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

Abstract

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.

Melt Flow Properties of Block Copolymers

“…34 The value where both the dynamic elastic modulus and the viscosity form one curve corresponds to Lcr = r( w = 5·5 X 105 dyn cm -2 for S-B-S, in excellent agreement with the data of Arnold and Meier?…”

Rheology Pathway to Macroscale Ordered Nanostructures of Polymeric Nanotemplates: Nanopores, Nanosheets and Nanofibers

“…[42] For example, the T ODT can be determined from viscosity measurements as a function of temperature. [43,44] Another method is to use isothermal frequency scans at various temperatures. At the T ODT the dynamic storage modulus G 00 or the dynamic loss modulus G 0 shows an abrupt drop as a function of temperature.…”

Polymer applications

“…Widmaier and Meyer [256] studied the structure of an ABA polystyrene-isoprene block copolymer as a function of temperature by osmium tetroxide staining thin cast films. Hsiue and Yang [257] studied the morphology and properties of a-methylstyrene-butadiene diblock copolymer films cast from several solvents.…”