Chemical Modification of Chlorinated Microbial Polyesters

Abstract

Chlorination of microbial polyesters poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyoctanoate) (PHO) was carried out by passing chlorine gas through their solutions. The chlorine contents in chlorinated PHB (PHB-Cl) and chlorinated PHO (PHO-Cl) were between 5.45 and 23.81 wt % and 28.09 and 39.09 wt %, respectively. Molecular weights of the chlorinated samples were in the range of between one-half to one-fourth of the original values because of hydrolysis during the chlorination process. Thermal properties of the PHO-Cl were dramatically changed with an increase in its glass transition (T(g) = 2 degrees C) and the melting transition (T(m)). The T(g) of PHB-Cl varied from -20 to 10 degrees C, and its T(m) decreased to 148 degrees C. The chlorinated poly(3-hydroxyalkanoate)s (PHA-Cl) were converted to their corresponding quaternary ammonium salts (PHA-N(+)R(3)), sodium sulfate salts (PHA-S), and phenyl derivatives (PHA-Ph). Cross-linked polymers were also formed by a Friedel-Crafts reaction between benzene and PHA-Cl. The modified PHO derivatives were characterized by (1)H NMR and (13)C NMR spectrometry, Fourier transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry techniques.

Polyhydroxyalkanoates: Properties and chemical modification approaches for their functionalization

“…That study revealed that as the extent of chlorination increased, the PHA changed from soft and sticky to crystalline, brittle, and hard. The chlorinated PHA would serve as a very useful intermediate for blending of polymers and for further modifications such as carboxylation …”

Bioplastics from waste glycerol derived from biodiesel industry

“…The unsaturated side chains containing double bonds offer potentials for functionalizing these mcl-PHAs with improved properties or extended applications through chemical modification, such as chlorination, 126,127 crosslinking, [128][129][130][131] carboxylation, 131,132 hydroxylation, 133,134 and epoxidation. [135][136][137][138][139][140][141] Such modifications for the pedant groups make these mcl-PHAs functional with unusual physicochemical and mechanical properties.…”

Microbial Polythioesters

“…Like rubber, these PHAs were used for sulfur vulcanization to provide three‐dimensional network structures comprising a decrease of tensile modulus, tensile strength and tear resistance 34,35. Another example of chemically modified PHAs containing sulfur was the preparation of PHA sodium sulfate salts, which were obtained by treatment of chlorinated PHAs with sodium thiosulfate 36. However, the sulfur atoms of these PHAs were not incorporated biologically.…”