Kelen-Tudos Method Research Articles

Preparation and surface properties of poly(2,2,2-trifluoroethyl methacrylate) coatings modified with methyl acrylate

A series of copolymers of 2,2,2-trifluoroethyl methacrylate (FMA) and methyl acrylate (MA) with different copolymer compositions were synthesized by solution polymerization. The chemical structure of copolymers was characterized by fourier transform infrared spectroscopy (FTIR), 1H NMR, and 19F NMR. The reactivity ratios for FMA (r 1) and MA (r 2) were found to be 1.83 and 0.31 by the Fineman–Ross method and 1.91 and 0.34 by the Kelen–Tudos method, respectively. The glass transition temperature of the copolymers decreased with increasing MA content and ranged from 77.5 to 13.4°C for a feed composition of 90 mol% MA monomer, while, according to water contact angle data, the hydrophilic properties of the copolymer coatings increased with increasing MA feed composition. Remarkably, when the feed composition of MA was 60 mol%, the glass transition temperature was reduced to 29.2°C, while the obtained copolymer exhibited comparable hydrophobic property to the PFMA homopolymer.

Ambient Temperature Photocopolymerization of Tetrahydrofurfuryl Methacrylate and Isobornyl Methacrylate: Reactivity Ratios and Thermal Studies

Photocopolymerization of heterocyclic monomer namely, tetrahydrofurfuryl methacrylate with bulky bicyclic monomer, isobornyl methacrylate with different feed ratios was carried out in bulk with low concentration of an α-hydroxyl ketone based photoinitiator. The ambient temperature photocopolymerization was carried out by using a UV-Visible lamp with fixed low intensity of 0.4 mW cm−2 for a period of 6 min. The residual monomer remained in the polymerization process were determined by using gas chromatography. The reactivity ratio values for the two monomers were calculated from the copolymer composition data by using Fineman-Ross, Kelen-Tudos, Extended Kelen-Tudos and Mao-Huglin methods. Individually, as well as the average of all the methods revealed that the monomer reactivity ratios of tetrahydrofurfuryl methacrylate were higher than isobornyl methacrylate. The dyad sequence distribution and dyad sequence lengths were calculated using the Igarashi and Pyun method and the sequence length distribution for tetrahydrofurfuryl methacrylate was observed to be higher with an increase in its feed content. This supports the reactivity ratio studies that a higher monomer reactivity ratio value for tetrahydrofurfuryl methacrylate was observed as compared to its comonomer. The thermal studies showed that the glass transition temperatures of the copolymers increased with an increase in isobornyl methacrylate content.

STUDYING REACTIVITY RATIOS AND PHYSICAL PROPERTIES OF METHACRYLIC ACID - ETHYL ACRYLATE COPOLYMER

The copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was performed by free radical polymerization in ethanol, in the presence of 2,2-azobisisobutyronitrile (AIBN) as an initiator. The reactivity ratios of monomers were caculatured by Kelen-Tudos method using data from elemental analysis. The charaterstics of the copolymes were studied by IR spectroscopy, DSC, gel permeation chromatography (GPC) and TGA analysis methods. The results showed that MAA has higher reactivity than EA (rMAA = 2.63 and rEA = 0.21), glass transiton temperature of copolyme Tg = 146 oC, the average molecular weight of the copolymers Mw = 251000 (u) and the polydispersity index (PDI) Mw/Mn = 1.70.

Synthesis and solution property of acrylamide-sulfobetaine copolymers

Sulfobetaine 3-[N,N-dimethyl-N-(2-methacryloxylethyl)ammonio]-propane sulfonate (DMAPS) was used to copolymerize with acrylamide (AM) to prepare salt-sensitive copolymers. The optimal reaction conditions, such as initiator concentration, temperature, and reaction time, to achieve the largest weight averaged molecular weight (M w) and the lowest polydispersity index (PDI) were studied. The reactivity ratios of AM and DMAPS (r 1, r 2) were calculated to be (0.45, 0.84) by the Fineman-Ross method, and (0.47, 0.91) by the Kelen-Tudos method. The Q-e values of DMAPS were calculated to be (0.30, −0.38). DMAPS was found to be more easily to add into the copolymer than AM to form random copolymers with a slight alternating tendency. Solution rheology and molecular size of the copolymers as a function of M w were studied in 1 M NaCl solution, a near θ-solution, by rotational rheometer and light scattering methods, respectively. Undisturbed dimension of the copolymers was evaluated according to Stockmayer-Fixman relation.

