Synthesis of high molecular weight polyoxyethylene with a quaternary catalyst and study of its conductive blends with poly(2‐vinyl pyridine)

High molecular weight polyoxyethylene (PEO) was synthesized by using a quaternary catalyst composed of triisobutyl aluminum, phosphoric acid, water, and N,N‐dimethylaniline (DMA). Optimum synthesis conditions and some properties of the product were studied. This catalyst showed high activity and the molecular weight of the polyoxyethylene obtained can approach one million. The activity of polymerization mainly depends upon the composition of catalyst. The optimum composition is as follows: i‐Bu₃Al:H₃PO₄:H₂O:DMA = 1 : 0.17 : 0.17 : 0.10–0.15 (molar ratio).The active centers of the catalyst was thus proposed. The high molecular weight PEO synthesized by this catalyst was blended with poly(2‐vinyl pyridine) (PVP) and then doped with LiClO₄ and TCNQ to obtain a conductive elastomeric material. Ionic, electronic, and mixed (ionic–electronic) conductivities of blends were investigated. At a Li/EO molar ratio of 0.1 and a TCNQ/VP molar ratio of 0.5, the mixed conductivity of the blend of PEO/PVP/LiCIO₄/TCNQ is higher than the sum of ionic conductivity of PEO/PVP/LiCIO₄ and electronic conductivity of PEO/PVP/TCNQ, when the weight ratio of PEO to PVP is 6/4 or 5/5. It can reach 4 × 10^?6 S/cm at room temperature. Differential scanning calorimetry, thermal gravimetric analysis, and the appearance of the blend showed that both TCNQ and LiClO₄ can complex with PEO and PVP, thus enhancing the compatibility between PEO and PVP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Study on electrical conductivity of 2‐vinylpyridine‐methyl methacrylate copolymer in presence of cobalt acetate

2‐Vinyl pyridine (2VP)‐methyl methacrylate (MMA) copolymers with different molar ratios were prepared. Their electrical properties were studied in the presence of Co(CH₃COO)₂. It was found that the electrical properties of the copolymer were changed by altering the molar ratio of 2VP : MMA and by varying the concentration of Co(CH₃COO)₂. The highest electrical conductivity was found when the 2VP : MMA molar ratio was 1 : 1. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2145–2153, 2001     

Influence of crystalline complexes on electrical properties of PEO:LiTFSI electrolyte

Polymer electrolytes of poly(ethylene oxide) matrix with lithium imide salt LiN(CF₃SO₂)₂ were prepared by casting from solution. Thin films with compositions corresponding to molar ratios 6:1, 3:1 and 2:1 EO:Li were investigated by impedance spectroscopy, impedance spectroscopy simultaneous with polarizing microscope observation, X-ray diffraction and differential scanning calorimetry. The presence of PEO:LiTFSI stoichiometric complexes was found to significantly decrease conductivity at temperature of crystallization, which indicates that those complexes should be regarded as poorly conductive. Changes of properties of amorphous phase related to crystallization were also observed. Crystallization induced phase segregation, which in some cases caused considerable shift of the glass transition temperature of amorphous phase remaining in a semicrystalline system. For PEO:LiTFSI electrolyte with molar ratio of 3:1 EO:Li this effect was found to be responsible for enhancement of conductivity of semicrystalline sample in respect to the amorphous one, which was observed at low temperatures. Phase separation involving precipitation of LiTFSI salt was also found to be a likely explanation for significant enhancement of conductivity for PEO:LiTFSI 2:1 electrolyte subjected to rapid cooling below the glass transition temperature.     

