Photon transmission technique for monitoring formation and swelling of polyacrylamide gels

Pekcan O., Kara S.

POLYMER-PLASTICS TECHNOLOGY AND ENGINEERING, vol.41, no.3, pp.573-588, 2002 (SCI-Expanded) identifier identifier


The in situ, real-time photon transmission technique was used to monitor the free radical crosslinking copolymerization of acrylamide and N,N'-methylenebisacrylamide (Bis). Gelation experiments were performed with various Bis contents at various wavelengths. It was observed that the transmitted photon intensity, I-tr decreased dramatically at a certain reaction time, which is attributed to the increase in scattered light intensity, I-sc during the formation of microgels in the system. The increase in I-sc was modeled using Rayleigh's equation where the reaction time was found to be proportional to the volume of the microgels. The disc-shaped polyacrylamide (PAAm) gels were dried before use during swelling experiments. Transmitted light intensity, I-tr, from the gel increased at initial stages when PAAm gels were immersed in water and then decreased exponentially as the swelling time increased. Decrease in I-tr was attributed to the lattice heterogeneities, which might have originated between microgels and holes in the swelling gel. Decrease in I-tr was modeled using the Li-Tanaka equation from which cooperative diffusion coefficients, D-c, were determined for gels of various Bis contents. It is observed that the D-c values increased with the Bis content.