Copolymers Of Different Compositions Research Articles

Donor-acceptor-based poly(toluidine-co-chloroaniline)s: Synthesis and characterization

A series of poly(o-/m-toluidine-co-o-/m-chloroaniline) copolymers of different compositions were synthesized by an emulsion method with ammonium persulfate as the oxidant. The conductivity of the copolymers was two to five orders of magnitude higher than that of the homopolymers poly(o-toluidine) and poly(m-chloroaniline). Among the copolymers, the copolymer of o-toluidine and m-chloroaniline exhibited a maximum conductivity of 0.14 S cm−1. The conductivity of these copolymers was also higher than that of poly(aniline-co-chloroaniline). The properties of the copolymers were greatly influenced by the positions of the substituents and the concentrations of the individual monomers in the feed. All the copolymers were completely soluble in polar solvents such as dimethyl sulfoxide and showed higher heat stability as the chloroaniline concentration increased. These effects could be interpreted in terms of extensive hydrogen bonding and interchain linking and, therefore, higher electron delocalization in these copolymers due to the presence of electron-rich toluidine rings adjacent to electron-deficient chloroaniline. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1579–1587, 2005

Temperature and concentration effects on supramolecular aggregation and phase behavior for poly(propylene oxide)-b-poly(ethylene oxide)- b-poly(propylene oxide) copolymers of different composition in aqueous mixtures, 1.

The phase behavior (temperature vs composition) and microstructure for the two binary systems Pluronic 25R4 [(PO)19(EO)33(PO)19]-water and Pluronic 25R2 [(PO)21(EO)14(PO)21]-water have been studied by a combined experimental approach in the whole concentration range and from 5 to 80 degrees C. The general phase behavior has been identified by inspection under polarized light. Precise phase boundaries have been determined by analyzing 2H NMR line shape. The identification and microstructural characterization of the liquid crystalline phases have been achieved using small-angle X-ray scattering (SAXS). The isotropic liquid solution phases have been investigated by self-diffusion measurements (PGSE-NMR method). 25R2 does not form liquid crystals and is miscible with water in the whole concentration range; with increasing temperature, the mixtures split into water-rich and a copolymer-rich solutions in equilibrium. 25R4 shows rich phase behavior, passing, with increasing copolymer concentration, from a water-rich solution to a lamellar and copolymer-rich solution. A small hexagonal phase, completely encircled in the stability region of the water-rich solution, is also present. In water-rich solutions, at low temperatures and low copolymer concentrations, the copolymers are dissolved as independent macromolecules. With increasing copolymer concentrations an interconnected network of micelles is formed in which micellar cores of hydrophobic poly(propylene oxide) are interconnected by poly(ethylene oxide) strands. In copolymer-rich solutions water is molecularly dissolved in the copolymer. The factors influencing the self-aggregation of Pluronic R copolymers (PPO-PEO-PPO sequence) are discussed, and their behavior in water is compared to that of Pluronic copolymers (PEO-PPO-PEO sequence).

Effect of melt structure and monomer ratio on condensation equilibrium parameters in copolycondensation of 4-acetoxybenzoic and 6-acetoxy-2-naphthoic acids

Transacylation of 4-acetoxybenzoic and 6-acetoxy-2-naphthoic acids is athermal outside of the dependence on the structural organization of the melt and the initial ratio of monomers but is characterized by negative values of Δ Se0 in a smectic and positive values in a nematic melt. The solubility of CH3COOH vapors increases unevenly in going from a smectic to a nematic melt and is a function of the initial ratio of monomers. The different solubility of CH3COOH vapors in melts of copolymers with different structural organization is determined by the difference in both the energy of reaction of the acid molecules with the polymer and in the character of its distribution over the volume of the polymer. The difference in the solubility of CH3COOH in melts of copolymers of different composition is only determined by the difference in the energy of its reaction with the polymer.

