Synthesis of Very Small Polymer Particles by Catalytic Polymerization in Aqueous Systems

The preparation of aqueous dispersions of very small particles (size < 30 nm) of various polymers (polyethylenes, stereoregular 1,2-polybutadiene, and polyalkenamers) by catalytic polymerization with a water-soluble catalyst, or with microemulsions of lipophilic catalysts is reviewed.     

Synthetic Polyester from Algae Oil

Current efforts to technically use microalgae focus on the generation of fuels with a molecular structure identical to crude oil based products. Here we suggest a different approach for the utilization of algae by translating the unique molecular structures of algae oil fatty acids into higher value chemical intermediates and materials. A crude extract from a microalga, the diatom Phaeodactylum tricornutum, was obtained as a multicomponent mixture containing amongst others unsaturated fatty acid (16:1, 18:1, and 20:5) phosphocholine triglycerides. Exposure of this crude algae oil to CO and methanol with the known catalyst precursor [{1,2‐(tBu₂PCH₂)₂C₆H₄}Pd(OTf)](OTf) resulted in isomerization/methoxycarbonylation of the unsaturated fatty acids into a mixture of linear 1,17‐ and 1,19‐diesters in high purity (>99 %). Polycondensation with a mixture of the corresponding diols yielded a novel mixed polyester‐17/19.17/19 with an advantageously high melting and crystallization temperature.     

Degradable and Recyclable Polyesters from Multiple Chain Length Bio- and Waste-Sourceable Monomers

Monomers sourced from waste or biomass are often mixtures of different chain lengths; e.g. catalytic oxidation of polyethylene waste yields mixtures of dicarboxylic acids (DCAs). Yet, polyesters synthesized from such monomer mixtures have rarely been studied. We report polyesters based on multiple linear aliphatic DCAs, present in chain length distributions that vary in their centers and ranges. We demonstrate that these materials can adopt high-density polyethylene-like solid state structures, and are ductile (e.g. E_t 610 MPa), allowing for injection molding, or film and fiber extrusion. Melting and crystallization points of the polyesters show no odd-even effects as dipoles cannot favorably align in the crystal, similar to traditional odd carbon numbered, long-chain DCA polyesters. Biodegradation studies of ¹³C-labelled polyesters in soil reveal rapid mineralization, and depolymerization by methanolysis indicates suitability for closed-loop recycling.     

Direct Synthesis of Imidazolium‐Functional Polyethylene by Insertion Copolymerization

Cationic imidazolium‐functionalized polyethylene is accessible by insertion copolymerization of ethylene and allyl imidazolium tetrafluoroborate (AIm‐BF₄) with phosphinesulfonato palladium(II) catalyst precursors. Imidazolium‐substituted repeat units are incorporated into the main chain and the initiating saturated chain end of the linear polymers, rather than the terminating unsaturated chain end. The counterion of the allyl imidazolium monomer is decisive, with the chloride analogue (AIm‐Cl) no polymerization is observed. Stoichiometric studies reveal the formation of an inactive chloride complex from the catalyst precursor. An effect of moderate densities (0.5 mol%) of ionic groups on the copolymers' physical properties is exemplified by an enhanced wetting by water.

     

Reactor blending with early/late transition metal catalyst combinations in ethylene polymerization

Ethylene is polymerized by heterobimetallic combinations of early and late transition metal catalysts. Dual combinations of zirconocenes and cationic nickel and iron catalysts with multidentate nitrogen‐donor ligands are described. Reactor blends of linear and branched ethylene homopolymers are obtained. With zirconocene / nickel complex catalyst combinations, addition of hydrogen selectively reduces the molecular weight of the linear polyethylene formed by the metallocene catalyst.