Facile synthesis and characterization of hyperbranched poly(ether amide)s generated from Michael addition polymerization of in situ created AB(2) monomers

A new straightforward strategy for synthesis of novel hyperbranched poly (ether amide)s from readily available monomers has been developed. By optimizing the reaction conditions, the AB(2)-type monomers were formed dominantly during the initial reaction stage. Without any purification, the AB(2) intermediate was subjected to further polymerization in the presence (or absence) of an initiator, to prepare the hyperbranched polymer-bearing multihydroxyl end-groups. The influence of monomer, initiator, and solvent on polymerization and the molecular weight (MW) of the resultant polymers was studied thoroughly. The MALDI-TOF MS of the polymers indicated that the polymerization proceeded in the proposed way. Analyses of H-1 NMR and C-13 NMR spectra revealed the branched structures of the polymers obtained. These polymers exhibit high-moderate MWs and broad MW distributions determined by gel permeation chromatography (GPC) in combination with triple detectors, including refractive index, light scattering, and viscosity detectors. In addition, the examination of the solution behavior of these polymers showed that the values of intrinsic viscosity [eta] and the Mark-Houwink exponent a were remarkably lower compared with their linear analogs, because of their branched nature.

Synthesis, molecular structures, and norbornene addition polymerization activity of the neutral nickel catalysts supported by beta-diketiminato [N, N], ketiminato [N, O], and Schiff-Base [N, O] ligands

A series of neutral nickel complexes [Ni(Ph)(PPh3)(N, O)] with Schiff-base ligands (N, O) [N, O = 5-Me-3-tert-Bu-(Ar-N=CH)C6H2O (1, Ar = 2,6-Me2C6H3; 2, Ar = 2,6-i-Pr2C6H3)], [Ni(Ph)(PPh3)(N,O)1, with beta-ketiminato ligands (N, O) [N, O = CH3COCHC=(CH3)N-Ar (3, Ar = 2,6-Me2C6H3; 4, Ar = 2,6-i-Pr2C6H3)] and [Ni(N, N)(PPh3)], and with beta-diketiminato ligands (N, N) [5, N, N = [2,6-i-Pr-2(C6H3)N=C(CH3)](2)CH] have been synthesized and characterized. The molecular structures of complexes 1, 4, and 5 have been confirmed by X-ray single-crystal analyses. Although their ligands have similar structures, complex 4 possesses a structure similar to that of four-coordination nickel with complex 1, while complex 5 reveals a rare three-coordination nickel geometry. These compounds show high catalytic activities of up to 3.16 x 10(7) g PNB mol(-1) Ni h(-1) for the addition polymerization of norbornene in the presence of modified methylaluminoxane (MMAO) as cocatalyst. Catalytic activities, polymer yield, molecular weights, and molecular weight distributions of polyborbornene have been investigated under various reaction conditions.

Synthesis and characterization of novel neutral nickel complexes bearing fluorinated salicylaidiminato ligands and their catalytic behavior for vinylic polymerization of norbornene

A series of salicylaldimine-based neutral Ni(II) complexes (3a-j) [ArN = CH(C6H40)]Ni(PPh3)Ph [3a,Ar = C6H5; 3b,Ar = C6H4F(o); 3c, Ar = C6H4F(m); 3d, Ar = C6H4F(p); 3e, Ar = C6H3F2(2,4); 3f, Ar = C6H3F2(2,5); 3g, Ar = C6H3F2(2,6); 3h, Ar = C6H3F2(3,5); 3i, Ar = C6H2F3(3,4,5); 3j, Ar = C6H5] have been synthesized in good yield, and the structures of complexes 3a and 3i have been confirmed by X-ray crystallographic analysis. Using modified methylaluminoxane as a cocatalyst, these neutral Ni(II) complexes exhibited high catalytic activities for the vinylic polymerization of norbornene.

