Synthesis and characterization of poly(N-propionyl)iminoethylene

Summary The cationic polymerization of 2-ethyl-2-oxazoline using CH₃I as initiator at different monomer/initiator ratios, temperatures, solvents and times of polymerization was carried out. The effect of these variables on the polymerization yield and viscosity of the polymers was studied. The poly(N-propionyl)iminoethylene was hydrolyzed in acid medium obtaining a linear poly(ethyleneimine) (PEI). All the polymers were characterized by elemental analysis, IR,¹H NMR, and¹³C NMR spectroscopy.     

Aqueous free-radical polymerization of PEGMEMA macromer: kinetic studies via an on-line 1H NMR technique

Free-radical polymerization of polyethylene glycol methyl ether methacrylate macromer (PEGMEMA) was studied in aqueous media and in the presence of potassium persulfate (KPS) as water soluble initiator. An on-line nuclear magnetic resonance (NMR) method was applied to record the reaction data and determine the monomer conversion at various times during the polymerization reaction progress. ¹H NMR spectrum of reaction mixture containing monomer, initiator and resultant polymer was continuously recorded in NMR instrument with the increase of reaction time. By processing the obtained data from NMR spectrum, the rate equation can be derived and reaction order can be determined with regard to monomer and initiator concentration. In other words, to determine the order of polymerization with regard to the concentration of reactants in free-radical polymerization of PEGMEMA, macromer samples with different amounts of monomer and KPS were prepared and polymerized at 50?°C. Orders of reaction with respect to monomer and initiator molar concentrations were equal to 1.025 and 0.480, respectively. The obtained values for reaction orders in this study were consistent with the classical kinetic rate equation in which the dependency of polymerization rate (R _p) on monomer and initiator concentrations was equal to 1 and 0.5, respectively. To measure polymerization activation energy (E _a), the effect of reaction temperature on the polymerization rate was investigated and E _a?=?37.08?kJ/mol was obtained at the temperature range of 40?C50?°C.     

Ring‐opening polymerization of trimethylenecarbonate and its copolymerization with ϵ‐caprolactone by lanthanide (II) aryloxide complexes

Lanthanide metal (II) 2,6‐di‐tert‐butylphenoxide complexes (ArO)₂Ln(THF)₃ (Ln = Sm 1 , Yb 2 ) alone have been developed to catalyze the ring‐opening polymerization of trimethylenecarbonate (TMC) and random copolymerization of TMC and ε‐caprolactone (ε‐CL) for the first time. The influence of reaction conditions, such as initiator, initiator concentration, polymerization temperature, and polymerization time, on monomer conversion, molecular weight, and molecular weight distribution of the resulting PTMC was investigated. It was found that the divalent complex 1 showed higher activity for the polymerization of TMC than complex 2 . The random structure and thermal behavior of the copolymers P(TMC‐co‐CL) have been characterized by ¹H NMR, ¹³C NMR, GPC, and DSC analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of A<Subscript>2</Subscript>B<Subscript>2</Subscript> miktoarm star copolymers from a new heterobifunctional initiator by combination of ROP and ATRP

Abstract  

A new heterobifunctional initiator, 2,3-bis(2-bromo-2-methylpropionyloxy) succinic acid, was synthesized and used in preparation of A₂B₂ miktoarm star copolymers, (polystyrene)₂(poly(ε-caprolactone))₂, by combination of atom transfer radical polymerization (ATRP) and Controlled ring-opening polymerization (ROP). The structures of products were confirmed by the ¹H NMR, ¹³C NMR, FT–IR, elemental analysis, differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). GPC traces show that the obtained polymers have a relatively narrow molecular weight distribution. The compositions of resulting miktoarm star copolymers were very close to theoretical.     

Atom transfer radical polymerization of styrene initiated by 2-(4-chloromethyl-phenyl)-benzoxazole with high activity and fluorescent property

Functionalized polystyrene (PSt) was synthesized utilizing atom transfer radical polymerization (ATRP), which was conducted by using 2-(4-chloromethyl-phenyl)-benzoxazole (CMPB) as initiator, CuCl/PMDETA as catalyst, and cyclohexanone as solvent. The mechanism of ATRP was proved by characterizing the structure of PSt via ¹H NMR and preparing of PSt-b-PMMA block copolymer. The polymerization showed first order with respect to monomer concentration and relatively narrow polydispersity (M_w/M_n range from 1.30 to 1.50). Factors such as different reaction temperatures, mole ratio of monomer to initiator and so on, which can affect the ATRP system, were discussed in the paper. Moreover, CMPB showed high activity and could initiate styrene polymerization even at ambient temperature. The optical property of initiator was well preserved in the obtained PSt, and the end-functionalized PSt exhibited strong fluorescent emission at 351 nm.     

