Lanthanide-based luminescent hybrid materials.

A comprehensive review summarizing the effect of electrospinning parameters and potential applications of nanofibers in biomedical and biotechnology

http://dspace.dtu.ac.in:8080/jspui/bitstream/repository/17491/1/A.P.%20Gupta.pdf

New emerging trends in synthetic biodegradable polymers – Polylactide: A critique

pH-Responsive polymers

The review summarizes recent developments in the preparation and use of new initiators for the ring opening polymerization of lactide. The review compares different classes of initiator including metal complexes, classed according to their group in the periodic table, and carbon‐based initiators/organocatalysts. Emphasis is placed on the polymerization kinetics and the control exhibited by the different types of initiators. Where useful properties, such as high rates or stereocontrol, have been observed a more detailed examination of the initiator is provided. A further focus of the review is initiators displaying low toxicity and biocompatibility.

Biocompatible Initiators for Lactide Polymerization

On the basis of the strategy of promoting thermostability of α-diimine nickel catalyst by ligand backbone framework, a series of α-diimine nickel(II) complexes with bulky camphyl or diaryl-substituted backbones, [2,6-(R2)2C6H3−N═C(R1)−C(R1)═N−2,6-(R2)2C6H3]NiBr2 (1a, R1 = Ph, R2 = CH3; 2a, R1 = 4-methylphenyl, R2 = CH3; 3a, R1 = 4-fluorophenyl, R2 = CH3; 4a, R1 = camphyl, R2 = CH3; 4b, R1 = camphyl, R2 = i-Pr), were synthesized and used as catalyst precursors for ethylene polymerization. Crystallographic analysis revealed that the bulky camphyl backbone has a valid steric-effect on the nickel center by blocking the axial site for the metal center and suppressing the potential rotation of the CAr−N bond. Ethylene polymerizations catalyzed by these nickel α-diimine complexes activated by MAO were systematically investigated and the influences of the substituted backbones as well as reaction temperature on the catalytic activity, molecular weight and branching structure of the polymers were evaluated. It was...

Thermostable α-Diimine Nickel(II) Catalyst for Ethylene Polymerization: Effects of the Substituted Backbone Structure on Catalytic Properties and Branching Structure of Polyethylene

Development of thermally stable nickel-based catalysts is highly desirable for industrial gas-phase olefin polymerizations. On the basis of the strategy of promoting the thermostability of nickel catalyst by the ligand backbone, we herein reported novel dibenzobarrelene-derived α-diimine nickel precatalysts for ethylene polymerization. Increasing the steric bulk on the ligand backbone was expected to inhibit the N-aryl rotation of the α-diimine ligands by the repulsive interactions, thus enhancing thermal stability (100 °C) and living fashion a temperatures up to 80 °C. Bulk ligand backbone also improved tolerance of nickel catalyst toward polar groups, and the α-diimine nickel catalyst containing a 2,6-tBu-dibenzobarrelene backbone catalyzed living copolymerization of ethylene and methyl 10-undecenoate.

Enhancing Thermal Stability and Living Fashion in α-Diimine–Nickel-Catalyzed (Co)polymerization of Ethylene and Polar Monomer by Increasing the Steric Bulk of Ligand Backbone

Substituent Effects of the Backbone in α-Diimine Palladium Catalysts on Homo- and Copolymerization of Ethylene with Methyl Acrylate

Ferric alkoxides (Fe(OR)3), where R = Et, nPr, iPr, and nBu, were used as initiators for bulk ring-opening polymerization of lactides. It was showed that these ferric alkoxides were efficient initiators for the ring-opening polymerization of lactides with higher than 90% of monomer conversions polymerized at 130 °C for 36 h. Maximum molecular weights were achieved at 1/1000 of [I]/[M] mole ratio and then decreased gradually with increasing amount of initiator and prolonging polymerization time. Poly(dl-lactide) and poly(l-lactide) with the maximum viscosity-average molecular weights (Mv) of 7.28 × 104 and 19.00 × 104, respectively, were synthesized by using ferric ethoxide as initiator. The molecular weight decreased and the molecular weight distribution broadened as the polymerization temperature increased. With increasing the bulkiness of the ligands of the ferric alkoxides, the molecular weight decreased and the molecular weight distribution broadened. 1H and 13C NMR analyses indicated that no racemiza...

Bulk ring-opening polymerization of lactides initiated by ferric alkoxides

Chiral (1S)- and (1R)-camphyl α-diimine nickel complexes were synthesized respectively with (1S)-(+) camphorquinone and (1R)-(−) camphorquinone as raw reagents and used as catalyst precursors for olefin polymerizations. It is found that the ligand chirality has no influence on catalytic activity and regioselectivity for olefin polymerizations. Ethylene, propylene, 1-hexene, and 4-methyl-1-pentene polymerizations with the camphyl α-diimine nickel activated by AlEt2Cl can exhibit some living characteristics under the optimized conditions. The resultant polypropylenes and poly(1-hexene)s have significantly narrow molecular weight distributions (PDI < 1.2) in a wide temperature range, even at an elevated temperature of 70 °C. Sustainable period of the linear relationship of Mn vs polymerization time depends on temperature for propylene and 1-hexene polymerizations. Additionally, high 1,3-enchainment fraction of 45% is observed even at −60 °C for propylene polymerization using the camphyl α-diimine catalyst du...

Qing Wu

Papers

Thermostable α-Diimine Nickel(II) Catalyst for Ethylene Polymerization: Effects of the Substituted Backbone Structure on Catalytic Properties and Branching Structure of Polyethylene

Enhancing Thermal Stability and Living Fashion in α-Diimine–Nickel-Catalyzed (Co)polymerization of Ethylene and Polar Monomer by Increasing the Steric Bulk of Ligand Backbone

Substituent Effects of the Backbone in α-Diimine Palladium Catalysts on Homo- and Copolymerization of Ethylene with Methyl Acrylate

Bulk ring-opening polymerization of lactides initiated by ferric alkoxides

Polymerization of α-Olefins Using a Camphyl α-Diimine Nickel Catalyst at Elevated Temperature