Functionalized oligoesters from poly(3-hydroxyalkanoate)s containing reactive end group for click chemistry: Application to novel copolymer synthesis with poly(2-methyl-2-oxazoline)

Well defined poly(3-hydroxyalkanoates) PHAs containing an alkyne end group were prepared in a one step reaction by direct alcoholysis from natural polyesters using propargyl alcohol. The reactions were allowed to proceed with dibutyltin dilaurate as catalyst at different concentrations from 0.5 up to 24% mol/mol of the alcohol. Oligoesters were obtained with molar masses ranging from 44,500 to 2700 g mol−1. Analysis of the MALDI-TOF mass spectra of the obtained oligomers has revealed the presence of alkyne group on one side and hydroxyl end group on the other side when the reaction was conducted in dried chloroform. The reaction rate of oligomer formation was depending on the nature of the PHAs and decreased with the length of the side chains. The Huisgen 1,3-dipolar cycloaddition has been investigated between the alkyne group of PHAs and 2-azido-2-deoxy-d-glucose or azido-poly(2-methyl-2-oxazoline) (N3-POXZ). The click reaction allowed the preparation of novel diblock copolymer PHA-b-POXZ soluble in water.