Synthesis and thermal analysis of crosslinked imidazolium-containing polyester networks prepared by Michael addition polymerization
摘要:
Several new covalently crosslinked imidazolium-containing polyester networks were prepared by Michael addition polymerization to probe how ionic functionality might affect thermal properties such as glass transition temperature (T-g) and thermal decomposition (T-d5%). A structure-activity relationship was investigated involving a variation of the methylene spacer and the counteranion of the acetoacetate precursors. Analysis of T-g by differential scanning calorimetry (DSC) indicated that a longer methylene spacer (n = 6 versus 2) resulted in lower T-g values due to increased chain mobility. It was also discovered that the larger the counteranion, the lower the T-g(Br- > NO3- approximate to BF4- CF3CO2- > NTf2-). Thermogravimetric analysis (TGA) indicated that the thermal stability of the polyesters was inversely related to the basicity of the counteranion used, following the trend: (NTf2- > BF4- > NO3- > Br-). The exception was the trifluoroacetate-containing polyester, which exhibited the lowest thermal stability. Published by Elsevier Ltd.
Functionalized imidazoline-2-ylidene complexes of rhodium and palladium
作者:Wolfgang A. Herrmann、Lukas J. Gooβen、Michael Spiegler
DOI:10.1016/s0022-328x(97)00434-8
日期:1997.12
N-Heterocyclic ‘carbene’ ligands derived from imidazole are alternatives for the well-established phosphine ligands in organometallic catalysis. In contrast to phosphines, the carbene ligands do not undergo ready dissociation from palladium and rhodium so that immobilization techniques appear reasonable. The synthesis of novel, functionalized imidazoline-2-ylidene complexes suitable for reactions with