Total monomer concentration

Baker, JP Hong, LH Blanch, HW Prausnitz, JM, Effect of Initial Total Monomer Concentration on the Swelling Behavior of Cationic Acrylamide-Based Hydrogels, Macromolecules 27, 1446, 1994. 

First, it was necessary to determine the position of the maxima on the plots of TBSM — MA copolymerization rate vs. composition of the monomer mixture at various total monomer concentrations. The observed shift of the maxima of the rate as a function of the dilution of the monomer mixture toward higher MA concentrations is a consequence of a complex mechanism, i. e. both free and com-... 

The methods of gel synthesis, immobilization of monomer conjugated enzyme, assay of enzyme activity, and determination of gel water content have been published elsewhere (4,5). A schematic of the synthesis is shown in Fig. 1. The gel compositions are identified as NA-100" (100% NIPAAm), "NA-95" (95% NIPAAm, 5% AAm), NA-90 (90% NIPAAm, 10% AAm) and "NA-85" (85% NIPAAm, 15% AAm) all are based on mole percents of monomers. Total monomer concentration was always 1.75 M. The experiment to determine the temperature dependence of enzyme activity was carried out after the enzyme reversibility experiment. 

Both the cross-propagation and complex mechanisms may be operative in alternating copolymerizations with the relative importance of each depending on the particular reaction system. The tendency toward alternation, with or without added Lewis, acid, is temperature-and concentration-dependent. Alternation decreases with increasing temperature and decreasing total monomer concentration since the extent of complex formation decreases. When the alternation tendency is less than absolute because of high reaction temperature, low monomer concentration, absence of a Lewis acid, or an imbalance in the coordinating abilities of the two monomers, copolymerization proceeds simultaneously by the two mechanisms. The quantitative aspects of this situation are considered in Sec. 6-5. 

Ideal Mixed Micelles. The Critical Micelle Concentration (CMC) is the lowest surfactant concentration at which micelles form the lower the CMC, the greater the tendency of a system to form micelles. When the total surfactant concentration equals the CMC, an infintesimal fraction of surfactant is present as micelles therefore, the CMC is equal to the total monomer concentration in equilibrium with the micellar pseudo—phase. The CMC for monomer—micelle equilibrium is analogous to the dew point in vapor—liquid equilibrium. 

The total monomer concentration of a binary mixture o-f two similarly structured sur-factants o-f like charge (an ideal system) lies between the CMC s o-f the individual sur-factants involved -for total sur-factant concentrations at or above the mixture CMC. Analogously, the vapor pressure of a mixed ideal liquid is intemediate between the vapor pressures of the components of which it is composed, whether there is substantial liquid present or the system is at the dew point (where an infintesimal amount of liquid is present). 

Table 1. Total Monomer Concentrations and Micellar Compositions For a Binary SurFactant System at Various Deviations From Ideality...

Systems with low monomer concentrations are o-f value when micelles are participating in use-ful processes directly (e.g., solubilization), where monomer is "wasted" sur-factant. However, o-f ten the monomer composition as well as total monomer concentration is important, when the monomer is participating in important processes and each component interacts dif-ferently (e.g., adsorption). The sur-factant combinations discussed here can result in low monomer concentrations and the model outlined can predict the monomer concentration o-f each sur-factant species. 

Butler et al. have reported crosslinking leading to gelation for the DAD-MAC/AAM copolymerization at a total monomer concentration of 4 mol L"1 and 40 °C [66]. However, gelation only occurred for 20/80 DADMAC/AAM monomer... 

The gel was formed by mixing equal volumes of a solution of 20% (w/v) total monomer concentration... 

Separations of complex steroid mixtures were achieved recently by Que et al. [76] using both isocratic and gradient elution. Mass spectrometric detection gave femto-mole detection limits while laser-induced fluorescence of dansylated ketosteroids ranged in attomole levels (Fig. 10.16). Monolithic column packings were used with a 35 cm (25 cm packed bed) x 100 pm i.d. capillary packed with a polymer prepared from 5% T (total monomer concentration), 60% C (total crosslinker concentration), 3% polyethylene glycol, 10% vinylsulfonic acid and 15% lauryl acrylate. Details of the monolithic column preparation can be found in refs. 36,76, and 193. Similar monolithic columns can be used for the separation of bile acids [194],... 