Copper mediated controlled radical copolymerization of styrene and 2-ethylhexyl acrylate and determination of their reactivity ratios.

Copolymerization is an important synthetic tool to prepare polymers with desirable combination of properties which are difficult to achieve from the different homopolymers concerned. This investigation reports the copolymerization of 2-ethylhexyl acrylate (EHA) and styrene using copper bromide (CuBr) as catalyst in combination with N,N,N′,N″,N″- pentamethyldiethylenetriamine (PMDETA) as ligand and 1-phenylethyl bromide (PEBr) as initiator. Linear kinetic plot and linear increase in molecular weights vs. conversion indicate that copolymerization reactions were controlled. The copolymer composition was calculated using 1H NMR studies. The reactivity ratio of styrene and EHA (r1 and r2) were determined using the Finemann–Ross (FR), inverted Finemann–Ross (IFR), and Kelen–Tudos (KT) methods. Thermal properties of the copolymers were also studied by using TGA and DSC analysis.

Photo-induced controlled/living copolymerization of styrene and acrylic acid and determination of reactivity ratios

A controlled/living photopolymerization of styrene (St) and acrylic acid (AA) mediated by FeCl3·6H2O/tetramethylethylenediamine (TMEDA) was performed in N,N-dimethylformamide using 4-bromomethylbenzophenon (4-BMBP) as photoinitiator at room temperature under UV irradiation. 4-BMBP was first used as ATRP initiator and photoinitiator. A well-defined poly(styrene-co-acrylic acid) with predetermined molecular weight and narrow molecular weight distribution was obtained. The kinetic rule of controlled free radical photopolymerization of St and AA was studied. The kinetic results showed that the obtained random poly(St-co-AA) copolymers produced narrow polydispersity (PDI) within the range of 1.25–1.32 when the conversion was beyond 16.5 %, which was characterized by GPC. The plots of number average molecular weight versus conversion and ln([M]0/[M]) versus time were linear, indicating a controlled/living photopolymerization process. The system proceeded under mild and environmentally friendly conditions. The effects of initiator, catalyst, ligand, and vitamin C(VC) concentrations on polymerization process were investigated. The copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR). The methods of Mayo-Lewis (ML), Kelen-Tudos (KT), and Yzrielev-Brokhina Roskin (YBR) were used to calculate the monomer reactivity ratios of controlled/living photopolymerization of St and AA at low conversions under selected conditions. The monomer reactivity ratios of St and AA were calculated to be r St = 0.82 and r AA = 0.30, respectively in this system. The living characteristics were demonstrated by chain extension experiment.

Reactivity ratios and sequence structures of the copolymers prepared by photo-induced copolymerization of MMA with MPMP

The copolymers were prepared by the photo-induced copolymerization of methyl methacrylate (MMA, M 1 ) with 4-methacryloyl-1,2,2,6,6-pentamethyl-piperidine (MPMP, M 2 ) in benzene solution at ambient temperature. The reactivity ratios for these monomers were measured by running a series of reactions at various feed ratios of initial monomers, and the copolymer compositions were determined by 1H NMR spectroscopy. The reactivity ratios of the monomers were found to be r 1 = 0.28 and r 2 = 1.63 by the application of extended Kelen-Tudos method. The results showed that, MMA preferred to copolymerization while MPMP tended to homopolymerization in the copolymerization system. The sequence structures of the MMA/MPMP copolymers were characterized by 1H NMR spectroscopy. The backbone structures of the MMA/MPMP copolymers were mainly composed of a syndiotactic and an isotactic configuration. Three kinds of the sequences of rr, rr’ and lr’ in the syndiotactic configuration and two kinds of the sequences of km’ and mm’ as the isotactic configuration were found. The sequential distribution and the sequence-length distribution in the MMA/MPMP copolymers were also obtained.

