Formation of hybrid wormlike micelles upon mixing cetyl trimethylammonium bromide with poly(methyl methacrylate-co-sodium styrene sulfonate) copolymers in aqueous solution.

The association of cetyltrimethylammonium bromide, CTAB, with a series of P(MMAx-co-SSNa) random copolymers of sodium styrene sulfonate (SSNa) with methyl methacrylate (MMA) was explored in aqueous solution as a function of the MMA molar content, x, of the copolymers. The polyelectrolyte/surfactant complexation in aqueous solution was verified through pyrene fluorescence probing. In addition, turbidimetry studies in dilute or more concentrated aqueous solutions elucidated the phase separation behavior of the P(MMAx-co-SSNa)/CTAB systems as a function of the copolymer composition x and the surfactant to polyelectrolyte mixing charge ratio. It is found that practically phase separation is completely suppressed within the studied mixing range when the MMA content of the copolymers is ∼30-40 mol%. For lower MMA contents the polyelectrolyte/surfactant complex separates out from water, while for higher x values the solubility limits of the copolymers in water are attained. For the intermediate MMA contents, viscoelastic systems are obtained in more concentrated polymer/surfactant solutions provided that the polyelectrolyte is fully complexed with the cationic surfactant ((1)H NMR results). Moreover, the (1)H NMR studies indicate that hybrid P(MMAx-co-SSNa)/CTAB wormlike micelles are formed in water under these conditions. Finally, it is shown that addition of salt prevents syneresis problems and facilitates the rheological investigation.

Novel composites materials from functionalized polymers and silver coated titanium oxide capable for calcium phosphate induction, control of orthopedic biofilm infections: an "in vitro" study.

Three copolymers containing the functional groups P=O, S=O and C=O were prepared, and upon the introduction in calcium phosphate aqueous solutions at physiological conditions, "in vitro" were induced the precipitation of calcium phosphate crystals. The investigation of the crystal growth process was done at constant supersaturation. It is suggested that the negative end of the above functional groups acts as the active site for nucleation of the inorganic phase. In order to obtain the copolymer further antimicrobial activity, titania (TiO(2)) nanocrystals were incorporated in the polymer matrix after silver coverage by UV radiation. The antimicrobial resistance of the composite material (copolymer-titania/Ag) was tested against Staphylococcus epidermidis (SEM), Staphylococcus aureus (SAM), Candida parapsilosis (CAM) and Pseudomonas aeruginosa (PAM), microorganisms, using cut parts of "pi-plate" that covered with the above mentioned composite. The antimicrobial effect increased as the size of the nanocrystals TiO(2)/Ag decreased, the maximum achieved with the third polymer that contained also quartenary ammonium groups.

Incorporation of low molecular weight biocides into polystyrene-divinyl benzene beads with controlled release characteristics.

Triclosan and phosphonium salt biocides have been separately incorporated into polystyrene-divinylbenzene (PS-DVB) beads by suspension polymerization. Ultraviolet (UV) absorption measurements have been used to monitor the release of these low molecular weight biocides out of the PS-DVB beads immersed in water-ethanol mixtures and in physiological saline. The release of the biocide agents is strongly dependent on either the DVB or/and the antimicrobial composition ratio in the beads. An increase of biocide incorporation in the PS/DVB beads was accompanied by a corresponding enhancement of its concentration in liquid mixtures. On the contrary, higher cross-linking densities hindered the biocide migration out of the beads by diminishing its release rate into either the aqueous ethanol solutions or the natural serum. Moreover, Fourier transform Raman (FT-Raman) spectra and Attenuated Total Reflectance Infrared (ATR-FTIR) measurements of the PS-DVB-Triclosan and PS-DVB-phosphonium salt beads, before and after their immersion in water-ethanol solutions, gave a similar qualitative evidence of the biocide release.

Direct observation of odd-even effect in dilute polymeric solutions: A time-resolved fluorescence anisotropy study.

The odd-even effect is demonstrated, for the first time, in dilute polymeric solutions of polyethers, consisting of substituted luminescent quinquephenyl units which are connected by flexible aliphatic chains of 7-12 methylene groups. The effect, which is demonstrated by means of steady state and time resolved fluorescence anisotropy, has been attributed to the different mutual orientation of the luminescent dipoles, in the odd (7, 9, 11) and even (8, 10, 12) polymers. Namely, as the temperature of the solution is lowered the flexible aliphatic chains adopt the nearly all-staggered lowest energy conformation, which results in different mutual orientations of the fluorophores in the two types of polymers.