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Structure Evolution of Thermotropic Polymers by Thermal Annealing. A Light and X-Ray Scattering Study

Published online by Cambridge University Press:  01 October 2015

Adriana Reyes-Mayer ,
Angel Romo-Uribe  and
Michael Jaffe
Adriana Reyes-Mayer
Affiliation:
Laboratorio de Nanopolímeros y Coloides, Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca Mor. 62210, MEXICO. Centro de Investigación en Ingeniería y Ciencias Aplicadas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Cuernavaca, Mor. 62209, MEXICO.
Angel Romo-Uribe*
Affiliation:
Laboratorio de Nanopolímeros y Coloides, Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca Mor. 62210, MEXICO.
Michael Jaffe
Affiliation:
Medical Device Concept Lab, New Jersey Institute of Technology, Newark NJ 07103, USA.
*
*To whom correspondence should be addressed: [email protected]
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Abstract

Small-angle light scattering (SALS) and wide-angle X-ray scattering (WAXS) were used to study the influence of heat treatment on the texture and microstructure of extruded films of high-performance thermotropic liquid crystal polymers (LCPs). The microstructure was correlated with tensile mechanical properties. LCPs based on random units of hydroxybenzoic acid (B), hydroxynaphthoic acid (N), terephthalic acid (TA) and biphenol (BP) were supplied by the former Hoechst Celanese Corp. as 50 μm thick extruded films. The LCPs, denoted B-N, COTBP and RD1000, have B and N as common co-monomers and vary the other co-monomers. Thus, this study also enabled the investigation of the influence of monomer composition on microstructure and mechanical properties. Heat treatments were carried out at temperatures close to the solid-to-nematic transition (Ts→n) for periods up to 5 h, under dry air conditions. The thermal treatment produced either two endotherms or a small increase of Ts→n (B-N and RD1000), or Ts→n increased significantly (COTBP). Moreover, when heat treatment was carried out approximately 40°C below the respective Ts→n, the mechanical Young’s modulus, E, along the extrusion axis increased for all LCPs. Strikingly, for COTBP, E increased over 100% relative to the as-extruded film. The results also showed that the optimum treatment time for improving the Young modulus was between 3 and 4 h. Wide-angle X-ray scattering showed a significant sharpening of crystalline reflections and concentration of the 002 meridional reflection as a result of thermal treatment, suggesting the elimination of defects and a better alignment of the molecular chains along the extrusion axis. This would explain the increase in tensile modulus.

Keywords

liquid crystalpolymerX-ray diffraction (XRD)
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1765: Symposium 4A – Advanced Structural Materials—2014 , 2015 , pp. 65 - 70
Copyright
Copyright © Materials Research Society 2015 

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