Effect of PEO-PPO-PEO structure on the compressed ethylene-induced reverse micelle formation and water solubilization

Some of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymers aggregate in p-xylene upon addition of ethylene and form reverse micelles at higher temperature at which the reverse micelles cannot be formed without addition of compressed ethylene. An abrupt increase of water solubilization is observed at a certain ethylene pressure. The effects of surfactant structure, such as the ratio of EO (EO weight percent) and the molecular mass, on the copolymer micellization and the solubilization of water in such systems are studied. For the copolymers with the same length of PO block, higher EO ratios facilitate the reverse micelle formation. However, as the EO ratio reaches 70%, it cannot form reverse micelles because the hydrophilicity is too high. For the copolymers with same composition, higher molecular weight is favorable to forming the reverse micelle due to the hydrophilic and folding effects, respectively. The reverse micelle solution can solubilize water with W₀ (molar ratio of water to EO segment) up to 4.1.     

Synthesis and properties of unsaturated polyoxyethylene and its graft copolymers with styrene

The unsaturated polyoxyethylene (PEO) was synthesized by copolymerization of ethylene oxide with allyl glycidyl ether in toluene using bimetallic-oxo-alkoxide as a catalyst. The effects of polymerization conditions on conversion and intrinsic viscosity of the copolymer were studied. The unsaturated copolymer was characterized with infrared spectra, ¹H NMR, and wide-angle X-ray diffraction. The relationship between crystallinity of the copolymers and conductivity of their LiClO₄ complexes were investigated. The copolymer with ∼ 65 wt % PEO content exhibits a room temperature conductivity of 1 × 10⁻⁴ S cm⁻¹ at a molar ratio of EO/Li = 20. The unsaturated PEO was graft-copolymerized with styrene using 2,2′-azobis(isobutyronitrile) as initiator in toluene, with grafting efficiency ∼ 50%. The purified graft copolymer was characterized with infrared spectra, ¹H NMR, and wide-angle X-ray diffraction, and was shown to have good emulsifying properties and a phase-transfer catalytic property. LiClO₄ complex of the graft copolymer with 70 wt % PEO content exhibits a room temperature conductivity approaching 1 × 10⁻⁴ S cm⁻¹ at molar ratio of EO/Li = 20/1. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2417–2425, 1998     

Poly(Li‐2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine): Molar mass effects on strong electrorheological response

Electrorheological (ER) fluids display remarkable rheological behavior, being able to convert rapidly and repeatedly from a fluid to a solid‐like when an external electric field (E) is applied or removed. In this study, electrical and ER properties of poly(Li‐2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine), poly(Li‐HEMA)‐co‐poly(4‐VP), copolymeric salts (ionomers) were investigated. For this purpose six ionomers were synthesized with different molar masses. They were then ground‐milled for a few hours to obtain micron size ionomers. The particle sizes of the ionomers were determined by dynamic light scattering. Suspensions of ionomers were prepared in silicone oil (SO), at a series of concentrations (c = 5–30%, m/m). The gravitational stability of suspensions against sedimentation was determined at constant temperature (T = 25°C). Flow times of the suspensions were measured under no electric field (E = 0 kV/mm), and under an external applied electric field (E ≠ 0 kV/mm) strengths and a strong ER activities were observed for all the poly(Li‐HEMA)‐co‐poly(4‐VP)/SO suspensions. Further, the effects of suspension concentration, mole ratios of poly(HEMA) and poly(4‐VP), and the overall molar mass of the copolymers, shear rate, electric field strength, frequency, promoter, and temperature onto ER activities of ionomer suspensions were investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1065–1074, 2006     

Preparation of electrorheological active ionomers from poly(2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine)

In this study, synthesis, characterization, partial hydrolysis, and salt formation of poly(2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine), (poly(HEMA)‐co‐poly‐(4‐VP)) copolymers were investigated. The copolymers were synthesized by free radical polymerization using K₂S₂O₈ as an initiator. By varying the monomer/initiator ratio, chain lengths of the copolymers were changed. The copolymers were characterized by gel permeation chromatography (GPC), viscosity measurements, ¹H and ¹³C NMR and FTIR spectroscopies, elemental analysis, and end group analysis methods. The copolymers were partially hydrolyzed by p‐toluene sulfonic acid monohydrate (PTSA·H₂O) and washed with LiOH_(aq) solution to prepare electrorheological (ER) active ionomers, poly(Li‐HEMA)‐co‐poly(4‐VP). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3540–3548, 2006     

