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The morphology and molecular mobility of polyethylene were investigated by X-ray diffraction and 13C solid-state NMR as a function of temperature. The test specimens chosen are melt films, single-crystal mats, undrawn dry gel films, and ultradrawn films with a draw ratio of 300. The semilogarithmic plot of the 13C magnetization of the peak height of the line at 33 ppm indicated the existence of three different kinds of spin-lattice relaxation time (Tic): a slow decay time, an intermediate decay time, and a rapid decay time for the orthorhombic crystal form. Among the test specimens, the decay time of the ultradrawn gel film was the longest. The spin-spin relaxation time (^c) indicated that the noncrystalline component consists of an interfacial region and a rubber-like amorphous region with extensive molecular mobility. For single-crystal mats and dry gel films, the lenght of the interfacial region calculated using both the mass fraction of the interfacial region by 13C NMR and the long period by X-ray scattering was almost equal to the length of the interfacial region estimated by analyzing a systematic deviation of the X-ray scattering curves at large angle tail from Porod's law. Furthermore, the crystallinity at room temperature estimated by 13C NMR was also in good agreement with the results by density and X-ray diffraction. With increasing temperature, Tic for the crystalline region became shorter, while Tic for the noncrystalline region became longer, indicating more active molecular mobility. The crystallinity estimated by 13C NMR was confirmed to decreased with increasing temperature. This tendency was in good agreement with the results obtained by X-ray diffraction using Ruland's method.

ABSTRACT:The crystal lattice modulus of poly(vinyl alcohol) was measured by X-ray diffraction using films which were prepared by gelation/crystallization from solution and elongated in a silicon oil after evaporating solvent. The measured crystal lattice modulus of specimen with Young's modulus 13-20GPa was in the range 200-220GPa. These values were lower than that for polyethylene measured by using ultradrawn films. To check the morphology dependence of the measured crystal lattice modulus of poly(vinyl alcohol), a numerical calculation was carried out by considering molecular orientation and crystallinity. In this calculation, a three-dimensional model was employed, in which oriented crystalline layers are surrounded by oriented amorphous phase and the strains of the two phases at the boundary are identical. The theoretical results indicate that the difference between the crystal lattice modulus as measured by X-ray diffraction and the intrinsic value becomes less pronounced and Young's modulus of a sample becomes lower when a series coupling between crystalline and amorphous phases is predominant. A series of numerical calculations for the system with low crystallinity and orientational degree of amorphous chain segments indicates that the real value of the crystal lattice modulus is slightly higher than 200-220 GPa measured by X-ray diffraction.KEY WORDS Poly(vinyl alcohol) / Crystal Lattice Modulus / Numerical Calculation/ X-Ray Diffraction/ Series Coupling/ Since 1974, the preparation of polymeric fibers and films with high-strength and highmodulus has been extensively investigated for flexible polymers by gel-state spinning, 1 ultradrawing of dried gel films 2 • 3 ultradrawing of single-crystal mats,4 and two-step drawing of single-crystal mats. 5 This research is based on the assumption that the theoretical Young's modulus and tensile strength of polymeric materials could be realized if the chains are fully aligned and if the specimen is almost completely crystalline. Results of interest have been obtained for polyethylene and polypropylene whose Young's moduli at 20°C are higher than 200 GPa 3 • 4 and 40 GPa, 6 • 7 respectively. These values are nearly equal to their crystal lattice moduli as measured by X-ray diffraction technique. Although the theoretical Young's modulus of polyethylene is one of the highest among crystalline polymers, the range of application is limited by its low melting point. Therefore, it is important to achieve ultradrawing of other crystalline polymers such as polyamide, polyester, and poly(vinyl alcohol) (PV A).

We have easily fabricated channel patterns of organic field-effect transistors (OFET), in which channel lengths were ca. 5 μm, by using wet-spun poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) microfibers with diameters of ca. 5 μm. Pentacene-based OFETs with a bottom-contacted configuration, fabricated on the channel patterns, showed a hole mobility of 10−3 cm2 V−1 s−1 simply reflecting FET characteristics of the pentacene, and showed large current of 8 μA (VDS=−50 V; VG=−50 V) reflecting shorter channel length of the devices.