Syntheses and ethylene polymerization behavior of supported salicylaldimine-based neutral nickel(II) catalysts

Two novel salicylaldimine-based neutral nickel(II) complexes, [(2,6-iPr(2)C(6)H(3))NCH(2-ArC6H3O)]Ni(PPh3)Ph (6, Ar = 2-(OH)C6H4; 8, Ar = 2-OH-3-(2,6-iPr(2)C(6)H(3)NCH)C6H3), have been synthesized, and their structures have also been confirmed by X-ray crystallography, elemental analysis, and H-1 and C-13 NMR spectra. An important structural feature of the two complexes is the free hydroxyl group, which allows them to react with silica pretreated with trimethylaluminum under immobilization by the formation of a covalent bond between the neutral nickel(II) complex and the pretreated silica. As active single-component catalysts, the two complexes exhibited high catalytic activities up to 1.14 and 1.47 x 10(6) g PE/mol(Ni)center dot h for ethylene polymerization, respectively, and yielded branched polymers. Requiring no cocatalyst, the two supported catalysts also showed relatively high activities up to 4.0 x 10(5) g PE/mol(Ni)center dot h and produced polyethylenes with high weight-average molecular weights of up to 120 kg/mol and a moderate degree of branching (ca. 13-26 branches per 1000 carbon atoms).

Synthesis, structure and norbornene polymerization behavior of nickel complexes bearing two beta-ketoiminato chelate ligands

A series of nickel(II) complexes bearing two nonsymmetric bidentate beta-ketoiminato chelate ligands have been prepared, and the structures of complexes [(2,6-Me2C6H3)NC(CH3)C(H)C(Ph)O](2)Ni (4a) and [(2,6-Me2C6H3)NC(CH3)C(H)C(CF3)O](2)Ni (4c) have been confirmed by X-ray crystallographic analysis. These nickel(II) complexes were investigated as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display very high activities and produce high molecular weight polymers. Catalytic activity of up to 1.16 x 10(4) kg/mol(Ni) .h and the viscosity-average molecular 9 weight of polymer of up to 870 kg/mol were observed. Catalyst activity, polymer yield, and polymer molecular weight could be controlled over a wide range by the variation of the reaction parameters such as Al/Ni molar ratio, norbornene/catalyst molar ratio, monomer concentration, polymerization reaction temperature and time.

Novel highly active binuclear neutral nickel and palladium complexes as precatalysts for norbornene polymerization

A series of binuclear neutral nickel and palladium complexes [(XC6H2CH=NC6H3-iPr(2))MRL](2) 4b-f (X=NO2, M=Ni, R=Ph, L=PPh3, 4b; X=H, M=Pd, R=Me, L=PPh3,4c; X=H,M=Pd, R=Me, L=Py, 4d; X=NO2,M=Pd, R=Me, L=PPh3, 4e; X=NO2, M=Pd, R=Me, L=Py, 4f) and [(C10H7CH=NC6H3-iPr(2))MRL](2) 8a-c (M=Ni, R=Ph, L=PPh3, 8a; M=Pd, R=Me, L=PPh3, 8b; M=Pd, R=Me, L=Py, 8c) have been synthesized and characterized. The structures of complexes 4e and 8b have also been confirmed by X-ray crystallographic analysis. With modified methylalummoxane (MMAO) as cocatalysts, these complexes and complex [(C6H3CH=NC6H3-iPr(2))NiPh(PPh3)](2) 4a are capable of catalyzing the addition polymerization of norbomene (NBE) with the high activity up to 2.3 x 10(8) g PNBE/(mol(M) h). The structure of complexes affects considerably catalytic activity towards norbomene polymerization. The polymers obtained with nickel complexes are soluble, while those obtained with palladium complexes are insoluble. Palladium complexes 4c, 4e and 8b bearing PPh3 ligands exhibit much higher activities than the corresponding complexes 4d, M and 8c bearing pyridine ligands under the same conditions.

Synthesis of novel star-like hyperbranched polymers with poly(amido amine) core and poly(L-lysine) shell

Hyperbranched poly(amido amine)s containing vinyl and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with equal molar ratio in feed. H-1, C-13 and HSQC NMR techniques were used to clarify the structure of hyperbranched polymers and polymerization mechanism.

