Polyanionic systems, mechanism

We have previously shown that when PPV is self-assembled with specific electronically active polyanions such as poly(thiophene acetic acid) (PTAA) or sulfonated fiillerenes (S-C60 )(7), the photoluminescence of the PPV is essentially completely quenched by the polyanion. The mechanism of this quenching is believed to be due to a photoinduc electron transfer process taking place between the excited PPV and the adjacent electroactive polyanion molecules. The quenching process, in this case, is not associated with a Forster type energy transfer since in both cases, the required spectral overlap of a donor emission band with an acceptor absorption band is not fulfilled. In addition, photo-induced electron transfer processes have previously been confirmed in PPV/C60 systems and can be exploited to fabricate thin film photovoltaic devices (77). In order to mediate this electron transfer process, we have constructed multilayer heterostructures in which the PPV donor and the polyanion electron acceptor are separated from each other with electronically inert spacer layers of known thickness. In addition to allowing studies of the electron transfer process, such structures provide important insights into the thermal stability of the multilayer structure. The "spacers" used in this study were bilayers of SPS/PAH with an experimentally determined bilayer thickness of 30 +/-5 A. 

Polyanionic polymers can enter into biological functions by distribution throughout the host and they behave similar to proteins, glycoproteins and polynucleotides which modulate a number of biological responses related to the host defense mechanism. These are enhanced immune responses, and activation of the reticuloendothelial system (RES) macrophages. 

In a previous publication [8] we described a systematic screening of the binary interactions between 36 polyanions and 40 polycations. As a result of this study it became clear that capsules prepared from simple binary polymer complexes would not be mechanically adequate and multicomponent polymer systems would offer advantages. The rationale for capsule improvement, and for the use of a multicomponent system, has been presented in the Introduction. We have elected to investigate the methods outlined in Sects. 1.2.7 and 1.2.8 (polymer... 

There has been much speculation concerning the mechanism of tionor Inhibition by these polyanlonlc systems. Many polyanions Induce Interferon production (22) and this fact has also been suggested as the source of the activity. More recently, it has been observed that DIVEMA is not cytotoxic to tumor cells (23) and that only those polymers that activated macrophages showed antlneoplastlc activity (24). Inhibition via macrophages Is believed to be the mode of action for DIVEMA (V) if not for all polyanlonlc polymers (16). 

Some applications of polypyrrole, such as drug delivery devices, require specific ion transport. Control of the ion transport process requires determination of the identity of the mobile ion, which is complicate by the fact that there are several ions present in the system. Moreover, Shimidzu and co-woiicers [138,139] demonstrated that ion transport in polypyrrole can be modified by the use of polymeric anions as dopants. Miller and Zhou [140] proved that the electrochemical switching of polypyrrole could achieve controlled release of small anions (such as CIO4), while the incorporation of an immobile polyanion (such as polystyrene sulfonate) resulted in cation transport. The polyanions become trapped within the polypyrrole matrix due to their large size and, perhaps more important, their entanglement with the polypyrrole chains. This increases the stability and mechanical strength of polypyrrole and improves electrical conductivity and electroactivity [141,142]. Therefore it has been of significant interest in the polymerization of pyrrole in polyanion electrolyte solutions [143,144]. 

HA, a naturally occurring polyanion, plays an important structural and mechanical role in various tissues. The inhibitive effects of HA with respect to hyperplasia, observed after either systemic or local delivery, suggest that the antiproliferative effects of HA may be related to its anti-inflammatory properties... 

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