A zirconium complex having two phenoxy-imine chelate ligands, bis[N-(3-tert-butylsalicylidene)anilinato]zirconium(IV)dichloride (1), was found to display a very high ethylene polymerization activity of 550 kg of polymer/mmol of cat‚h with a viscosity average molecular weight (M v ) value of 0.9 × 10 4 at 25 °C at atmospheric pressure using methylalumoxane (MAO) as a cocatalyst. This activity is 1 order of magnitude larger than that exhibited by Cp 2 ZrCl 2 under the same polymerization conditions. The use of Ph 3 CB(C 6 F 5 ) 4 / i-Bu 3 Al in place of MAO as a cocatalyst resulted in extremely high molecular weight polyethylene, M v 505 × 10 4 , with an activity of 11 kg of polymer/mmol of cat‚h at 50 °C. This M v value is one of the highest values displayed by homogeneous olefin polymerization catalysts. Complex 1, using Ph 3 CB(C 6 F 5 ) 4 /i-Bu 3 Al as a cocatalyst, provided a high molecular weight ethylene-propylene copolymer, M v 109 × 10 4 , with 8 kg of polymer/mmol of cat‚h activity at a propylene content of 20.7 mol %. X-ray analysis revealed that complex 1 adopts a distorted octahedral coordination structure around the zirconium metal and that two oxygen atoms are situated in trans position while two nitrogen atoms and two chlorine atoms are situated in cis position. DFT calculations suggest that the active species derived from complex 1 possesses two available cis-located sites for efficient ethylene polymerization. Changing the tert-butyl group in the phenoxy benzene ring enhanced the polymerization activity. Bis[N-(3-cumyl-5-methylsalicylidene)cyclohexylaminato]zirconium(IV)dichloride ( 7) with MAO displayed an ethylene polymerization activity of 4315 kg of polymer/mmol of cat‚h at 25 °C at atmospheric pressure. This activity corresponds to a catalyst turnover frequency (TOF) value of 42 900/s‚ atm. This TOF value is one of the largest not only for olefin polymerization but also for any known catalytic reaction. Ligands with additional steric congestion near the polymerization reaction center gave increased M v values. The maximum M v value, 220 × 10 4 using MAO, was obtained with bis[N-(3,5-dicumylsalicylidene)-2′-isopropylanilinato]zirconium(IV)dichloride (15). Thus, polyethylenes ranging from low to exceptionally high molecular weights can be obtained from these zirconium complexes by changing the ligand structure and the choice of cocatalyst.

Seven titanium complexes bearing fluorine-containing phenoxy-imine chelate ligands, TiCl(2)[eta(2)-1-[C(H)=NR]-2-O-3-(t)Bu-C(6)H(3)](2) [R = 2,3,4,5,6-pentafluorophenyl (1), R = 2,4,6-trifluorophenyl (2), R = 2,6-difluorophenyl (3), R = 2-fluorophenyl (4), R = 3,4,5-trifluorophenyl (5), R = 3,5-difluorophenyl (6), R = 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl(4) in good yields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structure in which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and the two chlorine atoms are located cis to one another, the same spatial disposition as that for the corresponding nonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 are very similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O, N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogen are different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms. Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to produce high molecular weight polyethylenes (M(n) > 400 000) with extremely narrow polydispersities (M(w)/M(n) < 1.20). Very high activities (TOF > 20 000 min(-1) atm(-1)) were observed that are comparable to those of Cp(2)ZrCl(2)/MAO at high polymerization temperatures (25, 50 degrees C). Complexes 2-4, which have a fluorine atom adjacent to the imine nitrogen, behaved as living ethylene polymerization catalysts at 50 degrees C, whereas complexes 5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having M(w)/M(n) values of ca. 2 with beta-hydrogen transfer as the main termination pathway. These results together with DFT calculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirement for the high-temperature living polymerization, and the fluorine of the active species for ethylene polymerization interacts with a beta-hydrogen of a polymer chain, resulting in the prevention of beta-hydrogen transfer. This catalyst system was used for the synthesis of a number of unique block copolymers such as polyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.

A technique for recording and retrieving small marks beyond the optical diffraction limit was proposed. The basic experiment with this technique was also carried out at a constant linear velocity of 2.0 m/s, rotating a disk with a multi-layered structure of Sb and GeSbTe, which were separated by a thin film of SiN. By use of the optically nonlinear property of the Sb thin film, carrier to noise ratio of more than 10 dB was obtained from recorded marks of 90 nm, using an optical system with the laser wavelength of 686 nm and a numerical aperture of 0.6.

