Structural evolution of an ABA poly(styrene-b-isoprene) block copolymer with temperature

Autor:	J. M. Widmaier, G. C. Meyer
Rok vydání:	1980
Předmět:	Diffraction Materials science Transition temperature General Engineering Analytical chemistry Atmospheric temperature range Styrene chemistry.chemical_compound chemistry Polymer chemistry Copolymer Lamellar structure Elastic modulus Isoprene
Zdroj:	Journal of Polymer Science: Polymer Physics Edition. 18:2217-2225
ISSN:	1542-9385 0098-1273
DOI:	10.1002/pol.1980.180181106
Popis:	The structural evolution with temperature of an anionically synthesized ABA poly(styrene-b-isoprene) (SIS) lamellar block copolymer (total molecular weight 45,000; isoprene content 38% by weight) was studied by melt-rheological measurements, electron microscopy, and x-ray and light diffraction. Above 225°C, the dynamic viscosity was found to be independent of frequency up to a critical frequency. The variation of the elastic modulus confirmed the occurence of a transition between 215 and 225°C. For the temperature range considered, all results superimposed well on a two-branch master curve. It was concluded that above 225°C, our SIS behaves like a Newtonian material, whereas for lower temperatures and/or higher frequencies classical non-Newtonian behavior is found. The melt-rheological properties were explained by microscopy and diffraction investigations, which allowed us to follow morphological changes as the temperature was raised. It was found that the two-phase lamellar structure is progressively destroyed, and the transition temperature of 225°C corresponds to the temperature above which complete mixing occurs.
Databáze:	OpenAIRE
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