Synthesis of palladium clusters with surface initiator for polymerization of 2-methyl-2-oxazoline

Summary Palladium clusters were synthesized by reduction of palladium(II) acetate in the presence of a bipyridyl ligand (1) with an initiator for polymerization of 2-methyl-2-oxazoline. The 1-protected palladium clusters were soluble in CHCl₃ and CH₂Cl₂. The 1-protected palladium clusters were combined with 2-methyl-2-oxazoline in chloroform. After polymerization, the reacted bipyridyl ligand was removed from the palladium cluster by suspending the obtained palladium clusters with pyridine. The ¹H NMR measurement indicated that the reacted bipyridyl ligand was formed via surface polymerization of 2-methyl-2-oxazoline. Received: 19 April 2001/Accepted: 2 May 2001     

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

The ring‐opening polymerization of ε‐caprolactone initiated with a divalent samarium bis(phosphido) complex [Sm(PPh₂)₂] is reported. The polymerization proceeded under mild reaction conditions and resulted in polyesters with number‐average molecular weights of 8.2 × 10³ to 12.5 × 10³. The yield and molecular weight of poly(ε‐caprolactone)s were dependent on the experimental parameters, such as the monomer/initiator molar ratio, the monomer concentration, the reaction temperature, and the polymerization time. The obtained polymers were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and differential scanning calorimetry. On the basis of an end‐group analysis of low‐molecular‐weight polymers by NMR spectroscopy, a coordination–insertion mechanism is proposed for the polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1558–1564, 2005     

Cationic Polymerization of Epoxides using Novel Xanthenyl Phosphonium Salts as Thermo-latent Initiator

The present article describes the effect of steric and electronic factors on the efficiency of initiators based on novel xanthenyl phosphonium salts for cationic polymerization of epoxide monomers. 2-substituted (I_H, I_Cl, I_Me, and I_OMe) xanthenyl phosphonium hexafluoroantimonate were synthesized and characterized by NMR (¹H, ¹³C and ³¹P) and IR spectroscopy. The order of initiator activity in polymerization of glycidyl phenyl ether (GPE), was found as I_H> I_Cl>I_Me>I_OMe. To understand the effect of steric factor, the polymerization of cyclohexene oxide (CHO) was performed and the order of activity was found as I_Cl>I_H>I_Me >I_OMe. All the initiators were found to be latent at ambient temperature and initiates polymerization on thermal initiation. The order of initiator activity was influenced by electronic and steric factors in the system. The thermal stability of these salts was measured by Thermo gravimetric analysis (TGA). The solubility of the initiators in various organic solvents and epoxy monomers is also discussed.     

Ring-opening Polymerization of <Subscript>D,L</Subscript>-Lactide by the Single Component Rare Earth Tris(4-<Emphasis Type="Italic">tert</Emphasis>-butylphenolate)s

Summary Ring-opening polymerization of _D,L-lactide (_D,L-LA) initiated by single component rare earth tris(4-tert-butylphenolate)s has been carried out for the first time. The influences of rare earth element, solvent, temperature, monomer and initiator concentration as well as reaction time on the polymerization were investigated in detail. The kinetics study indicates that the polymerization rate is first order with respect to monomer concentration and initiator concentration, respectively. The overall activation energy of the ring-opening polymerization is 81.7 kJ.mol^-1. The intensity distribution of the various stereosequence resonances in the NMR spectra reveals that transesterification proceeds slowly during the polymerization at the temperatures 90 ^oC. DSC data confirm the random distribution of the polymer. Mechanism studies showed that the _D,L-lactide monomer inserted into the growing chains with the acyl-oxygen bond cleavage.     

Kinetics of atom transfer radical polymerization of crosslinkable terpolymer P(MMA‐BA‐HEMA)

A crosslinkable terpolymer P(MMA‐BA‐HEMA) was prepared by atom transfer radical copolymerization of 2‐hydroxyethyl methacrylate, methyl methacrylate and butyl acrylate. The structure of the terpolymer was characterized by ¹H NMR and gel permeation chromatography. The effects on the polymerization of ligand, initiator, solvent, CuCl₂ added in the initial stage and reaction temperature were investigated. The optimal reaction conditions were ethyl 2‐bromopropionate as initiator, CuCl/PMDETA as catalyst, cyclohexanone as solvent, catalyst/ligand = 1:1.5, [M]₀:[I]₀ = 200:1 and temperature 70 °C. The reaction followed first‐order kinetics with respect to monomer concentration, indicating the best control over the polymerization process, a constant concentration of the propagating radical during the polymerization, efficient control over M_n of the polymer and low polydispersity (M_w/M_n < 1.3). © 2013 Society of Chemical Industry     