The quasibinary GeTe-Sb 2 Te 3 system (primarily the Ge 2 Sb 2 Te 5 composition, or GST225) has been long used in optical memory devices such as re-writable DVD-RAM and are also a leading candidate for the nonvolatile electronic memory known as phase-change random-access memory (PC-RAM); last year Samsung and Micron have started shipping these devices into the market. The basis of the phase-change storage is a large property contrast between the crystalline and amorphous phases; the idea dates back to the 1960s. [ 1 ] In a PC-RAM device, when a voltage exceeding a certain value (a threshold voltage) is applied to the high-resistivity amorphous phase, the material switches into the low-resistivity crystalline (SET) phase. The process can be reversed (RESET) by applying another pulse, of appropriately chosen amplitude and duration, that reverts the structure to the amorphous phase.Non-volatile memory devices are currently key elements of various electronics and portable systems (digital camera, solid state disks, smartphones, computers, e-books, tablets, etc.) and their market has been increasing exponentially over the last decade. One important aspect is to develop new memory storage concepts and devices that can integrate multiple functionalities. It was recently found by some of the present authors [ 2 ] that when GeTe and Sb 2 Te 3 components are spatially separated in forms of nm-thick layers to form a superlattice (interfacial phase-change memory, or iPCM), the energy effi ciency of devices increases by orders of magnitude, the resistivity contrast is lower in iPCM and, in stark contrast to the composite material, iPCM remains in a crystalline phase in both SET and RESET states. [ 2 ] These results demonstrate that the storage mechanism is different from conventional (composite) phase-change materials, where the GeTe and Sb 2 Te 3 phases are intermixed.It is instructive to note that both individual constituents of iPCM possess rather specifi c properties. Sb 2 Te 3 is one of the best known examples of three-dimensional (3D) tolopogical insulators (TI). [ 3 ] GeTe, on the other hand, is the simplest known ferroelectric material with just two atoms in the primitive cell. [ 4 ] This conclusion was primarily reached based on structural studies; [ 5 ] the main challenge in direct studies of ferroelectricity in GeTe by conventional electrical spectroscopic techniques, such as hysteresis loop and transient current measurements, is its high conductivity: free charge carriers screen the applied electric fi eld inhibiting polarization reversal and result in high dielectric loss. Ferroelectric order has been demonstrated for nm-sized nanocrystals. [ 6,7 ] and ferroelectric switching in GeTe has been observed experimentally in polycrystalline samples using piezoresponse force microscopy (PFM) and capacitance measurements. [ 8 ] Furthermore, stable ferroelectric switching has been recently observed in epitaxial GeTe fi lms, [ 9 ] which provides tangible reasons to expect the scaling of the ferroelectric switching functio...

The propylene polymerization behavior of a series of Ti complexes featuring fluorine-containing phenoxy-imine chelate ligands is reported. The Ti complexes combined with methylalumoxane (MAO) can be catalysts for living and, at the same time, stereospecific polymerization of propylene at room temperature or above. DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a beta-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization. Although the Ti complexes possess C(2) symmetry, they are capable of producing highly syndiotactic polypropylenes. (13)C NMR is used to demonstrate that the syndiotacticity is governed by a chain-end control mechanism and that the polymerization is initiated exclusively via 1,2-insertion followed by 2,1-insertion as the principal mode of polymerization. (13)C NMR spectroscopy also elucidated that the polypropylenes produced with the Ti complexes possess regio-block structures. Substitutions on the phenoxy-imine ligands have profound effects on catalytic behavior of the Ti complexes. The steric bulk of the substituent ortho to the phenoxy oxygen plays a decisive role in achieving high syndioselectivity for the chain-end controlled polymerization. Over a temperature range of 0-50 degrees C, Ti complex having a trimethylsilyl group ortho to the phenoxy oxygen forms highly syndiotactic, nearly monodisperse polypropylenes (94-90% rr) with extremely high peak melting temperatures (T(m) = 156-149 degrees C). The polymerization behavior of the Ti complexes can be explained well by the recently proposed site-inversion mechanism for the formation of syndiotactic polypropylene by a Ti complex having a pair of fluorine-containing phenoxy-imine ligands.