Inflatable Elastomeric Macroporous Polymers Synthesized from Medium Internal Phase Emulsion Templates

Abstract

Closed cell elastomeric polydimethylsiloxane (PDMS) based polymerized medium internal phase emulsions (polyMIPEs) containing an aqueous solution of sodium hydrogen carbonate (NaHCO3) have been produced. Via thermal decomposition of NaHCO3, carbon dioxide was released into the polyMIPE structure to act as a blowing agent. When placed into an atmosphere with reduced pressure, these macroporous elastomers expanded to many times their original size, with a maximum expansion of 30 times. This expansion was found to be repeatable and reproducible. The extent of volume expansion was determined primarily by the dispersed phase volume ratio of the emulsion template; polyMIPEs with 60% dispersed phase content produced greater volume expansion ratios than polyMIPEs with 50% dispersed phase. Increasing the concentration of NaHCO3 in the dispersed phase also led to increased expansion due to the greater volume of gas forming within the porous structure of the silicone elastomer. The expansion ratio could be increased by doubling the agitation time during the emulsification process to form the MIPEs, as this decreased the pore wall thickness and hence the elastic restoring force of the porous silicone elastomer. Although MIPEs with 70% dispersed phase could be stabilized and successfully cured, the resultant polyMIPE was mechanically too weak and expanded less than polyMIPEs with a dispersed phase of 60%. It was also possible to cast the liquid emulsion into thin polyMIPE films, which could be expanded in vacuum, demonstrating that these materials have potential for use in self-sealing containers.

Storage Moduli and Porosity of Soft PDMS PolyMIPEs Can Be Controlled Independently Using Thiol–Ene Click Chemistry

“…[15][16][17][18] This has been used to prepare porous PDMS materials. [19][20][21][22][23][24] The term high is defined as when the volume fraction of the dispersed-phase of the emulsion exceeds 74% of the global volume. An emulsion with 24-74% dispersed phase by volume is called a medium internal phase emulsion (MIPE), and low internal phase emulsions (LIPEs) contain less than 24% of dispersed phase by volume.…”

Collapse and cavitation during the drying of water-saturated PDMS sponges with closed porosity

“…Moreover, these materials were used to fabricate novel acoustic metamaterials 2 and gradient lenses 3 due to extremely low values of the sound speed obtained at ultrasound frequencies 4 . To achieve a controlled porous structure, a template consisting of liquid droplets 5 or solid particles 6 is dispersed in the liquid prepolymer, usually polydimethylsiloxane (PDMS), which is then crosslinked to obtain an elastomer. The template is then removed by etching 7 (in the case of solid particles), washing and drying to obtain pores with sizes and volume fraction similar to that of the template.…”

Generation of Silicone Poly‐HIPEs with Controlled Pore Sizes via Reactive Emulsion Stabilization

“…This requires the control over the size, organization, and relative volume of the cells, and also over the stability of the liquid template with respect to ageing effects like cell coalescence. While such questions have been investigated successfully for different types of polymers, only few advances have been made for materials with a silicone matrix such as poly(dimethylsiloxane) (PDMS) . This is due to the difficulty of finding sufficiently efficient stabilizing agents for the liquid template which allow to obtain high volume fractions of the internal phase.…”