Diffusion coefficients of the monomer and oligomers in hydroxyethyl methacrylate (pages 2491–2501)
Jelica Strauch, James McDonald, Bogdan E. Chapman, Philip W. Kuchel, Brian S. Hawkett, G. Evan Roberts, Matthew P. Tonge and Robert G. Gilbert
Article first published online: 26 JUN 2003 | DOI: 10.1002/pola.10789
Diffused coefficients Di of i-meric oligomers were obtained by pulsed-field gradient NMR in rubbery systems comprising polymer, monomer, and oligomers (synthesized using cobalt catalytic chain transfer agent) for 2-hydroxyethyl methacrylate (HEMA), with polymer weight-fraction 0 ≤ fp ≤ 0.4. The Di were much smaller than for monomers such as MMA, ascribed to hydrogen bonding in HEMA, and fitted the empirical relation Di(fp)/D1(fp) ≈ i, which also fits corresponding data for styrene and various methacrylates. This relation is useful for taking into account chain-length dependent termination (dominated by diffusion of small chains) and the gel effect when modeling free-radical polymerizations.