Activation of polymers

The flocculation activity of polymers increases with increasing molecular weight. Linear macromolecules are better flocculents than branched ones with the same total molecular weight. In the future the largest growth of polymer applications is expected to be in waste and water treatment, because of ecological problems. 

We modified polyanionic polymers by use of a grafting reaction of hydrophobic groups onto the polymers. After an extensive evaluation for the affinity of the hy-drophobically modified (hydrophobized) polymers to cell membrane, the immuno-stimulating activity of polymers was investigated by in vitro or ex vivo experiments. Consequently, the increased biological activity was found in the hydrophobized polymer, indicating that... 

Modes of attachment of functional groups to crosslinked polystyrene are discussed ( 1). Attention is drawn to improved stability and activity of polymer-bound reagents and catalysts incorporating dimethylene spacer between polystyrene aryl and functional group heteroatom, and the simplicity and versatility of their synthesis through high-conversion functional group modifications. 

Akashi and coworkers prepared small platinum nanoparticles by ethanol reduction of PtCl in the presence of various vinyl polymers with amide side chains [49]. These authors studied the effects of molecular weight and molar ratio [monomeric unit]/[Pt] on the particle sizes and size distributions by electron microscopy, and in some cases by the dispersion stability of the Pt colloids. The hydrogenation in aqueous phase of allyl alcohol was used as a model reaction to examine the change in catalytic activity of polymer-stabilized Pt colloids upon addition of Na2S04 to the reaction solution. The catalytic tests were performed in water or in Na2S04 aqueous solution at 25 °C under atmospheric pressure of... 

In order to compare the catalytic activity of polymer-supported... 

Carboxylated polymers can be prepared by mechanical treatment of frozen polymer solutions in acrylic acid (Heinicke 1984). The reaction mechanism is based on the initiation of polymerization of the frozen monomer by free macroradicals formed during mechanolysis of the starting polymer. Depending on the type of polymer, mixed, grafted, and block polymers with a linear or spatial structure are obtained. What is important is that the solid-phase reaction runs with a relatively high rate. For instance, in the polyamide reactive system with acrylic acid, the tribochemical reaction leading to the copolymer is completed after a treatment time of 60 s. As a rule, the mechanical activation of polymers is mainly carried out in a dry state, because the structural imperfections appear most likely here. 

Carraher, C. and Gebelein, C. 1982. Biological Activities of Polymers. ACS, Washington, DC. 

It is critical to remove mass transfer as an experimental variable if one wishes to compare activities of polymer-supported catalysts as a function of any other vairable. 

Parameters which affect the intrinsic activity of polymer-supported phase transfer catalysts are listed in Fig. 1. 

Only limited information is available on the effect of active site structure on activity of polymer-supported quaternary ammonium ion catalysts for alkylation of phenylacetonitrile (Eq. (7)). Dou and co-workers 10l) reported approximately the same activity for six different type 1 (2) and type 2 (14) Dowex105) ion exchange resins. Conversions of 5(1-70% were obtained in 10 h at 70 °C using 0.1 mol each of phenylacetonitrile and 1-bromobutane, 40 ml of 50% NaOH and 1 4 g (3.5-18 mequiv) of resin. The triphase mixtures were vigorously stirred by a method not reported. The similar results from resins of widely different cross-linking and porosity, both macro-... 

Polymer-supported crown ethers and cryptands were found to catalyze liquid-liquid phase transfer reactions in 1976 55). Several reports have been published on the synthesis and catalytic activity of polymer-supported multidentate macrocycles. However, few studies on mechanisms of catalysis by polymer-supported macrocycles have been carried out, and all of the experimental parameters that affect catalytic activity under triphase conditions are not known at this time. Polymer-supported macrocycle... 

The activity of polymer-supported crown ethers depends upon the degree of substitution of the polymer support. Fig. 11 reports dependence of kobsd on % RS and solvent for iodide displacement reactions (Eq. (4)) with catalysts 34,35 and 41149). The rate with 6% RS 41 was smaller than that with 17 % RS 35, though the former catalyst had a 7-atom spacer. Reduced % RS makes the catalysts more lipophilic, and results in the slower intraparticle diffusion of the KL Therefore, the lowest % RS catalysts... 

The activity of polymer-supported crown ethers is a function of % RS as shown in Fig. 11 149). Rates for Br-I exchange reactions with catalysts 34, 35, and 41 decreased as % RS increased from 14-17% to 26-34%. Increased % RS increases the hydro-philitity of the catalysts, and the more hydrated active sites are less reactive. Less contribution of intraparticle diffusion to rate limitation was indicated by less particle size dependence of kohMi with the higher % RS catalysts149). 