Synthesis and micellization of star-like hyperbranched polymer with poly(ethylene oxide) and Poly(epsilon-caprolactone) arms

Novel star-like hyperbranched polymers with amphiphilic arms were synthesized via three steps. Hyperbranched poly(amido amine)s containing secondary amine and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with feed molar ratio of 1:2. H-1, C-13, and HSQC NMR techniques were used to clarify polymerization mechanism and the structures of the resultant hyperbranched polymers

Radiation-induced reactions in swollen polymers /

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Radiation-induced reactions in swollen polymers /

The content was printed on only one side of the paper.

Reversible addition fragmentation chain transfer (RAFT) polymerization : mechanism, process and applications

The present article gives an overview of the reversible addition fragmentation chain transfer (RAFT) process. RAFT is one of the most versatile living radical polymerization systems and yields polymers of predictable chain length and narrow molecular weight distribution. RAFT relies on the rapid exchange of thiocarbonyl thio groups between growing polymeric chains. The key strengths of the RAFT process for polymer design are its high tolerance of monomer functionality and reaction conditions, the wide range of well-controlled polymeric architectures achievable, and its (in-principle) non-rate-retarding nature. This article introduces the mechanism of polymerization, the range of polymer molecular weights achievable, the range of monomers in which polymerization is controlled by RAFT, the various polymeric architectures that can be obtained, the type of end-group functionalities available to RAFT-made polymers, and the process of RAFT polymerization.

A strategy for synthesis of ion-bonded supramolecular star polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization

We have developed a novel strategy for the preparation of ion-bonded supramolecular star polymers by RAFT polymerization. An ion-bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert-butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by H-1 NMR and GPC. The results show that the polymerization possesses the character of living free-radical polymerization and the ion-bonded supramolecular star polymers PSt, PtBA, and PSt-b-PtBA, with six well-defined arms, were successfully synthesized.

Reversible addition-fragmentation chain transfer mediated radical polymerization of asymmetrical divinyl monomers targeting hyperbranched vinyl polymers

Reversible addition-fragmentation chain transfer (RAFT) mediated radical polymerizations of allyl methacrylate and undecenyl methacrylate, compounds containing two types of vinyl groups with different reactivities, were investigated to provide hyperbranched polymers. The RAFT agent benzyl dithiobenzoate was demonstrated to be an appropriate chain-transfer agent to inhibit crosslinking and obtain polymers with moderate-to-high conversions. The polymerization of allyl methacrylate led to a polymer without branches but with five- or six-membered rings. However, poly(undecenyl methacrylate) showed an indication of branching rather than intramolecular cycles. The hyperbranched structure of poly(undecenyl methacrylate) was confirmed by a combination of H-1, C-13, H-1-H-1 correlation spectroscopy, and distortionless enhancement by polarization transfer 135 NMR spectra. The branching topology of the polymers was controlled by the variation of the reaction temperature, chain-transfer-agent concentration, and monomer conversion. The significantly lower inherent viscosities of the resulting polymers, compared with those of linear analogues, demonstrated their compact structure,

2-cyanoprop-2-yl dithiobenzoate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2-cyanoprop-2-yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANS were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. H-1 NMR analysis confirmed the high chain-end functionality of the resultant polymers.

Dibenzyl trithiocarbonate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile

Reversible addition-fragmentation chain transfer polymerization has been successfully applied to polymerize acrylonitrile with dibenzyl trithiocarbonate as the chain-transfer agent. The key to success is ascribed to the improvement of the interchange frequency between dormant and active species through the reduction of the activation energy for the fragmentation of the intermediate. The influence of several experimental parameters, such as the molar ratio of the chain-transfer agent to the initiator [azobis(isobutyronitrile)], the molar ratio of the monomer to the chain-transfer agent, and the monomer concentration, on the polymerization kinetics and the molecular weight as well as the polydispersity has been investigated in detail. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and H-1 NMR analyses have confirmed the chain-end functionality of the resultant polymer.