Analysis of Temperature and Alkyl Chain Length Impacts on the Morphological Peculiarities of Nonionic Surfactant Clusterization. A Quantum Chemical Approach

Using the quantum chemical model for description of the clusterization thermodynamics of nonionic surfactants at the air/water interface ( J. Phys. Chem. B 2015, 119, 3281), it is shown that temperature increase and shortening of the alkyl chain length results in an increase of the content of infinite “linear” one-dimensional (1D) clusters leading to branching of the formed monolayer. In the framework of the approach assess the “temperature effect” of surfactant clusterization ( J. Phys. Chem. B 2012, 116, 8996), the temperature dependences of the clusterization Gibbs’ energy for 1D and two-dimensional clusters are obtained in the range of 278–318 K with steps of 5 K for amphiphiles with the alkyl chain length of 10–25 carbon atoms. The preferential formation of the associates comprised of dimers with “parallel” orientation of the hydrophilic head groups gives rise to the formation of “linear” 1D clusters. This is caused by the larger destabilizing increment of the “sequential” interactions of the head groups in the clusterization Gibbs’ energy and the loss of CH···HC interactions between “sequentially” orientated molecules with voluminous hydrophilic parts. The derived results are corroborated by experimental data obtained by Brewster angle microscopy of nervonic acid monolayers.