Extent of branching from linear viscoelasticity of long‐chain‐branched polymers

Abstract

We present new results and examine literature data concerning the linear viscoelastic behavior of polyethylene with sparse to intermediate levels of long‐chain branching (LCB). These branched polymers displayed a common rheological signature, namely, a region of frequency‐independent loss tangent along with the corequisite scaling of the storage and loss moduli to the same frequency exponent. This apparent power‐law response occurred within a finite frequency window and bore resemblance to the behavior of physical gels. The appearance of this region, however, was the consequence of the presence of two distinct, yet partially overlapping, terminal relaxation processes. After considering the analogous relaxation behavior of wholly linear polymers with bimodal molecular weight distributions, we considered the polymers with LCB as blends of linear and branched species to develop a simple method of quantifying the extent of LCB. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1671–1684, 2004

Glass Transition and Interfacial Segmental Dynamics in Polymer-Particle Composites

“…The gives rise to a terminal dispersion (loss tangent peak), rather than the usual divergence of tanδ toward infinity with increasing temperature (or decreasing frequency). A similar phenomenon is observed in sparsely branched polymers and bidisperse polymer blends, [24][25][26] crosslinked polymer networks containing unattached chains, 27-29 and particle-reinforced polymers. [30][31][32] This ambiguity in the results of Tsagaropoulos and Eisenberg 11,12 illustrates the caution required when interpreting viscoelastic data in terms of the effect of filler on the glass transition behavior.…”

Analytical Rheology of Polymer Melts: State of the Art

“…For example, Robertson et al [302] used the van GurpPalmen plot and correlated the peak in δ at intermediate frequencies with LCB by appealing to blending rules. Trinkle et al [297,300] found that using a reduced van GurpPalmen plot by plotting δ against |G * (ω)|/G 0 N allows one to study the effects of molecular weight and molecular weight distribution in LPs systematically.…”

“…They found rheology to be more sensitive to branching, as expected, but reported that a combination of both the methods resulted in better overall characterization. Some of the works previously referenced also employ multidetector methods [88,219,220,302,315].…”

A Comprehensive Review on Controlled Synthesis of Long‐Chain Branched Polyolefins: Part 3, Characterization of Long‐Chain Branched Polymers

“…The height of this plateau represents δ c and it is determined by the www.advancedsciencenews.com degree of LCB. [29,178,179] Consequently, δ c can be used as a parameter to semiquantitatively analyze LCBD, as shown by the work of Robertson group, [180] who used Equation (39) n n 1 , where / 90…”