Polyelectrolyte chain size

The transition of the compressibility, and other properties of the polyelectrolyte brnshes, is most likely accounted for in terms of the transition in the binding mode of the connterion to the polyelectrolytes, from the loosely bonnd state to the tightly bound one, which rednces inter- and intrachain repulsive interactions. The following snpports this ac-connt (1) At the critical density, = 0.20 chain/nm, the separation distance between polyelectrolyte chains, d, is 2.4 nm. This distance is close to the snm, 2.6 nm, of the chain diameter, 1.3 nm, and the size of two hydrated connterions, 1.32 nm, indicating that the abrupt... 

In many biological systems the biological membrane is a type of surface on which hydrophilic molecules can be attached. Then a microenvironment is created in which the ionic composition can be tuned in a controlled way. Such a fluffy polymer layer is sometimes called a slimy layer. Here we report on the first attempt to generate a realistic slimy layer around the bilayer. This is done by grafting a polyelectrolyte chain on the end of a PC lipid molecule. When doing so, it was found that the density in which one can pack such a polyelectrolyte layer depends on the size of the hydrophobic anchor. For this reason, we used stearoyl Ci8 tails. The results of such a calculation are given in Figure 26. 

From the experiments just outlined [74-76], a few points are worth being emphasized A powerful procedure was developed to gradually approach phase boundaries of polyelectrolyte precipitation. The approaches can be performed in a highly systematic manner and lead to states which are located extremely close to the precipitation threshold. Approaches could successfully be accompanied by LS experiments. The experiments demonstrated, that the polyelectrolyte chains shrank dramatically in size immediately before the phase boundaries were reached. A sudden increase of the scattering intensity indicated the phase boundaries. These developments give rise to the hope that intermediates may be revealed which have not become accessible in preceding investigations [78-81]. 

Systematic studies on micellar size and structure have been published for poly(styrene-h-acrylic acid) (PS-PAAc) [7, 8], poly(styrene-fr-sodium acrylate) (PS-PAAcNa) [9], or quaternized poly(styrene-h-4-vinyl-pyridine) (PS-P4VPMeI) [10, 11]. It was concluded that the polyelectrolyte chains in the micellar corona are almost fully stretched [8]. The effect of salt concentration was investigated by Guenoun et al. on poly(f-butylstyrene-fr-sodium styrene sulfonate) (PtBS-PSSNa) who observed a weak decrease of micellar size and aggregation number when the salt concentration was increased beyond 0.01 mol/1 [12]. Using small-angle neutron scattering (SANS), the authors could provide additional support for the rod-like conformation of the polyelectrolyte chains in the micellar corona [13]. 

Li Y, Dubin PL, Dautzenberg H, Lueck U, Hartmann J, Tuzar Z. Dependence of structure of polyelectrolyte/micelle complexes upon polyelectrolyte chain-length and micelle size. Macromolecules 1995 28 6795—6798. 

The polymers considered above have been uncharged. Another class of polymers are polyelectrolytes whose chains carry a fixed charge. For Debye lengths small in comparison with the chain size, polyelectrolytes take on a coiled structure. Despite the presence of charge, the description for a polyelectrolyte fluid is similar to that which is obtained for a neutral polymer corresponding to the ideal chain regime (de Gennes 1990). 

Higgs and Joanny also considered a non-neutral polyampholyte with/-g f+g for the case when V=0. In pure water the chain has the characteristics of both a polyelectrolyte (excess of charges /-g) and of a neutral polyampholyte (neutral part 2g f+g). The polyelectrolyte blob size is ... 

Fig. 2 Snapshots of Monte Carlo simulations of a polyelectrolyte chain of N = 100 monomers of size b, taken as the unit length. In all simulations the bare persistence length is fixed at to/b =, and the screening length and the charge interactions are tuned such that the electrostatic persistence length (f osf) is constant and fosp/h = 100, see Eq. (18). The parameters used are (a) k jb = and t Lb(o = (b) K fb = n/200 and b o = 2 (c) K lb = /m and b o = 1A and (d) K jb = V3200 and = 1 /8. Noticeably, the weakly charged chains crumple...

Huck et al. prepared Au NPs inside IL-based polyelectrolytes [70], The nanocomposite synthesis relies on loading the macromolecular film with AuCl precursor ions followed by their in situ reduction to Au nanoparticles. It was observed that the nanoparticles are uniform in size and are fully stabilized by the surrounding polyelectrolyte chains. Moreover, XRR analysis revealed that the Au NPs are formed within the polymer-brush layer. Interestingly, AFM experiments confirmed that the swelling behavior of the brush layer is not perturbed by the presence of the loaded NPs (Fig. 4.22]. The Au NP-poly-METAC nanocomposite is remarkably stable to aqueous environments, suggesting the feasibility of using this kind of nanocomposite systems as robust and reliable stimuli-responsive platforms. 

Although their free solution behaviors are similar, flexible molecules (like DNA and denatured proteins) exhibit dramatically different behavior in a sieving matrix. Once the size of the pores in the gel becomes small relative to the radius of gyration of the polyelectrolyte chain, the polyelectrolyte chain must uncoil in order to move through the gel. Although the uncoiling process is entropically unfavorable (since it reduces the number of available conformations for the chain), the entropy loss is offset by the reduction in the electrical potential energy as the chain moves in the field. 

Fig. 4.13 Illustration of the concentration-dependent scaling laws for coil sizes of the polyelectrolyte chain shown as a bead string in a poor solvent...

Since the chain conformation appears as unperturbed in the concentrated solutions, the coil sizes will not depend on the concentration any more. With further increase of concentrations, C 1, and eventually the electrostatic repulsion between charged monomers will be completely screened. In the end, the polyelectrolyte chain will behave like a charge-neutral polymer chain in highly concentrated solutions. Correspondingly, the coil sizes will increase in a sudden, leading to an increase of characteristic relaxation time as well as the intrinsic viscosity, and appearing as a gelation process, as demonstrated in Fig. 4.13 (Dobrynin and Rubinstein 2005). 

As reflected in size measures such as the mean radius of gyration i g or mean-square end-to-end distance an isolated polyelectrolyte chain in dilute solu-... 

In dilute solutions, the distance between chains is larger than their size such that the intrachain electrostatic interactions dominate over the interchain ones. Thus, to describe the properties of a chain, one can effectively consider a single polyelectrolyte chain with counterions surrounding it in a large cell whose size is on the order of the distance between chains. 

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