Steric and electronic effects on mesophase stability of segmented liquid crystalline polymers with arylazomethine pendant groups

Summary The kinetics of DL-lactide polymerization was studied in CH₂Cl₂ at 25°C and in toluene at 70°C with HAPENAlOMe, a new Schiff's base complex derived from 2-hydroxyacetophenone and ethylenediamine. A higher polymerization rate is observed with this initiator as compared to other previously reported Al-alkoxides complexes. The polymerization with HAPENAlOMe is also shown to be a living process in both solvents. Moreover, the polymerization proceeds to quite high conversion without significant occurrence of transesterification reactions as confirmed from ¹³C NMR and SEC analysis. Received: 4 October 1999/Accepted: 6 December 1999     

CuBr2/Me6TREN-mediated living radical polymerization of methyl methacrylate at ambient temperature

A universal nitrogen based ligand, tris[2-(dimethylamino) ethyl] amine (Me₆TREN), was firstly employed as both reducing agent and ligand for atom transfer radical polymerization with activators regenerated by electron transfer (ARGET ATRP) of methyl methacrylate (MMA) in bulk and solution, using CuBr₂ as the catalyst and 2-bromoisobutyrate as the initiator. Remarkably high activity catalytic system (CuBr₂/Me₆TREN) enabled the ambient temperature polymerization and thus biradical termination reactions were low. The polymerization exhibited typical living radical polymerization features, including pseudo first-order kinetics of polymerization, linear increase in the molecular weight versus monomer conversion, and low polydispersity index values. Moreover, effects of solvent and reaction temperature on the polymerization were investigated in detail. The rate of polymerization increased with reaction temperature and the apparent activation energy of the polymerization was calculated to be 51.11 kJ/mol. Gel permeation chromatography and ¹H NMR analyses as well as chain extension experiment confirmed the living chain-end functionality.     

Atom transfer radical polymerization of styrene with FeCl2/acetic acid as the catalyst system

Summary Atom transfer radical polymerization with FeCl₂/CH₃COOH as the catalyst has been successfully implemented for styrene. Various initiators have been used, among which carbon tetrachloride is the most effective one. High molecular weight products were obtained when CCl₄ was used as the initiator, and the measured molecular weight was close to the calculated one. Block copolymerization (PS-b-PMMA) was performed to confirm the living/controlled nature of the polymerization. ¹H NMR was used to characterize the structure of the macromolecular initiator and the block copolymer. If other initiators, such as benzyl bromide, ethyl 2-bromopropionate and α-bromoethyl benzene, were used, the polymerization occurred at ambient temperature resulting in oligomer. The molecular weight of the oligomer approaches to 4600 (M_n,th= 10000). Thus acetic acid, which is cheaper and less toxicity, can be used as coordinative ligand in ATRP initiated by CCl₄ mediated by iron. Received: 13 March 2000/Revised version: 13 November 2000/Accepted: 20 November 2000     

Fe‐mediated ARGET atom transfer radical polymerization of methyl methacrylate in ionic liquid‐based microemulsion

Poly(methyl methacrylate) (PMMA) was synthesized by activator regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP) of MMA in ionic liquid‐based microemulsion with polyoxyethylene sorbitan monooleate (Tween 80) as surfactant. The polymerization was carried out at 25°C with CCl₄ as initiator, FeCl₃·6H₂O/N,N,N′,N′‐tetramethyl‐1,2‐ethanediamine (TMEDA) as catalyst complex in the presence of reducing agent ascorbic acid (VC). The polymerization kinetics showed the feature of controlled/″living″ process as evidenced by a linear first‐order plot. The well‐controlled polymers were obtained with narrow polydispersity indices and the ionic liquid‐based microemulsions were transparent with a particle size less than 30 nm. The obtained polymer was characterized by ¹H NMR and gel permeation chromatography. The chain extension was successfully achieved by the obtained PMMA macroinitiator/FeCl₃·6H₂O/TMEDA/VC initiator system based on ARGET ATRP method. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ring‐opening polymerization of lactones using RuCl2(PPh3)3 as initiator: Effect of hydroxylic transfer agents

ε‐Caprolactone and δ‐valerolactone were polymerized in bulk at 150°C using the ruthenium(II) complex RuCl₂(PPh₃)₃ as initiator in the presence of 1,3‐propanediol (PD) with a series of alcohols as coinitiators. Polymerization of lactones proceeds via ruthenium(II) alkoxide active centers. ¹H‐NMR analysis revealed that the ruthenium complex reacted with the alcohol, generating in situ a ruthenium alkoxide. This species became a more active initiator of ring‐opening polymerization than was RuCl₂(PPh₃)₃. The obtained polylactones were characterized by ¹H‐ and ¹³C‐NMR and matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF). The results showed the formation had occurred of α,ω‐telechelic PCL and PVL diols, in which PD had been incorporated into the polymer backbone. Depending on the nature of the alcohol used as coinitiator, PCLs with different end groups could be synthesized. Insertion of an alcohol as an end group (benzyl alcohol, n‐octanol, or isopropanol) or into the polymeric backbone (propanediol) provided support for the conclusion that a classical coordination–insertion mechanism was operating during lactone polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis of poly(ethylene glycol-b-styrene) block copolymers by reverse atom transfer radical polymerization

