Jordi J. Bou

Biosynthesis and ultrasonic degradation of bacterial poly(γ-glutamic acid)

A study of the production of poly(γ-glutamic acid) (PGGA) by Bacillus licheniformis NCIMB 11709 grown on medium E in shake flasks at 30°C is reported. The enantiomeric composition of PGGA was found to be highly sensitive to the concentration of Mn++, especially when the ion is present in small amounts (⩽ 20 μM). Polymers with D-unit contents ranging from 10 to 90 % and Mw between 0.4 and 2.0 million g mol−1 were obtained for [Mn++] ranging from 0 to 1230 μM. Ultrasonic degradation was proven to be an effective method to reduce both the molecular weight and the polydispersity of naturally produced PGGA without disturbing the chemical constitution of the polymer.

Mark–Houwink Parameters of Biosynthetic Poly(γ-glutamic acid) in Aqueous Solution

A combined viscosity–light scattering–gel permeation chromatography (GPC) study was carried out on bacterially produced poly(γ-glutamic acid) (PGGA). PGGA samples with weight-average molecular weights ranging from 8×104 up to 8×105 g·mol–1 dissolved in phosphate buffer at 0.13 M ionic strength were used. It was found that the Mark–Houwink relation is acceptably obeyed, giving K and a values of 1.84×10–6 dL·g–1 and 1.16, respectively. As expected, GPC analysis showed that PGGA does not follow the universal calibration plot and that deviations can not be avoided by modifying the ionic strength.

Alternating copoly(ester amide)s derived from amino alcohols and L-tartaric and succinic acids

A set of copoly(ester amide)s (s-PEASTn) containing equal amounts of amide and ester groups has been synthesized from succinic and tartaric acids, and aliphatic linear amino alcohols with 2, 3 and 6 carbon atoms. In these mixed poly(ester amide)s the amino alcohol unit adopts a syndioregic orientation and the succinic and tartaric units alternate regularly along the polymer chain. These compounds were characterized by elemental analysis, SEC and FT-IR and 1 H/ 13 C NMR spectroscopy. s-PEASTn are stereoregular polymers which display optical activity in solution and are crystalline in the solid state with melting points between 90 and 160° C. They all are non-water soluble at room temperature but take up water in amounts up to 30% of their weights when exposed to a humid atmosphere.

Synthesis of heterotelechelic poly(ethylene glycol)s and their characterization by MALDI-TOF-MS

Departamento de Ingenieri´a Qui´mica, Universidad Polite´cnica de Catalun˜a,E. T. S. de Ingenieros Industriales, Diagonal 647, 08028 Barcelona, Spain(Received: October 2, 1998; revised: November 26, 1998)SUMMARY: Two heterotelechelic poly(ethylene glycol)s were synthezised by end group modification of a-hydro-x-hydroxy-poly(oxyethylene) (PEG). The first reaction route starts from heterobifunctionala-hydro-x-octadecanoyloxy-poly(oxyethylene) (400) and comprises the synthesis ofa-hydro-x-carboxymethoxy-poly(oxyethylene). The second pathway starts from homotelechelic PEG(400) and leads to a-(2-propenyl)-x-carboxymethylthio-poly(oxyethylene). Purification of the desired products was accomplished by means ofion exchange chromatography on DEAE Sephadex. PEG derivatives were characterized by means of NMR,IR, HPLC and GPC. MALDI-TOF-MS recorded in the reflectron mode served as a fine method that providesinformation on chemical composition as well as molecular weight.

Synthesis, characterization and degradability of polyamides derived from tartaric acid and diaminoethers

Abstract A series of novel polyamides derived from l or d -tartaric acid and α,ω-diaminoethers containing 1, 2, 3 or approximately 70 oxyethylene units in the main chain were synthesized and characterized. Polycondensation in solution of the diaminoethers with di-O-methyl tartaric acid activated as pentachlorophenyl ester was used for the synthesis of these poly(ether tartaramide)s. Polymerization degrees oscillated between 10 and 140 depending on the length of the oxyethylene segment. These polyamides are highly hygroscopic and soluble in water. They are semicrystalline with melting temperatures ranging from 50 to 190 °C, and thermally stable up to 250 °C. Chiro-optical properties were found to depend on the configuration of tartaric acid showing both high specific rotations and characteristic circular dichroism ellipticities. Definite X-ray diffraction patterns consistent with the crystalline nature of these polyamides were recorded. Racemates made of enantiomeric pairs were also examined and some evidence indicative of the existence of a crystalline structure different from that present in the optically pure components was found.

Stereoregular polyamides entirely based on tartaric acid

Two new stereoregular polyamides, namely PTA-LL and PTA-LD, derived from (2S,3S)-(−)-2,3-dimethoxy-1,4-butanediamine and (2R,3R)-(+)- or (2S,3S)-(−)-2,3-dimethoxybutanedioic acid are described. The two diastereoisomeric polymers contain two pairs of stereocenters in the main chain of the repeating unit, one in the diamine and the other in the diacid counterpart. L and D refer to the configuration of the tartaric acid unit from which they proceed. These polyamides were prepared by polycondensation in solution and were fully characterized by elemental analysis, DSC, and IR/NMR spectroscopies. Number average molecular weights around 30,000 were estimated by GPC and viscosimetry. Both compounds are soluble in water and display large optical activity. CD and 1H-NMR measurements in chloroform solution suggested the presence of definite secondary structures in this solvent. Solid samples were found to crystallize upon annealing and the crystal structure of both polyamides was investigated by X-ray diffraction. PTA-LL crystallized in an orthorhombic lattice in the space group P22121 whereas PTA-LD seemed to adopt a P1 triclinic structure. In both cases the polymer chain appears to be in a folded conformation more contracted than in the common γ-form of conventional nylons.

The crystal structure of nylon 3,5 and nylon 5,7: a comparative study

A comparative analysis of the crystal structure of nylon 3,5 and nylon 5,7 was carried out. Lamellar crystals of both compounds were grown from diluted solutions and examined by electron microscopy and X-ray diffraction. A structure with chains in fully extended conformation was the only modification found for nylon 3,5. A similar structure was found also for nylon 5,7 although the structure largely preferred by this nylon is the contracted γ-form. A rational explanation for the dissimilar behavior displayed by the two nylons was provided by a comparative estimation of their packing energies using molecular mechanics methods. Details concerning the displacement of sheets in nylon 3,5 and the arrangement of hydrogen bonds in the γ-form of nylon 5,7 were further unraveled by energy calculations. All these features were discussed with regard to the chemical constitution of the polymers and to the structures reported for other closely related nylons.

Synthesis of vegetable-oil based polymer by terpolymerization of epoxidized soybean oil, propylene oxide and carbon dioxide

Although carbon dioxide (CO2) is well known as one of the major green-house gases, it is also an economical C1 resource. Thus, CO2 has been regarded as an appealing starting material for the synthesis of polymers, like polycarbonates by the reaction with epoxides. Herein the reaction between natural epoxidized soybean oil (ESO), propylene oxide (PO) and CO2 under high pressure (4.0MPa) with the presence of Co-Zn double metal cyanide (Co-Zn DMC) catalyst was studied. Temperature and reaction time were varied accordingly and the products obtained were characterized by FTIR, GPC and 1H NMR. The results obtained indicate the formation of polycarbonates in the samples collected with yields vary from 60 to 85%. The number average molecular weight (Mn) of the resultant polymer prepared at reaction temperature of 80°C and reaction time of 6h can reach up to 6498g/mol.