Solid Polymer Electrolyte Complexes of Polyoxyethylene-Containing Star-Shaped Block Copolymers and Copolymers with Uniform Grafts

Ionic conductivities of salt complexes of polyoxyethylene (PEO)-containing star-shaped block copolymers and copolymers with uniform grafts were measured. The results were compared with the thermal characteristics and crystallinity of the complexes obtained from DSC and WAXD analysis. The conductivity increases with PEO content of the copolymers, more noticeably at PEO contents over 50%. For the complexes of the star-shaped block copolymers of styrene (S) and ethylene oxide (EO), conductivity decreases in the following order of salts: KCNS > NH₄CNS > NaCNS. The room temperature conductivity of the KCNS complex with EO/K ratio = 20 can reach a value of 2 × 10^?5 S cm^?1 at 57% PEO content of the copolymer. The complex with FeCl₂ displays a conductivity even higher than that of the NaCNS complex. Addition of γ-butyrolactone reduces the crystallinity and enhances markedly the ionic conductivity. For complexes of the copolymers with uniform PEO grafts the conductivity decreases in the following order of salts: KCNS > LiClO₄ > FeCl₂. Complexes with LiClO₄ exhibit a maximum conductivity at EO/Li = 20. For different kinds of copolymers with uniform PEO grafts, conductivity of the complexes increases in the order: PS-g-PEO < PMMA-g-PEO < polymethyl acrylate-g-PEO.     

Bioengineering functional copolymers. XI. Copper(II)-poly(N-vinyl-2-pyrrolidone-co-N-isopropylacrylamide) macrocomplexes

A series of poly(N-vinyl-2-pyrrolidone-co-N-isopropylacrylamide)s, poly(VP-co-NIPA) copolymers with different compositions were prepared by radical copolymerization of VP and NIPA in N,N′-dimethylformamide at 65°C using 2,2′-azobisisobutyronitrile as initiator. Cu(II)-copolymer macrocomplexes were prepared by complexation of the copolymers with copper sulfate in aqueous solution at 40°C. The structure and composition of the copolymers, and the formation of coordinated Cu(II)-complexes between amide VP units and Cu²⁺ ions, were studied by FTIR spectroscopy, DSC and TGA-DTG in addition to electrical conductivity. Studies on the relationship between composition and thermal behavior showed that the values of T_g and T_d of the copolymers and their coordinated macrocomplexes increased with increasing VP content. The copolymers predominantly show amorphous structure while their Cu(II)-macrocomplexes show the presence of a crystalline phase. The conductive properties of the synthesized Cu(II)-poly(VP-co-NIPA) complexes are also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymerization and characterization of ethylene/propylene and ethylene/1-octene copolymers produced with bridged Zr- and Hf-based metallocenes

Ethylene/propylene (E/P) and ethylene/1-octene (E/O) copolymers were polymerized with two bridged metallocene catalyst systems, Et(Ind)₂ZrCl₂/MAO and Et(Ind)₂HfCl₂/MAO, respectively. The copolymers produced and some commercial reference copolymers were characterized by DSC, SEC, DMA and ¹³C NMR. The Hf-catalysed E/P polymerizations showed much lower activities than the corresponding Zr-catalysed polymerizations but gave polymers with high molar mass. The Hf-based copolymers also showed two melting peaks which may be indicative of several active sites of the catalyst. A comparison of E/P copolymers, containing about 20 mol-% propylene and produced with Zr, Hf and homogeneous V-catalysts, respectively, indicated that the Hf and V-catalysts gave material more similar to each other. The E/O copolymers produced with Zr-catalysts gave very low molar masses and the reactivity ratios, calculated from the NMR data, indicated that the Hf-catalyst has a slightly higher reactivity for 1-octene and the Zr-catalyst some better reactivity for ethylene. Segregation fractionation studies by DSC indicated that a lower 1-octene feed gives more heterogeneous copolymers and the DMA measurements reveal the existence of a linear correlation between the 1-octene content and the intensity of the tan δ_max peak.     

