scholarly journals Methylene-Bridged Tridentate Salicylaldiminato Binuclear Titanium Complexes as Copolymerization Catalysts for the Preparation of LLDPE through [Fe]/[Ti] Tandem Catalysis

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1114 ◽  
Author(s):  
Yani Luo ◽  
Jian Li ◽  
Derong Luo ◽  
Qingliang You ◽  
Zifeng Yang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Temperature ◽  
Gel Permeation Chromatography ◽  
13C Nmr Spectroscopy ◽  
Molar Ratio ◽  
Tandem Catalysis ◽  
Titanium Complexes ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
Branching Degree

A novel tandem catalysis system consisted of salicylaldiminato binuclear/mononuclear titanium and 2,6-bis(imino)pyridyl iron complexes was developed to catalyze ethylene in-situ copolymerization. Linear low-density polyethylene (LLDPE) with varying molecular weight and branching degree was successfully prepared with ethylene as the sole monomer feed. The polymerization conditions, including the reaction temperature, the Fi/Ti molar ratio, and the structures of bi- or mononuclear Ti complexes were found to greatly influence the catalytic performances and the properties of obtained polymers. The polymers were characterized by differential scanning calorimetry (DSC), high temperature gel permeation chromatography (GPC) and high temperature 13C NMR spectroscopy, and found to contain ethyl, butyl, as well as some longer branches. The binuclear titanium complexes demonstrated excellent catalytic activity (up to 8.95 × 106 g/molTi·h·atm) and showed a strong positive comonomer effect when combined with the bisiminopyridyl Fe complex. The branching degree can be tuned from 2.53 to 22.89/1000C by changing the reaction conditions or using different copolymerization pre-catalysts. The melting points, crystallinity and molecular weights of the products can also be modified accordingly. The binuclear complex Ti2L1 with methylthio sidearm showed higher capability for comonomer incorporation and produced polymers with higher branching degree and much higher molecular weight compared with the mononuclear analogue.

scholarly journals Properties and structure of high temperature resistant cyanate ester/polyethersulfone blends using solvent-free toughening approach

2020 ◽  
Author(s):  
Lyaysan Amirova ◽  
Fabian Schadt ◽  
Markus Grob ◽  
Christian Brauner ◽  
Thomas Ricard ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Temperature ◽  
Network Formation ◽  
Mechanical Analysis ◽  
Solvent Free ◽  
Cyanate Ester ◽  
Low Molecular Weight ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
The Difference

AbstractA high temperature resistant novolac cyanate ester was blended with polyethersulfone (PES) with different molecular weights using the solvent-free approach. The phase separation, curing behavior and thermal properties were studied using hot stage microscopy, differential scanning calorimetry and dynamic mechanical analysis. Results showed the difference in the morphology for blends with different molecular weight PES explained by possible network formation. The influence of PES content on the glass transition temperature and mechanical properties was investigated. The most significant toughening effect (increase of 132% in fracture toughness) was achieved on a functionalized low molecular weight PES (20 parts per hundred of resin, phr). Rheology investigation allowed to estimate the optimal content of PES (15 phr) for further prepreg manufacturing.

Binary molybdenum-based catalyst for coordination polymerization of styrene

2016 ◽  
Vol 49 (5) ◽  
pp. 408-421 ◽  
Author(s):  
Jieting Geng ◽  
Youguo Shao ◽  
Feng Song ◽  
Feng Li ◽  
Jing Hua
Keyword(s):  
Molecular Weight ◽  
Catalyst Activity ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Catalyst System ◽  
Bulk Polymerization ◽  
Molar Ratio ◽  
Scanning Calorimetry ◽  
Coordination Polymerization ◽  
Co Catalyst

Coordination polymerization of styrene (St) using molybdenum pentachloride supported by phosphite ligand in the presence of metal organic compound was studied for the first time. The types of phosphite and co-catalysts significantly affected the catalytic activity of the molybdenum (V) (Mo(V)) active center and the number-average molecular weight ( Mn) of the resultant polymer. Among the examined catalysts, tri(nonylphenyl)phosphite (TNPP) ligand and AlOPhCH3( i-Bu)2 as co-catalyst provided the polymer with highest yield (up to 87.1%), metallocene as co-catalyst provided the polymer with highest Mn (up to 5.32 × 105). The effect of [P]/[Mo] molar ratio on catalyst activity of the polymerization was discussed and the structures of Mo·TNPP complexes were preliminarily studied by infrared (IR) and ultraviolet spectroscopies. Besides, the polystyrene (PS) samples synthesized through bulk polymerization and solution polymerization were characterized by gel permeation chromatography, IR, carbon 13 nuclear magnetic resonance, and differential scanning calorimetry, respectively, and the results indicated both of the PS had high molecular weight (approximately 105) and atactic structure. All these results demonstrated that Mo(V) catalyst system was very effective for St polymerization.

