The effect of para-divinyl benzene on styrenic emulsion-templated porous polymers: a chemical Trojan horse

Emulsion-templated porous polymers such as polymerized high internal phase emulsions (polyHIPEs) are an exciting class of porous polymer due to tunable physical and chemical properties. One original use of polyHIPEs was in high-energy laser experiments. However, a density heterogeneity issue has been identified in polyHIPEs during screening for suitability as a laser target. To understand this problem, we studied the physical properties in detail of a well-understood polyHIPE system, styrene-co-divinyl benzene (S-co-DVB). Dynamic mechanical analysis (DMA), scanning electron microscopy, Mercury porosimetry, and time domain nuclear magnetic resonance (TD-NMR) identified that para-DVB, a component of divinyl benzene (DVB80), was an unstable species—effectively behaving as a chemical Trojan horse. TD-NMR spin–lattice and spin–lock relaxation times elucidated more structural detail on the polymer structure for all the polyHIPEs studied, such as long spin–lattice times corresponded to high modulus values. Furthermore, we observed that the Young’s modulus was reduced by 40% in polyHIPEs containing para-DVB as the cross-linker. Understanding the factors affecting polyHIPE physical properties is an important step to further enhance their effectiveness in the many growing applications of polyHIPEs.