Quantitative small angle light scattering of liquid crystalline copoloyester films

A new detection apparatus for small angle light scattering (SALS) was developed and used to characterize liquid crystalline copolyesters of poly(ethylene terephthalate) (PET), and para-oxybenzoic acid (FOB). The detection device combines video and microcomputer technology to allow for a two-dimensional position sensitive detector SALS. Using this detector, the compression molded films of PET/POB were found to be composed of randomly ordered fibrillar domains, that do not orient upon cold stretching. Also, the size of these domains were found to be slightly dependent on their molding temperature, but independent of their cooling condition. Also, extrusion drawn films were found to contain a high degree of order suggesting that the copolyesters must have their orientation imposed while still in the melt. In performing this work, a unique analytical technique employing a polynomial regression analysis to data slices in the form of intensity versus the square of the scattering vector. It was found that the moments of the particle size distribution calculated from this analysis yielded values which were all very similar in magnitude. Indicating that higher moments of the size distribution calculated from the polynomial analysis are strongly influenced by the smaller particle sizes in the distribution.