Rheology of hyperbranched polymer melts undergoing planar Couette flow.

The melt rheology of four hyperbranched polymer structures with different molecular weights has been studied using nonequilibrium molecular dynamics (NEMD). Systems were simulated over a wide range of strain rates to capture the crossover behavior from Newtonian to non-Newtonian regimes. Rheological properties including shear viscosity and first and second normal stress coefficients were computed and the transition to shear thinning was observed at different strain rates for hyperbranched polymers of different sizes. The results were consistent with previous findings from NEMD simulation of linear and dendritic polymers. Flow birefringence was characterized by taking into account both form and intrinsic birefringences, which result from molecular and bond alignment, respectively. The stress optical rule was tested and shown to be valid only in the Newtonian regime and violated in the strong flow regime where the rule does not take into account flow-induced changes of the microstructure.

[1]  A. McHugh,et al.  Effects of Molecular Variables and Architecture on the Rheological Behavior of Dendritic Polymers , 2000 .

[2]  E. Maginn,et al.  Rheology, dynamics, and structure of hydrocarbon blends: a molecular dynamics study of n-hexane/n-hexadecane mixtures , 1999 .

[3]  B. D. Todd,et al.  Viscoelastic properties of dendrimers in the melt from nonequlibrium molecular dynamics. , 2004, The Journal of chemical physics.

[4]  Fréchet,et al.  The Melt Viscosity of Dendritic Poly(benzyl ether) Macromolecules. , 1998, Macromolecules.

[5]  H. C. Andersen,et al.  Role of Repulsive Forces in Determining the Equilibrium Structure of Simple Liquids , 1971 .

[6]  R. Larson,et al.  Rheooptical Study of Isotropic Solutions of Stiff Polymers , 1990 .

[7]  C. Tiu,et al.  Rheological Behaviour of Polymer Blends Containing only Hyperbranched Polyesters of Varying Generation Number , 2001 .

[8]  K. Yasuda.  A Multi-Mode Viscosity Model and Its Applicability to Non-Newtonian Fluids , 2006 .

[9]  G. Fuller,et al.  Birefringence and stress growth in uniaxial extension of polymer solutions , 2000 .

[10]  W. Hayes,et al.  Synthesis and applications of hyperbranched polymers , 2004 .

[11]  Y. H. Kim,et al.  Structure and rheology of hyperbranched and dendritic polymers. II. Effects of blending acetylated and hydroxy‐terminated poly(propyleneimine) dendrimers with aqueous poly(ethylene oxide) solutions , 2000 .

[12]  H. Manfred.  Nonlinear rheology of polymer melts: a new perspective on finite chain extensibility effects , 2006 .

[13]  Kremer,et al.  Molecular dynamics simulation for polymers in the presence of a heat bath. , 1986, Physical review. A, General physics.

[14]  Suneel,et al.  Rheology and Molecular Weight Distribution of Hyperbranched Polymers , 2002 .

[15]  T. Le,et al.  Structural properties of hyperbranched polymers in the melt under shear via nonequilibrium molecular dynamics simulation. , 2009, The Journal of chemical physics.

[16]  W. Feast,et al.  Size exclusion chromatography and rheology of AB/AB2 hyperbranched polymersBasis of a presentation given at Materials Discussion No. 6, 12?14th September 2003, Durham, UK. , 2003 .

[17]  S. Edwards,et al.  The Theory of Polymer Dynamics , 1986 .

[18]  Y. H. Kim,et al.  Structure and rheology of hyperbranched and dendritic polymers. I. Modification and characterization of poly(propyleneimine) dendrimers with acetyl groups , 2000 .

[19]  M. M. Cross.  Rheology of non-Newtonian fluids: A new flow equation for pseudoplastic systems , 1965 .

[20]  J. Rothstein,et al.  A comparison of the stress and birefringence growth of dilute, semi-dilute and concentrated polymer solutions in uniaxial extensional flows , 2002 .

[21]  James Lance Sander Wales,et al.  The application of flow birefringence to rheological studies of polymer melts , 1976 .

[22]  D. Venerus,et al.  Stress and birefringence measurements during the uniaxial elongation of polystyrene melts , 1999 .

[23]  Gary P. Morriss,et al.  Statistical Mechanics of Nonequilibrium Liquids , 2008 .

[24]  J. V. Meerveld.  Validity of the linear stress optical rule in mono-, bi- and polydisperse systems of entangled linear chains , 2004 .

[25]  C. Tiu,et al.  Melt rheology of aliphatic hyperbranched polyesters with various molecular weights , 2001 .

[26]  L. Lue.  Volumetric behavior of athermal dendritic polymers: Monte Carlo simulation , 2000 .

[27]  B. D. Todd,et al.  Nonlinear shear and elongational rheology of model polymer melts at low strain rates , 2007 .

[28]  P. Daivis,et al.  Concentration dependence of viscometric properties of model short chain polymer solutions , 2004 .

[29]  F. Morrison,et al.  Rheology of Dendrimers. 2. Bulk Polyamidoamine Dendrimers under Steady Shear, Creep, and Dynamic Oscillatory Shear , 2000 .

[30]  Martin Kröger,et al.  Rheology and structural changes of polymer melts via nonequilibrium molecular dynamics , 1993 .

[31]  M. Kröger,et al.  Polymer Melts under Uniaxial Elongational Flow: Stress−Optical Behavior from Experiments and Nonequilibrium Molecular Dynamics Computer Simulations , 1997 .

[32]  Jean M. J. Fréchet,et al.  Molecular Ball Bearings: The Unusual Melt Viscosity Behavior of Dendritic Macromolecules , 1995 .

[33]  J. D. Atkinson,et al.  Effect of Molecular Shape on Rheological Properties in Molecular Dynamics Simulation of Star, H, Comb, and Linear Polymer Melts , 2003 .

[34]  R. Kannan,et al.  Unusual contributions of molecular architecture to rheology and flow birefringence in hyperbranched polystyrene melts , 2001 .

[35]  Y. H. Kim,et al.  Role of End Groups on the Glass Transition of Hyperbranched Polyphenylene and Triphenylbenzene Derivatives , 1994 .

[36]  C. W. Gear,et al.  Numerical initial value problem~ in ordinary differential eqttations , 1971 .

[37]  R. Bird.  Dynamics of Polymeric Liquids , 1977 .

[38]  Billy D. Todd,et al.  Homogeneous non-equilibrium molecular dynamics simulations of viscous flow: techniques and applications , 2007 .

[39]  D. Yan,et al.  Hyperbranched polymers: from synthesis to applications , 2004 .