Melt Chain Dimensions of Poly(ethylene−1-butene) Copolymers via Small Angle Neutron Scattering

• Published in: Macromolecules Vol. 30; no. 17; pp. 4973 - 4977
• Main Authors: Fetters, L. J, Graessley, W. W, Krishnamoorti, R, Lohse, D. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 25-08-1997
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis; Small angle neutron scattering; Molten state; Property composition relationship; Butylene derivative copolymer; Temperature effect; Ethylene copolymer; Unperturbed dimension; Radius of gyration; Experimental study; Conformation
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma961408c

The radii of gyration for a series of poly(ethylene−1-butene) copolymers of varying ethyl branch content were measured as a function of temperature in the melt via small angle neutron scattering (SANS), and their temperature coefficients, d ln C ∞/dT = κ, changed from negative to positive. The characteristic ratio C ∞ decreased with increasing ethyl branch frequency. When possible, these results were compared with those obtained from ϑ solvents and from rotational isomeric (RIS) state theory. The SANS-based chain dimensions were slightly larger than those obtained from ϑ solvents. The values of κ differed significantly from those extracted from ϑ-solvent measurements. Serious discrepancies with RIS-based calculations were observed.