A team of scientists at the University of Wisconsin-Madison has been focusing on how to control theses hydrophobic reactions. They believe that by focusing on the barrier that forms during this process the next step could be to design a new a range of formulations, particularly ointments in emulsions.
Although water is invariably the largest element in most liquid-based formulations, when mixed with other oily or greasy ingredients, the resulting hydrophobic reaction is often one of the biggest challenges formulators must overcome.
Designing the hydrophobic reaction
Invariably surfactants come to the rescue, because they contain both hydrophobic and hydrophilic qualities that help to control hydrophobic reactions.
To drill down further on the matter, the research team built simple molecules with stable structures that incorporated both hydrophilic and hydrophobic groups in determined patterns. They then used an atomic microscope to probe the surface of the molecules to measure the ‘stickiness’ between each molecule.
“We show that if you have two nonpolar groups, and they are going to interact through water, the way they interact depends on their neighbors,” says Nicholas Abbott, a UW–Madison chemical and biological engineering professor.
“It’s just like a pair of friends having a conversation. The way in which they interact will depend on who is standing close enough to hear.”
Solution maybe in the hydrophobic barrier
The findings of the group’s study were published in the peer-reviewed journal Nature and what they found out about the stickiness proved to be interesting.
“That sticky interaction is defined by the hydrophobic effect,” said professor Sam Gellman, another member of the Wisconsin-Madison University team.
“And our measurements show that it’s possible to place polar groups in a way that can dial up or dial down the adhesion between two hydrophobic surfaces in water.”
The team believes that it is this aspect of control in the polar groups could provide the means to designing new molecules that perform specific functions in water-based formulations.
“You can imagine new designs of switchable materials, smart materials, and maybe drug delivery systems that can release an active agent in a controlled manner by manipulating this interaction,” Abbott says.