ABSTRACT
In this study, we prepared a difunctionalized cyanate ester double-decker silsesquioxane (DDSQ-OCN) cage with a char yield and thermal decomposition temperature (Td) which were both much higher than those of a typical bisphenol A dicyanate ester (BADCy, without the DDSQ cage) after thermal polymerization. Here, the inorganic DDSQ nanomaterial improved the thermal behavior through a nano-reinforcement effect. Blending the inorganic DDSQ-OCN cage into the epoxy resin improved its thermal and mechanical stabilities after the ring-opening polymerization of the epoxy units during thermal polymerization. The enhancement in the physical properties arose from the copolymerization of the epoxy and OCN units to form the organic/inorganic covalently bonded network structure, as well as the hydrogen bonding of the OH groups of the epoxy with the SiOSi moieties of the DDSQ units. For example, the epoxy/DDSQ-OCN = 1/1 hybrid, prepared without Cu(II)-acac as a catalyst, exhibited a glass transition temperature, thermal decomposition temperature (Td), and char yield (166 °C, 427 °C, and 51.0 wt%, respectively) that were significantly higher than those obtained when applying typical organic curing agents in the epoxy resin. The addition of Cu(II)-acac into the epoxy/BADCy and epoxy/DDSQ-OCN hybrids decreased the thermal stability (as characterized by the values of Td and the char yields) because the crosslinking density and post-hardening also decreased during thermal polymerization; nevertheless, it accelerated the thermal polymerization to a lower curing peak temperature, which is potentially useful for real applications as epoxy molding compounds.
ABSTRACT
Two new dihydroflavonols, phellodensin-A (1) and phellodensin-C (2); three new coumarins, phellodenol-A (3), phellodenol-B (4), and phellodenol-C (5); one new chlorophyll, phellophyll-a (6); and one new phenyllactate, (2R)-sodium 3-phenyllactate (7), in addition to 35 known compounds have been isolated from the leaves of Phellodendron amurense var. wilsonii. The structures of the new compounds were established based on 1D, 2D NMR and mass spectral analyses. The stereochemistry at the C-2, C-3, and C-2' ' positions of new dihydroflavonol 1 was determined by CD spectroscopy. The known compounds were identified by comparison with authentic samples. The antioxidant and antityrosinase activities were also described.
Subject(s)
Antioxidants/isolation & purification , Chlorophyll/isolation & purification , Coumarins/isolation & purification , Enzyme Inhibitors/isolation & purification , Flavonols/isolation & purification , Monophenol Monooxygenase/antagonists & inhibitors , Phellodendron/chemistry , Plants, Medicinal/chemistry , Antioxidants/chemistry , Antioxidants/pharmacology , Chlorophyll/chemistry , Chlorophyll/pharmacology , Coumarins/chemistry , Coumarins/pharmacology , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Flavonols/chemistry , Flavonols/pharmacology , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , Plant Leaves/chemistry , Stereoisomerism , TaiwanABSTRACT
Three new compounds, phellodensin G, phellodenols D and E have been isolated from the leaves of Phellodendron chinense Schneid (Rutaceae), together with thirteen known compounds. Their structures were established by means of spectroscopic analysis, including extensive 2D NMR and mass spectra.