Pierre A. Berger

Synthesis and characterization of a fire-retardant polyester: Copolymers of ethylene terephthalate and 2-carboxyethyl(phenylphosphinic) acid

This article describes the synthesis and characterization of a polymer-bound nonhalogen fire retardant (NHFR). The reactive fire retardant used in this study is 2-carboxyethyl(phenylphosphinic) acid (CEPP); the polymer is poly(ethylene terephthalate) (PET). Fire-retardant and other modifiers of polymer properties must be bound to the polymer for use in fiber, medical, and food contact applications. Copolymers containing very high levels of CEPP have been prepared. Although fire retardancy in PET is achieved at relatively low levels of CEPP, our ability to produce copolymers with high levels of phosphorous makes them very attractive as polymeric nonfugitive fire retardants for other polymers, such as polycarbonate, nylon, acrylonitrile–butadiene–styrene (ABS), poly(butylene terephthalate) (PBT), and various polymer blends. This article also describes NHFR polyester compositions containing 4,4′-biphenyl dicarboxylic acid and CEPP. It is shown that an increase in aromaticity gained by incorporating the 4,4′-biphenyl dicarboxylic acid leads to higher limiting oxygen index values.

Polyhydroxyalkanoate accumulation in Burkholderia sp.: a molecular approach to elucidate the genes involved in the formation of two homopolymers consisting of short-chain-length 3-hydroxyalkanoic acids.

Burkholderia sp. accumulates polyhydroxyalkanoates (PHAs) containing 3-hydroxybutyrate and 3-hydroxy-4-pentenoic acid when grown on mineral media under limited phosphate or nitrogen, and using sucrose or gluconate as a carbon and energy source. Solvent fractionation and NMR spectroscopic characterization of these polyesters revealed the simultaneous accumulation of two homopolyesters rather than a co-polyester with random sequence distribution of the monomers [Valentin HE, Berger PA, Gruys KJ, Rodrigues MFA, Steinbüchel A, Tran M, Asrar J (1999) Macromolecules 32: 7389–7395]. To understand the genetic requirements for such unusual polyester accumulation, we probed total genomic DNA from Burkholderia sp. by Southern hybridization experiments using phaC-specific probes. These experiments indicated the presence of more than one PHA synthase gene within the genome of Burkholderia sp. However, when total genomic DNA from Burkholderia sp. was used to complement a PHA-negative mutant of Ralstonia eutropha for PHA accumulation, only one PHA synthase gene was obtained resembling the R. eutropha type of PHA synthases, based on amino acid sequence similarity. In addition to the PHA synthase gene, based on high sequence homology, genes encoding a β-ketothiolase and acetoacetyl-CoA reductase were identified in a gene cluster with the PHA synthase gene. The arrangement of the three genes is quite similar to the R. eutropha poly-β-hydroxybutyrate biosynthesis operon.

Synthesis and characterization of oligoethylene bibenzoate with hydroxyethyl end groups

In the process of exploring the potential advantage of 4,4′-biphenyl dicarboxylic acid (BDA) as a comonomer in poly(ethylene terephthalate) (PET), it was found that BDA needs to be derivatized for effective incorporation in PET specifically if high levels of BDA incorporation are desired. Bis-hydroxyethylbibenzoate (HEB) was synthesized with the anticipation that it would be compatible with both the continuous PET process which uses high-purity terephthalic acid as well as the batch PET process which utilizes dimethyl terephthalate. This article describes the synthesis of HEB and some of the oligoethylene bibenzoates produced in the process. Diethylene glycol is produced as an undesirable by-product during the reaction. In an effort to produce a minimum amount of diethylene glycol, a catalytic process was investigated which resulted in diethylene glycol levels of less than 0.5%. Quantitative analysis of diethylene glycol, performed by gas chromatography, and the oligomer structure studies performed by 1H- and 13C-NMR are described.