Topochemical polymerization can also be triggered by pressure. It has been reported that the cocrystal of diododiacetylene (guest) and bispyridyl oxalamide (host) could be polymerized under pressure. Interestingly, no polymerization was observed under light or heat due to the unfavorable distance between diacetylene units. The researcher postulated that the high pressure might "squeeze" the reactive site together and initiate the polymerization.