Block Copolymers of Methyl Vinyl Ether and Isobutyl Vinyl Ether With Thermo‐Adjustable Amphiphilic Properties

AbstractThe thermo‐adjustable hydrophilic/hydrophobic properties of AB, ABA and BAB block copolymers in which A is poly(methyl vinyl ether) (PMVE) and B is poly(isobutyl vinyl ether) (PIBVE) have been investigated. The block copolymers were prepared by “living” cationic polymerization using sequential addition of monomers. The polymerizations were carried out with the system acetal/trimethylsilyl iodide as initiator and ZnI2 as activator. The initiating system based on diethoxyethane leads to AB block copolymers whereas the initiating system based on tetramethoxypropane leads to ABA or BAB triblock copolymers. Well‐defined block copolymers of different composition with controlled molecular weights up to approx. 10 000 have been prepared. When IBVE is added to living PMVE, PIBVE‐blocks form only in the presence of an additional amount of ZnI2, which is attributed to the fact that part of the ZnI2 is inactive because of complex formation with PMVE. At room temperature, the combination of hydrophilic (PMVE) and hydrophobic (PIBVE) segments provides the copolymers with surfactant properties. Above the lower critical solution temperature (LCST) of PMVE, situated around 36 °C, the PMVE‐blocks become hydrophobic and the amphiphilic nature of the block copolymers is lost. The corresponding changes in hydrophilic/hydrophobic balance have been evaluated by investigation of the emulsifying properties of the block copolymers for water/decane mixtures as a function of the temperature. Below the LCST, the block copolymers have emulsifying properties similar to or better than those of the commercial PEO‐PPO block copolymers (Pluronic®). Either oil‐in‐water or water‐in‐oil emulsions can be obtained, depending on the polymer architecture and the water/decane volume ratio. The emulsifying properties are strongly reduced or completely lost above 40 °C. Emulsions obtained with a PMVE36‐b‐PIBVE54 block copolymer for a water/decane (v/v) ratio of 85/15 remained stable for more than six months.50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36‐b‐PIBVE54 block copolymer at 20 °C.magnified image50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36‐b‐PIBVE54 block copolymer at 20 °C.

Electrical conductivity and thermal properties of poly(m‐aminophenyl acetic acid) and its copolymers with aniline

AbstractPoly(m‐aminophenyl acetic acid) was synthesized under different conditions from the respective monomer, using ammonium persulfate as oxidizing agent in both the presence and the absence of CuCl2 in HCl(aq). Moreover, the copolymers between aniline and m‐aminophenyl acetic acid were prepared at several feed mol ratios (f1) of aniline. Copper was introduced by the Batch method in the homo‐ and copolymers of different compositions. The polymers were characterized by FTIR and UV‐vis spectroscopy, elemental analysis, thermal analysis, and electrical conductivity. The thermal stability and the content of copper increased as the content of aniline was increased in the copolymers. Moreover, the copolymers showed a high thermal stability; at 400°C a weight loss < 10% was observed. The electrical conductivity was increased with a higher content of aniline in the copolymers, achieving semiconduction values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1484–1492, 2003

Investigation of microstructure of 4-vinyl pyridine-methacylonitrile copolymers by NMR spectroscopy

4-Vinyl pyridine–methacrylonitrile (V/M) copolymers of different composition were prepared by bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition was determined from quantitative 13C{1H}-NMR spectra. The reactivity ratios for V/M copolymer obtained from a linear Kelen-Tudos method (KT) and nonlinear error-in-variables method (EVM) are rV = 0.79 ± 0.12, rM = 0.38 ± 0.09 and rV = 0.79 ± 0.13, rM = 0.38 ± 0.07, respectively. The complete spectral assignment in term of compositional and configurational sequences of these copolymers were done with the help of distortionless enhancement by polarization transfer (DEPT), two-dimensional heteronuclear single quantum coherence spectroscopy (HSQC). Total correlated spectroscopy (TOCSY) experiment was used to assign the various three-bond 1H-1H couplings in the V/M copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3232–3238, 2003

Re-examination of the miscibility behavior of SMMA copolymers using various techniques

The phase behavior of blends of SMMA copolymers with other SMMA copolymers of different compositions, with monodisperse PS homopolymers, and with monodisperse PMMA homopolymers was studied using static light scattering to assess the state of miscibility at three different temperatures: 120, 150, and 180 °C. Contrary to prior reports, the phase diagrams were found to be consistent with the binary interaction model. Quantitative evaluation of the binary interaction energy density between S and MMA, B S/MMA, was made at each temperature by analyzing the miscibility data using the copolymer/critical molecular weight and copolymer composition mapping methods. Values of B S/MMA determined by two different approaches agree well. The slight temperature dependence of B S/MMA is well described by the Sanchez–Lacombe lattice fluid theory using a constant bare interaction energy ΔP S/ MMA ∗ by considering the temperature dependence of the characteristic parameters for PS and PMMA. Quantum mechanical calculations of the total partial charges for different triads clearly show that the electrostatic charge distribution within S and MMA repeat units remains almost unchanged as their neighboring segments change chemical identity. The experimental and theoretical results are inconsistent with the so-called ‘screening’, ‘asymmetric miscibility’ or sequence distribution effects.

