caa a22 4500 475764331 CHVBK 20180406123600.0 cr unu---uuuuu 170329e20001001xx s 000 0 eng 10.1007/s003960000344 doi (NATIONALLICENCE)springer-10.1007/s003960000344 Coil-to-globule-type transition of poly( N -isopropylacrylamide) adsorbed on colloidal silica particles [Elektronische Daten] [C. Walldal, S. Wall]  The temperature dependence of the dimensions of poly(N-isopropylacrylamide) (PNIPAM) adsorbed on two different colloidal silica particles was studied with dynamic light scattering. The hydrodynamic diameter was measured when the temperature was varied stepwise from 10 to 60 °C. PNIPAM molecules free in solution undergo a conformational transition at the θ temperature. We have found that PNIPAM adsorbed onto silica particles also undergoes a transition below the θ temperature. When a small amount of polymer was adsorbed the coil-to-globule transition at the θ temperature did not occur. Potentiometric titrations showed that the surface charge of the silica particles was not affected by the polymer adsorption. Sodium dodecyl sulfate (SDS) (100-1200 mg/l) was added to improve the stability. The particles with a higher zeta potential required a smaller addition of SDS to prevent coagulation compared to the particles with a smaller surface potential. For low additions of SDS the transition curves of adsorbed PNIPAM were unaffected. For larger additions of SDS the collapse of PNIPAM was shifted to higher temperatures. When as much as 1200 mg/l SDS was added, two regions with weak transitions were observed before the collapse. It was also observed that the presence of SDS results in a smaller adsorption of PNIPAM onto the particles. The addition of SDS strongly increased the magnitude of the electrophoretic mobility of the polymer-particle unit. From the electrophoretic measurements an electrokinetic layer thickness was calculated and it was found to be smaller than the corresponding hydrodynamic layer thickness, as obtained by dynamic light scattering. Springer-Verlag Berlin Heidelberg, 2000 Key words Poly(N-isopropylacrylamide) nationallicence Silica particles nationallicence Coil-to-globule transition nationallicence Hydrodynamic thickness nationallicence Walldal C. Department of Physical Chemistry Göteborg University 412 96, Göteborg, Sweden e-mail: charlott@phc.chalmers.se Tel.: +46-31-7722815 Fax: +46-31-167194, SE aut Wall S. Department of Physical Chemistry Göteborg University 412 96, Göteborg, Sweden e-mail: charlott@phc.chalmers.se Tel.: +46-31-7722815 Fax: +46-31-167194, SE aut https://doi.org/10.1007/s003960000344 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s003960000344 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Walldal C. Department of Physical Chemistry Göteborg University 412 96, Göteborg, Sweden e-mail: charlott@phc.chalmers.se Tel.: +46-31-7722815 Fax: +46-31-167194, SE aut NATIONALLICENCE 700 1- Wall S. Department of Physical Chemistry Göteborg University 412 96, Göteborg, Sweden e-mail: charlott@phc.chalmers.se Tel.: +46-31-7722815 Fax: +46-31-167194, SE aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer