Light scattering by glassy polystyrene (original) (raw)
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Journal of Polymer Science: Polymer Physics Edition, 1976
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Light Scattering Studies of Polymer Solutions and Melts
Polymer Journal, 1985
Static and dynamic properties of polymer solutions and melts can be investigated by means of modern scattering techniques. While small angle X-ray scattering (SAXS) and smallangle neutron scattering (SANS) have made advances particularly in studies related to the static structure factor S(K), laser light scattering including the use of Fabry-Perot interferometry and photon correlation spectroscopy has become a standard tool in studying polymer molecular motions. In polymer solutions, the main technique is to use measurements of angular distribution of integrated scattered intensity by means of visible light, SAXS or SANS for S(K) and measurements of angular distribution of the spectrum of scattered light by means of photon correlation spectroscopy for the dynamic structure factor, S(K, w). Recent advances have been made in the method of data analysis related to the ill-posed Laplace inversion problem. The new approaches include the singular value decomposition technique and methods of regularization with different criteria for the smoothing operator. By combining static and dynamic light scattering measurements with appropriate algorithms for the Laplace inversion of the time correlation function, a new analytical technique has been developed for polymer molecular weight characterizations. The nonintrusive method has been applied to determine the molecular weight distributions of linear and branched polyethylene in 1,2,4-trichlorobenzene at 135°C and of poly(l,4-phenyleneterephthalamide) in concentrated sulfuric acid. In addition, a new prism light scattering cell is being developed to integrate the above capabilities with chromatographic and other separation techniques. Aside from translational motions of the center of mass of polymers in dilute solution, photon correlation spectroscopy also permits us to investigate rotational, flexual and internal segmental motions. Polymer molecules entangle in semidilute solution. Light-scattering spectroscopy measures a cooperative diffusion coefficient and a slow mode which has been shown to be different in magnitude from the self-diffusion coefficient. The entanglement behavior varies from coils to rod-like polymers. Static and dynamic properties of polymer solutions in semidilute and semiconcentrated regimes can be related to those of bulk polymer melts where measurements of polarized Rayleigh-Brillouin spectra and depolarized Rayleigh spectra yield information on localized structural relaxation and collective segmentallmolecular orientational motions. Relaxation times covering a very broad frequency range will be discussed.
Dynamic light scattering study of a 1,4-isoprene-b-styrene copolymer
2000
Local optical anisotropy fluctuations within polystyrene (PS)-rich region in a disordered 1,4-isoprene-b-styrene (PI-b-PS) copolymer with XN≈5.3 (N=44) and glass transition temperature T g=13°C were analyzed by photon correlation spectroscopy (PCS) over a broad time range (10−7−103 s). There is strong experimental evidence that composition fluctuations in the present system can affect the segmental orientational fluctuations of the two foreign blocks.
Dynamic light scattering from polymers
Die Makromolekulare Chemie, 1979
Applications of both polarized and depolarized dynamic light scattering to the study of polymers are described. Polarized light scattering is used to study translational diffusion, diffusion virial coefficients, rotational motion of long rod-shaped polymers, longwavelength intramolecular motions, dynamics of pseudogels and gels and density fluctuations in bulk polymers. Depolarized scattering is used to study rotational diffusion of rigid macromolecules, local and long-wavelength intramolecular motions, dynamics in semi-dilute solutions, rotational motion of small molecules in glassy polymers and optical anisotropy fluctuations of bulk polymers.
Colloids and Surfaces A-physicochemical and Engineering Aspects, 2001
The stability of monodispersive polystyrene spheres suspended in water has been studied at high pressure and temperature in the range of 0.1-28 MPa and 24 -325°C. The diffusion coefficient of the latex was measured with dynamic light scattering using a special experimental cell for performing measurements at elevated pressure and temperature. It is found out that the influence of the increased pressure on the measured results is negligibly small. The elevation of temperature significantly increases the particle diffusion coefficient due to the viscosity decrease of the medium, but its dependence is well described by the theoretical predictions for the diffusion coefficients of the particles with constant size calculated at 24-275°C. This result means that the polystyrene spheres do not change in size and the suspension remains stable below 275°C at least in the time scale of our experiments. The change in the size of latex was observed at 300 and 325°C. The measured decrease of the diffusion coefficient with time could be related to the increase in the average particle size due to the beginning of the coagulation process, but some other effects as swelling of polystyrene might be also possible.
Journal of Polymer Science Part B: Polymer Physics, 2010
This work deals with the application of the static light scattering (SLS) model of Vrij (VM) for the characterization of a spherical polydisperse concentrated polymer particle system. This model is the exact solution for the SLS of such mixture of particles in the Percus-Yevick approximation. The analyzed polymer particle samples are obtained by solution polymerization of isobornyl methacrylate in polyisobutylene. At the end of the polymerization, as a result of phase separation, a particle system of micrometer sized particles with a moderate distribution of sizes and a volume fraction between 5 and 10% is formed. The SLS data were also analyzed using the local monodisperse approximation (LMA), a well-known approximation to the model of Vrij. As expected, the estimations with the VM gave better results than those performed with the LMA model for the parameters related to the shape of the particle size distribution as compared with independent determinations of these quantities obtained from scanning electron microscopy micrographs. However, the main motivation to use the more rigorous model seems to be the fact that the volume fraction of particles can be extracted from the data even when relative SLS measurements are used. V
Light-scattering characterization of polyblends in the presence of multiple-scattering conditions
Polymer Engineering and Science, 1987
A novel approach is described for the noncontact evaluation of structural morphology in polyblends by light scattering. Optical methods are attractive for the on-line characterization of translucent materials because they are noninvasive, rapid, and applicable to high temperature materials. One limitation of conventional light-scattering techniques is their requirement for relatively thin samples in order to avoid multiple-scattering effects that smear out the details of the light diffraction pattern. The approach described in this paper is meant to circumvent this limitation by resorting to turbidimetric measurements, which provide useful information on the average size, shape, concentration, and orientation of the dispersed phase particles even in the presence of multiple scattering. The sample thickness is no longer restricted, and methods are described by which the near-surface volume of infinitely thick parts may be inspected with access to a single side of the material. Results are presented for polypropylenepolycarbonate (PP/PC) samples of different thicknesses and microstructural morphology, including fibrillar-type oriented structures.
Calculations of scattered light from rigid polymers by Shifrin and Rayleigh-Debye approximations
Biophysical Journal, 1989
We show that the commonly used Rayleigh-Debye method for calculating light scattering can lead to significant errors when used for describing scattering from dilute solutions of long rigid polymers, errors that can be overcome by use of the easily applied Shifrin approximation. In order to show the extent of the discrepancies between the two methods, we have performed calculations at normal incidence both for polarized and unpolarized incident light with the scattering intensity determined as a function of polarization angle and of scattering DiupI1ywcI a,iopnysicai ocew