Polyester chain length composite

Like other emulsifiers, an EUP forms micelles at a critical micelle concentration (CMC). For comonomer-free EUP-emulsions of the (MA+HD)- type the CMC is about 5 X 10"4 g/ml [115,118]. The CMC depends on the composition and chain length of the polyester, the presence of an electrolyte [118] and the temperature. 

Grubelrrik A, WiesU L, Furrer P, Rentsch D, Hany R, Meyer VR (2(X)8) A simple HPLC-MS method for the quantitative determination of the composition of bacterial medium chain-length polyhydroxyalkanoates. J Sep Sd 31 1739-1744 Ha CS, Cho WJ (2002) Miscibility, properties and biodegradabiUty of microbial polyester containing blends. Prog Polym Sd 27 759-809... 

Initially, it was expected that the use of fatty acids was the most interesting way to produce and control these materials composition, once the polyester composition reflects the carbon chain length from the offered source. When the main source is nonanoic acid, for example. Pseudomonas oleovorans produces PHAmcl composed of 3-hydroxynonanoate predominantly. However, it was discovered in the 90s that a group of Pseudomonas accumulates PHAmcl from carbohydrates. When produced from carbohydrates, PHAmcl presents 3-hydro)ydecanoic acid (HD) as the main constituent and other... 

This phenomenon is attributed to the melting point of the material - a correlation already demonstrated by Tokiwa and co-workers for different aliphatic polyesters [79]. In aliphatic-aromatic copolyesters, the melting behaviour is mainly determined by the length of the aromatic sequences in the polymer chains, which depends both on the composition and structure [86, 87]. For many aliphatic polyesters, a correlation of the degradability with the melting point was observed [2]. Marten [86] interpreted it as a decrease in the mobility of the polyester chains at lower temperatures in this situation the polymer chains are highly fixed in the polymer crystals and cannot adjust easily into the active sites of the extracellular enzymes. A random insertion of some aromatic monomers in aliphatic polymer chains disturbs the formation of crystals. 

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