Synthesis and structural study of new copolymers, based on acrylamide and N-acryloyl acids, with persistent drag reduction activity

Syntheses of acryloyl amino acid monomers, some of which were optically active, have been carried out. These compounds have been copolymerized with acrylamide and characterized. The polymers prepared from optically active monomers form a compact structure in solution. Aqueous solutions of these macromolecules were then tested to assess their drag reduction effect under turbulent flow conditions. For this series of macromolecules, including partially hydrolysed polyacrylamide, a particular persistent activity is observed, which is similar to the behaviour of natural products and different from the drag reduction activity of polyethyleneoxide (PEO) and polyacrylamide (PAM). It is shown that the particular main chain structure induced by the chiral monomers is not responsible for this persistence. Moreover, relationships between the polymer structure and drag reduction properties enabled us to propose a mechanism which emphasises the role of the branch chain and the terminal charge. This persistent drag reduction activity is also linked with a critical energy level. (C) 1998 Elsevier Science Ltd. All rights reserved.