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The order–disorder transition (ODT) and the ordering kinetics have been studied in two symmetric diblock copolymers of styrene and isoprene and their binary mixtures with rheology. The binary mixtures formed a single microdomain (with lamellar morphology) composed of short and long chains as confirmed by small angle x-ray scattering (SAXS). The order–disorder transition temperature (TODT), obtained from the discontinuity in the storage modulus G′, varies linearly with the number average degree of polymerization. For shallow quenches, the ordering kinetics proceed via nucleation and growth. The characteristic time of this process scales with N-1/3, where N is the Ginzburg parameter, in agreement with the theoretical predictions [G. H. Fredrickson and K. Binder, J. Chem. Phys. 91, 7265 (1989)]. Our results indicate that the ordering kinetics of symmetric diblock copolymers near the ODT are fluctuation controlled. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Electronic and geometric properties of chromium oxide nanowires deposited on self-assembled block copolymer templates are evaluated by means of synchrotron radiation based spectroscopic methods like X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The geometric distribution of the nanowires is monitored with X-ray photoelectron emission microscopy (XPEEM) and atomic force microscopy (AFM). XAS and XPS of Cr 2p emissions for chromium oxide nanostructures determine an oxidation state different from the most common chromium oxides and additional satellite peaks are derived from localization effects induced by the nanostructuring. [Copyright &y& Elsevier]

Nanostructured polymer surfaces resulting from the dewetting in the final phase of the spin-coating process are investigated in the model system poly(styrene-block-isoprene). The surface topography is determined with atomic-force microscopy (AFM). It is well characterized by droplets as a typical dewetting morphology. From the combination of grazing incidence small and ultrasmall angle scattering the internal order inside the nanostructures is determined. A periodic arrangement of the diblock copolymers resulting from a microphase separation process is observed. The characteristic distance increases as compared with the bulk periodic structure. [ABSTRACT FROM AUTHOR]

We studied the retardation of the dewetting process due to the addition of a functional copolymer in a polymer bilayer film. The model system consists of fully deuterated polystyrene (PS-d) on top of an amorphous polyamide (PA) sublayer on silicon substrates. Bilayer films were prepared with different content (0, 5, 10 and 30 vol. %) of a statistical copolymer (protonated styrene maleic anhydride acid (SMA2) containing 2% MA groups along the chain) being capable of forming hydrogen bonds with PA. The asprepared as well as the annealed samples were investigated by neutron-reflectivity (NR) experiments, scanning force microscopy and optical microscopy. A significant retardation of dewetting is observed with the addition of SMA2. From model fits of NR curves the scattering length density profiles perpendicular to the sample surface were determined and an enrichment layer of SMA2 is detected. Retardation is explained by the intermixing of SMA2 and PS-d at the interface. [ABSTRACT FROM AUTHOR]

We investigated the film-thickness dependence of structure formation in ultra-thin polymer blend films prepared from solution. As a model system we used binary blends of statistical poly(styrene-co-p-bromostyrene) copolymers of different degrees of bromination. Ultra-thin-film samples differing in miscibility and film thickness were prepared via spin coating of common toluene solutions onto silicon (100) substrates. The resulting morphologies were investigated with scanning force microscopy, reflectometry and grazing-incidence scattering techniques using both X-rays and neutrons in order to obtain a picture of the sample structure at and below the sample surface. [ABSTRACT FROM AUTHOR]

We investigated the adaptive adhesion properties of comb-likerandomcopolymer brushes made of poly(ethylene glycol) (PEG)–poly(dimethylsiloxane)(PDMS) grafted on flat and rough substrates. The properties of thebrush layers were investigated using ARXPS, contact angle, electrokinetics,null ellipsometry, and adhesion measurements. It was found that hydrophobicPDMS segments segregate at the brush topmost layer in the dry state.However, hydrophilic PEG chains segregate at the brush topmost layerin the wet state. The adhesion properties of fabricated materialswere tested using the AFM colloid probe technique and probe tack tester.It was found that the adhesive properties depend strongly on the mechanicalproperties (stiff/soft) and chemical functionality (hydrophobicity/hydrophilicity)of the applied adhesion tester as well as on the chemical composition,surface roughness, and thickness of the brush. In particular, hydrophobicPDMS and hydrophilic PEG adhere more strongly to hydrophobically modifiedand hydrophilic native colloid probes, respectively. Thick brushesare more adhesive than thin ones, and brushes grafted to flat substratesare stickier than those grafted to rough substrates when measuredwith a hard AFM probe. Unlike the results of adhesion measurementsperformed using hard AFM probes, the PDMS surface probed by soft pressure-sensitiveadhesives (PSA) is almost nonadhesive. However, PEG is strongly adhesive,and the adhesion increases with the PEG fraction in the brush whenprobed by both hydrophilic and hydrophobic soft adhesives. The surfacesroughness also has a considerable effect on adhesion. Contrary tothe adhesion measurements performed by hard AFM colloid probes, theadhesion of rough surfaces measured with a soft PAA or SIS tack testeris greater than that on the corresponding flat one. [ABSTRACT FROM AUTHOR]