Polymer-micelle complexes complexation

Nagarajan, R., Drew, C. and Mello, C.M. (2007) Polymer—micelle complex as an aid to electrospinning nanofibers from aqueous solutions. Journal of Physical Chemistry C, 111, 16105-16108. 

The principal goal of this paper is to examine the physical forces responsible for this latter type of polymer-surfactant micelle association. Since the formation of a polymer-micelle complex gives rise to gross conformational changes in the polymer molecule, a measurement of the solution viscosity provides the simplest means for monitoring polymer-micelle association. Here, the viscosity data on solutions containing polymer and surfactant of different molecular structures are used to explore the nature of polymer-miceUe complex formation. 

Figure 4. Influence of electrolyte NaCl concentration on the relative viscosity of solutions containing 1000 ppm polyethylene oxide and 8-phenyl hexadecane benzene sulfonate micelles. The polyelectrolyte type behavior of the polymer-micelle complex can be noted.

For an aqueous solution containing free micelles of size M and polymer-micelle complexes in which n micelles of size are associated with each polymer molecule, the total mole fraction of the surfactant (Sx) is given3 5 by... 

Polymer-micelle complexation may affect the conformation of the polymer, but is assumed not affect Kb and gb. The relative magnitudes of Kb,Kf and gb determine whether complexation with the polymer occurs as well as the critical surfactant concentration exhibited by the system. If kf > kb and fb = g( then free micelles occur in preference to complexation. If Kf < Kb and gb = gf, then micelles bound to polymer occur first. If Kf < JQ, but gb gf, then the free micelles can occur prior to saturation of the polymer. A first critical surfactant concentration (CAC) occurs close to Xi = K t second critical concentration occurs near Xi = Kj t, Depending on the magnitude of nXp, one may observe only one critical concentration over a finite range of surfactant concentrations. 

This multitude of properties the polymer must possess dictate that better polymer performance will be obtained from materials with complicated structures. Such polymers are complex polymers l) random copolymers, 2) block copolymers, 3) graft copolymers, 4) micellizing copolymers, and 5) network copolymers. There has been a dramatic increase in the past decade in the number and complexity of these copolymers and a sizable number of these new products have been made from natural products. The synthesis, analysis, and testing of lignin and starch, natural product copolymers, with particular emphasis on graft copolymers designed for enhanced oil recovery, will be presented. 

Then we address the dynamics of diblock copolymer melts. There we discuss the single chain dynamics, the collective dynamics as well as the dynamics of the interfaces in microphase separated systems. The next degree of complication is reached when we discuss the dynamic of gels (Chap. 6.3) and that of polymer aggregates like micelles or polymers with complex architecture such as stars and dendrimers. Chapter 6.5 addresses the first measurements on a rubbery electrolyte. Some new results on polymer solutions are discussed in Chap. 6.6 with particular emphasis on theta solvents and hydrodynamic screening. Chapter 6.7 finally addresses experiments that have been performed on biological macromolecules. 

Similarly, this amphiphilic polymer micelle was also used to dismpt the complex between cytochrome c (Cc) and cytochrome c peroxidase (CcP Sandanaraj, Bayraktar et al. 2007). In this case, we found that the polymer modulates the redox properties of the protein upon binding. The polymer binding exposes the heme cofactor of the protein, which is buried in the protein and alters the coordination environment of the metal. The exposure of heme was confirmed by UV-vis, CD spectroscopy, fluorescence spectroscopy, and electrochemical kinetic smdies. The rate constant of electron transfer (fc°) increased by 3 orders of magnimde for the protein-polymer complex compared to protein alone. To establish that the polymer micelle is capable of disrupting the Cc-CcP complex, the polymer micelle was added to the preformed Cc-CcP complex. The observed for this complex was the same as that of the Cc-polymer complex, which confirms that the polymer micelle is indeed capable of disrupting the Cc-CcP complex. 

In conclusion, the incorporation of Gd(III) complexes into macromolecular systems (dendrimers, linear polymers, micelles) does not significantly affect the water exchange kinetics, exceptions have only been found for few protein bound chelates. 

Nishiyama, N., Yokoyama, M., Aoyagi, T., Okano, T., Sakurai, Y. and Kataoka, K. (1999) Preparation and characterization of self-assembled polymer-metal complex micelle from cis-dichlorodiammineplatinum(II) and poly(ethylene glycol)-poly(, -aspartic acid) block copolymer in an aqueous medium. Langmuir, 15, 377-383. 

Figure 47.1. Types of naiiocaniers for dmg delivery. A liposomes B nanopaiticles C nanospheres D nanosuspensions E polymer micelles F- nanogel G block ionomer complexes H nanofibers and nanot ...

Nishiyama, N. Kato, Y. Sugiyama, Y. Kataoka, K. Cisplatin-loaded polymer-metal complex micelle with time-modulated decaying property as a novel drug delivery system. Pharm. Res. 2001, 18, 1035-1041. 

In this study we restrict our consideration by a class of ionic liquids that can be properly described based on the classical multicomponent models of charged and neutral particles. The simplest nontrivial example is a binary mixture of positive and negative particles disposed in a medium with dielectric constant e that is widely used for the description of molten salts [4-6], More complicated cases can be related to ionic solutions being neutral multicomponent systems formed by a solute of positive and negative ions immersed in a neutral solvent. This kind of systems widely varies in complexity [7], ranging from electrolyte solutions where cations and anions have a comparable size and charge, to highly asymmetric macromolecular ionic liquids in which macroions (polymers, micelles, proteins, etc) and microscopic counterions coexist. Thus, the importance of this system in many theoretical and applied fields is out of any doubt. 

In the second approach, metal-ion/complex was first attached to one of the polymer blocks. A thin film of the resulting polymer metal complex was then obtained by spin coating/solution casting. Alternatively, the polymer metal complex may also be dissolved in a suitable solvent system that selectively dissolves one of the blocks. Micelles or nanosized aggregates formed in this case. The micellization of amphiphilic block copolymers and their use in the formation of metal nanoparticles has been discussed previously.44 A monolayer of micelles was introduced on a substrate surface by dipping or electrostatic attraction. The substrate was then subjected to further chemical or physical treatments as mentioned earlier. The third approach involves the formation of micelles from the metal-free block copolymer in a suitable solvent system. The micelle solution was then added with metal ion, which was selectively coordinated to one of the blocks. These micelle-metal complexes can also be processed by a procedures similar to the second approach. 

Iron(III) and cobalt(II) complexes of these polymeric ligands were found to be effective catalysts for the oxidation of cyclohexane and ethylbenzene with H2Oz or 02 in biphasic media. The authors proposed that the oxidation takes place inside polymer micelles which can be regarded as microreactors. However, no recycle experiments were performed to ascertain the stability of these catalysts. A priori one would expect acetylacetonate ligands to undergo facile degradation under oxidizing conditions. 

---