Aromatic polymers include novel and extant functional materials although none has been produced from biotic building blocks derived from primary biomass glucose. Here we screened microbial aromatic metabolites, engineered bacterial metabolism and fermented the aromatic lactic acid derivative β-phenyllactic acid (PhLA). We expressed the Wickerhamia fluorescens gene (pprA) encoding a phenylpyruvate reductase in Escherichia coli strains producing high levels of phenylalanine, and fermented optically pure (>99.9 %) D-PhLA. Replacing pprA with bacterial ldhA encoding lactate dehydrogenase generated L-PhLA, indicating that the produced enzymes converted phenylpyruvate, which is an intermediate of phenylalanine synthesis, to these chiral PhLAs. Glucose was converted under optimized fermentation conditions to yield 29 g/l D-PhLA, which was purified from fermentation broth. The product satisfied the laboratory-scale chemical synthesis of poly(D-PhLA) with M w 28,000 and allowed initial physiochemical characterization. Poly(D-PhLA) absorbed near ultraviolet light, and has the same potential as all other biomass-derived aromatic bioplastics of phenylated derivatives of poly(lactic acid). This approach to screening and fermenting aromatic monomers from glucose exploits a new era of bio-based aromatic polymer design and will contribute to petroleum conservation and carbon dioxide fixation.
Controlling the chain growth process in non-living polymerization
reactions is difficult because chain termination typically occurs
faster than the time it takes to apply an external trigger. To overcome
this limitation, we have developed a strategy to regulate non-living
polymerizations by exploiting the chemical equilibria between a metal
catalyst and secondary metal cations. We have prepared two nickel
phenoxyphosphine–polyethylene glycol variants, one with 2-methoxyphenyl
(Ni1) and another with 2,6-dimethoxyphenyl (Ni2) phosphine substituents. Ethylene polymerization studies using these
complexes in the presence of alkali salts revealed that chain growth
is strongly dependent on electronic effects, whereas chain termination
is dependent on both steric and electronic effects. By adjusting the
solvent polarity, we can favor polymerizations via non-switching or
dynamic switching modes. For example, in a 100:0.2 mixture of toluene/diethyl
ether, reactions of Ni1 and both Li+ and Na+ cations in the presence of ethylene yielded bimodal polymers
with different relative fractions depending on the Li+/Na+ ratio used. In a 98:2 mixture of toluene/diethyl ether, reactions
of Ni2 and Cs+ in the presence of ethylene
generated monomodal polyethylene with dispersity <2.0 and increasing
molecular weight as the amount of Cs+ added increased.
Solution studies by NMR spectroscopy showed that cation exchange between
the nickel complexes and alkali cations in 98:2 toluene/diethyl ether
is fast on the NMR time scale, which supports our proposed dynamic
switching mechanism.
A cerium‐based metal‐organic framework, namely MOF‐589, was synthesized using benzoimidephenanthroline tetracarboxylic acid (H4BIPA‐TC) as an organic linker. Full characterization including single‐crystal and powder X‐ray diffraction analysis, thermogravimetrical analysis, scanning electron microscopy, and N2 adsorption measurements at low pressure and 77 K were carried out. The material was employed as an efficient heterogeneous catalyst for decomposition of methylene blue (MB) dye (40 ppm) in the presence of H2O2 in 15 minutes. Interestingly, comparison studies showed that the activity of MOF 589 was higher than that of other iron‐based heterogeneous and cerium‐based catalysts. Further experiments to clarify the MOF 589 activity indicated that the BIPA‐TC linker might have an important impact through a cooperative effect on the metal cluster. Control studies confirmed that the presence of catalyst was necessary for the reaction to occur and the catalyst recyclability. In particular, catalysis from leached cerium in the reaction filtrate is unlikely and the solid material could be reused at least eight times without a remarkable loss in activity.
Poly(l-phenyllactic acid)s (PlPhLAs) with high molecular weight were prepared by a direct polycondensation of l-phenyllactic acid in the presence of stable Lewis acids such as HfCl4·2THF under various reaction conditions. As a result, PlPhLAs with a number-average molecular weight (Mn) more than 100000 g mol−1 were obtained and showed specific optical rotation [α ]D25 of −46° and the glass-transition temperature (Tg) of 55 °C whose absolute values were higher than the reported values and was comparable with Tg of poly(l-lactic acid).
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