Mechanical properties and lipase-catalyzed biodegradation of alpha-methyl, epsilon-caprolactone/epsilon-caprolactone copolymers obtained by chemical modification of poly(epsilon-caprolactone)

Novel (e-caprolactone)-based copolymers of different compositions were synthesized by allowing methyl iodide to react with the polycarbanion that resulted from the action of lithium diisopropylamide on poly(e-caprolactone) in THF at −70°C under argon atmosphere. The copolymers were characterized by various techniques, namely 1H nuclear magnetic resonance, size exclusion chromatography, differential scanning calorimetry, x-ray diffraction and viscoelasticimetry. They were submitted to hydrolytic and lipase-catalyzed enzymatic degradation in comparison with genuine PCL. The Young modulus depended on the degree of methylation. In contrast, loss angle and glass transition temperature did not depend on this parameter. It is shown that the lipase-catalyzed degradation of methylated PCL is much slower than in the case of genuine PCL.

Compositional and configurational sequence determination of methyl methacrylate/ethyl acrylate copolymers by one‐ and two‐dimensional nuclear magnetic resonance spectroscopy

AbstractEthyl acrylate (E)/methyl methacrylate (M) copolymers of different compositions were prepared, and their compositions were determined with 1H NMR spectra. The complete spectral assignments, in terms of the compositional and configurational sequences of these copolymers, were made with the help of distortionless enhancement by polarization transfer and two‐dimensional heteronuclear single quantum coherence spectroscopy. The α‐(CH3)M, CH (E), CH2, and 〉CO carbons of both M and E units were found to be sensitive to various compositional and configurational sequences. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 313–326, 2003

Novel Red Electroluminescent Polymers Derived from Carbazole and 3,6-Bis(2-thienyl)-1,2,7-benzothiadiazole

A series of novel carbazole-based soluble copolymers of different composition was synthesized by Suzuki coupling reaction. Efficient energy transfer from the wide-band-gap segment polycarbazole due to exciton trapping on narrow-band-gap bis(thienyl)ben-zothiadiazole sites has been observed. Maximum electro-luminescence wavelengths of the copolymers varied between 668 nm and 716 nm, and the external quantum efficiency for copolymer devices is 0.3% for copolymers with 20% benzothiadiazole content.

Characterization of glycidyl methacrylate/styrene copolymers by one- and two-dimensional NMR spectroscopy

Glycidylmethacrylate/styrene copolymers of different compositions were prepared by free radical bulk polymerisation using benzoyl peroxide as an initiator. Copolymer composition was obtained from quantitative Carbon-13 NMR spectroscopy. Reactivity ratios for comonomers were calculated using the Kelen–Tudos (KT) and non-linear error in variable methods (EVM). The reactivity ratios obtained from KT and EVM are found to be r G=0.56±0.1, r S=0.44±0.07 and r G=0.60, r S=0.48 respectively. The triad sequence distribution in terms of G and S centered triad were obtained from 13 C{ 1 H} NMR spectroscopy. Complete spectral assignment of 13 C and 1 H-NMR spectra were done with the help of distortionless enhancement by polarization transfer and 2D 13 C– 1 H heteronuclear single quantum coherence.

