ORIGINAL PAPER Novel poly(3-hydroxy butyrate) macro RAFT agent. Synthesis and characterization of thermoresponsive block copolymers Baki Hazer 1,2 & Melike Eren 2 & Yetkin Senemoğlu 2 & Tina Modjinou 3 & Estelle Renard 3 & Valérie Langlois 3 Received: 16 December 2019 /Accepted: 22 April 2020 # The Polymer Society, Taipei 2020 Abstract A novel reversible addition fragmentation transfer (RAFT) agent based on the poly-3-hydroxy butyrate (PHB) with three hydroxyl 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 prepare hydroxylated 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 block copolymers obtained by the polymerization of NIPAM initiated by PHB-R2 were characterized by 1 H 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 LCST of the pure PNIPAM is 32 °C. Keywords Poly (3-hydroxy butyrate) . RAFT polymerization . Polymerization kinetics . Thermoresponsive polymer . PNIPAM Introduction Some microorganisms accumulate poly(3-hydroxy alkanoic acid) (PHA) into their cell as energy reserve material from carbon sources [1]. Regarding pendant groups, PHA can be classified in three types: short chain length (scl) PHA, medium chain length (mcl) PHA and long chain length (lcl) PHA [2–8]. However, they need modification reactions because of their limited properties for industrial and medical applications [9–16]. PHAs are biodegradable, biocompatible hydrophobic semi crystalline polyesters. Mcl-PHAs are soft elastomeric polyes- ters and show low thermal resistant (ca. T m 50 °C) while scl- PHAs are brittle solid materials and show higher thermal re- sistance (ca. T m 170 °C). There are fine modification reactions to enhance hydrophilicity of the mcl-, and scl-PHAs. Among them, thiol-ene reactions [17, 18], esterification with PEG [19, 20], water soluble PHA-sulfonate [21, 22], and aminolysis reactions [23] were successfully used in order to obtain mcl- PHA with enhanced hydrophilicity. There are some modification reactions of mcl-PHAs. In a combined reaction of thiol terminated poly (N-isopropyl acryl amide) (PNIPAM) with thiol-ene reaction of unsaturated mcl- PHA results in a thermoresponsive copolymer of PHA. In this manner, chain transfer agent terminated poly (N-isopropyl acryl amide) (PNIPAM) converted to PNIPAM with thiol end is used in the thiol-ene click reaction with a random co- polymer of 3-hydroxydodecanoate (3HDD) and 3-hydroxy- 10-undecylenate [24]. In a recent work, a novel elastomer, polystyrene copolymer of a mcl-PHA, have been described [25]. There are also some reports on PHB modification reac- tions. Chlorination reactions of PHB result in chloride deriv- ative of PHB for further modification reactions [26, 27]. A recent published article reports optical properties of blend of the chlorinated PHB and PMMA [28]. PEG is a hydrophilic and biocompatible polymer. It is widely used in preparation of amphiphilic PHB derivatives [29]. Atom transfer radical po- lymerization of NIPAM and dimethyl amino ethyl * Baki Hazer bhazer2@yahoo.com; bkhazer@beun.edu.tr * Valérie Langlois langlois@icmpe.cnrs.fr 1 Department of Aircraft Airframe Engine Maintenance, Kapadokya University, 50420 Ürgüp, Nevşehir, Turkey 2 Department of Chemistry, Department of Nano Technology Engineering, Bülent Ecevit University, 67100 Zonguldak, Turkey 3 CNRS, Inst Chim & Mat Paris Est, UMR 7182, 2-8 Rue Henri Dunant, University of Paris Est, F-94320 Thiais, France Journal of Polymer Research (2020) 27:147 https://doi.org/10.1007/s10965-020-02133-1