Refractive index heterogeneous polymers

In general, the multiphasic heterogenous nature of the impact grade styrene-based polymers is the root cause of their opaque-turbid nature. In determining the transparency of the blends, size and the size-distribution pattern of the dispersed phase along with the refractive index difference between the continuous and the dispersed phases are two very important criterion [133]. 

Microscopy. This is a powerful tool for studying visually the distribution of the two phases in the polyblend. One can tell not only the domain size of the dispersed phase but also which polymer forms the dispersed phase from refractive index. A phase contrast light microscope can detect heterogeneity at the 0.2-10 /x level. If the sample can be stained preferentially and sectioned with microtome, then under favorable conditions electron microscopy can show heterogeneity to a very fine scale. In a study of PVC-poly(butadiene-co-acrylonitrile) blend,... 

Heterogeneous or complex polymers are distributed in more than one molecular parameter. For functional homopolymers one has to deal Avith the overlapping effects of molar mass distribution and functionality type distribution, whereas copolymers are distributed at least in molar mass and chemical composition. For many years, detector development and the use of several detectors attached to SEC have been the major thrusts in chromatographic analysis of complex macromolecules. In particular, the combination of a refractive index and an ultraviolet detector has been used extensively, although only a limited number of polymers is UV active. Therefore the application of this technique is certainly not universal. On the other hand, SEC has its merits in the daily routine because it is simple, fast, and very reproducible. 

Equation (6) is obtained by using Debye s theory (14,IS). Here a (A) is called the correlation length and is a measure of the size of the heterogeneous structure inside the polymer. The symbol denotes the mean-square average of the fluctuation of all dielectric constants, n is the refractive index of medium, and A is the wavelength of light in a medium. 

Light Scattering (LS) performed in surfactant solutions is a very important experimental technique for the study of the size of micelles, polymers and particles. Light scattering in colloidal/micro-heterogeneous systems occurs due to differences in refractive index across the sample. The scattered intensity depends on four factors, as follows ... 

---