Microstructure analysis of N‐vinyl‐2‐pyrrolidone/vinyl acetate copolymers by NMR spectroscopy

AbstractN‐Vinyl‐2‐pyrrolidone (V) and vinyl acetate (A) copolymers of different compositions were synthesized by free radical bulk polymerization. The copolymer composition of these copolymers was determined using quantitative 13C{1H} NMR spectra. The reactivity ratios for these comonomers were determined using the Kelen–Tudos (KT) and non‐linear least‐square error‐in‐variable (EVM) methods. The reactivity ratios calculated from the KT and EVM methods are rV = 2.86 ± 0.16, rA = 0.36 ± 0.09 and rV = 2.56, rA = 0.33, respectively. 1H, 13C{1H} and 1H–13C heteronuclear shift correlation spectroscopy (HSQC) and 1H–1H homonuclear total correlation spectroscopy (TOCSY) were used for the compositional and configurational assignments of V/A copolymers. The 13C distortionless enhancement by polarization transfer (DEPT) technique was used to resolve the methine, methylene and methyl resonance signals in the V/A copolymers.© 2002 Society of Chemical Industry

Chemical synthesis, characterization and transport properties of copolymer: Poly(aniline-co-m-methylaniline)

Poly(aniline-co-m-methylaniline) were copolymerized by chemical peroxidation of aniline and m-methylaniline in aqueous acidic medium under nitrogen atmosphere at 0–4oC. The molar feed ratio of the monomers were varied to prepare copolymers of different composition. The copolymers product were characterized by solubility, spectroscopic methods, elemental analysis and electrical conductivity measurements. The solubility and spectroscopic analysis suggested that the product is a copolymer of aniline and m-methylaniline. The optical spectra of the copolymer shows hypsochromic shift with the increase in dielectric constant of the solvent and with increasing the content of m-methylaniline in the copolymer chain. The electrical conductivity of copolymer salts were measured as a function of temperature. The conductivity of copolymer decreases with increasing the content of m-methylaniline in the copolymer chain, due to change in coplanarity of polymer and reduction of mobility of charge carrier along the main chain. The conduction mechanism of copolymer is polaron hopping conduction as similar to the case of polyaniline. The coherence, most probable hopping distance, hopping energy and localization length of copolymers have been compared to those of homopolymers.

The Role of Different Factors in Creation of the Structure of Stabilized Acrylic Fibres

Chemical aspects of transformations of PAN fibres in the stage of thermooxidative stabilization are examined with methods of thermal analysis. The regions of cyclization and oxidation reactions are determined for three PAN copolymers of different composition. It is shown that the cyclization and oxidation reactions appearing on the DSC curves in the form of unseparated exothermic peaks can be separated by selecting the conditions of preliminary heat treatment of the fibres. It was found that preliminary heating of PAN fibres to a certain temperature causes the formation of a structure that does not undergo oxidation on repeated heating. An explanation of this phenomenon is proposed. Loading within certain limits does not affect the course of structural transformations of the fibres during thermooxidative stabilization.

Design of segmented poly(ether ester) materials and structures for the tissue engineering of bone

In this study, PEOT/PBT segmented copolymers of different compositions have been evaluated as possible scaffold materials for the tissue engineering of bone. By changing the composition of PEOT/PBT copolymers, very different mechanical and swelling behaviors are observed. Tensile strengths vary from 8 to 23 MPa and elongations at break from 500 to 1300%. Water-uptake ranges from 4 up to as high as 210%. The in vitro degradation of PEOT/PBT copolymers occurs both by hydrolysis and oxidation. In both cases degradation is more rapid for copolymers with high PEO content. PEOT/PBT scaffolds with varying porosities and pore sizes have been prepared by molding and freeze-drying techniques in combination with particulate-leaching. The most hydrophilic PEOT/PBT copolymers did not sustain goat bone marrow cell adhesion and growth. However, surface modification by gas plasma treatment showed a very much improved polymer–cell interaction for all PEOT/PBT copolymer compositions. Their mechanical properties, degradability and ability to sustain bone marrow cell growth make PEOT/PBT copolymers excellent materials for bone tissue engineering.

Characterisation of glycidylmethacrylate/methacrylonitrile copolymers by NMR spectroscopy

Glycidylmethacrylate/methacrylonitrile (G/M) copolymers of different compositions were prepared and a copolymer composition was obtained from quantitative 13C NMR spectroscopy. Reactivity ratios for comonomers were calculated using the Kelen–Tudos (KT) and non linear error in variable (EVM) methods. The reactivity ratios obtained from KT and EVM are r G=1.14±0.1, r M=0.76±0.06 and r G=1.12, r M=0.75, respectively. Complete spectral assignment of 13C- and 1H-NMR spectra were done with the help of Distortionless Enhancement by Polarization Transfer (DEPT) and 2D 13C– 1H heteronuclear single quantum coherence (HSQC).

