Polyelectrolytes branched

It has been described that a hydrogel with polyelectrolyte branched dangling poly-... 

In this chapter we describe the hydrodynamic properties of polymer solutions close to thermodynamic equilibrium, but ignore all the fascinating non-linear effects. We will also limit ourselves to neutral linear flexible macromolecules, although very similar theories have been applied to more complicated systems such as polyelectrolytes, branched polymers and rod-like polymers. 

Usually the acid-base properties of poly electrolyte are studied by potentiometric titrations. However it is well known, that understanding of polyelectrolyte properties in solution is based on the knowledge of the thermodynamic properties. Up to now, there is only a small number of microcalorimetry titrations of polyelectrolyte solutions published. Therefore we carried out potentiometric and microcalorimetric titrations of hydrochloric form of the linear and branched polyamines at 25°C and 65°C, to study the influence of the stmcture on the acid-base properties. 

Antonietti M., Briel A., Fosrster S. Quantitative Description of the Intrinsic Viscosity of Branched. Polyelectrolytes. Macromolecules 1997, 30, 2700-2704. 

Branched polyelectrolytes have become of special interest because of their industrial importance and scientifically interesting properties. Poly(ethyl-eneimine), which is important in various industrial applications, can provide an excellent example branched and linear polyelectrolytes have quite different properties due to both their different topographies and structures [89-91]. As another practical point, branched polyelectrolytes can act as precursor or fragments of polyelectrolyte gels. A variety of theoretical approaches have been reported on the investigations of branched polyelectrolytes [92-97]. However,... 

Scheme 4. Synthetic routes for a silica particle with hyperbranched polymer shell (a) and branched polyelectrolyte shell (b)...

The poly(vinylpyridine) and poly(tert-butyl methacrylate) copolymers can easily be converted to either cationic or anionic polyelectrolytes by protonation of the pyridine rings or by base hydrolysis of the tert-butyl ester units, respectively. The highly branched structure of the molecules, in combination with the polyelectrolyte effect, should confer useful properties to these materials in solution for applications such as pH-sensitive reversible gels. 

A variation of the aromatic polyester structure was utilized by Hawker et al. when they described hyperbranched poly(ethylene glycol)s and investigated their use as polyelectrolyte media [76]. The highly branched structure implies that no crystallization can occur. Linear poly(ethylene) glycols usually crystallize, which has a detrimental effect on their use as polyelectrolyte media. 

In this article I review some of the simulation work addressed specifically to branched polymers. The brushes will be described here in terms of their common characteristics with those of individual branched chains. Therefore, other aspects that do not correlate easily with these characteristics will be omitted. Explicitly, there will be no mention of adsorption kinetics, absorbing or laterally inhomogeneous surfaces, polyelectrolyte brushes, or brushes under the effect of a shear. With the purpose of giving a comprehensive description of these applications, Sect. 2 includes a summary of the theoretical background, including the approximations employed to treat the equifibrium structure of the chains as well as their hydrodynamic behavior in dilute solution and their dynamics. In Sect. 3, the different numerical simulation methods that are appHcable to branched polymer systems are specified, in relation to the problems sketched in Sect. 2. Finally, in Sect. 4, the appHcations of these methods to the different types of branched structures are given in detail. 

The influence of molar mass, charge density as well as chain branching was also determined in the presence of low molecular mass salt. As seen in Fig. 16, the differences between theory and experiment are more important to low molar masses. In Fig. 16 the concentration dependence of the activity of the low molecular salt has been taken into account when calculating fac=fexp/fo [H4, 126], where fac and fexp are calculated and experimentally determined counterion activity coefficients, respectively f0 is the activity coefficient of the added low molecular salt in aqueous solution without polyelectrolyte. 

Hard-sphere or cylinder models (Avena et al., 1999 Benedetti et al., 1996 Carballeira et al., 1999 De Wit et al., 1993), permeable Donnan gel phases (Ephraim et al., 1986 Marinsky and Ephraim, 1986), and branched (Klein Wolterink et al., 1999) or linear (Gosh and Schnitzer, 1980) polyelectrolyte models were proposed for NOM. Here the various models must be differentiated in detail—that is, impermeable hard spheres, semipermeable spherical colloids (Marinsky and Ephraim, 1986 Kinniburgh et al., 1996), or fully permeable electrolytes. The latest new model applied to NOM (Duval et al., 2005) incorporates an electrokinetic component that allows a soft particle to include a hard (impermeable) core and a permeable diffuse polyelectrolyte layer. This model is the most appropriate for humic substances. 

The number of counterions associated with the tetrahedral junction was less than sensitive not only to parameters that define the junction region, but also to the interbranch angle between 90° and 109.5° [74] The number of associated counterions is substantially larger in the four-way junction than other junction geometries and constructs studied [74]. As salt concentration is increased, the stability of the junction is enhanced over a linear polyelectrolyte molecule of identical length as the junction [74], For junctions with symmetrical branches, the counterions associated with the junction in excess of that of a linear construct increases with the length of the branches and then saturates [74],... 

Zeng F, Shen Y, Zhu S, Pelton R. (2000) Synthesis and Characterization of Comb-Branched Polyelectrolytes. 1. Preparation of Cationic Macromonomer of 2-(Dimethylamino)ethyl Methacrylate by Atom Transfer Radical Polymerization. Macromolecules 33 1628-1635. 

The PL method permits the investigation of polymers of any chemical structure linear or branched soluble polymers and even cross-linked insoluble polymers The only exceptions are polymers extingui iing luminescence. However, this property permits the development of new approaches based on this property For cross-linked polymers it was found sufficient to disintegrate the polymer into particles of a uniform size not exceeding 0.5 /Li. This approach is widely used in the investigation of polyelectrolytic networks ... 

Gum arabic (acacia) has been used in pharmacy as an emulsifier. It is a polyelectrolyte whose solutions are highly viscous owing to the branched stmcture of the macromolecular chains its adhesive properties are also believed to be due to, or in some way related to, this branched stmcture. Molecular weights of between 200 000 and 250 000 (MJ have been determined by osmotic pressure, values between 250 000 and 3 x 10 by sedimentation and diffusion, and values of 10 by light scattering, which also points to the shape of the molecules as short stiff spirals with numerous side-chains. Arabic acid prepared from commercial gum arabic by precipitation is a moderately strong acid whose aqueous solutions have a pH of 2.2-2.7. It has a higher viscosity than its salts, but emulsions prepared with arabic acid cream are not as stable as those made with its salts. 

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