For most people, smell is one of the main deciding factors when buying shampoo. But whether it's a hint of coconut, a whiff of wildflowers, or the aroma of some bizarre fruit cocktail, the smell doesn't last long after stepping out of the shower. Researchers from École Polytechnique Fédérale de Lausanne (EPFL) may now have found the answer to longer-lasting scents that can stay in the hair for up to 24 hours.

Manufacturers currently employ a couple of different methods involving delivery systems in an attempt to prevent expensive fragrance compounds from evaporating or being washed away. One technique, called profragrance, involves attaching a polymer to the scent, while another involves encasing the scent compound within polymer microcapsules. Although both of these approaches are effective in the short term, they don't aid the fragrances in adhering to the hair for long periods.

A team at EPFL has now identified a cyclic peptide that is effective at binding to hair under the conditions experienced during shampooing – i.e. a low pH environment with the presence of surfactants that lower the surface tension between two liquids and make it easier for the fragrance to be washed away.

The team conducted tests on the two aforementioned techniques and found that a profragrance model polymer that was bound to the peptide clung to hair around five times more efficiently, while a microcapsule proved 20 times more efficient. The researchers claim the higher rate of deposition caused by the peptide resulted in a stronger smell on the hair that lasted for up to 24 hours after shampooing.

It's unclear if or when peptide will be appearing in shampoos at your local store, but the team's research appears in the journal ACS Applied Materials.

Source: American Chemical Society