Side-chain intercrossing of poly(alkyl glutamate): LB and CP-MAS studies

The side-chain intercrossing of the substituted polyglutamate has been susp ected as the main reason for the inhomogeneous monolayer at the air/water i nterface as well as the multi-domains in bulk. Before the side-chain meltin g at 60 degreesC, the substituted chain intercrossing was confused by sever al experimental approaches. Here, we investigated the side-chain intercross ing of ethyl, hexyl, and stearyl substituted polyglutamate by surface press ure-surface area (pi -A) isotherms and CP-MAS (cross-polarization magic ang le spinning) NMR. We verify that the solvent drying process may be the main cause of the intercrossing of the side-chains in the glutamate polymers an d provide the quantitative information about the intercrossing ratios for t he side-chain polyglutamates. At room temperature, 60-90% of the total leng th of the side-chain intercrossed and the intercrossing ratios decreased at higher temperatures. (C) 2001 Published by Elsevier Science Ltd.