scholarly journals Synthesis and In Vitro Antimicrobial Evaluation of Photoactive Multi—Block Chalcone Conjugate Phthalimide and 1,8-Naphthalimide Novolacs

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1859
Author(s):  
Periyan Durairaju ◽  
Chinnasamy Umarani ◽  
Govindasami Periyasami ◽  
Perumberkandigai Adikesavan Vivekanand ◽  
Mostafizur Rahaman
Keyword(s):  
Spectroscopic Analysis ◽  
Photophysical Properties ◽  
Gel Permeation Chromatography ◽  
13C Nmr Spectroscopy ◽  
Antimicrobial Activities ◽  
Microbial Activities ◽  
E Coli ◽  
Molecular Weights ◽  
Antimicrobial Evaluation

Herein we report new multiblock chalcone conjugate phthalimide and naphthalimide functionalized copolymers with a topologically novel architecture synthesis using nucleophilic substitution and polycondensation methodology. The structures of the synthesized novolacs were elucidated on the basis of their spectroscopic analysis including FTIR, 1H NMR, and 13C NMR spectroscopy. Further, the number-average and weight-average molecular weights of the novolac polymers were determined by gel permeation chromatography (GPC). We examined the solubility of the synthesized polymers in various organic solvents including CHCl3, CH3CN, THF, H2O, CH3OH, DMSO, and DMF and found they are insoluble in both methanol and water. The novolac polymers were evaluated for their photophysical properties and microbial activities. The investigation of the antimicrobial activities of these polymers reveals significant antimicrobial activity against the pathogens E. coli, S. aureus, C. albicans, and A. niger.

Probing the molecular weights of sweetgum and pine kraft lignin fractions

TAPPI Journal ◽  
2021 ◽  
Vol 20 (6) ◽  
pp. 381-391
Author(s):  
JULIANA M. JARDIM ◽  
PETER W. HART ◽  
LUCIAN LUCIA ◽  
HASAN JAMEEL
Keyword(s):  
Molecular Weight ◽  
Black Liquor ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Systematic Investigation ◽  
Kraft Pulping ◽  
Molecular Weights ◽  
Lignin Recovery ◽  
Lignin Reactivity ◽  
Kinetics Of

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

Synthesis and characterization of novel methacrylate copolymers having pendant piperonyl group: monomer reactivity ratio, thermal degradation kinetics, and biological activity

2021 ◽  
Vol 29 (9_suppl) ◽  
pp. S1432-S1445
Author(s):  
Ibrahim Erol ◽  
Bayram Gencer ◽  
Zeki Gurler
Keyword(s):  
Biological Activity ◽  
Degradation Kinetics ◽  
Gel Permeation Chromatography ◽  
Reactivity Ratio ◽  
Thermal Degradation Kinetics ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
Monomer Reactivity Ratio ◽  
Bacteria And Fungi ◽  
Photo Stability

In this study, 2-{[(2H-1,3-benzodioxol-5-yl)methyl]amino}-2-oxoethyl 2-methylprop-2-enoate (BMAOME) monomer was synthesized, and copolymers were prepared with glycidyl methacrylate (GMA). Structural characterizations of the compounds were performed using FTIR, 1H-, and 13C-NMR techniques. Monomer reactivity ratio values were calculated by Finemann–Ross (FR) and Kelen–Tudos (KT) methods. The Tg value of the polymers was determined by differential scanning calorimetry (DSC) and their thermal stability was determined by thermogravimetric analysis (TGA). The molecular weights (w and n) and polydispersity index of the polymers were determined by gel permeation chromatography. The Ea value of thermal decomposition was determined by using the Ozawa and Kissinger methods. The photo-stability of the copolymers was investigated. Furthermore, the photo-stability of the copolymers and the biological activity of polymers against different types of bacteria and fungi were investigated.

