Interfacial tension of immiscible polymer blends: temperature and molecular weight dependence

• Published in: Macromolecules 1988-10, Vol.21 (10), p.2980-2987
• Main Authors: Anastasiadis, Spiros H, Gancarz, Irena, Koberstein, Jeffrey T
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma00188a015

Interfacial tensions between immiscible homopolymers are measured by using an automated pendant drop apparatus, which utilizes video digital image processing techniques. A recently developed robust shape analysis algorithm is used to analyze the experimental drop profiles. The data show the effect of temperature and number average molecular weight (M sub n ) on the interfacial tension for the immiscible blends polystyrene--poly(methyl methacrylate), polybutadiene--poly(dimethylsiloxane) and polystyrene--hydrogenated 1,2-polybutadiene. Interfacial tension decreases linearly with temperature and increases with molecular weight. The data are well represented by a C sub 1 + C sub 2 M sub n exp --z dependence on molecular weight, but are not of sufficient precision to determine a precise value for the exponent. The interfacial tension data for the latter blend system are compared with thermodynamic theories of polymeric interfaces. A square gradient theory approach, in conjunction with the Flory--Huggins expression for the free energy of mixing, predicts a magnitude and temperature dependence of interfacial tension which are in reasonable agreement with experimental data. The predicted molecular weight dependence corresponds well with experimental data at high molecular weights, but severely underestimates the interfacial tensions for low molecular weights. 71 ref.--AA