Self-Degrading Molecular Organogels: Self-Assembled Gels Programmed to Spontaneously Liquefy after a Set Time

Gels are used in the oilfield. For example, during oil recovery, organogels are pumped underground into fractures within oil-bearing rock, so as to block fluid flow. However, after several days, the gels must be degraded (liquefied) to enable oil extraction through the fractures. To degrade gels, 'degrading agents' as well as external stimuli have been examined. Here, a concept is demonstrated that avoids external agents and stimuli: self-degrading organogels based on the self-assembly of molecular gelators. The gels are a) extremely robust (free standing solids) at time t = 0 and (b) degrade spontaneously into a sol after a set time t = tdegr that can be minutes, hours, or days. These properties are achieved by combining two readily available molecules - the organogelator (1,3:2,4)-dibenzylidene sorbitol (DBS) and an acid (e.g., hydrochloric acid, HCl) - in an organic solvent. DBS self-assembles into nanoscale fibrils, which connect into a 3-D network, thereby gelling the solvent. The acid type and concentration set the value of tdegr at a given temperature. Degradation occurs because the acid slowly hydrolyzes the acetals on DBS, thereby converting DBS into small molecules that cannot form fibrils. DBS gels with a pre-programmed "degradation clock" can be made with both polar and non-polar organic solvents. The concept can be a game-changer for oil recovery as it promises to make it safer, more efficient, and sustainable. Self-degrading organogels remain robust for a set time, after which they spontaneously degrade to a sol without the need for external stimuli. A time-activated valve based on such a gel will open spontaneously when the gel liquefies. Such gels can be a game-changer for oil recovery as they can provide a solution to the 'lost circulation' problem during oil drilling. image