Non-porous and porous materials prepared by cross-linking of polyhydromethylsiloxane with silazane compounds

Abstract In the work, polyhydromethylsiloxane (PHMS) was cross-linked with two vinylsilazanes: 1,1,3,3-tetramethyl-1,3-divinyldisilazane ( Vi SiNSi Vi ) or 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasilazane (( Vi SiN) 4 ) in the presence of Karstedt’s catalyst. When the reactions were carried out in solvent-free conditions non-porous polysiloxane-silazane networks were obtained. The processes conducted in high internal phase emulsion (HIPE) resulted in macroporous materials. Their non-porous or porous morphology was established by SEM studies. They were also analyzed by elemental analysis, swelling measurements, FTIR and 29 Si MAS-NMR spectroscopies and thermogravimetry coupled with mass spectrometry (TG/MS). Results showed that the non-porous networks contained high amounts of silazane moieties and were fairly hydrolytically stable. In contrast, contents of silazane units in most porous materials were low. Moreover, hydrolysis of Si H groups of PHMS followed by condensation of the resulting Si OH groups took place in HIPE conditions. This led to additional cross-linking of PHMS by siloxane bonds. During preparation of porous systems using Vi SiNSi Vi , hydrolysis of silazane bonds (Si N) also occurred. All the materials studied in the work contained reactive Si H groups and therefore exhibit a great potential for various applications. Presence of nitrogen atoms in their structure as well as porosity may be additional advantages.