Polymerization of ethylene oxide initiated by lithium derivatives via the monomer-activated approach: Application to the direct synthesis of PS-b-PEO and PI-b-PEO diblock copolymers

The anionic polymerization of ethylene oxide (EO) initiated by lithium derivatives is extremely sluggish and only yields very low molar mass EO oligomers because of the low reactivity of lithium alkoxide species. We show here that using the monomer-activated anionic polymerization approach, one can activate the C-O-Li bonds towards EO polymerization at low temperature and in non polar media. Starting from living polystyryllithium and polyisoprenyllithium, addition of triisobutylaluminum (i-Bu₃Al) in excess to lithium species triggers the propagation reaction of EO, allowing the direct synthesis, in a few hours, of poly(styrene-b-ethylene oxide) and poly(isoprene-b-ethylene oxide) diblock copolymers, with a molar mass of the PEO block up to 10 000 g/mol.     

Enzyme-catalyzed polymerization and degradation of copolymers prepared from ?-caprolactone and poly(ethylene glycol)

Copolymerizations of ?-caprolactone (CL) with monohydroxyl or dihydroxyl poly(ethylene glycol) (PEG) were successfully performed using Novozyme-435 (immobilized lipase B from Candida antartica) as catalyst. Diblock and triblock copolymers with different compositions were characterized by ¹H NMR, GPC, DSC and X-ray diffraction. The enzymatic copolymerization carried out in toluene presented higher reaction rate and yield than that in bulk. Increasing the [CL]/[EO] feed ratio resulted in increases of molecular weight (M_n) of copolymers. Moreover, the compositions of triblock copolymers were closer to the monomer feed ratios than those of diblock copolymers. The resulting copolymers were all semicrystalline, the crystalline structure being of the PCL type. Solution cast films were allowed to degrade in a pH 7.0 phosphate buffer solution containing Pseudomonas lipase. Weight loss data showed that the introduction of PEG segments to the PCL main chain did not alter the enzymatic degradation of PCL significantly.     

Solid polymer electrolytes based on nanocomposites of ethylene oxide–epichlorohydrin copolymers and cellulose whiskers

With the aim of developing ion‐conducting solid polymer electrolytes that combine high ionic conductivity with good mechanical properties, we prepared and investigated nanocomposites of LiClO₄‐doped ethylene oxide‐epichlorohydrin (EO‐EPI) copolymers and nanoscale cellulose whiskers derived from tunicates. We show that homogeneous nanocomposite films based on EO‐EPI copolymers, LiClO₄, and tunicate whiskers can be produced by solution‐casting THF/water mixtures comprising these components and subsequent compression‐molding. The Young's moduli of the nanocomposites thus produced are increased by a factor of up to >50, when compared to the copolymers, whereas the electrical conductivities experience only comparably small reductions upon introduction of the whiskers. The nanocomposite with the best combination of conductivity (1.6 × 10^?4 S/cm at room temperature and a relative humidity of 75%) and Young's modulus (7 MPa) was obtained with a copolymer having an EO‐EPI ratio of 84 : 16, a whisker content of 10% w/w, and a LiClO₄ concentration of 5.8% w/w. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2883–2888, 2004     

Synthesis and characterization of novel fluorine‐containing methacrylate copolymers: Reactivity ratios,thermal properties,and antimicrobial activity

