IntroductionThe bacterial copolyester of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) has attracted industrial attention as a possible candidate for large-scale biotechnological production, since the copolyester is an environmentally degradable thermoplastic'). The copolyester has been produced from propionic acid in Alcaligenes eutrophus, and the range of compositions has been shown to vary from 0 to 47 mol-Vo 3HVRecently, we have found that copolyesters with a wide range of compositions up to 90 mol-qo of 3HV units are produced in A . eutrophus by using pentanoic acid as carbon source4). This communication reports the biosynthesis of an interesting terpolyester of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and Shydroxyvalerate (5HV) in A . eutrophus from 5-chloropentanoic and pentanoic acids. Experimental partA. eutrophus (NCIB 11599) was first grown at 30°C in a nutrient-rich medium (100 cm3) containing 1,0 g of yeast extract, 1,0 g of polypeptone, 0,5 g of meat extract, and 0,5 g of (NH&S04. The cells were harvested after 24 h and washed with water. Under these culture conditions an accumulation of polyesters in the cells was not observed. To promote polyester synthesis, about 0,4 g quantities of the washed cells were transferred into a nitrogen-free mediums) containing 5-chloropentanoic acid (ClCH2CH2CH2CH2COOH) and pentanoic acid (CH,CH2CH2CH2COOH). The cells were cultivated in this medium (100 cm3, pH = 7 3 ) for 48 h at 30 "C, harvested by centrifugation, washed with acetone, and finally dried under vacuum at room temperature. Polyesters were extracted from the dried cells with hot chloroform in a Soxhlet apparatus and purified by reprecipitation with hexane.The ' H NMR spectra of polyester samples were recorded on a JEOL GX-500 spectrometer operating at 500 MHz, using a CDCl, solution of polyester (5 mg/cm3). The spectra were obtained at 27OC, 45 pulse ( 3 3 ps), 6,O s pulse repetition, 7000 Hz spectral width, 32K data points, and 128 accumulations. The I3C NMR spectra of polyesters were recorded on a JEOL FX-100 spectrometer operating at 25 MHz, using a CDCl, solution of polyester (50 mg/cm3). The spectra were obtained at 27 "C, 45 O pulse (8,5 ps), 5,O s pulse repetition, 5000 Hz spectral width, 8 K data points, and 10000 accumulations. \ 0173-2803/87/$01 .OO8 h) Tab. 1. Biosynthesis of terpolyesters of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and 5-hydroxyvalerate (5HV) in Alculigenes eutrophus at 3OoC Sample Wt. of carbon sourcea) in g Wt. of dry Polyester Polyester compositionc) in mol-yo [tll d, cells in g contentb)

Unusual copolyesters of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) with a range of compositions varying from 0 to 49 mol % 4HB were produced by Alcaligenes eutrophus in a nitrogen-free culture solution of 4-hydroxybutyric or 4-chlorobutyric acid. The copolyesters were characterized by solution NMR, solid-state 13C NMR, and differential scanning calorimetry. The compositions of the copolyesters were determined by 500-MHz NMR and two-dimensional homonuclear ( ) correlated spectroscopy. The copolymers were shown to have a random sequence distribution of 3HB and 4HB units by analysis of the 125-MHz 13C NMR spectra. The solid-state 13C NMR spectra and thermal analyses showed that the crystallinity of copolyester decreases with an increase in the fraction of 4HB units.

No abstract

Poly(/3-hydroxybutyrate) (PHB) and a copolyester of /3-hydroxybutyrate and /3-hydroxyvalerate are isolated from Alcaligenes eutrophus H16 grown in nitrogen-free culture media containing CHgCOONa and CHgCH2COONa as carbon sources. The chain dynamics of PHB (Mw = 420000) in chloroform are studied by 13C NMR measurement at 25 MHz. The carbon-13 spin-lattice relaxation times (TJ and nuclear Overhauser enhancements (NOE) indicate that the average correlation times (tc) for segmental motion of the PHB molecule are in the range (6-8) x 10_u s at 27 °C, as expected for flexible linear polymers. The conformational structure generated by rotation about CH2-CH bonds of PHB is determined in chloroform and dimethylformamide over a temperature range of 20-100 °C by analysis of vicinal coupling in the 500-MHz NMR_spectra. In both solvents the gauche (G) and trans (T) conformers are found to exist predominantly, the G conformer being suppressed. The sequence distributions of the monomeric units in the copolyester of /3-hydroxybutyrate and /3-hydroxyvalerate are determined by analysis of 125-MHz 13C NMR spectra. The diad and triad sequence distributions are accounted for in terms of first-order Markov statistics.