Reverse atom transfer radical polymerization (RATRP) of styrene (S) was carried out in bulk using polyazoester prepared by the reaction of polyethylene glycol with molecular weight of 3000 and 4,4′-azobis(4-cyanopentanoyl chloride) as initiator and CuCl₂/2,2′-bipyridine (bpy) catalyst system to yield poly(ethylene glycol-b-styrene) block copolymer. The block copolymers were characterized ¹H NMR, FT-IR spectroscopy and GPC. The ¹H NMR, and FT-IR spectra showed that formation of poly(ethylene glycol-b-styrene) block copolymer. The polydispersities of block copolymers were observed between from 1.49 and 1.98 GPC measurements.     

Syntheses and characterizations of side-chain liquid crystalline poly(glycidyl ether)s with biphenyl mesogenic group

Summary Four three-armed poly(glycidyl ether)s with biphenyl mesogenic group and various lengths of spacer, new side-chain liquid crystalline polymers, were synthesized by cationic ring-opening polymerization of the corresponding monomers in the presence of 2,2-dihydroxymethylbutanol and BF₃·OEt₂ as initiator. The structures of the obtained poly(glycidyl ether)s were verified by ¹H and ¹³C NMR spectroscopy, and their liquid crystalline behaviors were studied by differential. scanning calorimetry (DSC and optical polarizing microscopy (OPM). Received: 5 January 1999/Revised version: 20 April 1999/Accepted: 26 April 1999     

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate

Ultrasonically initiated emulsion polymerization of n‐butyl acrylate (BA) without added initiator has been studied. The experimental results show that high conversion of BA can be reached in a short time by employing an ultrasonic irradiation technique with a high purge rate of N₂. The viscosity average molecular weight of poly(n‐butyl acrylate) (PBA) obtained reaches 5.24 × 10⁶ g mol^?1. The ultrasonically initiated emulsion polymerization is dynamic and complicated, with polymerization of monomer and degradation of polymer occurring simultaneously. An increase in ultrasound intensity leads to an increase in polymerization rate in the range of cavitation threshold and cavitation peak values. Lower monomer concentration favours enhancement of the polymerization rate. ¹H NMR, ¹³C NMR and FTIR spectroscopies reveal that there are some branches and slight crosslinking, and also carboxyl groups in PBA. Ultrasonically initiated emulsion polymerization offers a new route for the preparation of nanosized latex particles; the particle size of PBA prepared is around 50–200 nm as measured by transmission electron microscopy. © 2001 Society of Chemical Industry     

Reversible addition-fragmentation chain transfer polymerization of styrene initiated by tetraethylthiuram disulfide

The RAFT polymerization of styrene in bulk was carried out using tetraethylthiuram disulfide (TETD) as an initiator and 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as a chain transfer agent at different temperatures. The results of the polymerization showed that TETD could initiate the RAFT polymerization of styrene in the living way. The kinetics of the polymerization showed first order. The molecular weights of the polymers increased linearly with conversions and were close to the theoretical values (M_n,th). The polydispersities of the polymers remained relatively narrow (<1.3). The structure of the polymer was characterized by ¹H NMR. The result showed that there were moieties of CPDN and TETD attained at the end of the polymer. Using these double functional end capped polymers, the chain-extension experiments were successfully carried out not only in the conventional RAFT polymerization way, but also under UV irradiation.     

Microheterogeneous polymer systems prepared by suspension polymerization of methyl methacrylate in the presence of poly(ε‐caprolactone)

Poly(methyl methacrylate) – polycaprolactone (PMMA/PCL) microheterogeneous beads were synthesized by suspension polymerization starting from methyl methacrylate (MMA) monomer and PCL, which was synthesized by ring‐opening polymerization of ε‐caprolactone using ZnCl₂ as initiator. The resulting polymer was fully characterized by ¹H and ¹³C NMR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and dynamic mechanical thermal analysis (DMTA). The size distribution and morphology of the resulting beads were investigated by optical microscopy and scanning electron microscopy (SEM). Moreover, blends of PMMA beads and PCL in different proportions were prepared and the morphology of the films was examined by optical microscopy. The low compatibility between PMMA and PCL was clearly evidenced through these experiments.