3 research outputs found
From Microphase Separation to Self-Organized Mesoporous Phenolic Resin through Competitive Hydrogen Bonding with Double-Crystalline Diblock Copolymers of Poly(ethylene oxide-<i>b</i>-ε-caprolactone)
A series of immiscible crystalline–crystalline diblock copolymers, poly(ethylene oxide)-<i>b</i>-(ε-caprolactone) (PEO-<i>b</i>-PCL), were synthesized through ring-opening polymerization and then blended with phenolic resin. FT-IR analyses demonstrate that the ether group of PEO is a stronger hydrogen-bond acceptor with the hydroxyl group of phenolic resin than is the carbonyl group of PCL. Phenolic, after being cured with hexamethylenetetramine (HMTA), results in the excluded and confined PCL phase based on analyses by differential scanning calorimetry (DSC). This effect leads to the formation of a variety of composition-dependent nanostructures, including disorder, gyroid and short-cylinder structures. The self-organized mesoporous phenolic resin was found only at 40–60 wt % phenolic content by an intriguing balance of the contents of phenolic, PEO, and PCL. In addition, the mesoporous structure was destroyed at higher PCL/PEO ratios in the block copolymers, as determined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) experiments. In addition, the large and long-range order of bicontinuous gyroid-type mesoporous carbon was obtained from mesoporous gyroid phenolic resin calcined at 800 °C under nitrogen
Palladium-Catalyzed Annulation of 2,2′-Diiodobiphenyls with Alkynes: Synthesis and Applications of Phenanthrenes
A range of phenanthrene derivatives were efficiently
synthesized
by the palladium-catalyzed annulation of 2,2′-diiodobiphenyls
with alkynes. The scope, limitations and regioselectivity of the reaction
were investigated. The described method was adopted to synthesize
9,10-dialkylphenanthrenes, sterically overcrowded 4,5-disubstituted
phenanthrenes and phenanthrene-based alkaloids. Reactions of highly
methoxy-substituted biphenyls with 2-(2-propynyl)Âpyrrolidine and 2-(2-propynyl)Âpiperidine
gave 2-(9-phenanthylmethyl)Âpyrrolidines and 2-(9-phenanthylmethyl)Âpiperidines,
respectively. The products were transformed to phenanthroindolizidine
and phenanthroquinolizidine alkaloids by the Pictet–Spengler
reaction
The Role of Ti Buffer Layer Thickness on the Resistive Switching Properties of Hafnium Oxide-Based Resistive Switching Memories
Ti/HfO<sub><i>x</i></sub>-based resistive random access
memory (RRAM) has been extensively investigated as an emerging nonvolatile
memory (NVM) candidate due to its excellent memory performance and
CMOS process compatibility. Although the importance of the role of
the Ti buffer layer is well recognized, detailed understanding about
the nature of Ti thickness-dependent asymmetric switching is still
missing. To realize this, the present work addresses the effects of
Ti buffer layer thickness on the switching properties of TiN/Ti/HfO<sub><i>x</i></sub>/TiN 1T1R RRAM. Consequently, we have demonstrated
a simple strategy to regulate the FORMING voltage, leakage current,
memory window, and decrease the operation current, etc. by varying
the thickness of the Ti layer on the HfO<sub><i>x</i></sub> dielectrics. Accordingly, controllable and reliable bipolar, complementary,
and reverse bipolar resistive switching (BRS, CRS, and R-BRS) properties
have been demonstrated. This work also provides the direction to avoid
unwanted CRS properties during the first RESET operation by decreasing
the FORMING voltage. Furthermore, the memory device shows good nonvolatility
at ∼1 μA programming current by selecting a proper thickness
of Ti buffer layer. To achieve reliable BRS properties for low power
application, the operation current has been further optimized, whereas
the memory device shows pulse endurance of more than 7 million cycles
at a low pulse width of 50 ns and excellent data retention properties
of more than 40 h at 150 °C measurement temperature