Phenylene ring dynamics in phenoxy and the effect of intramolecular linkages on the dynamics of some engineering thermoplastics below the glass transition temperature

Silvia Arrese-Igor,Juan Colmenero,Angel Alegría,Arantxa Arbe,Bernhard Frick

doi:10.1103/physreve.75.051801

Abstract

We have investigated the dynamics of phenylene rings in the engineering thermoplastic bisphenol-A poly(hydroxyether) -- phenoxy -- below its glass transition temperature by means of neutron scattering techniques. A relatively wide dynamic range has been covered thanks to the combination of two different types of neutron spectrometers, time of flight and backscattering. Partially deuterated samples have been used in order to isolate the phenylene ring dynamics. The resulting neutron scattering signal of phenoxy has been described by a model that considers pi flips and oscillation motions for phenylene rings. The associated time scales are broadly distributed with mean activation energies equal to 0.41 and 0.21eV , respectively. Finally, a comparative study with the literature shows that the dielectric and mechanical gamma relaxation in phenoxy exhibit good correlation with the characteristic times of the aliphatic chain published elsewhere and with the characteristic times observed for the motion of phenylene rings by neutron scattering. These findings are discussed in a more general framework that considers, in addition, previous results on other polymers, which also contain the bisphenol-A unit.

Highlights

Engineering thermoplastics based on the bisphenol-A moietyBPAhave an important technological significance
We have investigated the dynamics of phenylene rings in the engineering thermoplastic bisphenol-A polyhydroxyether—phenoxy—below its glass transition temperature by means of neutron scattering techniques
A comparative study with the literature shows that the dielectric and mechanical ␥ relaxation in phenoxy exhibit good correlation with the characteristic times of the aliphatic chain published elsewhere and with the characteristic times observed for the motion of phenylene rings by neutron scattering

Summary

Introduction

Engineering thermoplastics based on the bisphenol-A moietyBPAhave an important technological significance. The microscopic origin of these interesting mechanical properties is not completely elucidated yet, it has been long believed that they are closely related with the so-called secondary relaxation processes, i.e., with those dynamic processes observed by spectroscopic conventional techniques such as dielectricDSor mechanicalMSspectroscopy. These techniques allow a good characterization of the shape and characteristic frequency of secondary relaxations in a broad frequency rangeϳ10−3– ϳ 109 Hz with standard techniques ͓1,2͔. A deep knowledge of the mechanisms and specific nature of the molecular motions behind the secondary relaxations will remarkably contribute to the understanding of the structure / dynamics / properties relationship, which would enable tailoring the polymer properties for demanding applications

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Conclusion