Asymmetric PS‐block‐(PS‐co‐PB)‐block‐PS block copolymers: morphology and deformation behavior of star block copolymer/PS blends

Abstract

The morphology and deformation behavior of blends comprising an asymmetric styrene/butadiene star block copolymer and polystyrene homopolymer (hPS) were investigated by means of transmission electron microscopy (TEM) and uniaxial tensile testing. The hPS samples used had a wide range of molecular weights. In spite of the high polystyrene (PS) content, the star block copolymer exhibited a morphology consisting apparently of a rubbery matrix, attributable to its asymmetric architecture and presence of polystyrene/polybutadiene random copolymer (PS‐co‐PB) as soft rubbery blocks. In the blends, depending on the molecular weight and modality of the added hPS and on the composition of the mixtures, different morphologies (ranging from microphase‐separated and macrophase‐separated ones to a combination of both of them) were observed. Consequently, it was possible to tailor the tensile mechanical properties based on the nature of the nanoscopic morphology of the star block copolymer/PS blends. Copyright © 2005 John Wiley & Sons, Ltd.

Micromechanical Studies of Styrenic Block Copolymer Blends Based Nanocomposites

“…However, surprisingly, under the given processing conditions, and with the special parent block copolymer architecture, the nanostructures of the block copolymer is maintained; there is no sign of macrophase‐separation as one would expect in the block copolymer blends comprising polystyrene with much higher molecular weight than the size of the corresponding block of the block copolymer. It should be noted that the molecular weight of GPPS used to prepare the blends has higher molecular weight (190,000 g/mol) . The PS chains should act as chains adhered feebly to the polystyrene domains of the block copolymer in the so called dry‐brush regime.…”

“…An overview of the morphology of some of the ST3/GPPS blends prepared by melt mixing followed by compression moulding is presented in Figure . The details on the morphology of the blends have been addressed in our earlier publications . Here, we summarize only the results.…”

“…The structure properties relations in the blends concerning block copolymers have been the object of several previous publications from different groups . In this work, using different microscopic techniques (such as scanning electron microscopy SEM and transmission electron microscopy, TEM), and tensile testing, we investigate the correlation between morphology and the micro‐deformation processes in the blends and nanocomposites based on a highly asymmetric star shaped polystyrene/polybutadiene block copolymer.…”

Three‐Phase Model of Two‐Component Blends Consisting of a Polystyrene–Polybutadiene Star Block Copolymer and a Polystyrene Homopolymer

“…Another study on four arm SB star block copolymer/PS homopolymer (hPS) blends has revealed that the hardness increased with the increase in the PS‐layer thickness . The mechanical behaviour and morphology of blends of SB block copolymers and hPS have been repeatedly investigated in the last decade, mainly by Adhikari el al . The morphology of blends of an SB star block copolymer and PS, which ranges from microphase‐separated to macrophase‐separated structure depending on the molecular weight of the PS and the composition of the blends clearly affects the tensile mechanical properties .…”

Biodegradable polymeric micro‐nanofibers by electrospinning of polyester/polyether block copolymers

“…As known, polymers chemical composition and morphology influence the bulk properties (rheological behavior, mechanical properties). Block copolymers are of particular interest, because the combination of the single components can be balanced by using suitable molecular weights and amount of the coupled segments to obtain the characteristics required for the desired application 16–20. The mechanical properties are, in particular, an issue that has to be often faced when a material is implanted in the human body as temporary (e.g., bioerodible–bioeliminable scaffold) or permanent (e.g.…”