Diffusion coefficients of the monomer and oligomers in hydroxyethyl methacrylate

Abstract

The diffusion coefficients are reported of rubbery ternary systems consisting of the polymer, its monomer analogue (i.e., the saturated equivalent of the monomer), and trace quantities of oligomers (dimer, trimer, tetramer and hexamer) for 2‐hydroxyethyl methacrylate (HEMA). These have been obtained with pulsed‐field‐gradient NMR spectroscopy with a polymer weight fraction (fp) of 0 ≤ fp ≤ 0.4. The oligomers are macromonomers synthesized with a cobalt catalytic chain‐transfer agent. The diffusion coefficients are about an order of magnitude smaller than those for monomers such as methyl methacrylate; this effect is ascribed to hydrogen bonding in HEMA. The diffusion coefficient Di of an i‐meric oligomer has been fitted with moderate accuracy by an empirical universal scaling relation, Di(fp)/D1(fp) ≈ i, previously found to provide an adequate fit to corresponding data for styrene and for methyl and butyl methacrylates. The approximate empirical scaling relation seems to hold for a remarkably wide range of types of monomer/polymer systems. These results are of use in modeling rates and molecular weight distributions in free‐radical polymerization, particularly for termination (which is chain‐length‐dependent and is controlled by the diffusion coefficient of chains of the low degrees of polymerization studied here). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2491–2501, 2003

RAFT polymerization kinetics: How long are the cross‐terminating oligomers?

“…Therefore, in this workwe incorporate the findings of Bathfield et al, and we extend the idea of initiator fragment/leaving group termination to the case where cross‐termination may occur between the RAFT intermediate and relatively short oligomers, while still neglecting long chain termination. This idea is also supported by experiments which show that the diffusion coefficient of a hexamer is almost an order of magnitude lower than the diffusion rate of a monomer 56. Furthermore, longer chain species are likely to have the radical sterically unavailable.…”

Chain‐Length‐Dependent Termination in Radical Polymerization of Acrylates

“…Therefore this is the first parameter that will be scrutinized. [31] n-butyl methacrylate (BMA), [31] 2-hydroxyethyl methacrylate [47] and styrene [32] have been carried out by pulsed-field-gradient NMR and have resulted in power-law exponents of -0.66, -0.66, -0.66 and -0.51, respectively, in dilute solution. To the best of our knowledge the literature contains no such chain-length-dependent diffusion coefficients for acrylate oligomers.…”

Fluorescence Recovery after Photobleaching as a Probe of Diffusion in Starch Systems

“…Figure 12. Diffusion coefficient of hydroxyethyl methacrylate in a solution of its polymer in water at 25°C as a function of weight-fraction polymer calculated using free-volume parameters fitted to experimental data, 35 treated in the same way as the data of Figure 10. Based on earlier work on starch gelatinization, 38 which showed that salt assists in forming an ordered structure within water and also interacts with the hydroxyl groups on the glucose units, it seems reasonable to assume that increasing salt concentrations enhances the interactions between water and the hydrophilic polymer, whether starch or dextran, and hence leads to chain expansion.…”