Search results for "polyelectrolyte"
showing 10 items of 214 documents
Competitive Adsorption of Functionalized Polymers
1996
The adsorption and desorption of functionalized polystyrene-block-polybutadiene diblock copolymers from dilute solutions in toluene onto silicon wafers are investigated by means of null ellipsometry. The short polybutadiene block is functionalized by a reaction with 4-(3,5-dioxo-1,2,4-triazolidin-4-yl)benzoic acid. On the average there are six functional groups per chain. The polystyrene block does not adsorb on the surface. The adsorption depends on the length of the polystyrene block, and chains with short polystyrene blocks yield higher surface coverage than larger ones. When short and long chains are put together, the short chains displace the long ones in equilibrium conditions nearly …
Polyelectrolytes in dilute solution: viscometric access to coil dimensions and salt effects
2015
Copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC), differing in molar masses M (52.3 to 227 kDa) and degrees of charging y (0.2 to 0.6), were studied with respect to their viscometric behavior in dilute aqueous solutions containing variable amounts of NaCl. Complementary measurements were performed on a Brookhaven 90 plus particle size analyzer. M dominates the intrinsic viscosities [η]. For the viscometric interaction parameters B this is only true for large concentrations of extra salt. [η] and B as a function of solvent salinity follow Boltzmann laws. Coil dimensions, determined either via dynamic light scattering or viscometry, agree well. For low salt contents…
Intrinsic Viscosities of Polymer Blends: Sensitive Probes of Specific Interactions between the Counterions of Polyelectrolytes and Uncharged Macromol…
2018
In joint dilute aqueous solutions of pullulan (PUL) and poly(sodium 4-styrenesulfonate) (PSS-Na) the Na+ ions of the polyelectrolyte interact so favorably with the monomeric units of PUL that isolated coils containing both types of macromolecules are formed upon dilution. When water is replaced against a 1 M solution of NaCl, this effect dies out because of the large surplus of Na+ ions. On the other hand, if the water contains increasing amounts of the respective counterpolymer instead of NaCl, the formation of mixed isolated coils is fostered, where a further diminution of the intrinsic viscosities is caused by the lower the solvent quality. The molar mass of PSS-Na plays an important rol…
Viscometry of polyelectrolyte solutions: Star-like versus linear poly[[2-(methacryloyloxy)ethyl] trimethylammonium iodide] and specific salt effects
2017
Abstract The intrinsic viscosities, [η], of the 3-arm star polyelectrolyte in pure water are for a given molar mass considerably lower than for the linear product because of the higher monomer concentration and charge density in isolated coils. These effects are much more pronounced than in the case of uncharged macromolecules. Extra salt (NaCl, NaI, CaCl2) reduces the solution viscosities of the 3-arm star polymer less than of the linear product. The transition of [η] from the value in pure water to the minimum saturation value at high salt concentrations follows a Boltzmann sigmoid. In saline solvents the changes of the viscosities with rising polymer concentration depend strongly on the …
Estimation of pKa shifts in weak polyacids using a simple molecular model: effects of strong polybases, hydrogen bonding and divalent counterion bind…
2004
Abstract The pKa values of ionizable groups in macromolecules can be significantly different than those of the isolated groups in solution. We have estimated theoretically the changes in the dissociation constant of a weak acid (a) in the vicinity of another ionizable group (b) on the basis of the theoretical approach by Hill (J. Am. Chem. Soc. 78 (1956) 3330) for matching pairs of interacting sites on two large molecules. Three cases are considered for group b: the strong base, the same weak acid as group a with hydrogen bonding between them, and the same weak acid as group a with divalent counterion binding. The pKa shifts are evaluated in each case as a function of the interaction energy…
Cylindrical polyelectrolyte-comb-surfactant complexes
2006
Abstract Quaternized polymer combs based on poly(2-vinylpyridine-macromonomers) and the surfactant sodium dodecylsulfate are employed in the synthesis of a novel cylindrical polyelectrolyte-comb-surfactant complex (PECSC). The complex formed has 1:1 stoichiometry with respect to the ratio of dodecylsulfate to pyridinium units. It is soluble in organic solvents such as 2-butanol or chloroform. Characterization of single particle properties of the complex in organic solution is possible and yields a radius of gyration of 〈Rg〉z = 78.4 nm, a hydrodynamic radius of 〈1/Rh〉z−1 = 51.4 nm and a cross-sectional radius of Rg,cross = 3.9 nm in chloroform. The characteristic ratio γ = 〈Rg〉z/〈1/Rh〉z−1 de…
Polymersynthesen durch repetitive N-alkylierungen
1994
The repetitive N-alkylation reaction, at first used by Marvel, turned out to be a very versatile method for the synthesis of polycations. Rembaum introduced the name ionenes for this type of polymers. In the first part of the lecture some examples of single-stranded ionenes are described. The second part shows how the repetitive N-alkylation can be used for the synthesis of spiro polymers. In these double-stranded polymers two spiro-conjugated rings of the main chain have a central quaternary nitrogen in common (spiro-ionenes or spiro-azonia polymers)
Intrinsic viscosities of polyelectrolytes in the absence and in the presence of extra salt: Consequences of the stepwise conversion of dextran into a…
2011
Abstract Viscosities of dilute polymer solutions were measured in capillary viscometers for samples varying in their fraction f of charged units from 0.00 to 0.90. The dependence of the logarithm of the relative viscosity on polymer concentration c is in all cases reproduced quantitatively by three characteristic parameters: [ η ], the intrinsic viscosity; B , a viscometric interaction parameter (related to the Huggins constant); [ η ] , a parameter required only for polyelectrolytes at low concentrations of extra salt. In pure water [ η ] increases more than 80 times as the fraction f rises from zero to 0.90 and [ η ] starts from zero and goes up to ≈71 mL/g. Upon the addition of NaCl [ η …
Some examples of the modification of polymers
1986
Reactions avec des groupes amide et amino dans la chaine principale, et avec un groupe terminal bromoacetyl. Polymerisation de la conidine en presence d'un polystyrene vivant
Surfactant-Induced Helix Formation of Cylindrical Brush Polymers with Poly(L-lysine) Side Chains
2008
The complex formation of oppositely charged surfactants with some polypeptides is known to induce β-sheet or helix formation. Here, we report on the complex formation of cylindrical brush polymers with poly(L-lysine) side chains and sodium dodecylsulfate (SDS). With increasing amount of added surfactant the cylindrical polymers first adopt a helical conformation with a pitch of approximately 14-24 nm followed by a spherically collapsed structure before eventually precipitation occurs. CD measurements suggest that the helix formation of the cylindrical brush polymers is driven by the hydrophobicity of the ,8-sheets formed by the PLL side chain-SDS complexes.