Table 10. Activities of Polymer-bound Crown Ether and Phosphonium Salts for Reactions of 1-Bromooctane in Toluene with Iodide or Cyanide Ions at 90 °C149)...

The activity of polymer-supported crown ethers depends on solvent. As shown in Fig. 11, rates for Br-I exchange reactions with catalysts 34 and 41 increased with a change in solvent from toluene to chlorobenzene. Since the reaction with catalyst 34 is limited substantially by intrinsic reactivity (Fig. 10), the rate increase must be due to an increase in intrinsic reactivity. The reaction with catalyst 41 is limited by both intrinsic reactivity and intraparticle diffusion (Fig. 10), and the rate increase from toluene to chlorobenzene corresponds with increases in both parameters. Solvent effects on rates with polymer-supported phase transfer catalysts differ from those with soluble phase transfer catalysts60. With the soluble catalysts rates increase (for a limited number of reactions) with decreased polarity of solvent60), while with the polymeric catalysts rates increase with increased polarity of solvent74). Solvents swell polymer-supported catalysts and influence the microenvironment of active sites as well as intraparticle diffusion. The microenvironment, especially hydration... 

Polymer-supported onium ions are relatively unstable under severe conditions, especially concentrated alkali154). Polymer-supported crown ethers and cryptands are stable under such conditions. In practice, they could be reused without loss of catalytic activity for the alkylation of ketones under basic conditions, whereas the activity of polymer-supported ammonium ion 7 decreased by a factor of 3 after two recycles of the catalyst147). 

The catalysts were conditioned in a 1-cyanooctane/aqueous NaCN mixture for 24 h at room temperature to avoid the induction period of the reaction. Rates (converted from a weight basis to a molar basis) with catalysts 47-49 significantly decreased as the % RS increased over the range 5 % to 50 %. With equal loadings activities of the polymer-supported amine oxides decreased with decreased lipophilicity of the catalysts (49 > 48 > 47). Lipophilic character appears to be an important factor for activity of polymer-supported cosolvents. 

It is the purpose of this article to discuss whether or not there are any differences between the chemical reactivity of a polymer-metal complex and that of the corresponding monomeric complex. Although various extensive investigations on polymer-metal complexes have been reported, most of these complexes are too complicated to be discussed quantitatively due to the nonuniformity of their structure. These compounds include not only complexes of macromolecules but also the structurally labile metal complex . Before detailed information can be obtained about the properties of polymer-metal complexes, and especially about the reactivity and catalytic activity of polymer-metal complexes, their structure must be elucidated. A polymer-metal complex having a uniform structure may be defined as follows ... 

Table 12. Catalytic activity of polymer-Cu complexes for oxidation of various substrates...

Substrate log [(Activity of polymer-Cu catalyst)/(Activity of monomeric... 

Metal complexes immobilized on crosslinked polymer matrices are hard to characterize by the customary physicochemical techniques, which is why no quantitative studies have been made on the catalytic activity of polymer complexes. 

Monomer Sign of optical activity of monomer at 589 mft Absolute configuration of monomer Sign of optical activity of polymer at 589 m/c Ref. 

As shown in Table 13, the sign of the optical activity of polymers of alkyl- or cycloalkyl-vinyl-ethers at 589 mp, in hydrocarbon solvent, can in general be foreseen on the basis of the absolute configuration of the asymmetric carbon atom that is the nearest to the ethereal group. A positive sign is observed when the asymmetric carbon atom of the monomer has absolute configuration (S), as in poly-a-olefins. 

Table 19. Optical activity of polymers of optically active...

Therefore the differences found in these cases between sign and values of the optical activity of polymers and of low-molecular-weight model compounds, can be substantially attributed to different conformational equilibria in the high-molecular-weight and in the low-molecular-weight compounds. 

Kristinsson KG, Jansen B, Treitz U et al. (1991) Antimicrobial activity of polymers coated with iodine-complexed polyvinylpyrrolidone. J Biomater Appl 5 173-184... 

Table 11. Comparison of the catalytic activities of polymers containing imidazole, carboxylate, hydroxyl moieties or two of them...

PospfSil J and NeSpurek S (in press) Highlights in the inherent chemical activity of polymer stabilizers, In Handbook of polymer degradation, 2nd edition, Hamid S H (Ed) Marcel Dekker Inc New York. 

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