Crystalline Moduli of Polymers, Evaluated from Density Functional Theory Calculations under Periodic Boundary Conditions.

ACS Omega

Department of Applied Chemistry and Biotechnology, Graduate School and Faculty of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.

Published: May 2018

A theoretical methodology based on quantum chemistry to calculate mechanical properties of polymer crystals has been developed and applied to representative polymers. By density functional theory calculations including a dispersion force correction under three-dimensional periodic boundary conditions, crystal structures of poly(methylene oxide) (PMO), polyethylene (PE), poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT) were optimized and their mechanical properties, such as crystalline moduli and linear and volume compressibilities, were calculated. The optimized crystal structures were proved to be fully consistent with those determined by X-ray and neutron diffraction. The crystalline moduli ( ) parallel to the chain axis were calculated to be 114 GPa (PMO), 333 GPa (PE), 182 GPa (PET), 7.1 GPa (PTT), and 20.8 GPa (PBT) and compared with those determined from X-ray diffraction, Raman spectroscopy, and neutron inelastic scattering experiments. Herein, the values thus determined are interpreted in terms of conformational characteristics of the polymeric chains and the validity of the homogeneous stress hypothesis adopted in the X-ray diffraction method is also discussed.

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6641976PMC
http://dx.doi.org/10.1021/acsomega.8b00506DOI Listing

Publication Analysis

Top Keywords

crystalline moduli
12
density functional
8
functional theory
8
theory calculations
8
periodic boundary
8
boundary conditions
8
mechanical properties
8
crystal structures
8
determined x-ray
8
x-ray diffraction
8

Similar Publications

Nonlinear Elasticity of Amorphous Silicon and Silica from Density Functional Theory.

J Phys Chem C Nanomater Interfaces

December 2024

Department of Chemistry, College of Staten Island, Staten Island, New York 10314, United States.

Density functional theory calculations and a finite deformation method are used to calculate second- and, most notably, third-order elastic constants of amorphous silicon and amorphous silicon dioxide, as represented by model structures generated via melt-quench force-field molecular dynamics simulations. Linear and nonlinear elastic constants are used to deduce macroscopic elastic moduli, such as the bulk and shear moduli, their pressure derivatives, and the elastic Grüneisen parameter. Our calculations show that the elastic properties of amorphous silicon reach the isotropic elastic limit within the nanometer length scale, attaining characteristics, both linear and nonlinear, comparable to those of crystalline silicon.

View Article and Find Full Text PDF

Adipose-derived lipid droplets (LDs) are rich in triacylglycerols (TAGs), which regulate essential cellular processes, such as energy storage. Although TAG accumulation and LD expansion in adipocytes occur during obesity, how LDs dynamically package TAGs in response to excessive nutrients remains elusive. Here, we found that LD lipidomes display a remarkable increase in TAG acyl chain saturation under calorie-dense diets, turning them conducive to close-packing.

View Article and Find Full Text PDF

Unveiling the Significance of Graphene Nanoplatelet (GNP) Localization in Tuning the Performance of PP/HDPE Blends.

Materials (Basel)

November 2024

International Institute for Nanocomposites Manufacturing (IINM), WMG, University of Warwick, Coventry CV4 7AL, West Midlands, UK.

Article Synopsis
  • HDPE and PP blends filled with graphene nanoplatelets (GNPs) are explored to understand how processing parameters like blending sequence and screw speed affect their performance.
  • *The study finds that the blending sequence significantly influences the crystallization behavior and tensile properties of the blends, particularly showing that GNPs premixed with PP lead to greater increases in crystallization temperature for PP than GNPs premixed with PE.
  • *Results indicate that while tensile moduli are stable under different processing conditions, elongation at break and tensile toughness exhibit significant changes, emphasizing the critical link between processing methods and material performance.
View Article and Find Full Text PDF

We carried out an experimental ultrasonic study of polyhydric alcohols with the general chemical formula CH(OH) with an increasing number of OH groups: glycerol ( = 3), erythritol ( = 4), xylitol ( = 5), sorbitol ( = 6). The baric and temperature dependences of the elastic characteristics of these substances in the crystalline and glassy states were studied both under isothermal compression up to 1 GPa and during the isobaric heating of 77-295 K. For glycerol, glasses were obtained at different cooling rates, glass-liquid transitions were studied at different pressures.

View Article and Find Full Text PDF

Fused deposition molding (FDM) is a commonly used 3D printing method, and polylactic acid (PLA) has become one of the most important raw materials for this technology due to its excellent warping resistance. However, its mechanical properties are insufficient. Polybutylene adipate terephthalate (PBAT) is characterized by high toughness and low rigidity, which can complement the performance of PLA.

View Article and Find Full Text PDF

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!