Novel poly(3-hydroxy butyrate) macro RAFT agent. Synthesis and characterization of thermoresponsive block copolymers

A novel reversible addition fragmentation transfer (RAFT) agent based on the poly-3-hydroxy butyrate (PHB) with threehydroxyl groups (PHB-R2) and thermoresponsive amphiphilic block copolymers derived from N-isopropyl acryl amide(NIPAM) are described. Hydroxylated PHB is obtained by the reaction between PHB and diethanol amine (DEA) to preparehydroxylated PHB (PHB-DEA). It is then reacted with a RAFT agent, 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid(DDMAT). Hydroxyl ends of the hydroxylated PHB are capped with carboxylic acid end of the trithiocarbonate. The blockcopolymers obtained by the polymerization of NIPAM initiated by PHB-R2 were characterized by1H NMR and physicochem-ical techniques. PHB content in the obtained block copolymers is varying between 14 and 45 wt%. The thermo-responsive PHB-PNIPAM block copolymers show the lower critical solution temperature (LCST) 28 and 30 °C while LCSTof the pure PNIPAMis 32 °C.