Polymer studies sodium chloride

Xylan-based micro- and nanoparticles have been produced by simple coacervation (Garcia et al., 2001). In the study, sodium hydroxide and chloride acid or acetic acid were used as solvent and non-solvent, respectively. Also, xylan and surfactant concentrations and the molar ratio between sodium hydroxide and chloride acid were observed as parameters for the formation of micro- and nanoparticles by the simple coacervation technique (Garcia et al., 2001). Different xylan concentrations allowed the formation of micro- and nanoparticles. More precisely, microparticles were found for higher concentrations of xylan while nanopartides were produced for lower concentrations of the polymer solution. When the molar ratio between sodium hydroxide and chloride acid was greater than 1 1, the partides settled more rapidly at pH=7.0. Regarding the surfactant variations, an optimal concentration was found however, at higher ones a supernatant layer was observed after 30 days (Garda et al., 2001). 

Loss of Tin. The preparation and characterization of organ-otin-epoxy polymers have been reported earlier (3). In an effort to determine the loss of tin from these controlled release formulations, 0.5-mm thick coatings were kept immersed in 4% sodium chloride solution under conditions approximating Figure 2a. The concentration of TBTC1 in the aqueous phase was maintained low by continuously extracting it into hexane. Analysis of the coating at the end of 16 months revealed that not more than 2% tin was lost in any of the four cases studied. 

This simplification was used by Ottewill and Walker (7) in their study of the adsorption of a nonionic surfactant onto polystyrene latex in aqueous sodium chloride. In the case of carboxylated emulsion polymers, evidence from conductometric titrations suggests that the carboxyl groups are generally concentrated near the particle surface. The resultant model of an expanded particle is that of a hydrated acid-rich shell surrounding a compact polymer core. The hydrated shell may be viewed as a dilute polymer solution where the density is close to that of water, i.e., Pe= P0. With this assumption, Equation 1 reduces to the form ... 

M. J. Garvey, D. Mitchell and A. L. Smith, Compression studies on a monolayer of polymer stabilized lattices at the air-2 molar sodium-chloride solution interface, Colloid Polym. Sci. 257, 70-74 (1979). 

A recent study has explored the potential of the ternary complex formed between a poly(p-cyclodextrin) (formed by polycondensation of p-cyclodextrin), a cationic surfactant (dodecyltrimethylammonium chloride), and a polyanion in water, to act as a delivery system for gene therapy,using a combination of viscometric and SANS studies as well as visual observations to determine the macroscopic and microscopic properties of the complexes. In the study, sodium dextran sulfate was used as a substitute for DNA. The potential advantages of the use of such ternary complexes over the more commonly investigated DNA-lipid or polymer complexes (lipoplexes and poly-plexes, respectively) include a high water solubility of the resulting complex (lipoplexes and polyplexes often... 

The conformation of a polyelectrolyte in solution is known to be highly dependent on the pH and ionic strength of the solution. Previous studies have shown that these also affect ionization of the polar groups and chain conformation of the adsorbed polymer so that thickness, surface roughness and charge density of the polyelectrolyte multilayers become a function of pH and ionic strength of the solutions used for layer-by-layer assembly [85-89]. In fact, SEM pictures of PAH/PSS membranes prepared either from acid or neutral solution, or acid solution in presence of sodium chloride, indicate... 

Fig. 22. Formation and disaggregation of complexes between soluble, carboxyl and amino Immobilines and histone like (HMG) proteins. Polymers with pure carboxyl and amino surfaces, having a threefold higher concentration of Immobilines than standard gels (approximately 30 m/W), were used in this experiment, and the stability of their complexes with HMG proteins was studied as a function of pH. For the carboxyl polymer, the disaggregation of its complex with the HGM protein by increasing sodium chloride molarities is also plotted. (From Righetti et al., 1983b. Reproduced with permission of the publisher.)...

