Order-Disorder Transition: Diblock versus Triblock Copolymers

Mark D. Gehlsen, Kristoffer Almdal, Frank S. Bates

Research output: Contribution to journalArticlepeer-review

124 Scopus citations

Abstract

A nearly symmetric cis-1,4-polyisoprene-1,2-polybutadiene (1,4-PI-1,2-PB) diblock copolymer was anionically polymerized and partially coupled to form a mixture of diblock and 1,4-PI-1,2-PB-1,4-PI triblock copolymers. This mixture was subsequently hydrogenated and fractionated, yielding a homologous pair of poly(ethylenepropylene)-poly(ethylethylene) (PEP-PEE) diblock and PEP-PEE-PEP triblock copolymers, along with three intermediate mixtures containing both molecular architectures. The orderdisorder transition temperature, TODT, which was determined for each mixture by dynamic mechanical spectroscopy, was found to vary significantly with molecular architecture. For the triblock material TODT was 72 °C higher than that for the homologous diblock specimen, which compares favorably with the 61 °C difference anticipated by mean-field theory. Above TODT the dynamic mechanical properties are insensitive to variations in molecular architecture, while below the order-disorder transition subtle variations in the low-frequency viscoelastic response are apparent.

Original languageEnglish (US)
Pages (from-to)939-943
Number of pages5
JournalMacromolecules
Volume25
Issue number2
DOIs
StatePublished - Mar 1 1992

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