Selection of solvents for the determination of the parameters P and Q for chemically heterogeneous copolymers by light scattering

✍ Scribed by J. Podešva

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 631 KB
• Volume: 18
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(82)90095-7

✦ Synopsis

A calculation method has been developed which makes possible, by using the refractive index values, the choice of solvents for a sufficiently accurate determination of the copolymer heterogeneity parameters (P and Q) by light scattering. If the expected P and Q values are estimated from other data (e.g. copolymerization kinetics), the method can be used to find out if land where) there exist(s) such intervalls) or discrete point(s) on the scale of the refractive index of the solvents for which the following two conditions are met simultaneously: (i) the excess Rayleigh factor is so large, even at the lowest copolymer concentration used and the angle of measurement 90:. that the apparent molecular weight of the copolymer. M,p, can be determined with sufficient accuracy: 0il mutual position of experimental points (three. at least) on the parabolic dependence M~v vs optical variabie lthe ratio of the difference of refractive index increments of parent homopolymers to the refractive index increment of the copolymerl is such that the determination of parameters of this parabola is sufficiently accurate. The application of the method is demonstrated for three examples (block copolymer, random copolymer, and a mixture of homopolymersl.