Synthesis and properties of acrylonitrile-methyl itaconate copolymers as spun carbon fiber precursors

Acrylonitrile-methyl itaconate (AN-MIA) copolymers were successfully prepared by free-radical solution copolymerization, and then were spun into precursors of carbon fibers by one-step wet-spun method in this study. Effect of methyl itaconate(MIA), itaconic acid (IA) and methyl acrylate (MA) on the characteristics of the copolymers and precursors were studied in contrast. The monomer reactivity ratios for AN/MIA system were determined by Kelen-Tudos (K-T) method with r 1=0.65, r 2=1.80. The viscosity test shows that using MIA as a co-monomer is an effective way to decrease the viscosity of PAN solution. During the spinning and stretching processes, polyacrylonitrile (PAN) copolymer with MIA as co-monomer can reach the higher total draw-ratio of 12.0 folds, while PAN copolymer with IA as co-monomer can reach only 8.5 folds. The fineness and elongation at-break of the PAN precursors with MIA as co-monomer improve, but the tenacity decreases. DSC test shows MIA is less effective in improving the thermal property than IA.

Synthesis and characterization of trans-1,4-butadiene/isoprene copolymers: Determination of monomer reactivity ratios and temperature dependence

A series of trans-1,4-butadiene/isoprene copolymers were prepared using the catalyst system TiCl4/MgCl2-Al(i-Bu)3 with bulk precipitation technology at different temperatures. Monomers reactivity ratios were calculated based on the Kelen-Tudos (K-T) method and the Mao-Huglin (M-H) method. The influence of temperature on copolymer composition and polymerization rate was discussed in detail. The increase of reaction temperature brought the decrease of butadiene reactivity ratio rBd and supplied an effective adjustment on copolymers’ composition distribution.

Cationic copolymerization of 1,3-pentadiene with α-pinene

Abstract The cationic copolymerization of 1,3-pentadiene (PD) with α-pinene (AP) initiated by aluminum trichloride (AlCl3) was carried out in N-pentane solvent. The effects of the polymerization temperature and the comonomer composition on the yield of the copolymer, softening point, Gardner color scale and number-average molecular weight (Mn) are discussed. The performance of the copolymer was better than that of AP homopolymer (PAP) and PD homopolymer (PPD). The structure of the copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), 1H-nuclear magnetic resonance (1H-NMR), 13C-NMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). In addition, the reactivity ratios for AP (M1) and PD (M2) determined by the Kelen-Tudos method from low-conversion data are r1=0.58 and r2=5.92, respectively.

Microstructure determination of isobornyl methacrylate-styrene copolymer by NMR spectroscopy

An investigation of the microstructure of isobornyl methacrylate - styrene (I/S) copolymers prepared by the atom transfer radical polymerization (ATRP) using methyl-2-bromopropionate as an initiator and PMDETA copper complex as catalyst under nitrogen atmosphere at 70 °C has been done by two-dimensional NMR techniques. 2D- HSQC and TOCSY have been utilized to resolve the complex 1H NMR spectrum and to establish the compositional and configurational sequences of isobornyl methacrylate-styrene (I/S) copolymers. 2D HSQC and TOCSY spectra showed compositional and configurational sensitivity of α-methyl carbon of I unit and methine proton of S unit and are assigned up to the triad level. The methylene carbon (C10) also shows triad level of compositional sensitivity in 2D HSQC spectra. Heteronuclear multiple-bond correlation (HMBC) spectroscopy has been used to study carbonyl/quaternary carbon-proton coupling. The carbonyl and quaternary carbons showed compositional and configurational sensitivity upto the triad level. The values of reactivity ratios were determined by Kelen-Tudos (KT) and nonlinear error in variable method (RREVM) using copolymer composition data that were determined by 1H NMR spectrum. Reactivity ratios of co-monomers in I/S copolymer, determined from a linear Kelen-Tudos method (KT) and non-linear Error-in-Variable Method (EVM), are rI = 0.39 ± 0.09, rS = 0.44 ± 0.08 and rI = 0.42, rS = 0.47, respectively.

