Cds-Containing Nano-Assemblies of Double Hydrophilic Block Copolymers in Water

Supporting Information

CdS-Containing Nano-Assemblies of Double Hydrophilic Block Copolymers in Water.

Mariusz Uchman,* Karel Procházka*

Department of Physical and Macromolecular Chemistry, Faculty of Science

CharlesUniversity, Hlavova 2030, 12840 Prague 2, CzechRepublic

Katerina Gatsouli,Stergios Pispas*

Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation,48 Vassilieos Constantinou Ave., 11635 Athens, Greece

Milena Špírková

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Square 2, 16206 Prague 6, Czech Republic

(M.U.);(K.P.); (S.P.)
*to whom correspondence should be addressed

Figure S1. AFM images of SCIEO-2/CdS 1:1 hybrid micelles (image dimensions 4 × 4 m). (a) phase scan (b) height scan (c) section analysis of the height scan (indicated by blue lines on scan)

CSIEO-1/Cd2+ Induced Micelles

The CSIEO-1 sample contains a relatively short PEO block that should stabilize the Cd2+ induced micelles in aqueous media and this is why its micellar solution is less stable. The analysis of DLS data of the CSIEO-1/Cd2+ 2:1 solutions reveals a bimodal distribution of sizes (see Fig.S2). The intensity-weighted fast peak is small as compared with the slow one due to high difference is sizes and therefore in the scattering power of both species. The analysis yields the hydrodynamic radius ofthe small particles, RHDLS = 9 nm and that of the large particles RHDLS = 79.5 nm. SLS provides linear Zimm plot and fairly high Mw = 5 x 106 g/mol and RG = 82 nm which suggests that, similarly to systems based on CSIEO-2, the solution contains a mixture of spheres and wormlike aggregates. Angular measurements confirmed the diffusive character of both modes (not shown). The LS measurements for higher CSI:Cd2+ ratios are unreliable due to the already mentioned instability of the particular solutions.

Figure S2. DLS CONTIN plots of CSIEO-1/Cd2+ 2:1 induced micelles for different concentration (intensity weighted, measured at the scattering angle = 90).

Figure S3. AFM height scan (top view) of the nanoparticles deposited from solution of (a) CSIEO-1/Cd2+ 2:1 (3.5 × 3.5 m) (b) phase scan of wormlike micelles CSIEO-1/Cd2+ 1:1(10 × 10 m).

The speculation on the presence of two types of particles can be corroborated by AFM imaging of nanoparticles on a mica surface. Fig. S3a depicts nanoparticles deposited from the CSIEO-1/Cd2+ 2:1 solution. A large area (3,5m x 3,5m) scan shows a mixture of spherical and wormlike objects. The light scattering data for the CSIEO-1/Cd2+ 1:1 solutions are influenced on one hand by filtration (probably some loss of the material and some induced change in the structure of the aggregates) and on the other hand by the observed instability of the non-filtered aggregates. However, thanks to AFMwe observed the large networks of wormlike structures at a molar ratio of CSIEO-1/Cd2+ 1:1 for not-filtered sample (Figure S3b). The formation of wormlike structures can be explained as an attraction of the micellar nanoparticles, destabilized after the formation of large insoluble CSI/Cd2+ clusters surrounded by insoluble isoprene units. Since the total charge of micelles is compensated and PEO block is relatively short, there is no significant barrier for fusion in wormlike structures as reported earlier by Burke and Eisenberg.1 One can argue that the structures adsorbed on the surface can be strongly influenced by the chemical nature of the substrate. A report by Regenbrecht and et al2 about the large networks studied by AFM, shows that absorption on strongly charged surfaces could induce shape transitions and one can observe structures, which do not exist in the solution. The authors observed transitions from complex structures to more simple (spherical) ones. In our system, more complex structures than spheres were detected on the surface. In our earlier studies we have shown that the freshly peeled out mica surface is covered by small cations and the surface charge is almost compensated. Hence the negatively charged micelles stick firmly to it. After washing the mica surface with distilled water, the surface becomes negative and the micelles with methacrylic shells do not stick on it and the deposition is more difficult.3 Moreover, the light scattering results and the fact that the micelles become unstable upon CdS creation suggest that large structures could exist even in the solution. Finally, further increase in the content of Cd2+ ions cause a collapse of the networks and formation of more compact aggregates.

References

1. Burke S. E.; Eisenberg, A. (2001)Langmuir 17:6705

2. Regenbrecht M, Akari S, Forster S, Mohwald H (1999)J. Phys. Chem. B 103:6669

3. Matějícek P, Humpolícková J, Procházka K, Tuzar Z, Špírková M, Hof M, Webber SE (2003)J. Phys Chem B 107:8232