Three kinds of MgC12-supported TiCI, catalysts (ester-free, ethyl benzoate (EB, monoester) and dibutyl phthalate (DNBP, diester) as internal donors) were prepared. Polymerization of propylene was carried out using these catalysts with and without phenyltriethoxysilane (PTES) as an external donor. Significant differences were observed in the kinetic behavior of polymerization among ester-free, monoester, and diester systems. Addition of PTES, however, did not change the kinetic behavior. The polymers produced were separated into three fractions by extraction with boiling heptane and octane, and the molar mass distribution (MMD) curves were measured for these three fractions. The heptane-insoluble, isotactic polymer obtained in the absence of PTES was found to consist of two fractions, octane-soluble and -insoluble. The octane-soluble polymer having lower molar mass contained appreciable amounts of syndiotactic stereoblocks in the chains, whereas the octaneinsoluble polymer did not contain such stereoblocks. Addition of PTES drastically increased the octaneinsoluble fraction without changing the average molar mass. On the other hand, the MMD curve for the heptanesoluble, atactic polymer gradually shifted to the lower molar mass range with an increase in the concentration of PTES. From these results, the effects of internal and external donors on catalyst activity and stereospecificity were discussed putting emphasis on the differences between monoesters and diesters.

Copolyesters of 3-hydroxybutyrate (B) and 3-hydroxyvalerate (V) are isolated from Alcaligenes eutrophus H16 grown in nitrogen-free culture media containing the sodium salts of acetate and propionate. The content of V units in the copolyesters increases with increasing mole fraction of propionate to acetate in the culture medium. The copolyester is formed even when propionate is used as the sole carbon source, and the content of V units increases up to 45 mol % with increasing concentration of propionate in the medium. The biosynthetic pathway of the copolyester is investigated by using [l-13C]acetate, [2-13C]acetate, and [l-13C]propionate as carbon sources. The use of 13C-labeled acetate and propionate results in the formation of copolyesters specifically labeled with 13C.

The structure of an end-grafted polymer layer immersed in poor solvent is investigated through Monte Carlo simulation based on Edward's Hamiltonian. When the solvent quality becomes sufficiently poor, lateral inhomogeneities are observed to develop in the monomer density in the direction parallel to the grafting plane. A micro-phase-separated conformation is observed at long times. The length scale characteristic of the micro-phase structure is found to be consistent with a two-dimensional random walk. The simulation gives results consistent with the stability line predicted by Yeung, Balazs and Jasnow (Macromolecules, 26 (1993) 1914).

We have studied the equilibrium structure of a grafted polymer layer composed of two distinct species of homopolymers, the “binary brush”, in various solvent conditions. By using a coarse-grained simulation method that involves direct calculation of the Edwards hamiltonian, we are able to simulate much larger systems than would otherwise be possible with a more standard lattice simulation. If the two species are made sufficiently immiscible, we find lateral binary microphase separation over a wide range of solvent conditions. Due to the presence of solvent, we find a stage where the brush expands in a laterally homogeneous manner as immiscibility increases. In this stage, laterally averaged quantities are well-described by a single solvent−related parameter: a modified excluded volume parameter. This is followed by lateral microphase separation in which the brush volume remains relatively constant. In ϑ solvent, this phase separation sets in at a degree of immiscibility consistent with a mean field prediction for melt layers. The onset of phase separation is delayed as solvent quality increases. Furthermore, a reduction in solvent quality results in a stronger crossover between mixed and phase-separated configurations. Under poor solvent conditions, we find interesting structural variations as a result of the combination of phase separation from solvent and phase separation of the two species.