Monomolecular film properties of cellulose and amylose triacetates at the air‐water interface

Abstract

Surface pressure‐area isotherms of cellulose triacetate and amylose triacetate at the air‐water interface were determined on a vertical and horizontal film balance. Both polymers show anomalous behavior on the vertical balance, including: higher compressibilities than obtained on the horizontal balance, movement of the vertical plate, and atypical hysteresis of the isotherms. The behavior of the cellulose triacetate film is attributed to heterogeneous gelation of the monolayer at low pressures. A mechanism involving the lateral tilting of pyranose units at the interface and subsequent stabilization of the monolayer by van der Waal's interactions accounts for the properties of this film. A helical conformation for amylose triacetate at the air‐water interface is proposed to explain the low compressibility of this monolayer.

Nanoparticle‐Imprinted Polymers: Shell‐Selective Recognition of Au Nanoparticles by Imprinting Using the Langmuir–Blodgett Method

“…From linear extrapolation to zero surface pressure a limiting molecular area per CA unit of approximately 42 Å 2 was obtained. This value is in good agreement with the limiting area reported by Hittmeier et al 15. and Adam 16…”

Preparation, characterization and applications of ultrathin cellulose acetate Langmuir–Blodgett films

“…In addition, during compression to high surface pressures, the Wilhelmy balance plate suffered from a deviation in its vertical orientation. This phenomenon, previously reported by Hittmeier et al 17 for cellulose triacetate and by Guiomar et al 28 for cellulose acetate propionate, is attributed to the movement of gelated patches against its front face while trying to pack more closely. It should be noted that the surface pressure-area isotherms we obtained for CA were highly reproducible for monolayers spread from chloroformacetone solution.…”

“…18 However, this value is somewhat larger than the values reported earlier (40-48 A ˚2). 14,15,17 The inconsistency may be due to the incomplete spreading of the CA on the surface of water, as reported in these papers. Since the surface pressure of a spread monolayer is an indication of the interactions between neighboring molecules, this value of limiting area supports the previous reports where a well-ordered solid-like monolayer is formed, in which the glucose rings are perpendicularly oriented to the water surface.…”

“…Langmuir monolayers of various cellulose esters and ethers (mainly with different alkyl side chains) have been extensively studied at the air-water interface. [14][15][16][17]21,23,24 Moreover, the structure and properties of LB films of CA derivatives transferred onto different supports have been studied. [18][19][20]22,25,[28][29][30] However, we are not aware of any report on the properties of CA LB films.…”

“…Borgin and Johnson 16 further studied the spreading of cellulose derivatives, concluding that the repeating glucose units were located parallel to the water surface. The possibility that cellulose triacetate could be fully spread and that the glucose units were oriented at an angle with the water surface, had been suggested later by Hittmeier et al 17 They studied the changes in molecular organization and intermolecular interactions in cellulose triacetate LB films following compression. A displacement of the Wilhelmy plate from its vertical position, which was attributed to the high surface viscosity of the film due to gelation at low pressures, was reported.…”