Temperature dependent dendritic domain shapes in Langmuir monolayers of tetradecanoyl N-ethanolamide at the air–water interface

The effect of temperature on the surface phase behavior of tetradecanoyl N-ethanolamide (NHEA-14) in Langmuir monolayers at the air–water interface has been investigated by film balance and Brewster angle microscopy (BAM). It has been observed that dendritic domains are formed in the coexistence region between liquid-expanded (LE) and liquid-condensed (LC) phases at different temperatures. At 10 and 15 °C, the domains are four-armed dendrites having wide arms which have a tendency to be fractal while growing in size. At 20 °C, five-armed dendritic domains are formed. At a temperature higher than 20 °C, the domains are mainly six-armed dendrites having very narrow and sharp arms. The formation of dendritic domains should be due to the presence of interfacial hydrogen bonding among the head groups of the amphiphile. Increased dehydration of the head groups with an increase in the temperature should be responsible for the temperature dependency of the dendritic domain shapes in the monolayers of NHEA-14.

Morphologies of NHEA-14 monolayers at different temperatures.Figure optionsDownload high-quality image (31 K)Download as PowerPoint slideResearch highlights
► Temperature dependent dendritic LC domains are formed in the monolayers of NHEA-14.
► The domains are four-armed dendrites having wide arms at 10 °C.
► The domains are mainly five-armed at 20 °C.
► The domains are six-armed dendrites having very sharp and narrow arms at 30 °C.
► The sharpness and the number of the arms increase with increasing temperature.