Title
Thermoreversible changes in aligned and cross-linked block copolymer melts studied by two color depolarized light scattering
Date Issued
25 September 2012
Access level
metadata only access
Resource Type
journal article
Author(s)
University of California
Abstract
We present a procedure for creating samples that can be repeatedly cycled between weakly aligned and strongly aligned states. Poly(styrene-b-isoprene) block copolymer samples were first shear-aligned and then cross-linked using a high energy electron beam. Samples with more than 1.0 cross-links per chain on average showed almost complete recovery of their initial alignment state even after 20 cycles of heating above the order-disorder transition temperature of the un-cross-linked block copolymer. Samples with 1.1 cross-links per chain, which showed over 90% loss of alignment on heating and almost 100% recovery of alignment on cooling, provided the best example of a reversible aligned-to-unaligned transition. Samples with lower cross-linking densities exhibited irreversible loss of alignment upon heating, while those with higher cross-linking densities exhibited less than 90% loss of alignment upon heating. Alignment was quantified by a technique that we call two color depolarized light scattering (TCDLS), an extension of the traditional depolarized light scattering experiment used to determine the state of order in block copolymers. Qualitative confirmation of our interpretation of TCDLS data was obtained by small-angle X-ray scattering and transmission electron microscopy. © 2012 American Chemical Society.
Start page
7590
End page
7598
Volume
45
Issue
18
Language
English
OCDE Knowledge area
Ciencias naturales
Química
Scopus EID
2-s2.0-84866697064
Source
Macromolecules
ISSN of the container
00249297
Sponsor(s)
National Science Foundation, 0822838, 0966626, NSF
Sources of information:
Directorio de Producción Científica
Scopus