Poly(3-hydroxyalkanoate) sulfonate: From nanoparticles toward water soluble polyesters

Abstract

A series of amphiphilic biodegradable polyesters based on short chain lengths, scl-PHAs, or unsaturated medium chain lengths poly(3-hydroxyalkanoate)s, mcl-PHA, bearing sulfonate groups (SO3−) have been synthesized using click chemistry. First, well-defined PHAs oligomers containing alkene or alkyne end groups were prepared by transesterification from natural polyesters using allyl alcohol or propargyl alcohol and by acid-catalyzed methanolysis in the case of unsaturated mcl-PHAs containing vinyl groups on the side chains. Radical mediated thiol–ene or thiol–yne reactions were then used to functionalize all PHAs oligomers using 3-mercapto-1-ethanesulfonate under photochemical initiation. This straightforward and highly efficient modification was confirmed by 1H NMR spectroscopy. The influence of the nature of PHAs and the molar composition of the ionic oligoesters on the self-assembled behavior in aqueous media has been studied. When the molar ratio of sulfonate groups is about 27% the ionic polyester is totally soluble in water for molar masses ranging from 5000 to 223,000gmol−1. Under 27% of sulfonate groups content, particles were obtained with different diameters (118–1746nm), depending on the nature of polyester, and short or medium chain lengths PHAs.