Polymer association complexes

A concept along similar lines was recently developed to account for the auto-accelerated character of the polymerization of carboxylic monomers and of acrylonitrile. Accelerated propagation is assumed to occur in oriented monomer-polymer association complexes. This conclusion is reached on the basis of kinetic evidence and the investigation of molecular associations present in these systems. 

Abstract. Auto-accelerated polymerization is known to occur in viscous reaction media ("gel-effect") and also when the polymer precipitates as it forms. It is generally assumed that the cause of auto-acceleration is the arising of non-steady-state kinetics created by a diffusion controlled termination step. Recent work has shown that the polymerization of acrylic acid in bulk and in solution proceeds under steady or auto-accelered conditions irrespective of the precipitation of the polymer. On the other hand, a close correlation is established between auto-acceleration and the type of H-bonded molecular association involving acrylic acid in the system. On the basis of numerous data it is concluded that auto-acceleration is determined by the formation of an oriented monomer-polymer association complex which favors an ultra-fast propagation process. Similar conclusions are derived for the polymerization of methacrylic acid and acrylonitrile based on studies of polymerization kinetics in bulk and in solution and on evidence of molecular associations. In the case of acrylonitrile a dipole-dipole complex involving the nitrile groups is assumed to be responsible for the observed auto-acceleration. 

Soaps and surfactants, lipids, cationic ingredients, and even polymers or polymer association complexes have been used as conditioning ingredients in shampoos and/or conditioning products. Soaps deposit their hydrophobic salts on the hair or bind by metal bridging. Cationic surfactants and polymers attach substantively to hair by ionic bonds enhanced by Van der Waals attractive forces. The substantivity of most polymer association complexes is probably due to their hydrophobic nature, enhanced by Van der Waals forces (entropy) and possibly ionic bonds. 

Association Complexes. The unshared electron pairs of the ether oxygens, which give the polymer strong hydrogen bonding affinity, can also take part in association reactions with a variety of monomeric and polymeric electron acceptors (40,41). These include poly(acryhc acid), poly(methacryhc acid), copolymers of maleic and acryflc acids, tannic acid, naphthoHc and phenoHc compounds, as well as urea and thiourea (42—47). 

Assets, identifying functions of, 15 476 Association complexes, ethylene oxide polymer, 10 682... 

The addition of a cryptand to some polyelectrolytes leads to significant increases in conductivity and in some cases IR and Raman spectroscopy demonstrate that the cryptand breaks up the ion-ion interactions (Chen, Doan, Ganapathiappan, Ratner and Shriver, 1991 Doan, Ratner and Shriver, 1991). Apparently the reduction of ion association more than offsets the reduction in mobility of the cation-crypt complex, which has a larger effective radius than the simple cation. It is also possible that the cryptand-ion complex is rendered more mobile by the reduction of polymer-cation complex formation, but this point has not been investigated in any detail. 

On the basis of the above experimental results, the expected conformations of polymer-surfactant complexes at the oil-water interface are depicted in Fig. 2.19. In case I, the added polymer associates with excess surfactants present in the bulk solution, but the complexes prefer to remain in the bulk phase. Alternately, the polymer-surfactant complexes are unable to displace the adsorbed surfactant molecules from the liquid-liquid interface. Irrespective of the amount of polymer-surfactant concentration in the bulk, the experimental decay length values remain comparable to the Debye lengths, corresponding to the concentration of ion species in the bulk solution (Eq. (2.11)). This means that the force profile is... 

The rheological behaviour of thermotropic polymers is complex and not yet well understood. It is undoubtedly complicated in some cases by smectic phase formation and by variation in crystallinity arising from differences in thermal history. Such variations in crystallinity may be associated either with the rates of the physical processes of formation or destruction of crystallites, or with chemical redistribution of repeating units to produce non-random sequences. Since both shear history and thermal history affect the measured values of viscosity, and frequently neither is adequately defined, comparison of results between workers and between polymers is at present hazardous. 

Arigita, C., Zuidam, N.J., Crommelin, D.J.A. and Hennink, W.E. (1999) Association and dissociation characteristics of polymer/DNA complexes used for gene delivery. Pharm. Res., 16, 1534-1541. 

Figure 2 Two-stage use of the QTL approach for competitive assay and/or drug discovery. In the upper part the polymer QTL complex (nonfluorescent) is treated with a bioagent-receptor and formation of the bioagent QTL complex results in freeing the polymer of the quencher and turning on the polymer fluorescence. If a mixture of polymer and bioagent QTL complex (fluorescent) is exposed to a new molecule capable of binding with the bioagent, release of the QTL from the complex leads to its association with the polymer and a turning off of the polymer fluorescence.

Hassan and Rizk developed potentiometric dipyridamole sensors based on lipophilic ion-pair complexes and native ionic polymer membranes [18]. The sensors are based on the use of the ion-association complexes of dipyridamole cation with tetraphenylborate and reineckate counteranions as ion-exchange sites in plasticized PVC matrices. A plasticized native polymer (carboxylated polyvinyl chloride) can also be used. These sensors exhibit linear and near-Nernestian responses for 10 mM-1 pM... 

Daniel, S., Praveen, R.S., Rao, T.P. Ternary ion-association complex based ion imprinted polymers (IIPs) for trace determination of palladium(II) in environmental samples. Anal. Chim. Acta 570, 79-87 (2006)... 

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