Synthesis via RAFT polymerization of thermo- and pH-responsive random copolymers containing cholic acid moieties and their self-assembly in water

Here we report the design and synthesis of polymers containing cholic acid pendant groups, a major bile acid synthesized in the liver from cholesterol. Random copolymers derived from 2-(methacryloyloxy)ethyl cholate (MAECA) with polyethylene glycol methyl ether methacrylate (PEGMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA) have been synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Compositions of co-monomers in the copolymers were determined by 1H NMR spectroscopy, which were further used to determine reactivity ratios of the monomers using the extended Kelen–Tudos method at high conversions. Copolymers from MAECA with PEGMA (P(MAECA-co-PEGMA)) series displayed lower critical solution temperatures (LCSTs) up to 23% MAECA content in the copolymer, which was studied by UV-visible spectroscopy. Both thermo- and pH-responsiveness were observed for the P(MAECA-co-DMAEMA) copolymers with an MAECA unit in the copolymer up to 11.8%. The critical aggregation concentration (CAC) of water soluble copolymers was determined by fluorescence spectroscopy. Self-assembly of random copolymers was investigated by 1H NMR spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM), which indicated micellar structures in water from cholic acid based random copolymers. The polymeric aggregates were further explored for their drug encapsulation capabilities in aqueous medium using nile red as a hydrophobic model compound.

Preparation and thermal properties of poly[acrylonitrile-co-(β-methylhydrogen itaconate)] used as carbon fiber precursor

In order to replace terpolymer with bipolymer, a bifunctional comonomer β-methylhydrogen itaconate (MHI) containing carboxyl group and ester group was synthesized to prepare poly[acrylonitrile-co-(β-methylhydrogen itaconate)] [P(AN-co-MHI)] bipolymers used as carbon fiber precursor for improving the stabilization and spinnability at the same time. The P(AN-co-MHI) bipolymers with different monomer feed ratios were characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The results show that both the polymerization conversion and molecular mass of P(AN-co-MHI) reduce with the increasing MHI amounts in the feed due to the larger molecular volume of MHI than acrylonitrile (AN). The monomer reactivity ratios were calculated by Fineman–Ross and Kelen–Tudos methods, the results show good agreement and MHI possesses higher reactivity than AN. Two parameters \( E_{\text{s}} = A_{{1,629\,{\text{cm}}^{ - 1} }} /A_{{2,244\,{\text{cm}}^{ - 1} }} \) and \( SI = (I_{0} - I_{\text{S}} )/I_{0} \) were defined to evaluate the extent of stabilization, and the activation energy (Ea) of the cyclization was calculated by Kissinger method and Ozawa method. The FTIR, XRD, and DSC results show that P(AN-co-MHI) bipolymers exhibit significantly improved stabilization characteristics than PAN homopolymer, such as larger extent of stabilization, lower initiation temperature, and smaller Ea of cyclization, which is attributed to the ionic initiation by MHI comonomer and it is beneficial to preparing high-performance carbon fiber.

