Analysis of Relaxation Functions Characterized by a Broad Monomodal Relaxation Time
Distribution

“…k is a normalization constant and τ * is the characteristic relaxation time of the long time cutoff. General properties of the GEX distribution and its application to DLS have been given in reference [20]. Experimentally, we find that we have to include a short time cut-off at the relaxation time of the cooperative PMMA diffusion.…”

Section: Appendix A: Dls Data Analysismentioning

confidence: 99%

Dynamic and static light scattering study of the formation of cross-linked PMMA gels

1999

View full text Add to dashboard Cite

Free radical co-polymerization of methyl methacrylate (MMA) and ethyl glycol dimethyl metacrylate (EGDMA) was investigated in solution at different molar ratios R = [EGDMA]/[MMA] between 0 and 0.05. Initially mainly linear PMMA was formed with weight average molar mass 7.5×10 4 g/mol independent of R. At larger reaction extents branched polymers were formed and the systems gelled. The scattering intensity rose initially with the reaction extent, but reached a plateau value at larger reaction extents. The plateau value increased strongly with R. Dynamic light scattering showed the appearance of a slow relaxation not observed in linear PMMA solutions. The data can be interpreted by assuming that the excess scattering originates from the branching points and relaxes through self diffusion of the branched particles. The results agree with predictions of the percolation model for gelation and Rouse dynamics. Viscosity measurements corroborate this interpretation. Measurements on a progressively diluted sample quenched close to the gel point again showed quantitative agreement with the percolation model for gelation.PACS. 36.20.-r Macromolecules and polymer molecules -61.10.-i X-ray diffraction and scattering -82.70.Gg Gels and sols

show abstract

“…A detailed discussion of the properties of this function can be found in reference [21]. Note that if we assume f (M/M * ) = exp[−(M/M * ) β ] then comparison of equation (12) with equation (19) gives p = d * f and s = βd f [21].…”

Section: Dynamic Light Scattering (Dls)mentioning

confidence: 99%

Characterization of the structure and the size distribution of branched polymers formed by co-polymerization of MMA and EGDMA

Lesturgeon¹,

Durand²,

Nicolai³

1999

Eur. Phys. J. B

View full text Add to dashboard Cite

Free radical co-polymerization of methyl methacrylate (MMA) and ethyl glycol dimethyl methacrylate (EGDMA) in solution leads to the formation of polydisperse branched PMMA which grows in size until the system gels. The structure and the size distribution of the PMMA aggregates were characterized at infinite dilution using static and dynamic light scattering and size exclusion chromatography (SEC). The reaction extent was measured using SEC and Raman spectroscopy. The results show that the structure and size distribution of PMMA aggregates formed close to the gel point are compatible with those of percolating clusters. The structure factor of semi-dilute solutions of PMMA aggregates is the same as that of dilute solutions at distance scales much smaller than the correlation length of the concentration fluctuations (ξ). However, the cut-off function of the pair correlation function at ξ for semi-dilute solutions is more gradual than the cut-off function at Rgz for dilute solutions.PACS. 36.20.-r Macromolecules and polymer molecules -61.10.-i X-ray diffraction and scattering

show abstract

Analysis of Relaxation Functions Characterized by a Broad Monomodal Relaxation Time Distribution

Cited by 23 publications

References 4 publications

Dynamic Light-Scattering Study of Aggregating and Gelling Colloidal Disks

Dynamic Light-Scattering Study of Aggregating and Gelling Colloidal Disks

Dynamic and static light scattering study of the formation of cross-linked PMMA gels

Characterization of the structure and the size distribution of branched polymers formed by co-polymerization of MMA and EGDMA

Contact Info

Product

Resources

About