NMR and FT-IR studies of sulfonated styrene-based homopolymers and copolymers

Improved antifouling properties of polymer membranes using a 'layer-by-layer' mediated method

Polymeric reverse osmosis membranes were modified with antifouling polymer brushes through a 'layer by layer' (LBL) mediated method. Based on pure physical electrostatic interaction, the attachment of LBL films did not alter separation performance of the membranes. In addition, the incorporation of an LBL film also helped to amplify the number of potential reaction sites on the membrane surfaces for attachment of antifouling polymer brushes, which were then attached to the surface. Attachment of the brushes included two different approaches, grafting to and grafting from. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements showed successful growth of the LBL films and subsequently the polymer brushes. Using this method to modify reverse osmosis membranes, preliminary performance testing showed the antifouling properties of the as-modified membranes were much better than the virgin membrane with no significant loss in water flux and salt rejection.

Comparative studies on the accumulation of strain and recovery ratio of Veriflex®, a shape-memory polymer for a high strain (∊m = 210%)

In the present study, the functional fatigue in the commercial SMP Veriflex®, which is associated with repeating up to maximum 40 programming/one-way effect (1WE) cycles, has been examined. The material is characterized by a glass transition temperature ( Tg) of 67°C, above which it looses all its strength. An interesting comparative investigation on thermomechanical cycles, including programming, cooling, unloading, and heating to trigger the 1WE, were carried out for Veriflex at 62°C ( T < Tg, below 5°C but near to Tg) and also at 72°C ( T > Tg, above 5°C but near to Tg) for strains of 140% and for a recovery time of 10 min. Accumulation of strain was estimated during the thermomechanical treatments for using strains of 140% at 62°C ( T < Tg) as well as at 72°C ( T > Tg). Recovery ratios for strains of 140% at 62°C ( T < Tg) as well as at 72°C ( T > Tg) were also estimated. It turns out that programming, cooling, unloading, and heating to trigger the 1WE causes an increase in irreversible strain and is associated with a corresponding decrease in the intensity of the 1WE in particular during the first thermomechanical cycles. Confocal laser scanning microscopic) study shows a very little wavy surface structure evolved during cycling up to strains of 140% at 72°C ( T > Tg). Infrared study features the chemical nature after cycling, processing, and programming of Veriflex.

Comparative studies on the accumulation of strain and recovery ratio of Veriflex®, a shape-memory polymer

A comparative investigation on thermomechanical cycles including programming, cooling, unloading and heating to trigger the one-way effect (1-WE) was carried out for Veriflex® between temperature ( T) and glass transition temperature ( Tg) at 62°C ( T <  Tg) and 72°C ( T >  Tg) for 140% strains and 10 min recovery time. Accumulation of strain and recovery ratios was estimated during the treatments. It turns out that the process causes an increase in irreversible strain and is associated with a corresponding decrease in intensity of the 1-WE in particular during the first thermomechanical cycle. The confocal laser scanning microscopic study shows a very little wavy surface structure evolved at 72°C. Infrared study features the chemical nature of Veriflex.

Functional polyelectrolyte multilayer membranes for water purification applications

A diverse set of supported multilayer assemblies with controllable surface charge, hydrophilicity, and permeability to water and solute was fabricated by pressure driven permeation of poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) solution through poly(ethylene terephthalate) (PET) track-etched membranes. The polyelectrolyte multilayer fabrication was confirmed by means of FTIR, SEM, AFM, ellipsometry, zetapotential, and contact angle characterization. The prepared membranes were characterized in terms of their pure water permeability, flux recovery, and resistance to organic and biofouling properties. The antifouling behavior of the membranes was assessed in terms of protein adsorption and antibacterial behavior. Finally, the membranes were tested for rejection of selected water soluble dyes to establish their usefulness for organic contaminant removal from water. The membranes were highly selective and capable of nearly complete rejection of congo red with sufficiently high fluxes. The feasibility of regenerating the prepared membranes fouled by protein was also demonstrated and good flux recovery was obtained. In summary, the multilayer approach to surface and pore modification was shown to enable the design of membranes with the unique combination of desirable separation characteristics, regenerability of the separation layer, and antifouling behavior.

Pulsed plasmachemical deposition of highly proton conducting composite sulfonic acid-carboxylic acid films

Graft polymerization of sulfonic acid monomers onto structurally well-defined pulsed plasma poly(maleic anhydride) layers yields a composite carboxylic acid-sulfonic acid network. These bifunctional films are shown to exhibit high proton conductivity (125 mS cm(-1)) as well as good stability in water.