The High Temperature Gel Permeation Chromatography Study on Poly (Phenylene Sulfide) Linear Chain Propagation

2010 ◽  
Vol 139-141 ◽  
pp. 661-665
Author(s):  
Yu Zhou ◽  
Bo Wen Cheng ◽  
Zhen Huan Li ◽  
De Xin Shen ◽  
Sheng Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Temperature ◽  
Sodium Sulfide ◽  
Linear Chain ◽  
Gel Permeation Chromatography ◽  
Chain Propagation ◽  
Chain Growth ◽  
Gel Permeation ◽  
Methyl Pyrrolidone ◽  
Phenylene Sulfide

A linear and high molecular weight poly(phenylene sulfide) (PPS) was synthesized from P-dichlorobenzene (P-DCB) and anhydrous sodium sulfide in N-methyl pyrrolidone (NMP), and the High Temperature Gel Permeation Chromatography (HTGPC) technique was utilized to investigate the effects of reaction condition on PPS chain propagation. The experiment results indicated that the high pro-reaction temperature or high post-temperature would interfere with PPS chain propagation, and post-reaction time was another important factor to influence PPS molecular weight (Mw) extension. Furthermore, the optimized ratio of high Mw PPS polymer synthesis was typically at 3-6% molar excess of Na2S over p-dichlorobenzene, and N-methyl-2-pyrrolidone (NMP) were beneficial to the production of high Mw PPS due to the formation of sodium 4-(N-methylamino) butanoate (SMAB). The alkaline reagents such as Na3PO4 and K3PO4 et al could capture the H of -SH, which changed -SH into -SNa and promoted the chain growth of PPS to achieve extension.

Comparison of Electron and Infrared Spectroscopy with Thermal Analysis to Study Molecular Weight Effects in PVC-PMMA Blends

1993 ◽  
Vol 47 (10) ◽  
pp. 1636-1642 ◽  
Author(s):  
Cindy A. Burkhardt ◽  
Joseph A. Gardella
Keyword(s):  
Thermal Analysis ◽  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Infrared Spectroscopy ◽  
Lower Molecular Weight ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
Solvent Cast ◽  
Pmma Blends

The effects of homopolymer molecular weight on the miscibility of PVC/PMMA solvent cast blends were studied. Two significantly different molecular weights were chosen for each of the homopolymers, and a series of blends was prepared from the four possible homopolymer-homopolymer combinations. Angle-dependent ESCA results suggest that the surfaces of the blends are enriched with PMMA. The extent of this enrichment is dependent on molecular weight, with the most enrichment seen in blends containing the lower-molecular-weight PMMA homopolymer. Differential scanning calorimetry (DSC) results are also presented.

scholarly journals Poly(lactic acid) polymer stars built from early generation dendritic polyols

2013 ◽  
Vol 91 (6) ◽  
pp. 392-397 ◽  
Author(s):  
Genny E. Keefe ◽  
Jean-d'Amour K. Twibanire ◽  
T. Bruce Grindley ◽  
Michael P. Shaver
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Gel Permeation Chromatography ◽  
Poly Lactic Acid ◽  
Reactive Site ◽  
Scanning Calorimetry ◽  
Early Generation ◽  
Sequential Reaction ◽  
Cyclic Esters ◽  
Total Molecular Weight

A family of polymer stars has been prepared from early generation dendritic cores with four, six, and eight arms. Four dendritic cores were prepared from the sequential reaction of a multifunctional alcohol with a protected anhydride, followed by deprotection to afford two or three new alcohol functionalities per reactive site. These cores were used as initiators for the tin-catalyzed ring-opening polymerization of l-lactide and rac-lactide to afford isotactic and atactic degradable stars, respectively. Two series of stars were prepared for each monomer, either maintaining total molecular weight or number of monomer units per arm. The polymers were characterized by NMR spectroscopy, light-scattering gel-permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Our results support previous work that suggests that the length of the arms dictates thermal properties rather than the total molecular weight of the star. Little effect was noted between aromatic and aliphatic cores, presumably due to the flexibility of the rest of the core molecule. We have shown that early generation dendrimers can serve as excellent core structures for building core-first polymer stars via the ring-opening of cyclic esters.

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