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Yao C.,CAS Changchun Institute of Applied Chemistry | Yao C.,University of Chinese Academy of Sciences | Liu D.,CAS Changchun Institute of Applied Chemistry | Li P.,Jinzhou City Health School | And 4 more authors.
Organometallics | Year: 2014

The amidino-modified N-heterocyclic carbene ligated lutetium bis(alkyl) complex 1, (Am-NHC)Lu(CH2SiMe3)2, was synthesized by treatment of (AmH-NHC-H)Br ((2,6-iPrC 6H3Nî - C(C6H5)NHCH 2CH2(NCHCHN(C6H2Me 3-2,4,6)CH)Br) with ((trimethylsilyl)methyl)lithium (LiCH 2SiMe3) and lutetium tris(alkyls) (Lu(CH 2SiMe3)3(THF)2) via double-deprotonation reactions and characterized by NMR spectroscopy and X-ray diffraction analysis. Under activation of an organoborate, complex 1 exhibited distinguished catalytic performance for the polymerization of isoprene with respect to high activity, 3,4-regioselectivity (99.3%), and livingness mode. In contrast to the systems reported to date, this system seemed not to be affected obviously by the polymerization temperature (0-80 C), solvents, monomer-to-initiator ratios (500-5000), and type of organoborate. The resultant polymers have high glass-transition temperatures (38-48 C) and moderate syndiotacticity (racemic enchainment triad rr 45%, pentad rrrr 20%). In addition, the living lutetium-polyisoprene active species could further initiate the ring-opening polymerization of ε-caprolactone to give selectively the poly(3,4-isoprene)-b-polycaprolactone block copolymers with controllable molecular weight (from 4.9 × 104 to 10.2 × 10 4) and narrow polydispersity. © 2014 American Chemical Society. Source


Zhao W.,CAS Changchun Institute of Applied Chemistry | Zhao W.,University of Chinese Academy of Sciences | Li C.,CAS Changchun Institute of Applied Chemistry | Li C.,University of Chinese Academy of Sciences | And 12 more authors.
Macromolecules | Year: 2014

A highly efficient strategy for synthesizing the first biocompatible polyesters with AIE characteristics has been established via immortal ring-opening polymerizations of cyclic esters bearing nonluminophores. In the process, the large excess hydroxyl-modified AIE active compound, acting as the chain transfer agent, attaches to the active rare-earth metal catalyst via the rapid-reversible exchange reaction to initiate the polymerization. Thus, more polyester chains appear to grow from one active metal species, and the AIE fragments are incorporated into the polymer chains at specific sites, in situ. The resultant polyesters have linear, block, or star-shaped microstructures mimicking those of the modified AIE compounds. The polymerization solutions can be directly fabricated to large-area thin solid films. The obtained PLA, for instance, emits fluorescence in water/THF mixtures owing to aggregation, the intensity of which is 2850-fold stronger than that in THF solution. This strategy avoids complicated preparation of AIE-active monomers and/or usage of toxic metal reagents for catalyzing the coupling reactions in order to introduce AIE-active fragments, which provides a straightforward approach to access AIE active or other functional polymers from hardly modified monomers. © 2014 American Chemical Society. Source


Xie H.,CAS Changchun Institute of Applied Chemistry | Xie H.,University of Chinese Academy of Sciences | Mou Z.,CAS Changchun Institute of Applied Chemistry | Mou Z.,University of Chinese Academy of Sciences | And 6 more authors.
Organometallics | Year: 2014

Alkane elimination reactions of phosphinimino-amine ligands HL 1-8 ((2,6-Me2-C6H3NH)C(Ph)î - CHPPh2(NAr) (Ar = C6H5 (HL1); 2,6-Me2-C6H3 (HL2); 2,6-Et 2-C6H3 (HL3); 2,6- iPr2-C6H3 (HL4); 2-OMe-C6H4 (HL5); 2-Cl-C6H 4 (HL6); 3-CF3-C6H4 (HL7); 4-MeO-C6H4 (HL8)) with MgnBu2, respectively, afforded a series of phosphinimino-amine-based complexes L1-8MgnBu(THF) (1-8) by releasing butane. Complexes 1-8 are phosphinimino-amine-ligated THF-solvated mono(alkyl)s, among which 1-4 adopt twisted tetrahedral geometries, whereas 5 contains a trigonal bipyramido geometry core. Complexes 1-8 all display high activity for the ring-opening polymerization of rac-lactide. The molecular weights of the resulting PLA are close to the theoretic values, and the molecular weight distributions are narrow. Moreover, these complexes show medium to high heteroselectivity, which, interestingly, increases with the decrease of the ligand steric hindrance; thus, complex 1, bearing a less bulky ligand, exhibits a heteroselectivity of Pr = 0.98, the highest value of a magnesium-based initiator achieved to date. The kinetics study showed that the polymerization rate is first-order dependent on both monomer and initiator concentrations, and the overall rate equation is -d[LA]/dt = 3.78 M-1 s-1 [LA][Mg]. © 2014 American Chemical Society. Source


Mou Z.,CAS Changchun Institute of Applied Chemistry | Mou Z.,University of Chinese Academy of Sciences | Liu B.,CAS Changchun Institute of Applied Chemistry | Wang M.,Jilin University | And 7 more authors.
Chemical Communications | Year: 2014

A highly isotactic stereoblock PLA has been obtained using the achiral heteroscorpionate zwitterionic zinc complexes as catalysts, for the first time, via a chain-end control mechanism. © the Partner Organisations 2014. Source

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