SAXS and TEM Studies on Poly(styrene)-block-poly(ethene-co-but-1-ene)-block-poly(styrene) in Bulk and at Various Interfaces

Abstract

SAXS and TEM measurements are employed in order to study the morphology of poly(styrene)-block-poly(ethene-co-but-1-ene)-block-poly(styrene) (SEBS) with 29 wt % styrene (Kraton G1652) in bulk and at interfaces to different polymers. Temperature-dependent SAXS measurements of the SEBS bulk sample reveal that PS cylinders are hexagonally packed in the EB matrix. The lattice constant increases during cooling from 200 to 120 °C from 27.5 to 29.5 nm and simultaneously an increase of the cylinder radius occurs from 7 to 7.5 nm. The lattice constant obtained by SAXS is in agreement with TEM measurements on ultrathin sections of the bulk sample. TEM tilting experiments confirm the existence of cylindrical microdomains in the SEBS bulk phase. Furthermore, the behavior of SEBS at the interface with various polymers is studied by TEM and peel tests. TEM measurements show that SEBS forms one lamella at the interface PS homopolymer having a molecular weight much larger than the PS blocks. This results only in a very weak adhesion between SEBS and PS homopolymer measured by a peel test using bilayer specimens. In contrast there is a strong adhesion at the interface of SEBS with poly(3,5-dimethylphenylene ether) (PPE) or isotactic polypropylene (i-PP) after thermal annealing. This can be explained by the miscibility of the PS blocks with PPE and of the EB matrix of the block copolymer with i-PP, respectively. This leads to interfacial phase transitions, to cooperative orientation processes of PS cylinders, and finally to diffusion processes of disordered micelles as verified by TEM micrographs.

Investigation of morphologies and nanostructures of polymer blends by tapping mode phase imaging

“…2a, which reveals dark domain structures embedded in a bright matrix. By comparing the relative sizes of the dark and bright areas, it is evident (1) The morphologies and mechanical properties of 30 : 70 and 70 : 30 SEBS/i-PP blends were studied by TEM [5,22]. This TEM study showed large irregularly formed domains of more than 1 µm in size, together with spherical domains a few hundred nanometers in size, all of which are very similar to those found in Figs.…”

“…Within the i-PP region, lamellae can be clearly seen. The lamellae have a typical diameter of 20 nm and exhibit the cross-hatched structure, as reported by TEM [5,22]. In both height and phase images, the SEBS tri-block copolymer regions are microphase separated, i.e.…”

Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior

“…On the basis of the mass densities of polystyrene 34 (1.01 g/cm 3 ) and the SEBS triblock copolymer 23 (0.91 g/cm 3 ) at the upper glass transition temperature of polystyrene (T g ϭ 100°C), we estimate the volume fraction of styrene in the copolymer to be about 0.28. Since a similar SEBS copolymer (Kraton G1652) of lower molecular weight (M n ϭ 87000) and styrene content (29 wt %) is reported 35 to be microphase-ordered (exhibiting hexagonally packed styrenic cylinders in an EB-rich matrix) at the T g of the copolymer, it follows that the copolymer examined here must likewise be ordered, due to its higher N. Assessment of the copolymer morphology is described below.…”

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“…In addition, with the same material, different morphologies can be observed in response to the application of shear forces, [5,6] type of solvent used, [7,8] solvent evaporation rate, [9] and film thickness. [10] Sulfonated block copolymers are commonly used as proton-conducting membranes [11 -14] (PCM) in protonexchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC). The application of sulfo-nated block copolymers as PCMs is possible due to the introduction of hydrophilic functional groups, i.e.…”