Abstract
This paper deals with the short branch effect in α-olefin copolymers on radius of gyration Rg and intrinsic viscosity [η] in trichlorobenzene at 135 °C. A wide range of structurally uniform copolymers of ethylene with propylene, 1-butene, 1-hexene, and 1-octene were analyzed by size exclusion chromatography with on-line refractive index, low-angle and multiangle light-scattering and viscometry detectors. Variation of refractive index increment with composition was determined, and corrections for finite concentration were applied. Both Rg and [η] are accurately described by power laws Rg = KsMαs and [η] = KvMαv. The coefficients Ks and Kv vary with comonomer type and amount, but the same exponents, αs = 0.58 and αv = 0.695, apply within the measurement uncertainty to all polymers studied. The ratios gSCB = Rg2/(Rg2)PE and g‘SCB = [η]/([η])PE vary linearly with comonomer weight fraction, with slopes that depend on the comonomer type. Various explanations for the observations are considered.
Published Version
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