The thermal behavior of a poly(styrene-b-N-isopropyl acrylamide) diblock copolymer was studied in aqueous solution as well as in thick and in thin films. The polymer was synthesized using reversible addition-fragmentation chain transfer. The critical micelle concentration in aqueous solution was determined using fluorescence correlation spectroscopy. The lower critical solution temperature (LCST) of micellar solutions was detected using microcalorimetry and turbidimetry at 31 °C. Using dynamic light scattering, the collapse of the micelles at the LCST as well as their clustering above was observed. These findings were corroborated with small-angle X-ray scattering. In thick films immersed in water, similar findings were made. In a thin film, however, the LCST is depressed and is found at 26-27 °C

No abstract

The crystalline structures in thin films of polystyrene-b-poly͑ethylene oxide͒ ͑PS-b-PEO͒ diblock copolymers were studied in dependence on the degree of supercooling. Atomic force microscopy showed that the crystalline domains ͑lamellae͒ consist of grains, which are macroscopic at low and intermediate degrees of supercooling, but of submicrometer size for strong supercooling. Using grazing-incidence wide-angle x-ray scattering, we could determine the grain orientation distribution function which shows that the chain stems are perpendicular to the lamellae at low supercooling, but tilted at intermediate and strong supercooling. These results suggest that, at intermediate and strong supercooling, the crystalline PEO lamellae do not grow homogeneously, but by the formation of small crystallites at the growth front.

Solvent annealing [1-3] has recently emerged as a powerful alternative to thermal annealing of block copolymer (BCP) thin films and nanocomposites. Taking a more general point of view, solvent treatment procedures, employing the selectivity of the solvents towards the different blocks, can produce new structures [4], and provide fascinating insights into the swelling kinetics and instabilities in such self-assembled and oriented thin films [5]. Taking a lamellar polystyrene-polybutadiene (PS-b-PB) film right from the spin coater into an in-situ vapor cell provided an intriguing trip through configuration space, with various lamellar reorientations encountered during swelling.

We have found very slow crystallization in thin films of cylinder-forming poly(isoprene-b-ethyleneoxide) (P(I-b -EO)) diblock copolymers with PEO being the minority block. The film was crystallized at room temperature after melting at 62 °C. Imaging methods were combined with X-ray reflectometry and grazing-incidence small-angle X-ray scattering and diffraction. Initially, hexagonally packed, amorphous PEO cylinders lie in the film plane. After 148 days, crystallized, finger-like terraces were observed over the entire film surface. The terrace height is 20% higher than the repeat distance in the as-prepared film. Thus, at the film surface, the cylinders have been destroyed by crystalline lamellae lying in the film plane. The PEO chain stems are perpendicular to the substrate surface and are once-folded and fully interdigitated. The substrate-near layers still consist of the hexagonally packed, amorphous PEO cylinders within the PI matrix.