Investigation of Polymer Systems in Solutions with Electron Microscopy and Scattering Methods

This work is focused on the visualization and thus in the aid in finding explanations for the behavior of polymer structures as they exist in solution. For this aim, preparation and imaging techniques based on cryo-TEM protocols were developed for a large variety of polymeric specimens using new commercially available devices and the results were compared with the findings of other means of structural investigations. The systems used in this work were chosen, as their investigations can be adapted to other polymer systems by slight adaptation of the preparation procedures

Investigation of Polymer Systems in Solutions with Electron Microscopy and Scattering Methods

This work is focused on the visualization and thus in the aid in finding explanations for the behavior of polymer structures as they exist in solution. For this aim, preparation and imaging techniques based on cryo-TEM protocols were developed for a large variety of polymeric specimens using new commercially available devices and the results were compared with the findings of other means of structural investigations. The systems used in this work were chosen, as their investigations can be adapted to other polymer systems by slight adaptation of the preparation procedures

Investigation of Polymer Systems in Solutions with Electron Microscopy and Scattering Methods

This work is focused on the visualization and thus in the aid in finding explanations for the behavior of polymer structures as they exist in solution. For this aim, preparation and imaging techniques based on cryo-TEM protocols were developed for a large variety of polymeric specimens using new commercially available devices and the results were compared with the findings of other means of structural investigations. The systems used in this work were chosen, as their investigations can be adapted to other polymer systems by slight adaptation of the preparation procedures

Semifluorinated PMMA Block Copolymers: Synthesis, Nanostructure, and Thin Film Properties

Diblock copolymers (BCP) with poly(methyl methacrylate) and poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PsfMA) blocks prepared by anionic polymerization in tetrahydrofuran at −78 °C and atom transfer radical polymerization (ATRP) at 60 °C, respectively, with stepwise varied composition over a wide range in the phase diagram are compared with respect to synthesis limits, phase separation behavior in bulk, and properties of thin films. Both methods yield BCPs with low dispersity (1.1–1.2) at molar masses below 100 kg mol$^{−1}$. Higher semifluorinated contents can be achieved by ATRP in 1,3-bis(trifluoromethyl)benzene which ensured solubility of PsfMA. BCPs obtained by anionic polymerization show a more distinct phase separation, that is, more regular nanostructures. Additionally, self-organization of the semifluorinated side chains occurs generating smectic layers which alters in turn the BCP morphology especially in thin films as compared to non-semifluorinated BCP. All BCPs show amphiphilic behavior and form micelles in organic solvents which can be used to deposit nanoparticles

Effect of the Cross-Linking Density on the Thermoresponsive Behavior of Hollow PNIPAM Microgels

We report on the fabrication of thermally responsive hollow pNIPAM particles through the oxidation of the metal core in an Au@pNIPAM system. The selective oxidation of the Au core is achieved by addition of AuCl₄^– to an aqueous dispersion of Au@pNIPAM particles in the presence of cetyltrimethylammonium bromide (CTAB). We fabricate hollow pNIPAM particles with three cross-linking densities (<i>N,N</i>′-methylenebis­(acrylamide), BA, at 5%, 10%, and 17.5%). The study of the effect of the amount of BA within the microgel network was performed by dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM), showing its key role in determining the final hollow structure and thermal response. While the thermal responsiveness is largely achieved at low cross-linking densities, the hollow structure only remains at larger cross-linking densities. This was further confirmed by cryo-TEM analysis of hollow pNIPAM particles below and above the volume phase transition temperature (VPTT). Thus, it clearly shows (i) the shrinking of particle size with the temperature at low cross-linking density and (ii) the dependence of particle size on the amount of cross-linker for the final hollow pNIPAM structure. Observed differences in the hollow pNIPAM structure are attributed to different elastic contributions (Π_elas), showing higher elasticity for microgels synthesized at lower amount of BA