Diblock copolymer architecture and complex viscosity

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040110 ◽  
Author(s):  
Mona A. Kanso ◽  
A. Jeffrey Giacomin ◽  
Chaimongkol Saengow ◽  
Jourdain H. Piette
Keyword(s):  
Diblock Copolymer ◽  
Linear Density ◽  
Complex Viscosity ◽  
Chem Phys ◽  
Dimensionless Frequency ◽  
Zero Shear Viscosity ◽  
Polymeric Liquids ◽  
Rod Theory ◽  
Number Ratio ◽  
Polymer Viscoelasticity

General rigid bead-rod theory [O. Hassager, J. Chem. Phys. 60, 4001 (1974)] explains polymer viscoelasticity from macromolecular orientation. By means of general rigid bead-rod theory, we relate the complex viscosity of polymeric liquids to the architecture of axisymmetric macromolecules. In this paper, we explore the complex viscosities of different axisymmetric diblock copolymer configurations. When nondimensionalized with the zero-shear viscosity, the diblock copolymer complex viscosity depends on the dimensionless frequency and the sole dimensionless architectural parameter, the macromolecular lopsidedness. In this paper, through this way, we thus compare the dimensionless relaxation time of different diblock macromolecular chains. We explore the effects of linear density, macromolecular length, and bead number ratio.

scholarly journals Complex viscosity of star-branched macromolecules from analytical general rigid bead-rod theory

2021 ◽  
Vol 33 (9) ◽  
pp. 093111
Author(s):  
S. J. Coombs ◽  
M. A. Kanso ◽  
K. El Haddad ◽  
A. J. Giacomin
Keyword(s):  
Complex Viscosity ◽  
Rod Theory

Rheological Studies of Dynamically Vulcanized and Mechanical Blends of Polypropylene and Ethylene-Propylene Rubber

1995 ◽  
Vol 68 (5) ◽  
pp. 728-738 ◽  
Author(s):  
Peter K. Han ◽  
James L. White
Keyword(s):  
Shear Viscosity ◽  
Liquid Crystalline ◽  
Complex Viscosity ◽  
Normal Stresses ◽  
State Structure ◽  
Newtonian Viscosity ◽  
Zero Shear Viscosity ◽  
Flexible Chain ◽  
Ethylene Propylene ◽  
Yield Value

Abstract An experimental study is presented of the rheological properties of (i) polypropylene, (ii) a commercial polypropylene/ethylene-propylene terpolymer a dynamically vulcanized blend (PP/EDPM-TPE) and (iii) a mechanical blend of a polypropylene and an ethylene-propylene copolymer. The polypropylene behaves as a typical flexible chain thermoplastic exhibiting a zero shear viscosity and higher shear rate non-Newtonian viscosity, well defined normal stresses, an elongational viscosity three times the zero shear viscosity, and an equality of the shear viscosity and the complex viscosity (Cox-Merz Rule). The PP/EPM-TPE exhibits an apparent yield value in shear flow, unmeasurable normal stresses and a complex viscosity which is much greater than the shear viscosity. This is behavior similar to that of particle filled compounds, block copolymers and liquid crystalline thermoplastics and suggests a material with a rest state structure. The behavior of the PP/EPM mechanical blend is intermediate.

scholarly journals Research on the Rheological Characteristics and Aging Resistance of Asphalt Modified with Tourmaline

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 69 ◽  
Author(s):  
Qunshan Ye ◽  
Wenzhuo Dong ◽  
Shipei Wang ◽  
Heng Li
Keyword(s):  
Storage Stability ◽  
Complex Viscosity ◽  
Negative Ion ◽  
Asphalt Binders ◽  
Test Results ◽  
Frequency Range ◽  
Zero Shear Viscosity ◽  
Two Phase ◽  
Modified Asphalt ◽  
Aging Resistance

Tourmaline modified asphalt (TMA) binders were prepared with different modifier types and contents in this research. The routine properties, rheological properties, and aging resistance were evaluated to research the function of tourmaline on the performances of asphalt binders. Test results show that the storage stability can be improved significantly by the smaller particle size and negative-ion treated surface of tourmaline modifier. It indicates that the stiffness and rutting-resistance of TMA binder can be enhanced significantly, and the elastic component of the viscoelastic characteristic can also be increased. Moreover, the complex viscosity and the Zero Shear Viscosity (ZSV) values of tourmaline modified asphalt are increased within the test frequency range, which results in the improvement of deformation resistance of tourmaline modified asphalt. When mixed with asphalt, the tourmaline modifier maintains a two-phase structure, which results in the good rheological property for tourmaline modified asphalt.

Surface segregation in model symmetric polyolefin diblock copolymer melts

1994 ◽  
Vol 4 (12) ◽  
pp. 2231-2248 ◽  
Author(s):  
Mohan Sikka ◽  
Navjot Singh ◽  
Frank S. Bates ◽  
Alamgir Karim ◽  
Sushil Satija ◽  
...  
Keyword(s):  
Diblock Copolymer ◽  
Surface Segregation ◽  
Copolymer Melts

Computational Investigation of the Asymmetry in Photosynthetic Reaction Center Models from First Principles

2020 ◽  
Author(s):  
Denis Artiukhin ◽  
Patrick Eschenbach ◽  
Johannes Neugebauer
Keyword(s):  
Spin Density ◽  
Reaction Center ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Chem Phys ◽  
Molecular Structures ◽  
Error Characteristic ◽  
Molecular Systems ◽  
Density Distributions ◽  
The Asymmetry

We present a computational analysis of the asymmetry in reaction center models of photosystem I, photosystem II, and bacteria from <i>Synechococcus elongatus</i>, <i>Thermococcus vulcanus</i>, and <i>Rhodobacter sphaeroides</i>, respectively. The recently developed FDE-diab methodology [J. Chem. Phys., 148 (2018), 214104] allowed us to effectively avoid the spin-density overdelocalization error characteristic for standard Kohn–Sham Density Functional Theory and to reliably calculate spin-density distributions and electronic couplings for a number of molecular systems ranging from dimeric models in vacuum to large protein including up to about 2000 atoms. The calculated spin densities showed a good agreement with available experimental results and were used to validate reaction center models reported in the literature. We demonstrated that the applied theoretical approach is very sensitive to changes in molecular structures and relative orientation of molecules. This makes FDE-diab a valuable tool for electronic structure calculations of large photosynthetic models effectively complementing the existing experimental techniques.

`Diet GMKTN55' Offers Accelerated Benchmarking Through a Representative Subset Approach

2018 ◽  
Author(s):  
Tim Gould
Keyword(s):  
Density Functional ◽  
Chem Phys ◽  
Comprehensive Analysis ◽  
Genetic Approach ◽  
Representative Subset ◽  
Phys Chem Chem Phys

The GMTKN55 benchmarking protocol introduced by [Goerigk et al., Phys. Chem. Chem. Phys., 2017, 19, 32184] allows comprehensive analysis and ranking of density functional approximations with diverse chemical behaviours. But this comprehensiveness comes at a cost: GMTKN55's 1500 benchmarking values require energies for around 2500 systems to be calculated, making it a costly exercise. This manuscript introduces three subsets of GMTKN55, consisting of 30, 100 and 150 systems, as `diet' substitutes for the full database. The subsets are chosen via a stochastic genetic approach, and consequently can reproduce key results of the full GMTKN55 database, including ranking of approximations.

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