Cooperative Gelation of Syndiotactic Polystyrene and Low Molecular Weight PEGDME

ABSTRACT

The cooperative gelation of sPS with the short PEGDME molecules (molecular weight M_W = 1.5 kg mol⁻¹) from a common THF solution is driven by the gelation tendency of sPS at a temperature around 40°C. The crystalline junctions in the wet gel are fibrillar morphologies, which are typically composed of sPS and PEG molecules, as shown by contrast variation SANS, and consist of sPS, which co‐crystallizes in d‐form with the solvent molecules, and to a certain extent with PEGDME molecules, as demonstrated by the conformational change of both polymer types from an amorphous to a helical form when the gelation temperature is exceeded, which was observed by in situ FTIR. XRD and SEM on drying gels have shown that the large‐scale morphology of dry gels, when the polymer strands collapse and crystalline polymer strands are formed, is determined by the presence and length of the PEGDME molecules. While the sPS dry gel exhibits a more homogeneous distribution of polymer strands and well‐defined pores, the polymer strands of the gel with short PEGDME connect at one end to form “tufted” macroassemblies, which, due to the additional co‐crystallization of PEGDME with sPS, leads to very large pores and voids.