Chitosan-fatty acid interaction mediated growth of Langmuir monolayer and Langmuir-Blodgett films

• Published in: Journal of colloid and interface science 2018-03, Vol.514, p.433-442
• Main Authors: Ahmed, Ikbal, Dildar, Lucky, Haque, Anamul, Patra, Prasun, Mukhopadhyay, Mala, Hazra, Satyajit, Kulkarni, Manish, Thomas, Sabu, Plaisier, Jasper R., Dutta, Shyamal Baran, Bal, Jayanta Kumar
• Format: Article
• Language: English
• Subjects: Chitosan; Compressibility; Elasticity; Fatty acid; Gibb’s free energy; Isotherm; Langmuir monolayer; Langmuir-Blodgett film
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2017.12.037

We have demonstrated that chitosan has strong affinity with fatty acid (stearic acid) and adsorbs at the fatty acid monolayer at air–water interface, despite its lack of surface activity. Chitosan insertion caused an expansion of chitosan-fatty acid mixed monolayers and reduced the elasticity and made the film heterogeneous. Chitosan endorses a local distortion of the fatty acid tails involving electrostatic, dipolar and hydrophobic interactions. The results could be rationalized in terms of a model in which at low surface pressure chitosan is situated at interface, interacting with stearic acid molecules via electrostatic and hydrophobic interactions whereas at high pressure chitosan mainly located at subsurface beneath stearic acid molecules. In the latter case the interaction is predominantly electrostatic yielding very small contribution to the surface pressure. Reduction of temperature allows more number of chitosan molecules to reach surface. In addition, chitosan could be transferred onto solid supports employing LB technique by mixing with fatty acid. [Display omitted] •Chitosan-fatty acid interactions at air–water interface.•Interactions modification by chitosan mole fraction and temperature.•Relocation of chitosan on solid substrate employing Langmuir-Blodgett technique via mixing with fatty acid.•Surface pressure induced 2D to 3D structural transition of chitosan-fatty LB films. The interaction of chitosan with bio-membranes, which plays important role in deciding its use in biological applications, is realized by investigating the interaction of chitosan with stearic acid (fatty acid) in Langmuir monolayers (at air–water interface) and Langmuir-Blodgett (LB) films (after transferring it onto solid substrate). It is found from the pressure-area isotherms that the chitosan insertion causes an expansion of chitosan-fatty acid hybrid monolayers, which reduces the elasticity and make the film heterogeneous. It is likely that at low surface pressure chitosan is situated at the interface, interacting with stearic acid molecules via electrostatic and hydrophobic interactions whereas at high pressure chitosan mainly located at subsurface beneath stearic acid molecules. In the latter case the interaction is predominantly electrostatic yielding very small contribution to the surface pressure. The reduction of temperature of the subphase water allows more number of chitosan molecules to reach surface to increase the pressure/interaction. On the other hand,