Characterization of Polystyrene-block-Polyethylene Oxide Diblock Copolymers and Blends of Homopolymers by Liquid Chromatography at Critical Conditions (LCCC) Pritish Sinha, * Monika Grabowsky, Muhammad Imran Malik, Gareth William Harding, Harald Pasch Summary: In the present study, diblock copolymers of PS-b-PEO synthesized by sequential living anionic polymerization as well as the blends of PS, PEO homo- polymers will be investigated by using liquid chromatography at critical conditions. Critical conditions will be established for the PS block of the copolymer. At these conditions, the PS block is chromatographically invisible and does not contribute to retention so the block copolymer is separated according to the block length of the PEO block. At the critical conditions of PS, it is also possible to separate the PS homopolymer formed. The critical conditions will be established in such a way that the non-critical PEO block elutes in size exclusion chromatography (SEC) mode. Keywords: blends; critical conditions; diblock copolymers; polyethylene oxide (PEO); polystyrene (PS) Introduction Block copolymers are a fascinating class of polymeric materials as they show ambiva- lent properties. Both in solution and in bulk they give a variety of microstructures which are used in a broad range of applications from advanced nanomaterials to biocom- patible drug delivery systems. [1–3] As they have the capability to self-organize they are used to fabricate high-density storage media, [4] to lithographically pattern semi- conductors with ultrasmall feature sizes, [5] and to prepare ultrafine filters or mem- branes. [6–8] Amphiphilic copolymers, con- sisting of hydrophilic and hydrophobic parts are significant due to their numerous chemical and biological properties. [9] Diblock (PS-b-PEO) and triblock (PS-b- PEO-b-PS) copolymers consisting of hydro- philic (PEO) and hydrophobic (PS) are used in many industrial applications. They are used as polymeric surfactants in oil, pharmaceutical, agriculture, paper and detergent industries. [10] These block copo- lymers are also used as compatibilizers in polymer blending, dispersions, stabili- zers, [11,12] templates for the preparation of inorganic nanoparticles. [13] Using the self-assembly of PEO-b-PS and PS-b-PEO- b-PS to ordered nanostructures, novel applications such as the preparation of mesoporous silica films with different pore sizes [14] and electrolytes for rechargeable batteries have been developed. [15] Block copolymers are very complex materials; therefore complete characterization of these promising materials is necessary. Since these materials exhibit heterogene- ities regarding molar masses, chemical compositions of the different blocks, func- tionalities, architectures and microstruc- tures they pose a major challenge for separation scientists to characterize them. The simplest technique to characterize Macromol. Symp. 2012, 313-314, 162–169 DOI: 10.1002/masy.201250318 162 University of Stellenbosch, Department of Chemistry and Polymer Science, Private Bag X1, 7602 Matieland, South Africa E-mail: pritish@sun.ac.za Copyright ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com