Study of the sulfonation of expanded polystyrene waste and of properties of the products obtained

Waste-expanded polystyrene (EPS) and virgin polystyrene (VPS) were converted into ion exchangers by chemical modification. For this purpose, we used silica sulfuric acid as the sulfonating agent and conducted sulfonation under heterogeneous conditions. For VPS, the influence of the quantity of the sulfonating agent, the temperature, and the reaction time on the product properties were studied. As it appeared, silica sulfuric acid simplifies the reaction in comparison with the conventional sulfonation methods. Fourier transform-infrared (FT-IR) spectra and elemental analysis revealed that products were cross-linked and the content of sulfonate groups in a polymer chain varied. Some of the yielded polymers exhibited good water absorption and cation-exchange properties. The ion-exchange capacity (IEC) for chosen products was also determined, and it turned out to be similar to the commercial resin. The batch method was used to study the purification of solutions of Zn2+ and Cu2+ by the obtained resins. The performed study proved the usefulness of waste PS derivatives for the water treatment process.

Self-Healing Anticorrosion Coatings Based on pH-Sensitive Polyelectrolyte/Inhibitor Sandwichlike Nanostructures

An anticorrosion layer of a smart polymer coating is developed. The nature and properties of the coating simultaneously provide three mechanisms of corrosion protection: passivation of the metal degradation by controlled release of an inhibitor, buffering of pH changes at the corrosive area by polyelectrolyte layers, and self-curing of the film defects due to the mobility of the polyelectrolyte constituents in the layer-by-layer assembly.

Forensic Analysis of Bicomponent Fibers Using Infrared Chemical Imaging

The application of infrared chemical imaging to the analysis of bicomponent fibers was evaluated. Eleven nominally bicomponent fibers were examined either side-on or in cross-section. In six of the 11 samples, infrared chemical imaging was able to spatially resolve two spectroscopically distinct regions when the fibers were examined side-on. As well as yielding characteristic infrared spectra of each component, the technique also provided images that clearly illustrated the side-by-side configuration of these components in the fiber. In one case it was possible to prepare and image a cross-section of the fiber, but in general the preparation of fiber cross-sections proved very difficult. In five of the 11 samples, the infrared spectra could be used to identify the overall chemical composition of the fibers, according to a published classification scheme, but the fiber components could not be spatially resolved. Difficulties that are inherent to conventional "single-point" infrared spectroscopy, such as interference fringing and sloping baselines, particularly when analyzing acrylic type fibers, were also encountered in the infrared chemical image analysis of bicomponent fibers. A number of infrared sampling techniques were investigated to overcome these problems, and recommendations for the best sampling technique are given. Chemical imaging results were compared with those obtained using conventional fiber microscopy techniques.

Two Polymerizable Derivatives of 2,2‘-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)

[structure: see text] A versatile strategy for the synthesis of polymerizable derivatives of the redox-active indicator dye 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) is reported. Two products are shown to illustrate how the final step in the synthetic strategy can be used to alter the physical properties of the product. Both products were characterized spectroscopically and electrochemically. The hydrophilic monomer (sABTS) was polymerized, and the utility of this polymer (polyABTS) is demonstrated in the context of bioelectrocatalysis.

High-flux nanofiltration membranes prepared by adsorption of multilayer polyelectrolyte membranes on polymeric supports

Layer-by-layer deposition of anionic and cationic polyelectrolytes readily converts polymeric ultrafiltration membranes into materials capable of nanofiltration. ATR-FTIR spectra confirm that layer-by-layer deposition occurs on the ultrafiltration substrates, and adsorption of as few as 2.5 bilayers of poly(styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) or 3.5 bilayers of PSS/poly(diallyldimethylammonium chloride) (PDADMAC) reduces the molecular weight cutoff of polyethersulfone ultrafiltration supports from 50 kDa to <500 Da. Deposition of multilayer polyelectrolyte films on 300 and 500 kDa membranes also decreases molecular weight cutoffs, but solute rejections are significantly lower when using these supports, suggesting that the polyelectrolyte films do not completely cover large (0.2-0.4 microm in diameter) pores. On the 50 kDa substrates, PSS/PDADMAC films containing 3.5 bilayers exhibit a 95% rejection of SO(4)(2-) and a chloride/sulfate selectivity of 27, whereas 4.5-bilayer PSS/PAH coatings show a glucose/raffinose selectivity of 100. Pure water flux for [PSS/PAH](3)PSS-coated membranes at 4.8 bar is 1.6 m(3)/(m(2)day), which is more than 2-fold higher than that through a commercial 500 Da membrane.

Oil-in-water microemulsions stabilized by charged diblock copolymers

We present here oil-in-water microemulsions stabilized by charged diblock copolymers alone, along with their structural characterization by small-angle neutron scattering measurements. They consist of swollen spherical micelles containing small amounts of oil in their core, which is surrounded by a corona of stretched polyelectrolyte chains. Structural changes, including core size variations, are evidenced when using a cosurfactant, or upon addition of salt, through a contraction of the charged corona. Attempts to relate the micellar structure to the individual copolymer characteristics are also presented, and show that the size of the hydrophobic block mainly determines that of the micelles.