This article describes the orientation of the crystal b-axis of poly-p-phenylenebenzobisoxazole (PBO) fibers, preferentially in a direction perpendicular to the fiber axis. Although the preferential orientation of the a-axis (i.e. the (200) crystal plane) in the various PBO fibers has already been reported, but to the best of our knowledge, there is a limited number of reports about the preferential orientation of the crystal b-axis of PBO. In order to estimate the degree of preferential orientation of different crystal planes, X-ray diffraction intensities of (010) and (210) for PBO were measured along the radial direction of the fiber and analyzed with an extended two-phase model and a micro-focus X-ray diffraction technique. The degree of preferential orientations of the crystal b-axis (i.e. the (010) crystal plane) was successfully estimated. Also, the positional dependence of apparent crystal size along the equator has been elucidated.

The lattice structures of spherical micelles in binary mixtures of polybutadiene-poly(ε-caprolactone) diblock copolymers and polybutadiene homopolymers were investigated using synchrotron small angle X-ray scattering technique. In the blend sample with a weight fraction of added homopolymer (φ_homo) of 40 wt%, hexagonally packed cylinders were formed, while spherical morphologies were arrayed into the Frank-Kasper σphase at φ_homo = 50 wt%. Closely packed spheres in hexagonal closely packed (HCP) and face-centered cubic (FCC) lattices were observed for the sample with φ_homo = 56 and 67 wt%, respectively. It was found that the lattices of spherical micelles assembled into the following phases with increasing φ_homo: Frank-Kasper σ, HCP,and FCC phases.

Highly stretchable poly(ethyl acrylate) (PEA) composites reinforced with a well-defined nanofiber network of bacterial cellulose (BC) were prepared via stepwise solvent exchange followed by in situ photoinitiated free radical polymerization. Despite the small volume fraction of BC (approximately 0.4 vol%), the BC/PEA composite showed significant increases in Youngʼs modulus (26 times larger than that of the neat PEA),tensile strength (3.5 times larger), and fracture energy (3.8 times larger), with its fracture strain (1520 %) almost the same as that of the neat PEA (1660 %). This composite was characterized by effective strain hardening. The changes in strain-hardening modulus and tensile strength were explained well by the rule of mixtures. Confocal laser scanning microscopic observations revealed the structure of the nanofibers embedded in the elastomeric matrix. The enhanced mechanical properties were discussed based on the rigidity and flexibility of the BC nanofibers and their entangled network and were ascribed to the well-defined BC nanofiber network produced by the bacterium.

Aqueous TEMPO-oxidized cellulose nanofiber (TOCN) dispersions can be converted to hydrogels by adding an acid or polyvalent metal salt solution. Here we report the mechanical properties of the TOCN hydrogels in terms of gelling additives. The mechanical properties of the hydrogels were significantly affected by the added amount and chemical structure of the additives. The breaking strength of the hydrogels became higher with a decrease in pH value of the gels, suggesting that surface-carboxylated TOCNs were more strongly aggregated at pH <4. At the same pH 2.8, the gel strength became higher when the valence of added metal ions was higher; the hydrogels of physically aggregated TOCNs were further reinforced by cross-linking of TOCNs with polyvalent metal ions. Moreover, the composite hydrogels of TOCN and water-soluble carboxymethylcellulose (CMC) were prepared by adding aluminum acetate to aqueous TOCN/CMC mixtures. The strength of the composite hydrogels had unique properties, different from the conventional composite theory. These results suggest that in the TOCN/CMC composite hydrogels, specific interactions or entangled structures are present between TOCNs and CMC molecules.

Ultra-high-molecular-weightpoly[(R)-3-hydroxybutyrate-co-3.2 mol%-(R)-3-hydroxyhexanoate] (UHMW-PHBH),withaweight-average molecular weight (M_w) of approximately 400×10⁴, is extracted from genetically engineered microbial cells via an optimized solvent extraction method. PHBH polymers with various molecular weights (various MW-PHBHs) are prepared from the UHMW-PHBH using H₂SO₄ treatment. The thermal properties and spherulite growth morphology of the UHMW-PHBH and various MW-PHBHs are analyzed in order to investigate the properties of UHMW-PHBH and the effect of the molecular weight on the above properties. The value of Tm and Tg were same regardless of M_w above 62 × 10⁴. The crystallization half time (t_1/2), as an index of overall crystallization speed, of UHMW-PHBH did not change, compared with that of normal molecular weight PHBH. The observation of crystallization morphology revealed that molecular chains with high-molecular-weight lead to decrease the growth rate of spherulite and increase the crystal nuclei forming frequency. Drawn films of UHMW-PHBH are prepared by one-step or two-step cold-draw methods, and their mechanical properties and highly ordered structure are analyzed by tensile tests and X-ray measurements, respectively. One-step cold-drawn UHMW-PHBH films exhibit enhanced properties relative to those of normal-molecular-weight PHBH. Wide-angle X-ray diffraction and small-angle X-ray scattering reveal that the one-step cold-drawn UHMW-PHBH possesses the rare β-form crystal structure. Additionally, the β-form crystal are increased drastically after two-step drawing process with increasing tensile stress. The crystal structure of those films were also investigated by synchrotron X-ray.