The free‐radical‐initiated copolymerization of 2‐(4‐acetylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (AOEMA) and 2‐(4‐benzoylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (BOEMA) with 2‐[(4‐fluorophenyoxy]‐2‐oxoethyl‐2‐methylacrylate (FPEMA) were carried out in 1,4‐dioxane solution at 65°C using 2,2′‐azobisisobutyronitrile as an initiator with different monomer‐to‐monomer ratios in the feed. The monomers and copolymers were characterized by FTIR and ¹H‐ and ¹³C‐NMR spectral studies. ¹H‐NMR analysis was used to determine the molar fractions of AOEMA, BOEMA, and FPEMA in the copolymers. The reactivity ratios of the monomers were determined by the application of Fineman‐Ross and Kelen‐Tudos methods. The analysis of reactivity ratios revealed that BOEMA and AOEMA are less reactive than FPEMA, and copolymers formed are statistically in nature. 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 reveals that the thermal stability of the copolymers increases with an increase in the mole fraction of FPEMA in the copolymers. Glass transition temperatures of the copolymers were found to decrease with an increase in the mole fraction of FPEMA in the copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of ABA‐type block copolymers of trimethylene carbonate and ϵ‐caprolactone

This paper describes the synthesis of a series of ABA‐type triblock copolymers of trimethylene carbonate and ?‐caprolactone with various molar ratios and analyses the thermal and mechanical properties of the resulting copolymers. The structures of the triblock copolymers were characterized by ¹H and ¹³C nuclear magnetic resonance spectroscopy, FT‐IR spectroscopy and gel permeation chromatography. Results obtained from the various characterization methods proves the successful synthesis of block copolymers of trimethylene carbonate and ?‐caprolactone. The thermal properties of the block copolymers were investigated by differential scanning calorimetry. The T_m and ΔH_m values of the copolymers decrease with increasing content of trimethylene carbonate units. Two T_gs were found in the copolymers. Furthermore, both of the T_g values increased with increasing content of trimethylene carbonate units. The mechanical properties of the resulting copolymers were studied by using a tensile tester. The results indicated that the mechanical properties of the block copolymers are related to the molar ratio of trimethylene carbonate and ?‐caprolactone in the copolymers, as well as the molecular weights of the resulting copolymers. The block copolymer with a molar composition of 50/50 possessed the highest tensile stress at maximum and modulus of elasticity. Block copolymers possessing different properties could be obtained by adjusting the copolymer compositions. Copyright © 2004 Society of Chemical Industry     

Phase transition in swollen gels 29. Temperature dependences of swelling and mechanical behaviour of poly(N-vinylcaprolactam-co-1-vinyl-2-pyrrolidone) gels in water

Summary Ionized networks of statistical copolymers of N-vinylcaprolactam (VCL), 1-vinyl-2-pyrrolidone (VP) (mole ratios of VCL/VP = 1/0, 0.9/0.1, 0.8/0.2, 0.7/0.3 and 0.5/0.5), an ionic comonomer, N,N-diallyl-(N,N-dimethyl)ammonium chloride (mole fractions 0, 0.005, 0.01 and 0.02) and a crosslinker, 1,1'-divinyl-3,3'-(ethane-1,1-diyl)di(2-pyrrolidone) (mole fractions 0.016, 0.024, 0.032 and 0.048) were prepared by radiation polymerization in water/ethanol mixture (H₂O/EtOH = 0.5/0.5 by vol). Their swelling and mechanical behaviour was investigated in water at various temperatures. For all copolymers, a continuous transition was found from the expanded (at low temperatures) to collapsed (at high temperatures) state; the transition temperature T _tr increases with increasing contents of VP and the ammonium salt in gels. The shift of T _tr to higher temperatures is caused by hydrophilicity of network chains increasing with increasing VP contents. The decrease in swelling with increasing temperature is accompanied by an increase in equilibrium modulus, so that mechanical behaviour is predominantly determined by swelling. Received: 31 October 2000/Revised version: 18 December 2000/Accepted: 18 December 2000     

Ring‐opening polymerization of epichlorohydrin and its copolymerization with other alkylene oxides by quaternary catalyst system

