title: Small-angle neutron scattering of dilute polystyrene chains at the protein limit of a colloid-polymer mixture.
abstract: The present work investigates the structure of large polystyrene (PS) chains in solutions of small poly(ethyl methacrylate) (PEMA) microgel particles in toluene. Toluene is a good solvent for the PS chains. The PEMA colloids have an outer radius of R=11 nm which is much smaller in size than the radius of gyration Rg=58 nm of the PS chains. The system is considered to represent the protein limit of polymer-colloid mixtures. Structural investigation is performed by small-angle neutron scattering (SANS) using an appropriate contrast matching. This could be achieved by dissolving fully deuterated PS chains (D8-PS) in solutions of hydrogenated PEMA colloids in hydrogenated toluene (H-toluene). It is first demonstrated that PEMA colloids are satisfactorily contrast matched for SANS in H-toluene if the PEMA concentration does not exceed 200 g/l. Based on these findings, D8-PS is investigated by SANS in pure H-toluene and three different PEMA concentrations in H-toluene. The results indicate a drastic shrinking of D8-PS chain dimensions with increasing PEMA content. Comparison with model curves of star-branched Gaussian chains and Gaussian rings suggest a striking similarity of the respective density-density correlation of those models with the shrunken D8-PS chains. Along with this, a shrinking as large as 0.5 was estimated when the PEMA content reached 200 g/l.
authors.affiliation: Department Chemie, Fakultät für Naturwissenschaften, Universität Paderborn, Warburger Strasse 100, D-33098 Paderborn, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kramer
authors.forename: Ralf
authors.initials: R
authors.lastname: Schweins
authors.forename: Klaus
authors.initials: K
authors.lastname: Huber
mesh_terms: D017122:Bacteriophage T4 / Q000235:genetics; D002412:Cations; D003102:Colloids / Q000737:chemistry*; D004247:DNA / Q000737:chemistry; D007700:Kinetics; D008854:Microscopy, Electron; D046529:Microscopy, Electron, Transmission; D015233:Models, Statistical; D009502:Neutrons; D011073:Polyamines / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D017510:Protein Folding; D012542:Scattering, Radiation; D013816:Thermodynamics
chemical_list: D002412:Cations; D003102:Colloids; D011073:Polyamines; D011108:Polymers; D011137:Polystyrenes; D004247:DNA