Micromechanical and positron annihilation lifetime study of new cellulose esters with different topological structures

Valentin Gaydarov; Zhangyan Chen; Galina Zamfirova; Meshude Akbulut Söylemez; Jinming Zhang; Nikolay Djourelov; Jun Zhang

doi:10.1016/j.carbpol.2019.05.022

Micromechanical and positron annihilation lifetime study of new cellulose esters with different topological structures

Carbohydr Polym. 2019 Sep 1:219:56-62. doi: 10.1016/j.carbpol.2019.05.022. Epub 2019 May 7.

Authors

Valentin Gaydarov¹, Zhangyan Chen², Galina Zamfirova¹, Meshude Akbulut Söylemez³, Jinming Zhang², Nikolay Djourelov⁴, Jun Zhang²

Affiliations

¹ Todor Kableshkov University of Transport, 158 Geo Milev str. Sofia, 1574, Bulgaria.
² CAS Key Laboratory of Engineering Plastics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing, 100190, China.
³ Hacettepe University, Chemistry Department, Polymer Chemistry Division, Beytepe, Ankara, 06800, Turkey.
⁴ Extreme Light Infrastructure - Nuclear Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, Bucharest-Magurele, 077125, Romania. Electronic address: nikolay.djourelov@eli-np.ro.

PMID: 31151546
DOI: 10.1016/j.carbpol.2019.05.022

Abstract

Two new groups of cellulose esters with a substituent, either trifluoromethylbenzoate or methylbenzoate, were synthesized in homogeneous conditions. The actual presence of aromatic substituents was demonstrated by ¹H-NMR spectra. The mechanical and structural peculiarities were determined by Depth Sensing Indentation (DSI) and Positron Annihilation Lifetime Spectroscopy (PALS) techniques. The relative position of CH₃ and CF₃ groups on the aromatic substituents influences the molecular packing differently and affects the formation of free volumes. The hardness characteristics and modulus of the corresponding cellulose esters were the lowest when the CH₃ and CF₃ groups are in m-position on the aromatic substituents. Meanwhile, they exhibited the highest number density of the free volume holes, as revealed by the o-Ps intensity values. An inverse linear relationship between the hardness, respectively on the modulus, and the o-Ps intensity was found. A simplified scheme of the structural feature of the investigated cellulose esters was proposed.

Keywords: Cellulose esters; Free volume hole; Hardness; Methylbenzoate; Positron annihilation; Trifluoromethylbenzoate.