Low molecular mass displacers

Gallant, S.R. and Cramer, S.M., Productivity and operating regimes in protein chromatography using low-molecular-mass displacers, J. Chromatogr. A, 771, 9, 1997. 

Kundu, A., Vunnum, S., and Cramer, S. M. (1995). Protected amino acids as novel low molecular mass displacers in ion exchange displacement chromatography. Biotechnol. Bioeng. 48, 452-460. 

Low Molecular Mass Displacer (L) Oligomeric Displacer (O) Polymeric Displacer (P)... 

Shukla AA, Barnthouse KA, Bae SS et al. Structural characteristics of low-molecular-mass displacers for cation-exchange chromatography. J Chromatogr 1998 814 83-95. 

Epoxy resins, which are used as adhesives, are also thermoset polymers that form by cross-linking when the two components of the resin are mixed. One component is a low-molecular-mass linear polymer formed by the reaction of the conjugate base of bisphenol A with epichlorohydrin. The nucleophilic oxygens of the phenolate dianion can either displace the chlorine or open the epoxide ring of epichlorohydrin. A slight excess of epichlorohydrin is used to keep these polymer chains short and to ensure that the linear molecules have epoxide groups at their ends. 

Intes, O. Renault, J.-H. Sinquin, C. Zeches-Hanrot, M. Nuzillard, J.-M. Fractionation of low-molecular-mass heparin by centrifugal partition chromatography in the ion-exchange displacement mode, J.Chromatogr.A, 2001, 918, 47-57. 

When the debinding temperature reaches higher values, generally beyond 180°C, the polymeric chains of the binders are snbjected to chemical degradation reactions. To the displacement of the binder in the liquid state is added the diffusion of the gas species within the porosity of the sample. The volatile species formed with low molecular mass (HjO, CO, CO2, CH4, light unsaturated hydrocarbons, etc.) are ehminated by diffusion and surface evaporation. 

The resulting catalyst was highly active for cyanide and acetate ion displacements on 1-bromobutane. As expected, soluble low molecular weight quaternary ammonium salts and a soluble quaternized linear poly(ethyleneimine) were even more active, presumably because they had no mass transfer and intraparticle diffusional limitations. These catalysts had a much higher density of charged sites (at least within the micro domains of the poly(ethyleneimine)) than any of the other active quaternary ammonium ion catalysts reported for nucleophilic displacement reactions. 

II) As soon as saturation is approached, discrimination sets in only the high-molecular-weight fraction is entirely adsorbed, whereas the smaller molecules have access only to the surface sites not occupied by the big ones. Consequently, low-molecular-weight polymer is left in the solution. As usually the adsorbed mass Increases with Increasing molecular weight of the adsorbate (see sec. 5.3b), preferential adsorption leads to an increase of the adsorbed mass. For the simple case of two fractions. F is linear in the solution concentration, until virtually all small molecules are displaced (see the rising part in flg. 5.8). 

Whenever the external vibrations produee large anisotropic displacement parameter values for the scattering atoms it will exaggerate the impact of any given value of Q. The phonon wing envelope will move to even higher frequencies and the response will broaden. Only two characteristics of a sample bear on its anisotropic displacement parameter (with samples at low temperatures), the effective molecular mass, Hef[, and the Einstein frequency, see ( 2.6.2.1). The lighter the... 

---