Recovery of poly-3-hydroxybutyrate (PHB) in three chlorinated solvents with or without acetone pretreatment and degradation of extracted PHB (99% pure) in hot chloroform were studied. When lyophilized Alcaligenes eutrophus biomass was used, the best results were obtained with acetone pretreatment and solvent reflux for 15 min in methylene chloride or chloroform. Recovered PHB had a 95% purity and molecular weights (w) of 1,050,OOO and 930,000 g/mol respectively. Further heating resulted in a serious & loss at reflux temperatures. Degradation of extracted PHB at 110°C in chloroform was due to random and chain-end scission, the former being predominant.

No abstract

Optically active β‐(1,1‐dichloroethyl)‐β‐propiolactone (CH3CCl2‐PL), β‐(1,1‐dichloropropyl)‐β‐propiolactone (C2H5CCl2‐PL), and β‐(1,1‐dichlorobutyl)‐β‐propiolactone (C3H7CCl2‐PL) were synthesized with enantiomeric excesses of 100, 100, and 84%, respectively. Polymerization was conducted in bulk and toluene solution, under vacuum, using mainly ZnEt2/H2O as initiator. Osmometry analyses indicate molecular weights in the range 10,000–25,000. The polymers thus prepared are semi‐crystalline and show large optical rotation values.13 C‐NMR was used to show that they have a high degree of isotacticity, indicating that little or no racemization occurs in the course of polymerization. Glass transition, melting and decomposition temperatures are given as a function of the size of the substituent, and their variations are discussed.

The polymerization of three optically active β‐1,1‐dichloroalkyl β‐propiolactones has been investigated in toluene, at 55°C, using aluminum triisopropoxide (Al(OiPr)3) as initiator in a range of monomer/initiator molar ratios smaller than 150. β‐1,1‐dichloroethyl β‐propiolactone polymerizes according to a living mechanism. However, the ability to polymerize decreases with an increase in the length of the alkyl substituent. For instance, β‐1,1‐dichloro‐n‐propyl β‐propiolactone is obtained only in low yields, whereas β‐1,1‐dichloro‐n‐butyl β‐propiolactone does not polymerize at all. Actually, each of the lactones investigated reacts with Al(OiPr)3 in an initiation step that obeys a coordination‐insertion mechanism. However, the size of the chloroalkyl substituent has a critical effect on the propagation: when the alkyl group contains more than two methylene units, the insertion of a second monomer becomes exceedingly slow.

In 1959, Smith, Winslow and Petersen have shown that upon mixing two transparent aqueous solutions of poly(ethy1ene oxide) (PEO) and poly(acrylic acid) (PAA), or poly(methacry1ic acid) (PMA), a white precipitate appears '). This precipitate is insoluble in water or in organic solvents; it has an x-ray pattern which is different from that of PEO; and its composition depends upon the concentration of the initial PEO and PAA (or PMA) solutions, but it normally contains between 30 and 50 wt.-To of PEO. From these observations, Smith, Winslow and Petersen concluded to the formation of a complex between PEO and PAA (or PMA).Following this initial study, a large number of authors have shown that the viscosity of PEO/PAA (and PEO/PMA) solutions goes through a minimum for a molar 50: 50 cornpo~ition~-~). This observation has been taken as indirect evidence for the formation of an equimolar complex between the two polymers.In this communication, we wish to report differential scanning calorimetry (DSQ measurements made on PEO/PAA precipitates which lead to evidence for the formation of a close-to but not-equimolar PEO/PAA complex. Experimental partThe PEO used in this study was a WSR-N-750 Polyox of Union Carbide having a molecular weight of 300 kg/mol. PAA was purchased from Aldrich Chemicals (# 18,1284) and it had a molecular weight of 250 kg/mol. Two separate aqueous PEO and PAA solutions were prepared with concentrations close to 0,5 wt.-Yo. The two transparent solutions were mixed in the desired proportions and a precipitate appeared immediately. After a contact time of 12 h, the precipitates were recovered by centrifugation at 2OOOO rpm and decantation of the sumatant solution. Three series of PEO/PAA precipitates were obtained from solutions having nominal mole ratios of 25 : 75, 50:50 and 75:25.The precipitates were dried in a vacuum oven at 70°C for several hours, and kept in a desiccator for a full year to allow the crystallization of PEO.DSC measurements were made using a Perkin-Elmer DSC-4 apparatus equipped with a TADS computer. The DSC was calibrated with ultrapure indium and the scans were made at a heating rate of 40 Wmin.For comparison purposes, a PEO/PAA mixture (mole ratio 1 : 1) was prepared mechanically, i. e. by mixing PEO and PAA powders and stirring vigorously, and also run in the DSC. This mixture was heated slowly six times at 400 K, kept each time 10 min at 400 K to allow a more intimate mixing and left three weeks at room temperature before the DSC scan.