Design of highly porous melamine-based networks through a bicontinuous microemulsion templating strategy
Designing low density polymeric porous materials with defined pore sizes (diameters in the 100 nm range) still remains a real synthesis challenge. Here, for the first time, we present a strategy by which bicontinuous microemulsions are used as templating agents for the in-situ aqueous polycondensation of organic resins (melamine formaldehyde, MF). The behaviour of surfactants with different head-groups in systems including oil and MF-containing aqueous phase is studied. While many surfactants are not compatible with aqueous MF precondensates, here we report a non-ionic surfactant either used solely or along with anionic surfactants which prove to be successful at keeping bicontinuous microemulsion systems homogeneous even during early stages of polymerisation. However, upon acid-catalysis it becomes clear that the pore structure of the organic material is largely controlled by the kinetics of phase separation due to the sol–gel process rather than by the thermodynamic equilibrium of the template (microemulsion). Indeed, despite numerous attempts, stabilising the microemulsion interface with zero curvature (bicontinuous) has remained problematic. Instead, we show a new behaviour for the MF resin whereby non-spherical MF morphologies (i.e. thread-like structures) can be obtained by specific interactions between the aqueous amino resin and the acid counterions.
KeywordsMelamine Sol–gel Microemulsion Template Bicontinuous
- 1.Payra P, Dutta PK (2003) In: Auerbach SM, Carrado KA, Dutta PK (eds) Handbook of zeolite science and technology. Marcel-Dekker, NYGoogle Scholar
- 3.Singh R, Dutta PK (2003) In: Auerbach SM, Carrado KA, Dutta PK (eds) Handbook of zeolite science and technology. Marcel-Dekker, NYGoogle Scholar
- 8.Handa YP, Zhang Z, Wong B (2001) Cell Polym 20(1):1–16Google Scholar
- 15.Sottmann T, Lade M, Stolz M, Schömacker R (2002) Tenside Surf Det 1:20–27Google Scholar
- 20.Blank WJ (1979) J Coating Technol 51:61–70Google Scholar