Polydisperse polyelectrolytes

Polydispersity of molecular weights of heparin was recognized in early studies (reviewed in Refs. 9 and 183). However, the polyelectrolyte nature and heterogeneity of charge distribution have hampered accurate determinations of molecular-weight distribution. 

In addition, polyelectrolytes such as poly(acrylic acid-alt-maleic anhydride) (pyran) are reticuloendothelial stimulants, induce resistance to tumor growth [462,463] and show interferon-inducing ability and antiviral activity. The pyran activity may be dependent upon molecular weight. Low molecular weight materials of narrow polydispersity activate macrophages however antitumor activity does not appear to be molecular weight dependent [460]. 

Fig. 2 Response of various PECs (first polyelectrolytes in initial solutions) to subsequent addition of salt a particle mass Mw b particle radius am (corrected for polydispersity, obeying the relation Mw=(4/r/3) p am3), c structure density p 1( ) - NaPSS/PDADMAC, X=0.3, 2(0) - NaPSS/PDADMAC, X=0.6, 3(B) - DADMAC-acrylamide copolymer (47 mol% DADMAC)/NaPMA X=0.6, 4(V) - DHP2 (block copolymer of poly(2-acry-lamido-2-methyl-1-propanesulfonic acid) and poly(ethylene glycol), PEG block length 10 kda)/PDADMAC, X=0.6,1-4 addition of NaCl, 5(A) - DADMAC-acrylamide copolymer (47 mol% DADMAC)/Na-PMA, X=0.6, addition of CaCl2...

Synthetic polyelectrolytes can be separated by capillary electrophoresis applying the same rules derived for the electrophoresis of biopolymers. In the reptation regime, determination of the molecular mass and polydispersity of the polyelectrolytes is possible. Introduction of chromophores facilitates the detection of non-UV-absorbing polymers. Indirect detection techniques can probably be applied when analytes and chromophores of similar mobilities are available. 

When all chains of a polymer or polyelectrolyte are equally long, the macromolecules are called homodisperse or monodisperse. If this condition Is not met the system is heterodisperse or polydisperse. Synthetic polymers and polyelectro-l)Ttes usually have a certain molar mass distribution and. hence, are to some extent polydisperse. This polydlsperslty has Important implications for the adsorption behaviour because fractionation will occur upon adsorption. 

When the averaged molecular masses determined by CGE are compared with those given by the suppliers (measured via SEC), molecular masses determined by SEC are always lower. When the CGE values are compared with results from MALDI-TOF measurements a closer correlation could be found. This may be an indication that in SEC polymer adsorption on the matrix was the reason for higher elution volumes, resulting in lower molecular masses. Of course, polydispersity is also affected by adsorption. Consequently CGE is a fast and reliable method for characterization of the molecular masses of polyelectrolytes and their distribution. 

The polyelectrolyte microgels have been established as model soft spheres as, in addition to the above features, their softness and properties can be tuned by altering the physico-chemical environment (pH, ionic strength, degree of ionization) [152-160], The response varies from that of colloidal (polydisperse hard-sphere) suspensions and that of polymer gels and in this respect such microgels fit within the theme of Fig. 1 [157-160],... 

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