Interpolymer complex complexation

The substantial decrease of polyacrylamide solution viscosity in mildly saline waters can be uti1i2ed to increase injection rates. A quaternary ammonium salt polymer can be added to the polyacrylamide solution to function as a salt and reduce solution viscosity (144). If the cationic charge is in the polymer backbone and substantially shielded from the polyacrylamide by steric hindrance, formation of an insoluble interpolymer complex can be delayed long enough to complete polyacrylamide injection. Upon contacting formation surfaces, the quaternary ammonium salt polymer is adsorbed reducing... 

A simple example of gel formation is provided by chitosan tripolyphosphate and chitosan polyphosphate gel beads the pH-responsive swelling abihty, drug-release characteristics, and morphology of the gel bead depend on polyelectrolyte complexation mechanism and the molecular weight. The chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution by ionotropic cross-hnking or interpolymer complexation, respectively. 

It has been shown that hydrogen bonding-mediated interpolymer complexes can be powerful drag reducers. The drag-reduction levels in such polymer systems increase dramatically by a factor of 2 to 6 when compared with their nonassociating polymeric precursors. Their shear stability is also shown to be significantly enhanced [1156]. 

Bell, C, L and Peppas, N. A. Biomedical Membranes from Hydrogels and Interpolymer Complexes, VoL 122, pp. 125-176. 

One effect of the electrochemical reactions in an aqueous system is a local pH change around the electrodes. By water electrolysis, hydronium ions (H30+) are generated at the anode, while hydroxyl ions (OH ) are produced at the cathode. These changes have been utilized for controlling the permeability of polyelectrolyte gel membrane or on-off solute release via ion exchange or surface erosion of interpolymer complex gels. 

Another mechanism for modulated drug release is local pH-induced surface erosion of interpolymer complex gels with entrapped solutes, as shown in... 

Duvdevani, I., Wagensommer, J., and Agarwal, P.K. "Novel Interpolymer Complexes of Sulfonated octene 1 Copolymer," US Patent 4,634,542(1987). 

Interpolymer complexes possess unique physical and chemical properties which are different from those of the initial components and have found applications in technology, medicine, and other fields (Bekturov and Bimendina, 1981). The unique properties of the complexes arise due to a higher degree of molecular ordering that is a result of secondary binding forces. The resulting secondary structures are dictated primarily by the primary structure (monomer sequence), solvent, and temperature of the system. Interpolymer complexes can be classified based on the nature of the secondary binding forces as ... 

It is the sensitivity of hydrogen bonds to their external environment that provide the pH-dependence of physical properties of hydrogen-bonding interpolymer complexes that are of interest to us. 

Philippova and Starodubtzev have also extensively studied the complex-ation behavior of polyacids and PEG, especially, the system of crosslinked of poly(methacrylic acid) and linear poly(ethylene glycol) (Philippova and Starodubtzev, 1995 Philippova et al., 1994). They observed that decreasing the molecular weight of PEG from 6000 to 1500 resulted in its slower diffusion into the swollen network of PMAA, and a drastic decrease in both the stability and equilibrium composition of the intermacromolecular complex. Analysis of dried polymer networks of PMAA with absorbed PEG chains by FT-IR spectroscopy revealed the presence of two types of hydrogen bonded structures (1) dimers of methacrylic acid at absorption frequency of 1700 cm-1 and (2) interpolymer complexes of PMAA and PEG at 1733 cm-1. In addition, they also suggested as a result of their studies, that the hydrogen bonded dimer of PMAA forms preferentially to the intermacromolecular complex between the PMAA network and PEG chains. 

Another promising class of hydrogels that exhibit responsive behavior is complexing hydrogels. Osada studied complex formation in PMAA hydrogels (Osada, 1980). In acidic media, the PMAA membranes collapsed in the presence of linear PEG chains due to the formation of interpolymer complexes between the PMAA and PEG. The gels swelled when placed in... 

Fig. 9. The effect of interpolymer complexation on the correlation length, , and the effective molecular weight between crosslinks, Mc, in P(MAA-g-EG) graft copolymer networks with permanent, chemical crosslinks ( ).

X.D. Huang, S.H. Goh, Interpolymer complexes through hydrophobic interactions C60-end-capped polyethylene oxide)/poly(methacrylic acid) complexes, Macromolecules, pp. 8894-8897, 2000. 

Nurkeeva ZS, Mun GA, Khutoryanskiy VV, Bitekenova AB, Dubolazov AV, Esirkegenova SZ. pH Effects in the formation of interpolymer complexes between polyfA-vinylpynoh-done) and poly(acrylic acid) in aqueous solutions. Eur Physical J E Soft Matter... 

Sotiropoulou M, Bokias G, Staikos G. Soluble hydrogen-bonding interpolymer complexes and pH-controlled thickening phenomena in water. Macromolecules 2003 36 1349-1354. 

Polyelectrolyte complexes have also been studied as tablet matrices for controlled release applications. For example, the interpolymer complexes of chitosan with pectin and acacia were investigated as tablet matrices for release of chlorpromazine HCL [353]. The complex formed in situ by mixing chitosan with either pectin or acacia displayed the most efficient sustained release (compared to either pectin, acacia or a preformed complex). The results were attributed to the swelling and gel-forming capacity of the freshly formed complex in contrast to the preformed version. 

Biomedical Membranes from Hydrogels and Interpolymer Complexes... 

---