Florian Stempfle

Long-chain linear C 19 and C 23 Monomers and Polycondensates from unsaturated fatty acid esters

Isomerizing alkoxycarbonylation of methyl oleate and ethyl erucate, respectively, yielded dimethyl 1,19-nonadecanedioate and diethyl 1,23-tricosanedioate in >99% purity. With [κ2-(P P)Pd(OTf)][OTf] as a defined catalyst precursor (PP = 1,2-bis[(di-tert-butylphosphino)methyl]benzene) the reaction can be carried out without the need for additional added diphosphine. Saponification of the diesters yielded 1,19-nonadecanedicarboxylic acid and 1,23-tricosanedicarboxylic acid in >99% purity. By ruthenium-catalyzed reduction of the diesters with H2, 1,19-nonadecanediole and 1,23-tricosanediole were formed in high yield and purity (>99%). From the latter, 1,19-nonadecanediamine and 1,23-tricosanediamine were generated. Polyesters with commercially available shorter-chain petrochemical or renewable diols exhibit high melting points due to the crystallizable long-chain methylene segments from the dicarboxylic acid component, e.g., poly[1,6-hexadiyl-1,23-tricosanedioate] Tm 92, Tc 75 °C. Thermal properties of nove...

Long-Chain Aliphatic Polymers To Bridge the Gap between Semicrystalline Polyolefins and Traditional Polycondensates

Other than their established short-chain congeners, polycondensates based on long-chain difunctional monomers are often dominated by the long methylene sequences of the repeat units in their solid-state structures and properties. This places them between traditional polycondensates and polyethylenes. The availability of long-chain monomers as a key prerequisite has benefited much from advances in the catalytic conversion of plant oils, via biotechnological and purely chemical approaches, likewise. This has promoted studies of, among others, applications-relevant properties. A comprehensive account is given of long-chain monomer syntheses and the preparation and physical properties, morphologies, mechanical behavior, and degradability of long-chain polyester, polyamides, polyurethanes, polyureas, polyacetals, and polycarbonates.

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-(tBu2 PCH2)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.

Which Polyesters Can Mimic Polyethylene

Self-metathesis of erucic acid by [(PCy(3))(η-C-C(3)H(4)N(2)Mes(2))Cl(2)Ru = CHPh] (Grubbs second- generation catalyst) followed by catalytic hydrogenation and purification via the ester yields 1,26-hexacosanedioate (>99% purity). Polyesterification with 1,26-hexacosanediol, generated from the diester, affords polyester-26,26, which features a T(m) of 114 °C (T(c) = 92 °C, ΔH(m) = 160 J g(-1)). Ultralong-chain model polyesters-38,23 (T(m) = 109 °C) and -44,23 (T(m) = 111 °C), generated via multistep procedures including acyclic diene metathesis polymerization, underline that melting points of such aliphatic polyesters do not gradually increase with methylene sequence chain length. Available data suggest that to mimic linear polyethylenes thermal properties, even longer sequences, amounting to at least four times a fatty acid chain, fully incorporated in a linear fashion are required.

Long-chain aliphatic polyesters from plant oils for injection molding, film extrusion and electrospinning

The polycondensation of long-chain α,ω-diesters with long-chain α,ω-diols, prepared by means of catalytic conversion of plant oils, affords linear aliphatic polyesters. They contain both long crystallizable polyethylene-like hydrocarbon segments and ester moieties in the backbone. In a convenient catalytic one-step process a high-purity polycondensation grade dimethyl-1,19-nonadecanedioate monomer is obtained directly from the technical grade methyl ester of high oleic sunflower oil. Likewise, dimethyl-1,23-tricosanedioate is derived from methyl erucate. The successful scale-up renders both intermediates available on a 100 g scale. Injection molded parts of polyester-19.19 and -23.23 with a number average molecular mass of Mn = 3 × 104 g mol−1 possess an elongation at break of >600% and a Youngs modulus of 400 MPa. Electrospinning produces non-woven meshes. The polyesters prepared even enable film extrusion and represent new blend components for a variety of thermoplastics including polyethylene.

Long-Chain Polyacetals From Plant Oils

Plant oil-derived α,ω-diacetals are polycondensated to the novel polyacetals [OCH(2) O(CH(2))(y)](n) (y = 19 and 23) with molecular weight of ca. M(n) = 2 × 10(4) g mol(-1). The long methylene sequences provide substantial melt and crystallization temperatures (T(m) = 88 °C and T(c) = 68 °C for y = 23), and rates of hydrolytic degradation are dramatically lower for the long-chain polyacetals versus a shorter chain analogue (y = 12) studied for comparison.

Promotion of Selective Pathways in Isomerizing Functionalization of Plant Oils by Rigid Framework Substituents

The 1,2-(CH2 P(1-adamantyl)2 )2 C6 H4 (dadpx) coordinated palladium complex [(dadpx)Pd(OTf)2 ] (1) is a catalyst precursor for the isomerizing methoxycarbonylation of the internal double bond of methyl oleate, with an unprecedented selectivity (96 %) for the linear diester 1,19-dimethyl nonadecanedioate. Rapid formation of the catalytically active solvent-coordinated hydride species [(dadpx)PdH(MeOH)](+) (3-MeOH) is evidenced by NMR spectroscopy, and further isolation and X-ray crystal structure analysis of [(dadpx)PdH(PPh3 )](+) (3-PPh3 ). DFT calculations of key steps of the catalytic cycle unravel methanolysis as the decisive step for enhanced selectivity and the influence of the rigid adamantyl framework on this step by destabilization of transition states of unselective pathways.

Selective isomerization–carbonylation of a terpene trisubstituted double bond

Selective catalytic carbonylation of the trisubstituted double bond of citronellic acid is enabled via an isomerization–functionalization approach. Alkoxycarbonylation with [{1,2-(tBu2PCH2)2C6H4}Pd(OTf)2] as a catalyst precursor occurs with >97% selectivity for the terminal diester dimethyl-3,7-dimethylnonane-dioate. This prevails much over the typical cationic methoxyaddition. The reactive primary carboxy group formed allows for e.g. the preparation of the high molecular weight novel polyester poly[3,7-dimethylnonanediyl-3,7-dimethylnonanedioate].

Thermoplastic polyester elastomers based on long-chain crystallizable aliphatic hard segments

A plant-oil derived long-chain (C23) α,ω-dicarboxylic acid and the corresponding diol provide entirely aliphatic hard segments in segmented thermoplastic polyester elastomers, with poly(tetramethylene glycol) (PTMG) or carbohydrate-based poly(trimethylene glycol) (PPDO) soft segments. Physical crosslinking is provided by their polyethylene-like crystallinity. Compared to materials derived from mid-chain (C12) analogs, thermal properties are significantly enhanced, with melting points up to 96 °C. These novel materials feature high ductility values in combination with a good elastomeric behavior.