Exploring Langmuir-Blodgett technique to investigate effect of various subphase conditions on monolayers formed by amphiphilic block co-polymers tetronic 701 and tetronic 90R4

Abstract

Tetronics are X-shaped octa block amphiphilic copolymer having multi-stimuli sensitive chemical and physical properties due to the presence of central ethylenediamine, polyethylene oxide (PEO) and polypropylene oxide (PPO) groups. Langmuir monolayers formed at the air-water interface by two tetronics namely tetronic 701 with normal sequence and reverse sequential tetronic 90R4, were studied on a comparative basis. The effects of different subphase conditions on the monolayer at the air-water interface were systematically investigated. Different spreading volumes of tetronics, different pH, temperature and ionic strength of the subphase were the parameters considered in this study. The corresponding Langmuir-Blodgett films were characterized with scanning electron microscopy (SEM). The SEM images of the films at different pH, temperature and salt environment showed a diversity of the copolymer arrangement at the air-water interface which corroborated with the explanation obtained from π-A isotherms analyses. The study revealed that the sequence of the block did not affect the nature of isotherm, instead the ratio of PPO/PEO and molecular weight played significant role in determining the characteristics of the films. This basic interfacial study on tetronics was not only a part of fundamental property-study but would definitely be helpful to design potential application involving tetronics in various fields.