Proton-accepting polymers

Interpolymer complexation between water-soluble polymers by hydrogen bonding was a frontier subject in the 1970s. Polyfcarboxylic acids), mainly po-lyfacryhc acid) (PAA) and poly( methacryflc acid) (PMAA), served as the most common proton-donating components. As for the proton-accepting polymers, poly(ethylene oxide ) (PEO or PEG) and poly(M-vinyl-2-pyrrolidone) (PVPo) were often used. The important results on the formation of complex aggregates and its dependence on the structur prameters have been reviewed [2,3,8]. In this section we select a few representative topics to look at recent advances in interpolymer complexes in aqueous media, with the emphasis on fluorescence probe studies. 

Effect of the Degree of Hydrolysis of Polyacrylamide on Its Complexation with Proton-Accepting Polymers... 

Iliopoulos et al. [22] studied complexation of proton-accepting polymers including PEO and PVPo with a series of PAA neutralized to different degrees, and found that even a low content of carboxylate sites (less than 15%) in the PAA chain was sufficient to prevent the chain from complexation. They emphasized the importance of a sufficiently long acid sequence for complex formation in other words, complexation can occur only when the polyacid is neutralized below a certain ionization degree characteristic of the system. Based on the re-... 

Table 2. Complexation of SAA with some proton-accepting polymers...

The effect of strong self-association of a proton-donating polymer on its com-plexation with proton-accepting polymers can be interpreted in terms of the competition of E p and the self-association force E j of the proton-donating polymer. Thus, the net driving force for interpolymer complexation is given by ... 

The formation of complexes containing hydrogen bonds is detected by the same methods as in the case of polyelectrolyte complexes. Moreover, spectroscopic methods such as Infrared, Raman and Nuclear Magnetic Resonance are used as efficient analytical methods. The composition of [proton-donating polymer unit]/[proton-accepting polymer unit] is generally 2/1 to 2/3 in dilute... 

Proton-accepting polymers and proton-donating polymers typically interact with each other in aqueous medium and organic solvents almost stoichiometri-cally. This complex formation is affected by temperature, polymer structure, polymer concentration, solvent and other interaction forces, e.g. hydrophobic interactions. In general, the ratio [proton-accepting polymer units]/[proton-donating polymer units] in mol/1 of the complex is almost unity in dilute solu-... 

Table 14 shows the formation of complexes between PMAA and proton-accepting polymers via hydrogen bonds. Tetramethylurea (TMU), N,N-... 

Table 15. Heat of mixing of proton-donating polymers and proton-accepting polymers in water and in organic solvents...

In heterogeneous systems, the complexation phenomena are quite different from those in homogeneous systems. Hie interactions between the PMAA membrane and proton-accepting polymers were studied as a function of the contraction of the membrane177. Figure 30 shows the profiles of the isothermal... 

Fig. 30 a, b. Formation of intermacromolecular complexes through hydrogen bonds in heterogeneous systems1771. (a) Time dependence of the poly(methacrylic acid) (PMAA) membrane contraction by complexation with poly(ethylene oxide) (PEO) with different chain length. O Mrao = 600, 3 Mpeo = 1000, MPEO = 2000, MPEO = 7500, A Mreo = 83000. (b) Time dependence of the PMAA membrane contraction by complexation with various proton-accepting polymers. O Poly(N-vinyl-2-pyrrolidone) (PVPo) (M. = 10000) 3 PVPo (M = 360000), poly (methyl vinyl ether) (Mw = 64000) poly (vinyl alcohol) (Mw = 22000)... 

Under acidic conditions, weak polybases (P2VP or PEI) are almost all protonated but a weak polyacid (PMAA) is scarcely dissociated. Thus, the complex of PMAA with the proton-accepting polymers (PEO or PVPo), which may form hydrogen bonds with PMAA, is preferentially formed. 

Next, in the system of two proton-accepting polymers, e.g. polyacrylamide) (PAAm), poly(vinyl alcohol) (PVA), PVPo and PEO, and a proton-donating polymer, e.g. PMAA, selective macromolecular complex formation is realized as shown in Table 24. Thus, under these experimental conditions, the complexation abilities of these proton-accepting polymers with respect to PMAA (mainly due to hydrogen bonds) follows the order... 

Interpolymer association has been most widely studied for polyelectolytes and hydrogen bonding polymers. Besides complex formation between polycation and polyanion represented by the complexes between polyionenes and poly(methacrylic acid) (7), the association of poly(carboxylic acid) with proton accepting polymers such as poly(ethylene oxide), poly(N-vinyl-2-pyrrolidone), and poly(vinyl alcohol) is the subject of active research (8). The main binding forces are attributed to Coulombic and hydrogen bonding interactions. The role of hydrophobic interaction cannot, however, be neglected. The different behaviors of poly(meth-acrylic acid) and poly(acrylic acid) in complex formation evidence the importance of hydrophobic interaction (9). 

High proton conductivity at high temperature and low relative humidity can be achieved using acid-base polymer complexes between basic polymers and strong acids or polymeric acids [1,14]. The proton-accepting polymers include... 

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