Keratin-based biological substrates like hair and skin are examples of natural hydrophobic surfaces. In both, the membranes of the living cells which generate these two evolved structures have formed a hydrophobic barrier against a more hydrophilic protein material. Most cosmetic formulations (shampoos, conditioners) used in hair care are based upon the subtle balance between the various interactions (hydrophobic, electrostatic) among cationic polyelectrolytes, surfactants and the hair surface itself that allows the conditioning agents to be adsorbed and restore or improve its functional properties.While several experimental approaches allow the process of co-assembly of polyelectrolytes with oppositely charged surfactants, to be modelled or simulated, it still remains a challenging topic. Modelling bulk co-assembly and corresponding adsorption on surfaces so far ignored the effect of the chain architecture of the polymers. This presentation will focus upon the effects of the chain architecture of polymers and surfactants on the co-operative adsorption of associative mixtures of these components onto both hydrophilic and hydrophobic surfaces. We adopt the self-consistent field theory of Scheutjens and Fleer and discuss adsorption scenarios originating either from pure electrostatic or other interactions between the segments of surfactants and/or polymers with the (charged) surfaces. We show that tuning the position of hydrophobic and hydrophilic fragments at the monomer level, e.g. through including short hydrophilic side chains attached to the hydrophobic backbone of the polymer or inserting short polyoxyethylene sequences may lead to tailored adhesive and tribological properties.

Understanding the forces at the surface of hair and skin and its modification by polymers

247th National Meeting (2014)

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