Free-standing, fully reversible thermo-responsive nanoporous membranes were fabricated from PS-PNIPAM block copolymers.

Block copolymer (BCP) thin films are interesting material systems for nanofabrication since they can form well-defined periodic nanostructures by microphase separation. However, attaining a specific morphology with the required orientation can be challenging. In this study, we investigated the morphological behavior of polystyrene-b-poly(N-isopropylacrylamide)-bpolystyrene (PS-b-PNIPAM-b-PS) BCP thin films by using Atomic Force Microscopy (AFM) and in-situ Grazing-Incidence X-ray Scattering (GISAXS) during selective solvent annealing. Thin films of a lamellar BCP were annealed by using various solvents with different selectivity for the blocks, such as PNIPAM-selective methanol, non-selective tetrahydrofuran (THF) and PS-selective toluene. Solvent annealing using methanol: THF 1:2 (v:v) or methanol: toluene 1:1 (v:v) resulted in the formation of hexagonally ordered perpendicular cylinders, whereas no sustained long-range order was found when only one type of solvent was used. PS-b-PNIPAM-b-PS BCP thin films that have hexagonally ordered perpendicular cylinders are promising for applications where thermo-responsiveness is desired, such as nanofiltration and biomedical applications.

In this study, polystyrene-clay nanocomposites (PSNC's) were prepared via in-situ bulk and in-situ emulsion polymerization. The effect of organoclay and the architecture of surfactant were investigated. For the investigation of the effect of surfactant, organoclays were synthesized containing clay modifiers having different structures. Trimethylhexadecyl ammonium chloride, dimethylbenzylhexadecyl ammonium chloride and dimethylbenzyl(4-vinyl) hexadecyl ammonium chloride, which is synthesized in laboratory, modified clays were synthesized. Pristine polystyrene (PS) was synthesized by bulk and emulsion polymerization for comparison, and PSNC's containing 3 wt.% organoclays were prepared by both these polymerization methods. Structural analysis of synthesized surfactant was identified by Nuclear Magnetic Resonance (NMR) Spectrometer. The interlayer spacing of silicate layers and the morphology of samples were examined by using the X-ray Diffraction (XRD) Spectrometer and Scanning Electron Microscopy (SEM) images, respectively. Thermal properties of nanocomposites were determined by Thermogravimetric analyzer (TGA) and Differential Scanning Calorimeter (DSC). It is observed that organoclays and PS were compatible to each other and each organoclay could form a nanocomposite structure with PS. PSNC's exhibited better properties than pristine PS. Nanocomposites prepared by in-situ emulsion polymerization resulted with better thermal properties and higher interlayer distances than that prepared by in-situ bulk polymerization. In order to improve some properties of PS such as thermal stability, preparation of PSNC's by in-situ emulsion polymerization has been suggested.