AbstractThe types of molecular architecture commonly present in many commercial elastomers include long branching, which in extreme cases results in crosslinked gel network. This architecture was modeled by preparing a series of ethylene–propylene copolymer samples in which the degree of branching was systematically varied. The frequency‐dependent viscoelastic properties of these model systems were measured over a temperature range of 80–230°C with a Rheometrics Mechanical Spectrometer. Time–temperature superposition was employed to obtain master curves of the storageG′ and lossG″ moduli and complex viscosity. The viscoelastic properties of the model samples change systematically with the variations in molecular architecture. Specifically, the low frequency Newtonian viscosity behavior is progressively replaced by non‐Newtonian power‐law behavior, and theG′ response relative to that of theG″ is significantly enhanced as long‐branching increases. The practical use of a modified Cole–Cole plot, in which the axes are expressed as the logarithms ofG′ andG″, for analysis of molecular architecture is demonstrated. Changes in the long‐branch architecture of the model samples were readily detected as systematic variations in shape and displacement of the modified Cole–Cole plot. On the other hand, the data of molecularly linear elastomer samples of differentMwbut similar MWDs were reduced t
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