Application of Pd nanoparticles supported thermo-responsive poly(N-isopropylacrylamide–b–ionic liquid) in Heck coupling reaction

Free radical polymerization is one of the most employed chain growth polymerization technique due to the versatility in terms offunctionality and reaction conditions [1]. Block copolymers are one of the most important polymeric materials in technologicalapplications and theoretical research because of their exceptional properties due to the microphaseseparation [2]. Heck reaction has proved to be a powerful method for C-C bond formation in organic synthesis since it was reported by Heck in 1968 [3]. In the present study, the synthesis and characterization of thermo-responsive PNIPAM–b– PIL based on modified vinylpyridine-type ionic liquidvia RAFT techniqueis reported. At first, CTA, AIBN as initiator and N-isopropylacrylamide as monomer were used for the preparation of PNIPAM. Then PNIPAM is used as macro-CTA in order to produce PNIPAM-bpolyvinylpyridine. Afterward, PNIPAM-b-PIL is synthesized through the reaction of this block copolymer with1,3-propanesultone.These new polymers were characterized by FT-IR and 1H-NMR spectroscopy. Block of PNIPAM-b-PIL supported PdNPs is prepared through the reaction with Pd(OAc)2. This efficient catalyst was used for the production of a variety of substituted alkenes at 80 oCin short reaction times and good to excellent yields. The strength and dramatic improvement in this work is related to the extremely reusability of the catalyst upon to 20 times and more, using water as a green reaction media and different catalytic behaviors below and upon its lower critical solution temperature (LCST). The catalyst was characterized by ICP, UV-Vis spectrophotometry, X-ray diffraction.