Polymerization of Isoprene Promoted by Aminophosphine(ory)-Fused Bipyridine Cobalt Complexes: Precise Control of Molecular Weight and cis-1,4-alt-3,4 Sequence

For the preparation of thermoresponsive copolymers, for e.g., tissue engineering scaffolds or drug carriers, a precise control of the synthesis parameters to set the lower critical solution temperature (LCST) is required. However, the correlations between molecular parameters and LCST are partially unknown and, furthermore, LCST is defined as an exact temperature, which oversimplifies the real situation. Here, random N-isopropylacrylamide (NIPAM)/dopamine methacrylamide (DMA) copolymers were prepared under a systematical variation of molecular weight and comonomer amount and their LCST in water studied by calorimetry, turbidimetry, and rheology. Structural information was deduced from observed transitions clarifying the contributions of molecular weight, comonomer content, end-group effect or polymerization degree on LCST, which were then statistically modeled. This proved that the LCST can be predicted through molecular structure and conditions of the solutions. While the hydrophobic DMA lowers the LCST especially the onset, polymerization degree has an important but smaller influence over all the whole LCST range.

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cis-1,4 Selective Coordination Polymerization of 1,3-Butadiene and Copolymerization with Polar 2-(4-Methoxyphenyl)-1,3-butadiene by Acenaphthene-Based α-Diimine Cobalt Complexes Featuring Intra-Ligand π-π Stacking Interactions

Polymers ◽

10.3390/polym13193329 ◽

2021 ◽

Vol 13 (19) ◽

pp. 3329

Author(s):

Beibei Wang ◽

Heng Liu ◽

Tao Tang ◽

Xuequan Zhang

Keyword(s):

Molecular Weight ◽

Cobalt Complexes ◽

Stacking Interactions ◽

Water Contact ◽

Coordination Polymerization ◽

Molecular Weights ◽

Angle Measurements ◽

Π Stacking ◽

High Yields ◽

Polar Monomer

Highly cis-1,4 selective (up to 98%) coordination–insertion polymerization of 1,3-butadiene (BD) has been achieved herein using acenaphthene-based α-diimine cobalt complexes. Due to the presence of intra-ligand π-π stacking interactions, the complexes revealed high thermostability, affording polybutadiene products in high yields. Moreover, all of the obtained polymers possessed a relatively narrow molecular weight distribution as well as high molecular weight (up to 92.2 × 104 Dalton). The molecular weights of the resultant polybutadienes could be finely tuned by varying polymerization parameters, including temperature, Al/Co ratio, etc. Moreover, the copolymerization of butadiene with polar monomer 2-(4-methoxyphenyl)-1,3-butadiene (2-MOPB) was also successfully realized to produce a type of polar cis-1,4 polybutadiene (cis-1,4 content: up to 98.1%) with a range of 2-MOPB content (0.46–1.83%). Water contact angle measurements indicated that the insertion of a polar monomer into a polymer chain could significantly improve the polymer’s surface property.

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Research of Atom Transfer Radical Polymerization of Methyl Polypropylene

Materials Science Forum ◽

10.4028/www.scientific.net/msf.852.720 ◽

2016 ◽

Vol 852 ◽

pp. 720-725

Author(s):

Yu Qing Xu ◽

Yong Ke ◽

Xiao Yong Hu ◽

Jin Cui ◽

Zhi Yuan Lin ◽

...

Keyword(s):

Molecular Weight ◽

Radical Polymerization ◽

Dispersion Coefficient ◽

Gel Permeation Chromatography ◽

Monomer Conversion ◽

Polymerization Reaction ◽

Polymer Dispersion ◽

Precise Control ◽

Copper Bromide ◽

Relative Molecular Weight

The methyl polypropylene was prepared bsaed on toluene as solvent, cuprous bromide (CuBr) / copper bromide (CuBr2)/tris (2-dimethylaminoethyl) amine (Me6TREN) as catalyst, azo dimethoxyisoquinolin heptanenitrile (V-70) as radical additive, 2-bromoisobutyrate (EtBiB) as initiator. The polymerization reaction was initiated by using the ultimate atomic radical polymerization (UATRPSM), whose chain reaction was manifested in linear first-order kinetics. In this study, the conversion of monomers, polymer dispersion coefficient and the relative molecular weight with monomer conversion rate changes were studied by gas chromatography (GC) and gel permeation chromatography (GPC). The results show that the final monomer conversion was 87%; with increasing monomer conversion, polymer dispersion coefficient (PDI) decreases and reaches the optimum value 1.19, while the relative molecular weight of the linear growth, and prove the reaction was precise control.

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Co(II) complexes with 2-pyrrolidinone

Canadian Journal of Chemistry ◽

10.1139/v69-277 ◽

1969 ◽

Vol 47 (10) ◽

pp. 1689-1693 ◽

Cited By ~ 1

Author(s):

O. Bohunovsky ◽

S. C. Jain ◽

R. Rivest

Keyword(s):

Molecular Weight ◽

Solid State ◽

Infrared Spectra ◽

Electronic Spectra ◽

Cobalt Complexes ◽

Acetone Solution ◽

Probable Structure ◽

Conductivity Measurements ◽

Infrared Study ◽

Boron Trichloride

For the known complexes CoL3X2 (X = Cl, Br, and L = 2-pyrrolidinone) a more detailed infrared study was made. Together with the electronic spectra this study indicates dissociation of CoL2X3 into CoL2X2 + L in chloroform and acetone solution. The conductivity measurements and the molecular weight determinations also support dissociation. The probable structure in the solid state is [CoL3X]X. The new 1:1 compound of 2-pyrrolidinone with boron trichloride was prepared to confirm the conclusions made from the infrared spectra of the cobalt complexes.

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