scholarly journals Computing flexibility parameters and modelling the structure of poly(4-methylpentene-1)

2019 ◽  
pp. 96-106
Author(s):  
O.I. Romanko ◽  
G.Yu. Lomakina
Keyword(s):  
Phase Transitions ◽  
Chemical Bond ◽  
Packing Density ◽  
Repeat Unit ◽  
Thermodynamic Characteristics ◽  
Structural Transformations ◽  
Kuhn Segment ◽  
Wide Scope ◽  
Flexible Polymer ◽  
Flexibility Parameters

We used the method of increments to compute thermodynamic characteristics of poly(4-methylpentene-1), specifically the Kuhn segment as a parameter of flexibility and packing density. In order to carry out the computations, we composed equations that take into account every atom in the repeat unit and the chemical bond types found in the macromolecule. The values obtained made it possible to classify poly(4-methylpentene-1) as a flexible polymer featuring high free volume. We consider possible structural transformation models for the polymer when the temperature varies in the 293...773 K range. Comparing model representations to structural transformations investigated experimentally explains a wide scope of experimentally detected relaxation and phase transitions.

scholarly journals Computational analysis of morphologies and phase transitions of cross-linked, semi-flexible polymer networks

2015 ◽  
Vol 471 (2182) ◽  
pp. 20150332 ◽  
Author(s):  
Kei W. Müller ◽  
Christian J. Cyron ◽  
Wolfgang A. Wall
Keyword(s):  
Phase Transitions ◽  
Computational Study ◽  
Polymer Networks ◽  
Constitutive Models ◽  
Structural Polymorphism ◽  
Flexible Polymers ◽  
Fibre Network ◽  
Flexible Polymer ◽  
Morphological Differences ◽  
Semi Flexible Polymer

The eukaryotic cytoskeleton is a protein fibre network mainly consisting of the semi-flexible biopolymer F-actin, microtubules and intermediate filaments. It is well known to exhibit a pronounced structural polymorphism, which enables intracellular processes such as cell adhesion, cell motility and cell division. We present a computational study on cross-linked networks of semi-flexible polymers, which offers a detailed analysis of the network structure and phase transitions from one morphology to another. We elaborate the morphological differences, their mechanical implications and the order of the observed phase transitions. Finally, we present a perspective on how the information gained in our simulations can be exploited in order to build both flexible and accurate, microstructurally informed, homogenized constitutive models of the cytoskeleton.

Ultrasonic studies of structural transformations and phase transitions in liquid crystal emulsions

2011 ◽  
Vol 57 (2) ◽  
pp. 264-270 ◽  
Author(s):  
G. I. Maksimochkin ◽  
S. V. Pasechnik ◽  
A. G. Maksimochkin
Keyword(s):  
Phase Transitions ◽  
Liquid Crystal ◽  
Structural Transformations

Multiple structural transformations coupled with switchable magnetic and dielectric responses in an amphidynamic crystal of 4′-tert-butylbenzylpyridinium bis(maleonitriledithiolate)nickelate

2015 ◽  
Vol 3 (30) ◽  
pp. 7906-7915 ◽  
Author(s):  
Wei-Hua Ning ◽  
Lu Zhai ◽  
Jian-Lan Liu ◽  
Xiao-Ming Ren ◽  
Katsuya Ichihashi ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Structural Transformation ◽  
Magnetic Phase ◽  
Structural Transformations ◽  
Magnetic Phase Transitions

An amphidynamic crystal shows a two-step structural transformation; the steps are coupled to both hysteretic magnetic phase transitions and dielectric anomalies.

