Measurement of diffusion coefficients of oligomeric penetrants in rubbery polymer matrixes

Griffiths, M.C., Strauch, J., Monteiro, M.J. and Gilbert, R.G. (1998) Measurement of diffusion coefficients of oligomeric penetrants in rubbery polymer matrixes. Macromolecules, 31 22: 7835-7844. doi:10.1021/ma980169l

Author Griffiths, M.C.
Strauch, J.
Monteiro, M.J.
Gilbert, R.G.
Title Measurement of diffusion coefficients of oligomeric penetrants in rubbery polymer matrixes
Journal name Macromolecules   Check publisher's open access policy
ISSN 0024-9297
Publication date 1998-11
Sub-type Article (original research)
DOI 10.1021/ma980169l
Volume 31
Issue 22
Start page 7835
End page 7844
Total pages 10
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Formatted abstract
The diffusion coefficients of oligomeric radicals in monomer-polymer systems have a major influence on properties such as polymerization rates and molecular weight distributions. The present work reports the results of an extensive set of studies of diffusion coefficients of rubbery ternary systems comprising polymer, diluent, and oligomer, determined by pulsed-field-gradient NMR, at 25 and 40°C. Oligomers of methyl methacrylate (MMA) and of butyl methacrylate (BMA) were synthesized by using a catalytic cobalt chain transfer agent to produce macromonomers with a terminal double bond. Where necessary, these were fractionated by preparative GPC to obtain samples ranging from dimeric to decameric; typical polydispersities were 1.08. Pulsed-field gradient NMR is facilitated by being able to monitor the proton NMR of the CH2 hydrogens on the double bond. Matrixes used were high molecular weight polyMMA and polyBMA, the weight fraction of polymer (wp) being varied by adding appropriate amounts of diluent (the saturated equivalents of MMA and BMA, viz., methyl isobutyrate and butyl isobutyrate). Above c* (the concentration at which chains start to overlap), all data for diffusion coefficients Di of an oligomer of degree of polymerization i could be fitted with acceptable accuracy by D1(wp)/Di(wp) = i0.664 + 2.02wp, for both BMA and MMA oligomers in both MMA and BMA matrixes; the same relation also fits earlier data on styrene oligomers in polystyrene. If more accurate scaling parameters are obtained experimentally for smaller oligomers, these can be used to predict data for higher oligomers with even better reliability. For MMA monomer in pMMA, where free-volume parameters are available, the predicted dependences of monomer diffusion coefficient on wp and temperature are in accord with experiment.
Keyword Free-radical Polymerizations
Catalytic Chain Transfer
Solvent Self-diffusion
Polyvinyl Methyl-ether) Solutions
Termination Rate-processes
Translational Diffusion
Linear Polystyrenes
Tracer Diffusion
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemistry and Molecular Biosciences
Centre for Nutrition and Food Sciences Publications
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