Molecular weight copolymer adsorption onto

Experimental studies of the adsorption of polyelectrolyte have been reported by several authors Pefferkom, Dejardin, and Varoqui (3) measured the hydrodynamic thickness of an alternating copolymer of maleic acid and ethyl vinyl ether adsorbed on the pore walls in cellulose ester filter as a function of the molecular weight and the concentration of NaCl. Robb et al. (4) studied the adsorption of carboxy methyl cellulose and poly (acrylic acid) onto surfaces of insoluble inorganic salts. However, their studies are limited to the measurements of adsorbance and the fraction of adsorbed segments. 

Figure 11 Adsorption isotherm for poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) ABA triblock copolymers adsorbed onto poly(styrene latex), molecular weight 3250 g/mol with 12 mol% ethylene oxide. (J. A. Shar, unpublished results.)... 

The adsorption of polymers typically increases with polymer molecular weight and is higher and best (e.g. thicker, denser adsorbed layers) from a solution containing a poor solvent. For these reasons, block-copolymers are excellent steric stabihzers. Block copolymers like poly(ethylene oxide) surfactants are suitable as one part of the stabilizer has a high tendency to adsorb onto the particle surface and the other has a high affinity for the solvent. 

A change in the hydrophilic nature of the polymer surface on irradiation of poly(p-phenylazoacrylanilide) or its copolymer with 2-hydroxyethyl methacrylate (HEMA) could affect the adsorption-desorption behavior of proteins or organic substances onto the polymer. Adsorption of lysozyme onto the copolymer of p-phenylazoacylanilide and HEMA decreased from 4.6 to 1.8 eg g of adsorbent on UV irradiation, which induces the isomerization from trans- to cis-form [16]. Table 2 summarizes the results of other proteins adsorption studies. Considering the similarity in molecular weight of the three proteins, the difference in adsorption behavior is probably due to the difference in the surface characteristics of these proteins. The decrease in adsorption ability on UV irradiation is attributable to the reduction of hydrophobic interaction between the protein and the polymer by the appearance of hydrophilic cis-azobenzene on the surface. 

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