Determination of bimodal molar mass distribution functions of polystyrene by photon correlation spectroscopy: numerical simulations and experimental realization in comparison with gel permeation chromatography data

The resolution of bimodal molar mass distribution functions of polymers by photon correlation spectroscopy (PCS) combined with the constrained regularization method and the estimation of the noise level of PCS measurements is presented. Electric field autocorrelation functions for the scattered ligh...

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Bibliographic Details
Published in:Macromolecules 1988-03, Vol.21 (2), p.415-420
Main Authors: Vancso, Gyula, Tomka, Ivan, Vancso-Polacsek, Klara
Format: Article
Language:English
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Summary:The resolution of bimodal molar mass distribution functions of polymers by photon correlation spectroscopy (PCS) combined with the constrained regularization method and the estimation of the noise level of PCS measurements is presented. Electric field autocorrelation functions for the scattered light on polymer solutions have been simulated. Molar mass distribution functions have been recalculated from the simulated autocorrelation functions. Simulation outputs show an increase of the polydispersity and a shift toward smaller molar masses with increasing statistical noise. The effective noise level of the present measurements was determined. Simulations show that, with the effective noise level, two peaks of bimodal distributions can be resolved if the relative position of the constituents (M2/M1) is greater than three. These simulations were compared with measured autocorrelation functions of bimodal molar mass distributions of certain mixtures of polystyrene standards (M1 = 0.675 x 10 exp 6 , M sub w /M sub n < 1.08, and M2 = 2.3 x 10 exp 6 , M sub w /M sub n < 1.07). The relative concentrations of the polystyrene standards c(M1)/c(M2) were 1:1 and 1:0.4. The two constituents of the bimodal molar mass distribution functions were resolved for the two mixtures by PCS as predicted by the simulations. The peak- and weight-average molar masses and the relative amounts of the components of the bimodal distributions correspond to the anticipated values. GPC measurements were performed on the same samples. The distributions determined by PCS and GPC match each other reasonably well. 25 ref.--AA
ISSN:0024-9297
1520-5835
DOI:10.1021/ma00180a022