MONOLAYERS OF CELLULOSE ETHERS AT THE AIR-WATER-INTERFACE

Aliphatic ethers of cellulose are found to form stable monolayers when spread from dilute chloroform solution at the air-water interface. Mo nolayer pressure-area isotherms exhibit a liquid analogous phase follo wed by a transition region of relatively high compression at constant pressure. Limiting molecular areas are found to depend an side-chain l ength, indicating that the hydrocarbon substituents do not adopt an or ientation strictly perpendicular to the water surface. Monalayers of m ixed others containing, on average, a single long chain substituent pe r repeat unit, form liquid analogous phases at molecular areas equival ent to the area of the anhydroglucose ring. It is thus concluded that the cellulose backbone lies flat on the water surface, The transition region observed upon compression beyond the liquid analogous phase is attributed to the formation of bi- or multilayers, with molecules leav ing the water surface. This interpretation is consistent with the obse rved decrease in plateau pressure with increasing temperature.