Influence of composition fluctuations on the linear viscoelastic properties of symmetric diblock copolymers near the order-disorder transition

Journal Article · Fri Aug 28 04:00:00 EDT 2015 · ACS Macro Letters

DOI:https://doi.org/10.1021/acsmacrolett.5b00014· OSTI ID:1194211

Hickey, Robert J. ^[1]; Gillard, Timothy M. ^[1]; Lodge, Timothy P. ^[1]; Bates, Frank S. ^[1]

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1. Univ. of Minnesota, Minneapolis, MN (United States)

Rheological evidence of composition fluctuations in disordered diblock copolymers near the order disorder transition (ODT) has been documented in the literature over the past three decades, characterized by a failure of time–temperature superposition (tTS) to reduce linear dynamic mechanical spectroscopy (DMS) data in the terminal viscoelastic regime to a temperature-independent form. However, for some materials, most notably poly(styrene-b-isoprene) (PS–PI), no signature of these rheological features has been found. We present small-angle X-ray scattering (SAXS) results on symmetric poly(cyclohexylethylene-b-ethylene) (PCHE–PE) diblock copolymers that confirm the presence of fluctuations in the disordered state and DMS measurements that also show no sign of the features ascribed to composition fluctuations. Assessment of DMS results published on five different diblock copolymer systems leads us to conclude that the effects of composition fluctuations can be masked by highly asymmetric block dynamics, thereby resolving a long-standing disagreement in the literature and reinforcing the importance of mechanical contrast in understanding the dynamics of ordered and disordered block polymers.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE Office of Science (SC)
• OSTI ID: 1194211
• Journal Information: ACS Macro Letters, Journal Name: ACS Macro Letters Journal Issue: 2 Vol. 4; ISSN 2161-1653
• Country of Publication: United States
• Language: ENGLISH