Determining the Dilution Exponent for Entangled 1,4-Polybutadienes Using Blends of Near-Monodisperse Star with Unentangled, Low Molecular Weight Linear Polymers
Venerus, David C.
Larson, Ronald G.
KAUST DepartmentChemical Science Program
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Polymer Synthesis Laboratory
Online Publication Date2019-02-11
Print Publication Date2019-02-26
Permanent link to this recordhttp://hdl.handle.net/10754/631840
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AbstractWe determine experimentally the “dilution exponent” α for entangled polymers from the scaling of terminal crossover frequency with entanglement density from the linear rheology of three 1,4-polybutadiene star polymers that are blended with low-molecular-weight, unentangled linear 1,4-polybutadiene at various star volume fractions, ϕs. Assuming that the rheology of monodisperse stars depends solely on the plateau modulus GN(ϕs) ∝ ϕs1+α, the number of entanglements per chain Me(ϕs) ∝ ϕs–α, and the tube-segment frictional Rouse time τe(ϕs) ∝ ϕs–2α, we show that only an α = 1 scaling superposes the Me(ϕs) dependence of the terminal crossover frequency ωx,t of the blends with those of pure stars, not α = 4/3. This is the first determination of α for star polymers that does not rely on any particular tube model implementation. We also show that a generalized tube model, the “Hierarchical model”, using the “Das” parameter set with α = 1 reasonably predicts the rheological data of the melts and blends featured in this paper.
CitationHall R, Kang B-G, Lee S, Chang T, Venerus DC, et al. (2019) Determining the Dilution Exponent for Entangled 1,4-Polybutadienes Using Blends of Near-Monodisperse Star with Unentangled, Low Molecular Weight Linear Polymers. Macromolecules 52: 1757–1771. Available: http://dx.doi.org/10.1021/acs.macromol.8b01828.
SponsorsR.H. and R.G.L. gratefully acknowledge the support of the National Science Foundation under Grants DMR 1403335 and 1707640. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation (NSF). N.H. gratefully acknowledges the support of the King Abdullah University of Science and Technology (KAUST).
PublisherAmerican Chemical Society (ACS)