Synthesis, characterization and reactivity ratios of poly N-(p-bromophenyl)-2-methacrylamide-Co-N-vinyl-2-pyrrolidone

The methacrylamide monomer, N-(p-bromophenyl)-2-methacrylamide (PBPMA) was synthesized by reacting p-bromoaniline dissolved in ethylmethylketone (EMK) with methacryloyl chloride in the presence of triethylamine. The copolymers of PBPMA with N-Vinyl-2-pyrrolidone (NVP) were synthesized by free radical solution polymerization using EMK as a solvent at 70±1°C and benzoyl peroxide as a free radical initiator. The copolymerization behavior was studied in a wide composition interval with the mole fractions of PBPMA ranging from 0.20 to 0.80 in the feed. The copolymers were characterized by FT-IR, 1H NMR, 13C NMR and GPC. The solubility was tested in various polar and non polar solvents. The thermogravimetric analysis of the polymers showed that the thermal stability of the copolymer increases with PBPMA content. The copolymer composition was determined by elemental analysis. The monomer reactivity ratios were determined by the application of conventional linearization methods such as Fineman–Ross, Kelen–Tudos methods, and a non-linear error-in-variable model (EVM) method using a computer program.

A comprehensive study on the kinetics of aqueous free-radical homo- and copolymerization of acrylamide and diallyldimethylammonium chloride by online 1H-NMR spectroscopy

Free-radical homo- and copolymerization of acrylamide (AAm) and diallyldimethylammonium chloride (DADMAC) initiated with potassium persulfate (KPS) were performed in the presence of 0.1 M NaCl solution in D2O at 50 °C. Online 1H-NMR kinetic experiments were used to study polymerization kinetics via determination of the individual and overall conversion of the comonomers and compositions of the comonomer mixture and produced copolymer as a function of the reaction time. Reactivity ratios of the AAm and DADMAC were calculated by Mao-Huglin (MH) and extended Kelen-Tudos (KT) methods to be 7.0855 ± 1.3963, 0.1216 ± 0.0301 and 6.9458 ± 2.0113, 0.1201 ± 0.0437 respectively. “Lumped” kinetic parameter (k p k − 0.5 ) was estimated from experimental data. Results showed that k p k − 0.5 value increases by increasing mole fraction of the AAm in the initial reaction mixture. Drift in the comonomer mixture and copolymer compositions with reaction progress was evaluated experimentally and theoretically. Theoretical values were calculated from Meyer-Lowry equation by using reactivity ratios obtained from MH method. A good fitting between the experimental and theoretical values was observed, indicating accuracy of the reactivity ratios estimated in the present work. It was found from following changes in the copolymer composition with the comonomer conversion that produced copolymer has a statistical structure.

Nickel(II) Complexes with Three-Dimensional Geometry α-Diimine Ligands: Synthesis and Catalytic Activity toward Copolymerization of Norbornene

A series of three-dimensional geometry 9,10-dihydro-9,10-ethanoanthracene-11,12-diimines (L1–L4) and their nickel(II) dibromide complexes (C1–C4) were synthesized and characterized. The nickel complexes C1–C4, with three-dimensional geometry, exhibited very high activities for norbornene (NB) homopolymerization with only B(C6F5)3 as cocatalyst,: for C2 even up to 5.53 × 107 g of polymer/((mol of Ni) h). To investigate the activation of polar monomer, complexes C2 and C3 were selected for copolymerization of NB and 5-norbornene-2-yl acetate (NB-OCOMe) in relatively high activities (1.6–5.8 × 105g of polymer/((mol of Ni) h)) and high molecular weights ((0.2–2.8) × 105 g/mol) as well as narrow molecular weight distributions (MWD < 2 for all polymers) depending on the variation of feed ratios. The reactivity ratios of the NB and NB-OCOMe monomers for C2/B(C6F5)3 system by the Kelen–Tudos method were determined to be rNB-OCOMe = 0.05 and rNB = 6.72, respectively. Moreover, the mechanism of polymerization catal...

