No abstract

Liquid/liquid separations using gravity and two phases of different density are a practical and viable way to recover, separate and reuse soluble polymer‐supported catalysts. Such separations are facilitated by using polymers that have phase‐selective solubility under biphasic conditions. Such polymers can be designed to be soluble either in a non‐polar or a polar phase. Since catalyst and ligand loading can be at a low mole percent level on the polymer, the polymer’s intrinsic solubility can be maintained with a variety of ligands and catalysts making such separation strategies general. Catalysis with such soluble polymer‐supported species can either be carried out under biphasic or monophasic conditions. In the former case, aqueous/organic, fluorous/organic or other biphasic regimes can be used. In the later case, thermomorphic or latent biphasic conditions can be employed. In either case, catalyst separation and recovery can be accomplished simply without using significant quantities of additional solvent.

The phase-selective solubility properties of polymer supports that could be used in thermomorphic and latent biphasic systems useful in synthesis and catalysis were evaluated using polymers tagged with either visible dyes or fluorescent probes. Heptane/DMF, heptane/90% ethanol-water, heptane/ethyl acetate, heptane/ethanol, and heptane/tert-butyl alcohol solvent mixtures were all studied as examples of thermomorphic or latent biphasic systems. A range of polymers including polyisobutylene (PIB), poly(tert-butylstyrene) (PTBS), poly(octadecyl acrylate) (PODA), and poly(octadecyl methacrylate) (PODMA) were tested for hydrophobic phase-selective solubility. The results of these studies are compared to prior work with polar and nonpolar poly(N-alkylacrylamide)s and polystyrene. Together with this prior work, these results show that a wide range of polymers and solvent mixtures can be used for the recycling of soluble polymer-bound catalysts, reagents, and sequestrants using either thermomorphic or latent biphasic separation strategies.

Organic chemistry Z 0200 Liquid/Liquid Biphasic Recovery/Reuse of Soluble Polymer-Supported Catalysts -[96 refs.]. -(BERGBREITER*, D. E.; SUNG, S. D.; Adv. Synth. Catal. 348 (2006) 12-13, 1352-1366; Dep. Chem., Tex. A&M Univ., College Station, TX 77842, USA; Eng.) -Nuesgen 43-236

Summary: Polyvinylpyrrolidone (PVP) is a commonly used polymer with many different applications in the pharmaceutical, cosmetic and food industries. However, the lack of reactive groups and the difficulty in copolymerizing the monomer, N‐vinylpyrrolidin‐2‐one (NVP) with most other monomers, limits the possibility of modifying the physical and chemical properties of the polymer. Monomers that are derivatives of NVP itself are expected to show small differences in radical reactivity as compared to the parent monomer and provide a way of adjusting the polymer properties without extensive compositional drift during copolymerization. Here we present the synthesis of two new functionalized NVP‐based monomers and their copolymerization with alkylated NVP‐monomers for the preparation of two functionalized PVPs with phase‐selective solubility in heptane. Both copolymers showed 99.99% selective solubility in heptane over DMF (thermomorphic system) and 99.99% in heptane over 90% EtOH‐H2O (latent biphasic system). These results suggest that the polymers could be used as soluble supports to facilitate recovery and recycling of catalysts or reagents from liquid/liquid systems after homogeneous reactions.Phase‐selectively soluble polyvinylpyrrolidone copolymer.magnified imagePhase‐selectively soluble polyvinylpyrrolidone copolymer.