The synthesis and characterization of Cell-SAC 3, a cellulose isopentyl (IP) ether with additional pendant S-acetyl (SAC) moieties (degree of substitution DSlp = 2.5, DSsAc = 0.4) are reported. Cell-SAC forms stable monolayers at the air-water interface once spread from dilute chloroform solution. The pressurearea isotherm of Cell-SAC is nearly identical to the parent Cell-IP 1, both exhibiting an expanded liquid phase at surface areas of 70 and 67 A, respectively. The similarity of the two isotherms shows that the presence of the S-acetyl substituent does not result in an increase in the molecular area, at which the liquid-crystal analogous phase occurs. This observation suggests that the side-chains with the pendant S-acetyl goup are oriented away from the water surface. Monolayers of Cell-SAC can be efficiently transferred onto silicon and hydrophobized glass or quartz substrates by a downstroke and upstroke technique. Resulting multilayers were characterized using X-ray reflection, FTIR, and UV-vis spectroscopy. The presence of S-acetyl moieties was found to increase the monolayer thickness relative to the parent Cell-IP. The cleavage of the S-acetyl group within the LB film is reported.
We assume a random placement of the functional groups. For simplicity, only one of the possible substitution patterns is shown.