CATALYTIC ACTIVITIES OF RARE-EARTH CALIXARENE COMPLEXES IN POLYMER SYNTHESES

The studies of our group on the catalytic activities of rare earth calixarene complexes in polymer syntheses are reviewed. Rare earth calixarene complexes are effect catalysts for the polymerizations of butadiene, isoprene, ethylene, styrene, propylene oxide, styrene oxide, trimethylene carbonate and 2,2-dimethyl-trimethylene carbonate.

RING-OPENING POLYMERIZATION OF TRIMETHYLENE CARBONATE BY CALIX[8]ARENE-NEODYMIUM

Ring-opening polymerization of trimethylene carbonate (TMC) with a rare earth calixarene compound as catalyst has been studied for the first time. The effect of TMC/Nd (molar ratio) and polymerization conditions were investigated in detail. It was found that calix[8]arene-neodymium is a highly effective catalyst for the bulk polymerization of TMC and gives high molecular weight (M-v = 60,000) polymer. The optimum conditions of TMC polymerization were found to be as follows:TMC/Nd (molar ratio) = 2,000, 80 degrees C, 16 h. The polymers were characterized by NMR, GPC and DSC. Studying the mechanism by NMR showed that the polymerization of TMC catalyzed by calix[8]arene-neodymium proceeds via a cationic mechanism.

Characterization of impurities in the bulk drug lisinopril by liquid chromatography/ion trap spectrometry

Two trace impurities in the bulk drug lisinopril were detected by means of high-performance liquid chromatography coupled with mass spectrometry(HPLC/MS) with a simple and sensitive method suitable for HPLC/MSn analysis. The frag-mentation behavior of lisinopril and the impurities was investigated,and two unknown impurities were elucidated as 2-(6-amino-1-(1-carboxyethylamino)-1-oxohexan-2-ylamino)-4-phenylbutanoic acid and 6-amino-2-(1-carboxy-3-phenylpro-pylamino)-hexanoic acid on the basis of the multi-stage mass spectrometry and exact mass evidence. The proposed structures of the two unknown impurities were further confirmed by nuclear magnetic resonance(NMR) experiments after preparative isola-tion.

Synthesis of α-Hydroxy-ω-Aminotelechelic Polypeptide from α-Amino Acid N-Carboxyanhydrides Catalyzed by Alkali-metal Borohydrides

It is reported that alkali-metal borohydrides （MBH4, M = Li, Na and K） are efficient catalysts for ring opening polymerization （ROP） of α-amino acid N-carboxyanhydrides （NCAs）. Polypeptides are prepared in quantitative yields with relatively narrow molecular weight distributions （MWDs = 1.1-1.5） which depend on the reaction temperature. End groups of the produced polypeptide are studied in detail by MALDI-ToF MS, IH-NMR, 13C-NMR, IH-1H COSY and IH-13C HMQC analyses. The results indicate that α-hydroxy-ω-aminotelechelic polypeptides are formed which are suitable for post- polymerization functionalization.

Mechanism of Janus Polymerization: A DFT StudyFig. S3 Energy profiles of anionic polymerization in Stage I under B3LYP/6-31G(d,p)(blue) and B3LYP/aug-cc-p VTZ//B3LYP/6-31G(d,p)(red). Scheme S1. Propagation process of CL/THF on cationic side in Stage I of J

Janus polymerization is featured as a combination of cationic and anionic growing ends in one living polymer chain. In the copolymerization of THF and CL catalyzed by lutetium triflates and initiated by propylene oxide, three stages are identified by kinetic study including(1) fast cationic polymerization with slow anionic one,(2) fast anionic polymerization with dormant cationic one, and(3)reactivation of cationic polymerization with coupling of anionic and cationic chain ends. In this work, density functional theory(DFT)calculation is employed to investigate the reaction details of ionic polymerization and dormancy. A “tripedal crow” configuration is proposed to illustrate the unique high-coordinated ligand exchange configuration in anionic polymerization in different stages. The trigger of dormancy is determined as chain structures rather than concentration of triflate anion according to both calculation and experimental results.

SYNTHESIS AND MAGNETIC PROPERTIES OF COMPLEXES OF A CONJUGATED HYPERBRANCHED POLYMER CONTAINING BITHIAZOLE RINGS

A novel conjugated hyperbranched polymer containing bithiazole rings （PBTADB） was synthesized by polycondensation of 1,3,5-benzenetricarboxaldehyde and 2,2＇-diamino-4,4＇-bithiazole （DABT）. The structure of the hyperbranched polymer was confirmed by FT-IR and 1H-NMR. PBTADB dissolved in organic polar solvents such as DMSO and NMP. Bithiazole tings were introduced to provide bidentate N-donor sites for binding metal ions. The metal complexes were prepared by chelation of the polymer with Co2＋ and Sm3＋. The magnetic behavior of coolcdination compounds was measured as a function of magnetic field strength （0-4.8 ×106 A/m） at 5 K and as a fimetion of temperature （5-300 K） at magnetic field strength of 2.4×106 A/re. The magnetic hysteresis loops of PBTADB-Sm3＋ and PBTADB-Co2＋ showed the typical ＇S＇ shape at 5 K with the Curie-Weiss temperature To = 96 K and 41 K respectively. The results show that they exhibit properties of soft ferromagnetic materials.

Synthesis of Poly[6-(2,6-bis(1＇-methylbenzimidazolyl)pyridin-4-yloxy)hexyl acrylate](PBIP) and Magnetic Property of Its Neodymium Complex(PBIP-Nd^(3＋))

Homopolymer（PBIP） containing 2,6-bis（1＇-methylbenzimidazolyl）pyridine（Me BIP） ligands in the side chain was synthesized by RAFT polymerization and its kinetics was studied. Polymeric complex PBIP-Nd^3＋ was prepared by chelating PBIP with lanthanide ion Nd^3＋. The homopolymers and PBIP-Nd^3＋ complex were investigated by NMR, FTIR, GPC and TGA. The optical property of PBIP-Nd^3＋ complex was characterized by UV-Vis spectroscopy. The magnetic property of PBIP-Nd^3＋ complex was measured as a function of temperature（5 K to 300 K） and as a function of field（-3.98×10^6 A/m to 3.98×10^6 A/m）. These results indicated that PBIP-Nd^3＋ complex is paramagnetic.

L-Lactide Homopolymerization and Copolymerization with ε-Caprolactone by Tetrahydrosalen Stabilized Yttrium Borohydride Complex

L-lactide（LLA） homopolymerization and copolymerization with ε-caprolactone（CL） in toluene initiated by tetrahydrosalen-supported yttrium borohydride complex were systematically investigated. A possible mechanism of LLA homopolymerization was proposed according to the 1H-NMR result. In addition, PCL-b-PLLA copolymers were synthesized by sequential addition of monomers and their structure was characterized by GPC, 1H-NMR and 13C-NMR.