This paper describes composite patterning elements that use a commercially available acryloxy perfluoropolyether (a-PFPE) in various soft lithographic techniques, including microcontact printing, nanotransfer printing, phase-shift optical lithography, proximity field nanopatterning, molecular scale soft nanoimprinting, and solvent assisted micromolding. The a-PFPE material, which is similar to a methacryloxy PFPE (PFPE-DMA) reported recently, offers a combination of high modulus (10.5 MPa), low surface energy (18.5 mNm(-1)), chemical inertness, and resistance to solvent induced swelling that make it useful for producing high fidelity patterns with these soft lithographic methods. The results are comparable to, and in some cases even better than, those obtained with the more widely explored material, high modulus poly(dimethylsiloxane) (h-PDMS).

The ordering kinetics of cylindrical and spherical microdomains in a polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymer were studied using synchrotron small-angle X-ray scattering (SAXS) and rheology upon quenching the sample from a disordered state to an ordered state having either spherical or cylindrical microdomains. The SIS exhibits an order to order transition at -181 "C, a lattice disordering transition at -21OOC and becomes disordered at higher temperatures. Higher order peaks in the SAXS profiles corresponding to hexagonally packed cylindrical (HEX) microdomains appeared after less than 1 h when the sample was quenched from 235°C to 170°C. When quenched from 235°C to 200°C, a broad higher order peak at -1.65 qm, corresponding to spheres with liquid-like short-range order, was persistent up to 4 h before higher order peaks corresponding to body-centered cubic (BCC) microdomains appeared. We repeated this experiment by changing temperature from one ordered state with BCC microdomains to another with HEX microdomains, and vice versa. The BCC microdomains were attained within 1 h when heating from 170 "C to 200 "C. The transition between HEX and BCC is thermoreversible. The time evolution of dynamic storage modulus G' is in good agreement with that of SAXS intensity.

No abstract

The phase behavior and rheology of binary blends of polystyrene (PS) and poly(α-methylstyrene) (PαMS), exhibiting upper critical solution temperature (UCST), and binary blends of PS and poly(vinyl methyl ether) (PVME), exhibiting lower critical solution temperature (LCST), were investigated. For the study, (i) PS-40/PαMS-18, (ii) PS-38/PαMS-39, (iii) PS-40/PαMS-48, and (iv) PS-110/PVME-95 blend systems were prepared by solution casting. The results of differential scanning calorimetry suggest that each blend system investigated is miscible over the entire blend composition as evidenced by the single composition-dependent glass transition temperature. However, from oscillatory shear rheometry we observed evidence suggesting that microheterogeneity is present in the miscible region, as determined by cloud point measurements, at temperatures as far away as approximately 70 °C above the UCST of the PS/PαMS blend system and at temperatures as far away as only approximately 7 °C below the LCST of the PS/PVME blend system. Such observation leads us to conclude that the extent of dynamical composition fluctuations near the critical point depends on the chemical structures of a polymer pair. The observed difference in the extent of dynamical composition fluctuations between PS/PαMS and PS/PVME blend systems is interpreted by the difference in the temperature coefficient of the interaction parameter between the PS/PαMS and PS/PVME blend systems.