Nafion 1 perfluorosulfonic acid polymer electrolyte membranes were uniaxially drawn at a temperature where the a-relaxation is active. Polarized UV-Raman spectra revealed the anisotropy developed. They strongly suggest that, upon uniaxial drawing, Nafion macromolecular chains are oriented parallel to the drawing axis, while the perfluorinated side chains exhibit a tendency to be oriented perpendicular to the draw axis. The drawing process resulted in the reduction of the membrane thickness in addition to an enhanced mechanical strength along the draw direction, measured with dynamic mechanical analysis. In a parallel study, a preliminary molecular orientation study of uniaxially drawn Teflon samples allowed a better assignment of the Raman bands of Nafion. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45:

ABSTRACT:The thermoresponsive properties in aqueous solution of the graft copolymer poly(acrylic acid-co-2-acrylamido-2-methyl propane sulfonic acid)-g-poly(N-isopropylacrylamide) [P(AA-co-AMPSA)-g-PNIPAM] were studied and compared to the corresponding behavior of the poly(acrylic acid)-g-poly(N-isopropylacrylamide) (PAA-g-PNIPAM) graft product. Both products contain about 40% (w/w) of PNIPAM, whereas the backbone, P(AA-co-AMPSA), of the first copolymer contains about 40% of AMPSA mole units. The strongly charged P(AA-co-AMPSA)-g-PNIPAM graft copolymer was water soluble over the whole pH range, whereas the PAA-g-PNIPAM copolymer precipitated out from water at pH Ͻ 4. As a result, the first product exhibited a temperature-sensitive behavior in a wide pH range, extended in the acidic region, whereas in semidilute aqueous solutions, an important thermothickening behavior was observed, even at low pH (pH ϭ 3.0).

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The formation of nano-pores in graphene crystal structure is alternative way to engineer its electronic properties, chemical reactivity, and surface interactions, enabling applications in technological fields such as sensing, energy and separation. The past few years, nano-perforation of graphene sheets has been accomplished by a variety of different methods suffering mainly from poor scalability and cost efficiency issues. In this work, we introduce an experimental protocol to engineer nanometer scale pores in CVD graphene membranes under ambient conditions, using low power ultra-short laser pulses and overcoming the drawbacks of other perforation techniques. Using AFM and SEM we visualized and quantified the nanopore network while Raman spectroscopy is utilized to correlate the nano-perforated area with the nanotopographic imaging. We suggest that Raman imaging provides the identification of nanoporous area and, in combination with AFM, we provide solid evidence for the reproducibility of the method, since under these experimental conditions, nanopores of a certain size distribution are formed.