Effects of trace phenolic hydroxyl groups on the cure behaviours and properties of cyanate esters

To improve the curing properties of cyanate esters and retain their heat resistance, dielectric properties and adhesion properties, modified cyanate copolymers were prepared by blending bisphenol A cyanate (BADCy) ester with phenol, hydroquinone (HO), resorcinol and phloroglucinol (LO). Differential scanning calorimetry analysis (DSC) and Fourier transform infrared spectroscopy were used to investigate the cure behaviours of the prepared compounds. The prepared materials were compared with the BADCy ester containing trace of cobalt acetylacetonate (CoAt). The CoAt/BADCy blend modified by HO exhibited better curing properties. The exothermic peak temperature ( T p) of the CoAt/BADCy blend dropped to 169°C after introducing 1 wt% HO, likely due to the hydroxyl functional groups at the para position of the benzene ring resulting in higher symmetry and reactivity for the HO. In addition, compared with original CoAt/BADCy, the cyanate esters modified by phenolic hydroxyl groups demonstrated higher adhesive properties and a similar glass transition temperature (approximately 290°C) as well as stable dielectric properties. The experimental results indicate potential applications of the cyanate ester under high-temperature conditions.

Cobalt(ii) catalyzed C(sp)–H bond functionalization of alkynes with phenyl hydrazines: facile access to diaryl 1,2-diketones

A cobalt acetylacetonate catalyzed oxidative diketonation of alkynes via C(sp)–H bond functionalization has been described. Its application to the synthesis of imidazoles has also been demonstrated.

In situ synthesis of nano-sized cobalt ferrite particle/organic hybrid

A CoFe2O4 particle/organic hybrid was synthesized using in situ processing of metalorganics of cobalt and iron below 100 °C. A mixture of cobalt (II) acetylacetonate (CA) and iron (III) 3-allylacetylacetonate (IAA) was hydrolyzed and polymerized yielding cobalt ferrite particle/organic hybrid. The crystallinity of cobalt ferrite depended upon the hydrolysis conditions of cobalt acetylacetonate-iron 3-allylacetylacetonate (CA-IAA). Nanocrystalline cobalt ferrite particles were uniformly dispersed in the organic matrix. The saturation magnetization of hybrid increased with increasing crystallinity of cobalt ferrite particles in the organic matrix. The hybrid showed a magnetization-applied field (BH) curve with no coercive force at room temperature. The magnetization versus H/T curves from 150 to 300 K were superimposed on the same curve and satisfied the Langevin equation. The hybrid revealed a saturation magnetization of 33.7 emu/g and a coercivity of 11 kOe at 4.2 K.

Supported catalytic epoxidation of polyisobutylene with alkene chain ends

Polystyrene beads functionalised with cobalt acetylacetonate or 1-phenylacetylacetonate were used as catalysts in the aerobic epoxidation of oligoisobutylene with alkene chain ends. The beads were produced in a range of porosities (22–45 vol.%) and were fully characterised by SEM and porosimetry.