Influence of Doping on the Structural Transformations of the Proton Conducting Perovskite BaCe1xYxO3-D

2011 ◽  
Vol 172-174 ◽  
pp. 1296-1300 ◽  
Author(s):  
Francesco Trequattrini ◽  
Francesco Cordero ◽  
Francesca Deganello ◽  
Valeria La Parola ◽  
Edoardo Roncari ◽  
...  
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Neutron Diffraction ◽  
Bond Length ◽  
Phase Transformations ◽  
Structural Transformations ◽  
Elastic Compliance ◽  
Ionic Conductor ◽  
Cation Substitution ◽  
Relaxation Experiments

From neutron diffraction it is known that the BaCeO3 perovskite undergoes a sequence of phase transformations from high temperature cubic C to rhombohedral R, to orthorhombic O1 (Imma) and to orthorhombic O2 (Pnma). Doping Y3+ on the Ce4+ site introduces charge compensating O vacancies (VO) that may be partially filled with OH complexes with exposition to H2O, so making the material an ionic conductor. Anelastic relaxation experiments have been carried out on samples doped with 2%Y and 10%Y; the real part s’(T) of the complex elastic compliance presents softenings at the transitions, and the loss s’’/s’ curves allow the content of VO and H to be monitored. Doping has a strong effect on the temperature of the Pnma/R transition: with 10%Y in the fully hydrated state TO1-R increases up to 750 K while after full outgassing falls to 500 K, meaning that the introduction of ~5% VO shifts the transition of 250 K. While the effect of cation substitution on the transitions temperature is easily explained in terms of simple arguments usually valid for perovskites based on bond length considerations, the remarkable stabilization of the R phase by VO requires to take into account the anomalous sequence of phase transitions of undoped BaCeO3, where the R structure transforms into orthorhombic Pnma on cooling with the loss of an octahedral tilt system.

Coupling of the lactone-ring conformation with crystal symmetry in 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin

2001 ◽  
Vol 58 (1) ◽  
pp. 125-133 ◽  
Author(s):  
Armand Budzianowski ◽  
Andrzej Katrusiak
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Molecular Conformation ◽  
Lactone Ring ◽  
Structural Transformations ◽  
Unit Cell ◽  
Crystal Symmetry ◽  
Translational Symmetry ◽  
Ring Conformation ◽  
Conformational Disorder

Conformational disorder and inversions of the lactone ring induce structural transformations in the crystals of 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin, C14H18O3. The onset of ordering of the lactone ring at 300 K proceeds continuously, changes the space group from P21/m to P21/c and doubles the unit cell; the abrupt inversion of the lactone rings at 225 K changes the crystal translational symmetry in the (010) plane. The mechanism combining the molecular conformation and dynamics with the crystal structure, its symmetry, and phase transitions is presented.

Quantitative description of the tilt of distorted octahedra in ABX 3 structures

2007 ◽  
Vol 63 (2) ◽  
pp. 190-200 ◽  
Author(s):  
Rafael Tamazyan ◽  
Sander van Smaalen
Keyword(s):  
Phase Transitions ◽  
Bond Length ◽  
Strain Tensor ◽  
Quantitative Description ◽  
Local Strain ◽  
Structural Transformations ◽  
Bond Lengths ◽  
The Family ◽  
Distorted Octahedra ◽  
Atomic Coordinates

A description of the tilt of octahedra in ABX 3 perovskite-related structures is proposed that can be used to extract the unique values for the tilt parameters φ, θ and δ of ABX 3 structures with regular and distorted octahedra up to the point symmetry \bar 1, from atomic coordinates and lattice parameters. The geometry of the BX 6 octahedron is described by three B—X bond lengths (r 1, r 2, r 3) and three X—B—X bond angles (ψ12, ψ13 and ψ23) or alternatively by a local strain tensor together with an average B—X bond length. Connections between the proposed method and Glazer's tilt system are discussed. The method is used to analyze structural transformations of I2/c, Pbnm and Immm structures. The proposed description allows the analysis of group–subgroup relations for the ABX 3 structures with distorted octahedra, in terms of octahedral deformations and tilting. The method might also be of interest in the study of the phase transitions in the family of ABX 3 structures.

Metastable phase transitions and structural transformations in solid-state materials at high pressure

2007 ◽  
Vol 80 (10-12) ◽  
pp. 1003-1032 ◽  
Author(s):  
Paul F. McMillan ◽  
Olga Shebanova ◽  
Dominik Daisenberger ◽  
Raul Quesada Cabrera ◽  
Edward Bailey ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Solid State ◽  
Metastable Phase ◽  
Structural Transformations ◽  
Solid State Materials
Sign in / Sign up

Export Citation Format

Share Document