We investigated the self-assembling structure of the 1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol (PDTS)/n-dibutylphthalate (DBP) system in the parameter space of temperature T and solute concentration Phi(PDTS). Optical microscopic studies revealed that the phase diagram can be divided into four regions. In region I at high T the system is a homogeneous solution. In region II at lower T and low Phi(PDTS), the system still has fluidity but has microgels having spherulitic texture of PDTS crystallites. Regions III and IV at even lower T but higher Phi(PDTS) are in a gel state. In region III, the PDTS forms volume-filling spherulites due to the solid-liquid phase transition of the saturated PDTS solutions. In region IV at the lowest T, both the liquid-liquid phase-separation process and the solid-liquid transition of the PDTS are involved in the self-assembling processes. In this region a bicontinuous phase-separated structure is first formed by liquid-liquid phase separation via spinodal decomposition (SD). The subsequent solid-liquid transition of the PDTS in the PDTS-rich region forms percolating crystalline fibrils rather than spherulites. The formation of the crystalline fibrils pins further growth of the bicontinuous structure via SD.     

(Nitronyl Nitroxide)‐Substituted Trioxytriphenylamine Radical Cation Tetrachlorogallate Salt: A 2p‐Electron‐Based Weak Ferromagnet Composed of a Triplet Diradical Cation

The synthesis and the solid state magnetic properties of (nitronyl nitroxide)‐substituted trioxytriphenylamine radical cation tetrachlorogallate, NNTOT+·GaCl4? , are reported. In the temperature region between 300 and 3 K, the magnetic behavior is characterized by the strong intramolecular ferromagnetic interaction (J/k_B=+400 K) between the radical ( NN ) and the radical cation ( TOT ⁺) and the weak intermolecular antiferromagnetic interaction (J/k_B=?1.9 K) between NNTOT⁺ ions. Below 3 K, a 3D‐type long‐range magnetic ordering into a weak ferromagnet was observed (T_N=2.65 K). The magnetic entropy (S_mag=8.97 J K^?1 mol^?1) obtained by the heat capacity measurement is in good agreement with the theoretical value of R ln3=9.13 J K^?1 mol^?1 based on the S=1 state.