Compatibilization of polystyrene/poly(dimethyl siloxane) solutions with star polymers containing a γ-cyclodextrin core and polystyrene arms

Solutions of polystyrene and poly(dimethyl siloxane) in chloroform are compatibilized by the addition of a small amount of a star polymer consisting of a gamma-cyclodextrin core and polystyrene arms. Compatibilization is visually observed when turbid PDMS/PS emulsions become clear upon addition of the CD-star molecule. The mechanism of compatibilization involves threading of the CD-core by PDMS and solubilization of the resulting "slip-ring graft copolymer" via the PS star arms. This process breaks up the undissolved PDMS domains into smaller, more stable micelles. Evidence for threading of the CD-core by PDMS is found using ROESY 2D-NMR. Intrinsic viscosity measurements for the compatibilized solutions show behavior similar to conventional graft copolymers which form micelles in a selective solvent. Dynamic light scattering measurements suggest that the micelle size is approximately 20 nm. The effects of varying the PDMS molecular weight, PDMS concentration and CD-star concentration are studied. (C) 2009 Elsevier Ltd. All rights reserved.