No abstract

The deformation behavior of polythiourethane (PTU) elastomers was investigated using in situ small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and X-ray absorption fine structure (XAFS) methods. Two PTUs were prepared from poly­(oxytetramethylene) glycol, 1,4-bis­(isocyanatomethyl) cyclohexane, and 1,4-butanedithiol (PTU-B) or 1,5-pentanedithiol (PTU-P). The effect of methylene length of the chain extender on molecular aggregation structure of PTU during the elongation process was evaluated. SAXS measurement revealed that the spacing of hard segment domains of PTUs increased and decreased in the directions parallel and perpendicular to the elongation direction and showed a constant value of strain above 2. The strain calculated from the spacing of the hard segment domains for PTU-B was larger than that for PTU-P, suggesting that well-developed hard segment domains were formed for PTU-B. WAXD measurement showed that strain-induced crystallization of the soft segment occurred at around the strain of 2. XAFS measurement showed that at the strain of 2 or 3, atoms in the vicinity of sulfur became more ordered, which is confirmed by the decrement of the extended XAFS Debye–Waller factor. It seems reasonable from these SAXS, WAXD, and XAFS results that the hard segment domains orientation occurred for both PTUs during the deformation process, followed by strain-induced crystallization of the soft segment. In addition, PTU-B exhibits more ordered hard segment domains that maintain their aggregation structure upon uniaxial deformation in comparison with PTU-P.

Summary: Isolation of a-cellulose from rice straw has been successfully carried out having 26.95% yield, with 74.28% crystallinity index. The a-cellulose is then chemically modified by grafting acrylic acid monomer onto cellulose using preirradiation graft copolymerization technique. The optimum condition for grafting is obtained at 30 kGy radiation doses, 10% monomer concentration, 60 C grafting temperature and 120 min reaction time, with 84.12% grafting average. The infrared spectroscopy showed a new absorption band at 1720 cm À1 in the modified cellulose, which can be attributed to the presence of carbonyl group of acrylic acid. FESEM imaging showed that the acrylic acid grafting leads to an increase in the roughness and width of the cellulose. The grafting process was found to increase final decomposition temperature of the fibers.

Nanocomposite magnetic polymer electrolytes based on poly(vinyl alcohol) (PVA) complexed with lithium hydroxide (LiOH) and containing magnetite (Fe3O4) nanoparticles were prepared using an in situ method, in which the nanoparticles were grown in the host polymer electrolyte. Ion carriers were formed during nanoparticle growth from the previously added LiOH precursor. If a high concentration of LiOH was added, the remaining unreacted LiOH was distributed in the form of an amorphous complex around the Fe3O4 nanoparticles, thus preventing agglomeration of the nanoparticles by the host polymer. By addition of Fe3O4 the composite polymer electrolytes improved the ionic conductivity, resulting in a maximum conductivity of 1.81×10-3 S⋅cm-1. The magnetic properties of the polymer electrolyte were investigated through magnetic susceptibility studies, and the material was predominantly ferromagnetic.