Sequence determination of N-vinyl-2-pyrrolidone/acrylonitrile copolymers by NMR spectroscopy

N-vinyl-2-pyrrolidone/acrylonitrile (V/A) copolymers of different compositions were prepared by free radical solution polymerization in DMF using benzoyl peroxide as an initiator. The composition of the copolymers was determined by using quantitative 13 C{ 1 H}-NMR spectra. The methine carbon of V- and A-centered resonances were used for the determination of the sequence distribution of V- and A-centered triads. The sequence distribution of V- and A-centered triads determined from 13 C{ 1 H}-NMR spectra of the copolymers are in good agreement with the triad concentration calculated from the Alfrey–Mayo statistical model. The comonomer reactivity ratios, determined by both the Kelen-Tudos and the non-linear error in variable methods are r V=0.06±0.005, r A=0.46±0.019; r V=0.06 and r A=0.46 respectively. Two-dimensional 1 H– 13 C-heteronuclear single quantum correlation spectroscopy was used to assign the aliphatic protons in the 1 H-NMR spectrum. Total correlated spectroscopy was used to assign the various 1 H– 1 H coupling in the copolymers.

Compositional Sequence Determination of 4-Vinylpyridine/Ethyl Methacrylate Copolymers by One- and Two-Dimensional NMR Spectroscopy

4-Vinylpyridine/ethyl methacrylate (V/E) copolymers of different compositions were prepared by bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition was determined from proton NMR spectra. The reactivity ratios for V/E copolymers were calculated using Kelen-Tudos method (KT) and non-linear error in variables method (EVM). The reactivity ratios obtained from KT and EVM methods are rV=0.48, rE=0.82, and rV=0.49±0.15, rE=0.83±0.08 respectively. The V- and E- centered triad concentrations were calculated from 13C{1H} NMR spectra of copolymers and compared with those calculated from Harwood’s program using terminal model reactivity ratios determined from EVM method. The complete spectral assignments in terms of compositional and configurational sequences of these copolymers were done with the help of distortionless enhancement by polarization transfer (DEPT), two dimensional heteronuclear single quantum coherence spectroscopy (HSQC). Total correlated spectroscopy (TOCSY) experiment was used to assign the various three bond 1H-1H coupling in copolymers.

SYNTHESIS AND CHARACTERIZATION OF HOMO- AND COPOLYMER OF 2-(N-PHTHALIMIDO)ETHYL METHACRYLATE AND STYRENE

2-(N-Phthalimido)ethanol (NPE) was prepared by reacting phthalic anhydride with ethanolamine in dimethy formamide medium. The NPE thus obtained was reacted with methacryloyl chloride in the presence of triethylamine to form the monomer, 2-(N-Phthalimido)ethyl methacrylate (NPEMA). Free radical polymerization technique was used to synthesize the homopolymers and copolymers of different composition of NPEMA and styrene in 2-butanone solution at 70ˆC ± 1ˆC using benzoyl peroxide as initiator. The monomer and the polymers were characterized by IR and 1H-NMR techniques. The molecular weights (M¯ w and M¯ n) and polydispersity index of the polymers were determined using gel permeation chromatography. Thermogravimetric analysis of the polymers were carried out in air. The solubility of the polymers were also studied. The composition of the copolymers was inferred from the 1H-NMR data obtained. The reactivity ratios of the monomers were determined by the application of FinemanRoss and Kelen-Tüdös methods.

Synthesis, characterization and degradation of ABA block copolymer of l-lactide and ε-caprolactone

Degradable ABA block copolymers were synthesized by the bulk copolymerization of PCL pre-polymers and l-lactide with stannous octanoate as the catalyst at 120°C for 120 h. The resulting copolymers were characterized by 1H NMR, 13C NMR, IR, GPC and DSC methods which confirmed the successful synthesis of block copolymers of l-lactide and ε-caprolactone. Mechanical properties showed that the introduction of poly(ε-caprolactone) made poly( l-lactide) a tough material. Hydrolytic degradation of the copolymers in a buffer of pH 7.4 at 37.0°C showed that block copolymers of different compositions degraded at different rates. Block copolymers of different properties could be obtained by adjusting the compositions of the copolymers.