Fig. 15. Caffeine as a gelator. (a) Chemical structure of caffeine, theophylline and theobromine; (b) photograph of gels derived from caffeine; (c) optical microscopy image of xerogel; (d) microcrystalline network formation and (e) 13C CP MAS NMR of commercial caffeine, recrystallized form and xerogels. Reproduced with permission from ref. 52, Copyright © 2016 by the authors.
