Catalyzed by the (pyridylamido)hafnium/organoboron system, a series of halogen-functionalized isotactic polypropylenes were synthesized via the stereospecific copolymerization of propylene with ω-halo-α-alkenes. The (pyridylamido)hafnium/organoboron system has been proved to be a potent catalyst for propylene/ω-iodo-α-alkenes copolymerization, producing well-defined poly(propylene-coω-iodo-α-undecene)s with outstanding properties. The high molecular weight (M w > 100 kg mol −1 ) functional iPPs possessing abundant iodoalkene units (up to 11.7 mol %) and unimodal molecular weight distributions (M w /M n ≈ 2) could be easily obtained under mild conditions with excellent catalytic activity. High isotactic selectivity of monomers, including propylene and polar comonomer, was unexpectedly observed ([mmmm] > 99%). Moreover, based on the unique copolymerization process and the highly reactive sites on the copolymers, the halogen groups of the resultant copolymers could be easily transformed into other polar groups via click chemistry, and the new functional iPPs with high molecular weights and abundant polar groups could be efficiently obtained.

Synergistic osteogenesis promoted by magnetically actuated mechanical stimuli, induced by the nano-deformation of IO-OA/PLGA nanocomposites under a SMF.

A new catalyst system, i.e., nickel acetylacetonate/1,3-bis(diphenylphosphino)propane (Ni(acac)2/dppp), was explored to catalyze the Kumada catalyst transfer polycondensation (KCTP) of three fluorene monomers with different substituents at 9-position. The “living” nature of the polymerization was confirmed by polymerization kinetic studies, “monomer addition” experiment and block copolymerizations. As a result, poly(9,9-dioctylfluorene)s (PF8s) with the number-average molecular weights (M ns) in the range 2.8–62.2 kDa and polydispersity indices (PDIs) of ∼1.20 were successfully synthesized in a controlled manner. The syntheses of fluorene-fluorene and fluorene-thiophene diblock copolymers with M ns up to 46 kDa were also demonstrated. A complex, i.e. Ni(dppp)(acac)2, with an octahedral coordination geometry was isolated and confirmed by X-ray crystallographic analysis. The polymerization experiments indicated that the in situ formed Ni(dppp)(acac)2 should be the active catalyst. To the best of our knowledge, this is the first report on the controlled synthesis of polyfluorenes (PFs) via KCTP.

No abstract

No abstract

Poly(5,6-difluoro-2,1,3-benzothiadiazole-alt-9,9-dioctylfluorene) was successfully synthesized via direct arylation polycondensation of 5,6-difluoro-2,1,3-benzothiadiazole and 2,7-dibromo-9,9-dioctylfluorene. The reaction conditions were optimized, and a polymer with number-average molecular weight (M n ) of 41,000 was obtained by using Pd(OAc) 2 , P t Bu 2 Me-HBF 4 , pivalic acid, K 2 CO 3 , and toluene as catalyst, ligand, additive, base, and solvent, respectively. The polycondensation was also performed with 5,6-dioctyloxy-2,1,3-benzothiadiazole or 2,1,3-benzothiadiazole as the comonomer, and the results indicate that the introduction of electronwithdrawing fluorine atoms at the ortho-positions to the CAH bonds is essential for the reactivity of the direct arylation.

The controlled synthesis of poly(3-hexylthiophene)s (P3HTs) with number-average molecular weights (Mns) up to 350 kg mol(-1) has been realized with Ni(IPr)(acac)2 as the catalyst.

The facile and efficient functionalization of polynorbornene has been achieved through direct copolymerization of norbornene (NB) with 5-norbornene-2-yl acetate (NBA) or 5-norbornene-2-methanol (NBM) using a series of b-ketiminato Ni(II)-Me pyridine complexes 1-4 (Scheme 2) in the presence of B(C 6 F 5 ) 3 . Remarkably, the monomer conversion could reach up to about 96% in 10 min in the NB/NBA copolymerization. The copolymers with wide NBA contents (3.3-38.4 mol %) were obtained by variation of reaction conditions. These copolymers have high molecular weights (MWs) (M n ¼ 41.8-144 kg/mol) and narrow MW distributions (M w /M n ¼ 1.80-2.27). In the absence of alkyl aluminum compounds, a monomer conversion of 81% was observed in the NB/NBM copolymerization, and copolymers with NBM content in the range of 11.2-21.8 mol % were obtained by variation of reaction conditions. In addition, Ni(II)-Me pyridine complexes 2 was very active at a low B/Ni molar ratio of 6, while bisligand complex 6 bearing the same ligand just showed moderate efficiency at a high B/Ni molar ratio of 20. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 562-570, 2012