Abstract
Viscosimetry is a simple, inexpensive characterization method that provides valuable information about the hydrodynamic volume and conformation of macromolecules in solution, in a solvent, at a given temperature. The viscosimetric parameters can be mathematically calculated by graphic extrapolation, in time-consuming experimental tests. It is possible, however, to achieve results by a single point determination. In this work we used the two calculation methods employing a series of six equations: Huggins, Kraemer and Schulz-Blaschke, by graphic extrapolation; and Schulz-Blaschke, Solomon-Ciuta and Deb-Chanterjee, by a single point determination, for solutions of polybutadiene and of random copolymers of 1,3-butadiene and 1-octene, with different mass ratios (Bd/Oct = 99/1 and 97/3). The viscosimetric determinations were carried out in toluene and hexane, at 30 ± 0.1 °C. The weight average molecular mass was determined by size exclusion chromatography (SEC). The values of intrinsic viscosity and of some constants indicated that both toluene and hexane were good solvents for the samples, with hexane being better owing to the higher intrinsic viscosities when compared to the former. It was also observed that the method of calculation by a single point was valid. By means of the intrinsic viscosity values and the parameter g' (ratio between the viscosities of branched and linear polymer) the occurrence of branching in the copolymer chain was suggested because g'<1 and the values of intrinsic viscosity were lower than those obtained for the homopolymer.
Highlights
Higher intrinsic viscosities when compared to the former
It was observed that the method of calculation by a single point was valid
By means of the intrinsic viscosity values and the parameter g’ the occurrence of branching in the copolymer chain was suggested because g’
Summary
O parâmetro c[η] (“dimensionless coil overlap parameter”, onde c é a concentração), pode ser definido como o volume total ocupado pelos novelos poliméricos; isto é, c[η] é a medida da fração, em volume, do polímero presente na solução. A literatura[15] descreve que o volume hidrodinâmico de um polímero ramificado é sempre menor do que o volume ocupado por um polímero linear de mesma massa molar, já que as ligações covalentes existentes entre as cadeias do polímero ramificado limitam o seu coeficiente de expansão e, assim, provocam uma diminuição na viscosidade intrínseca [η], em virtude de ocorrer a incorporação de ramificações na cadeia polimérica. O efeito da ramificação pode ser estudado a partir de medidas de viscosidade intrínseca, realizadas em bons solventes, utilizando-se o parâmetro g’ (Equação 6), onde se determina a razão entre as viscosidades do polímero ramificado e do polímero linear[15]. Os resultados mostrados nesta etapa do trabalho permitem sugerir que é possível avaliar a presença de ramificações em cadeias poliméricas a partir de medidas viscosimétricas realizadas em solução
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
