Molecular weight control of polyacrylamide with sodium formate as a chain-transfer agent: Characterization via size exclusion chromatography/multi-angle laser light scattering and determination of chain-transfer constant

We discuss the synthesis and characterization of polyacrylamide (PAM) homopolymers with carefully controlled molecular weights (MWs). PAM was synthesized via free-radical solution polymerization under conditions that yield highly linear polymer with minimal levels of hydrolysis. The MW of the PAM homopolymers was controlled by the addition of sodium formate (NaOOCH) to the polymerization medium as a conventional chain-transfer agent. MWs and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi-angle laser light scattering analysis; for polymerizations carried out to high conversion, PAM MWs ranged from 0.23 to 6.19 x 10(6) g/mol, with most samples having PDI approximate to 2.0. Zero-shear intrinsic viscosities of the polymers were determined via low-shear viscometry in 0.514 M NaCl at 25 degreesC. Data derived from the polymer characterization were used to determine the chain-transfer constant to NaOOCH under the given polymerization conditions and to calculate Mark-Houwink-Sakurada K and a values for PAM in 0.514 M NaCl at 25 degreesC. (C) 2003 Wiley Periodicals, Inc.