Polymer support monodisperse

For example, polymer-supported CSPs with Pirkle-concept SOs (e.g. (S)-valine-3,5-dimethylaniIide) attached to monodisperse macroporous polymethaciylate beads gave reasonable enantioselectivity and efficiency for 3,5-dinitrobenzamido derivatives of a-amino acids under normal-phase conditions [368.370], It could be demonstrated that such a CSP based on polymeric particles provided enhanced enantioselectivities... 

Abstract Enantioselection in a stoichiometric or catalytic reaction is governed by small increments of free enthalpy of activation, and such transformations are thus in principle suited to assessing dendrimer effects which result from the immobilization of molecular catalysts. Chiral dendrimer catalysts, which possess a high level of structural regularity, molecular monodispersity and well-defined catalytic sites, have been generated either by attachment of achiral complexes to chiral dendrimer structures or by immobilization of chiral catalysts to non-chiral dendrimers. As monodispersed macromolecular supports they provide ideal model systems for less regularly structured but commercially more viable supports such as hyperbranched polymers, and have been successfully employed in continuous-flow membrane reactors. The combination of an efficient control over the environment of the active sites of multi-functional catalysts and their immobilization on an insoluble macromolecular support has resulted in the synthesis of catalytic dendronized polymers. In these, the catalysts are attached in a well-defined way to the dendritic sections, thus ensuring a well-defined microenvironment which is similar to that of the soluble molecular species or at least closely related to the dendrimer catalysts themselves. 

Thermoreversible polymer hydrogels also represent a medium for synthesis of nanosized zeolite crystals. This support is recyclable and stable in the temperature range of interest for zeolite synthesis. In aqueous media, the voids between monodisperse polymer spheres can serve as a nanoreactor for controlled growth [157]. Recycling of the support can be done via dissolution of... 

In this specific case, the colloid stabilizers are dendrimers, for instance, polyamidoamine (PAMAM), which are hyperbranched polymers that ramify from a single core and form a porous sphere [103, 104] (Scheme 17.1). Dendrimer-encapsulated nanoparticles (DENs) are synthesized by sequestering metal ions within appropriate dendrimers, and then by chemically reducing the resulting composite. They can be synthesized in various media, such as water or ethanol. The size of the nanoparticles is usually nearly monodisperse, and can be tuned by varying the metal-to-dendrimer ratio prior to reduction. Supported catalysts can then he prepared by immobilizing DENs onto a sohd support. As in the case of colloids, the last step, which consists in the removal of dendrimers hy thermal treatment, may lead to an increase in both the metal-particle size and particle-size distribution. 

In the neighborhood of their c, monodisperse multiarm stars in a good solvent are expected to crystallize. This is a consequence of the concentration-induced enhanced osmotic pressure which outbalances the elastic energy of the sUetched arms. A variety of crystalline phases have been predirted from an effective interactions approach using V r) of eqn [ 18]. At higher concentrations c c, the crystal shoirld melt due to the enhanced osmotic pressure, hence recovering the semidilute polymer solution behavior. However, these prediaions have not been supported convincingly by experimental evidence. It has been... 

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