As seen in Equation (7.118), the copolymer and the feed compositions vary with the conversion during the polymerization process. The drift of a feed composition with the conversion favors the less reactive monomer. To obtain F, at different conversions, it is necessary to integrate the copolymer composition equation. Assume that the system contains a total of M moles of monomers and F, > f,. After dM moles of monomers have been polymerized, the copolymer contains F,dM moles of Mj. The feed then contains (M - dM)(fj - dl",) moles of M where the first term is the total monomer concentration and the second term is the mole fraction of M, in the feed. The mass balance of Mj reacted in the system is given by ... 

PNIPAAm terpolymers were obtained by free radical polymerization of NIPAAm, DMAAm, and DMIAAm (Scheme 2). Polymerization was initiated by AIBN using 1,4-dioxane as a solvent. DMAAm content was varied from 5 to 50 mol %. The total monomer concentration was 0.55 mol/L and the reaction was carried out at 70 °C for... 

To study the dynamics of the copolymerization it is necessary to know its reduced (i.e., divided by a total monomer concentration) rate. One can consider it to be practically independent on dilution [341, 342] and present it in the form of cp(x)/tp. It is convenient to take the characteristic time of homopolymerization of one of the monomers as a scaling factor. The dependence of the dimensionless... 

Chemical gels are covalently cross-linked polymer networks, featuring very high viscosity and well-defined pore structure. Polyacrylamide is the most widely used chemical gel material, usually cross-linked with N,N-methylene-bisacryl-amide (BIS). The pore size of the gel is determined by the relative concentration of monomer and cross-linker used during polymerization (%T, total monomer concentration and %C, cross-linker concentration as a percent of the total monomer and cross-linker concentration [34]). Highly cross-linked ( 5%C) poly-... 

Figure 10.5 The equilibrium monomer concentration as a function of the total monomers for a nucleation-elongation protein polymerization process described by Equations (10.7) and (10.13). The constant K = k+ /K is the association constant of a monomer to the polymer [A ]eq is the equilibrium free monomer concentration and A is the total monomer concentration. The variable a = 1 — K /K depends on the difference in equilibrium constants between elongation and nucleation steps. At a = 0 there is no difference in equilibrium constants at er = l nucleation is highly unfavorable compared to elongation and there is infinite cooperativity in the polymerization process.

The above equation can be rearranged to give an equation for free unbound monomer concentration (represented by the variable x = K[A eq) and the total monomer concentration (represented by the variable xt = K A0) ... 

When nucleation is highly unfavorable (i.e., a l) the polymer system exhibits a biphasic behavior depending on the total monomer concentration A0. In this case there is a sharp phase transition between the all-monomer state for A0 < 1 /K, where l/K is the critical monomer concentration. When A0 exceeds 1 /K the free monomer concentration stays fixed at [A eq = l/K. This type of nonsmooth behavior at x = lforcr = 1 is called a transcritical bifurcation in non-linear dynamics [191]. It is also widely known as phase transition in physics. Figure 10.5 shows that for a less than unity, the transition is smooth. Hence we see that the... 

In order to see which of the interactions, i.e. (1) or (2), could affect the copolymerization behavior, the copolymerization of MAOT and MAOA was carried out at different total monomer concentrations and at different temperatures. Table 7 shows the ratio of free monomer concentration to those of eomplexed monomers, calculated by using association constants at 1 1 monomer ratio. This table reveals that the eomplexed monomer to the free monomer ratios tend to be larger as the total mono-... 

Latex spheres with the same composition can be synthesized in a wide range of sizes by a similar procedure. Under the conditions described, the size of the spheres is dependent on the concentration of total monomer. As shown in Figure 1, the diameter of the spheres can be decreased from 3 0 nm to 35 nm by reducing the total monomer concentration from 35 to 3 A linear relation between these parameters is observed. 

Figure 1. Diameter of microspheres prepared by emulsion copolymerization (determined oy means of SEM) as a function of total monomer concentration...

In the course of this research we have al > briefly investigated the effect of monomer concentration on the reactivity ratios of isdrutylene and P-pinene. Three experiments have been carried out usit 60/40 (mole percent) isobutylene/(l-pinene charges with EtAlCl2 in EtCl at —110° and 8.3, S.0 and 2.8 mole/1 total monomer concentrations. Concentrations did not seem to affect reactivity ratic utder the coi tions employed. 

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