Other studies in 2000 by Drew et al. reported that it is very difficult to spin fibers of PANI complexed to sulfonated polystyrene (PANFSPS), even when solutions containing sodium chloride and dodecyl benzene sulfonic acid sodium salt were used to lower the surface tension and thereby enhance electrospinning [16,17]. However, PANFSPS nanofibers can be produced by adding a carrier polymer such as PEO, polyacrylonitrile, or polyurethane. Also reported was the use of electrostatically layered sulfonated polystyrene as a template for the surface polymerization of conjugated polymers in their conducting form. Enzymatic synthesis of PANI and a copolymer of pyrrole and PEDOT was done on electrospun nanofiber... 

Addition to purified and diluted solutions of xanthan. For this study, it was necessary to prepare a non-aggregated xanthan solution which was obtained by extensive ultrafiltration of a commercial xanthan sample which was initially non-aggregated. The absence of aggregation was confirmed by the Huggins constant which was 0.4 and the intrinsic viscosity which was 6.7 m kg. This corresponds to a molecular weight of 4.8x10 daltons. This xanthan solution was adjusted at a polymer concentration of 0.4 g.l"l in a protein-rich solution such as com steep liquor (CSL). Before use, the com steep solution was centrifuged and only the clear supernatant was added to the xanthan solution. The solvent was 0.1 M sodium chloride and the ratio of protein to xanthan was 10% (w/w). 

Polymers were hydrated in distilled, filtered water under mild agitation until dissolution of the polymer was complete. To prepare polymer solutions containing salt, concentrated sodium chloride brine solutions were added to previously dissolved polymer in distilled water. Final polymer concentrations ranging from 1000 to 4500 ppm and salt concentration of 2.0 wt. % NaCl were prepared in this manner for viscometric study. An alternative procedure was used to evaluate the effect of salinity on solution rheology. Solid sodium chloride was slowly added to various concentrations of polymer in solution. These solutions were allowed to equilibrate for approximately 12 to 24 hours prior to obtaining viscometric measurements. 

The nature of the association maintains a locally effective shielding of the sulfonate anions within the aggregate and preservation of the clustered structure. This suggests that for these block polymer structures, the energetics of maintaining hydrophobic association are more favorable than monomer dispersion due to ionic repulsion. This was further demonstrasted by the extreme salt sensitivity of these polymers to solution ionic strength. Small amounts of sodium chloride resulted in polymer precipitation and of course loss of viscosification. This precludes the use of these particular polymers for chemically enhanced oil recovery and indicates the need for nonionic functionality to provide water solubility. To further pursue this approach acrylamide based polymers were studied. 

A few studies considered the effect of pH on the viscosity of xanthan solutions. Jeanes et al. observed a rapid increase in the viscosity of xanthan solution at pH 9-11 [28]. Whitcomb and Macosko [29] and Philips et al. [30] found the viscosity of xanthan to be independent of pH. Szabo examined the stability of various EOR polymers in caustic solutions at room temperature, including Kelzan MF (a biopolymer) [6]. He found a fast initial drop in the viscosity of a xanthan solution containing 2 wt% sodium chloride and 5 wt% sodium hydroxide, at 12.5 s", which virtually stopped after 10 days. Krumrine and Falcone found that the effect of alkali (sodium silicates) on the viscosity of xanthan solution depended on the concentration of sodium and calcium ions present [31]. Ryles examined the thermal stability of bio-polymers in alkaline conditions [16]. He found that xanthan was totally degraded (in anaerobic conditions) upon the addition of 0.8 wt% sodium hydroxide at temperatures from 50 to 90°C (in a 1 wt% sodium chloride brine). Seright and Henrici observed total biopolymer degradation at pH > 8 and a temperature of 120°C [26]. 

Polymer Studies. General Procedure. The desired amount of BPA (generally 45.35g), sodium or potassium hydroxide, phase transfer catalyst (Aliquat 336 or tetrabutylammonium bromide), p - t-butylphenol (0.75% as a chain stopper) and methylene chloride or methylene chloride/chlorobenzene (1/3) were heated at reflux for a period of 5 hr under nitrogen. At this point the reaction mixture was diluted with methylene chloride and filtered through Celite. The mixture was then either a) poured directly into methanol to precipitate the polymer or b) split into two portions one portion was precipitated by methanol, the second was reverse precipitated using methanol/acetone. (see below)... 

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