N-Octyloxyallene homopolymerization and random copolymerization with styrene using catalyst system composed of lanthanide Schiff-base complexes and Al(i-Bu)3

The catalyst system composed of lanthanide Schiff-base complexes with [3,5-tBu2-2-(O)C6H2CH=NC6H5]3Ln(THF)(Ln(Salen)3, Ln = Sc, Y, La, Nd, Sm, Gd, Yb) and triisobutyl aluminum shows high activity for n-octyloxyallene (A) homopolymerization with narrow molecular weight distribution (MWD). The influences of reaction conditions on polymerization behavior are investigated, and poly(n-octyloxyallene) has a weight average molecular weight (M w) of 20.6 × 103 with MWD of 1.39 and 100% yield is obtained under the optimum conditions: [Al]/[Y] = 50 mol/mol, [A]/[Y] = 100 mol/mol, with polymerization at 80 °C for 16 h in bulk. The kinetic studies of n-octyloxyallene homopolymerization indicate that the polymerization rate is first-order with respect to the monomer concentration and shows some controlled polymerization characteristics. Random copolymer of n-octyloxyallene with styrene is obtained by using the same binary catalyst system; the reactivity ratios of the comonomer determined by Kelen-Tudos method are r A = 1.20 and r St = 0.35, respectively, the ratio of each segment and M w of the resulting copolymer could be controlled by varying the feed ratio of each monomer. Determined by differential scanning calorimetry, the copolymers obtained show only one glass transition temperature, which increases gradually with the increase of styrene content in the copolymer.

Synthesis and radioprotector activity of N-vinylpyrrolidone and 2-methyl-5-vinyltetrazole copolymers

Copolymers of N-vinylpyrrolidone and 2-methyl-5-vinyltetrazole with various ratios of monomer units were synthesized by radical polymerization using the injection method. The copolymerization parameters for these monomers were calculated by the Kelen―Tudos method (r1 = 14.34; r2 = 0.06) for high degrees of conversion. Copolymers with monomer-unit concentrations up to 70 ± 5 mol% were soluble in water, non-toxic, and effective as radioprotectors.

HYDROGELS BASED ON (DIMETHYLAMINO)ETHYLACRYLATE (DMAEA) AND N,N'-DIMETHYLACRYLAMIDE (NNDMAAM): SYNTHESIS, CHARACTERIZATION, AND SWELLING BEHAVIOR

Hydrogels of 2-(dimethylamino)ethylacrylate (DMAEA) with N,N'-dimethyl acrylamide (NNDMAAm) were synthesized by solution free-radical polymerization at different feed mol ratios. These copolymers were completely water-insoluble. Polymers were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The monomer reactivity ratios were determined by Kelen-Tudos method. According to that, the monomer reactivity ratios for poly(DMAEA-co-NNDMAAm) were r1 = 0.288 (M1=DMAEA) and r2 = 1.460 (M2=NNDMAAm), (r1x r 2 = 0.419). Low critical solution temperatures (LCST) values of hydrogels are around 60°C, which was significantly higher than that poly(NIPAAm) and increased with increasing of hydrophilic DMAEA unit content in the copolymers. The hydrogels achieved a water-absorption value of 188 g of water/g of dry polymer (xerogel) in distilled water. Effects of time, temperature, pH, salt concentration, cross-linking concentration, and solvent polarity on the water absorption were studied. Experimental results indicated that the copolymer poly(DMAEA-co-NNDMAAm) with a feed mol ratio 2:1 presents the best swelling properties.

Possibilities for reducing tractor engine friction losses at cold start using an ultrasonic irradiation technique

Redox copolymerization of N-vinyl-2-pyrrolidone (NVP) with methyl methacrylate (MMA) was carried out using titanium(III)-- dimethylglyoxime [Ti(III)-DMG] redox initiator in aqueous sulfuric acid-alcohol media. The resulting copolymer was characterized by FTIR, 1H-NMR, and 13C-NMR spectroscopic methods and elemental analysis. Thermal properties of the copolymer were determined by differential scanning calorimetric technique and thermogravimetric analysis. The reactivity ratios of the monomers were computed by Fineman-Ross, Kelen-Tudos, and extended Kelen-Tudos methods at lower conversion. The reactivity ratios obtained r1 (MMA) 1.69 and r2 (NVP) 0.03 showed richer content of MMA than NVP in the copolymer having extreme ideal behavior. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on reactivity ratios. Ti(III)-DMG redox initiator showed increased addition of NVP to MMA during copolymerization.