if you want to insulate or seal with polyurethane foam , instead of waiting two days for it to cure , you will be able to do it in a few hours using a foam can with our microcapsules . my team at lisboa was peacefully characterizing the microcapsules produced at palermo by transmission electron microscopy ( tem ) . we were heartbroken when the microcapsules unexpectedly exploded by pressure reduction , yielding blurred tem images . this drawback turned out to be a step forward , as it showed that the microcapsules were behaving exactly as they were intended releasing the encapsulated glycerol by depressurization . first , the microparticles are practically leach - proof , i.e. they do not release their content when mixed and pressurized within an aerosol can along with polyurethane precursors ( a diisocyanate and a polyol ) . surprisingly  and this is the second unique feature  the greencaps microcapsules have extensive microporosity and are permeable to the unreactive blowing - agent molecules . the microspheres thus become pressurized , and when sprayed at atmospheric pressure , they break , releasing their valued payload . these microspheres could be used as solid curing agents for innovative one - component spray polyurethane foams . they could also have extended applications in curing other polymers , starting from polyester resins , where the microspheres would act as reservoirs of the functional ingredient . this work is part of an ongoing collaboration in the field of sol - gel materials which started ten years ago , when one of us , temporarily at the cole nationale suprieure de chimie de montpellier ( enscm ) , stumbled across a paper on the sol - gel process published in chemistry  a european journal by ilharcos group . since then , we have managed to publish a large body of joint research papers that has impacted the applicative potential of functional sol - gel silicas , in catalysis , eco - friendly fragrances , and polymer curing .
invited for this months cover are the groups of professor mario pagliaro at the istituto per lo studio dei materiali nanostrutturati in palermo and professor laura ilharco at the instituto superior tcnico in lisboa . 
 the cover picture shows a greencaps microcapsule breaking and releasing encapsulated glycerol after the organosilica microspheres are sprayed from a pressurized polyurethane foam can . 
 this shows how glycerol acts as a solid curing agent , promoting crosslinking of partially polymerized diphenylmethane diisocyanate . for more details , see the full paper on p.  120  ff .