An effective quaternary catalyst consisting of trialkyl aluminum, phosphoric acid, electron donor, and water for ring‐opening polymerization of epichlorohydrin (ECH), as well as its copolymerization with ethylene oxide (EO), propylene oxide (PO), and allyl glycidyl ether (AGE) to obtain elastomers, were studied. We investigated the optimum composition for the quaternary catalyst; the character of the catalyst; the reactivity of the four alkylene oxides during homopolymerization and copolymerization; the behavior of ECH, EO, and PO during terpolymerization; and glass transition temperatures of the copolymer and terpolymers. The results showed that the nitrogen‐containing electron donors are suitable as the third component, whereas oxygen‐containing electron donors are not. Water as the fourth component can increase the molecular weight of the homopolymer and copolymers of ECH. According to the polymerizability of tetrahydrofuran with the quaternary catalyst and the reactivity ratios of the four alkylene oxides, the quaternary catalyst was assumed to be of a coordinated anionic type. The reactivity ratios for these four alkylene oxides were determined to be EO > PO > AGE > ECH. They were verified by terpolymerization of ECH, EO, and PO. The glass transition temperature of the terpolymer exhibits a minimum value at nearly 3:1 molar ratio of PO to EO, when the molar ratio of ECH used is constant at the beginning of terpolymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2446–2454, 2001     

Copolymerization of methyl methacrylate with 4‐vinylpyridine initiated by a novel Ni(II)α‐Benzoinoxime complex

Copolymerizations of methyl methacrylate (MMA) with 4‐vinylpyridine (4VP) were performed from different monomer feed ratios in 1,4‐dioxan at 30°C under free radical initiation experimental conditions, using Ni(II)α‐Benzoinoxime complex as initiator. The obtained copolymers (PMMA4VP) were examined by FTIR and ¹H NMR spectroscopies. The composition of these copolymers was calculated, using ¹H NMR spectra and elemental analysis. Monomer reactivity ratios were estimated from Fineman–Ross (FR, r_m = 0.550, r_v = 1.165) and Kelen–Tudos (KT, r_m = 0.559, r_v = 1.286) linearization methods, as well as nonlinear error in variables model (EVM) method using the RREVM computer program (RREVM, r_m = 0.559, r_v = 1.264). These values suggest that MMA‐4VP pair copolymerizes randomly. ¹H NMR spectra provide information about the stereochemistry of the copolymers in terms of sequence distributions and configurations. These results showed that the age of the Ni complex has an impact not only on its activity towards polymerization reactions but also on the features of the corresponding copolymers, whereas the chemical composition was insensitive to this prominent factor. The mechanism of MMA‐4VP copolymerization is consistent with a radical process as supported by microstructure and molecular weight distribution studies. Thermal behaviours of these copolymers were investigated by differential scanning calorimetry and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Dynamic mechanical and rheological properties of metallocene-catalyzed long-chain-branched ethylene/propylene copolymers

The dynamic mechanical and rheological properties of five long-chain branched (LCB) and three linear ethylene/propylene (EP) copolymers were investigated and compared using a dynamic mechanical analyzer (DMA) and an oscillatory rheometer. The novel series of LCB EP copolymers were synthesized with a constrained geometry catalyst (CGC), [C₅Me₄(SiMe₂N^tBu)]TiMe₂, and had various propylene molar fractions of 0.01-0.11 and long-chain branch frequencies (LCBF) of 0.05-0.22. The linear EP copolymers were synthesized with an ansa-zirconocene catalyst, rac-Et(Ind)₂ZrCl₂ (EBI), and contained similar levels of propylene incorporation as the CGC copolymers, but no LCB. In dynamic mechanical analysis, the dynamic storage moduli (G′) and loss moduli (G″) of the copolymers decreased with an increase of propylene molar fraction. The α- and β-transitions of the CGC copolymers were overlaid with each other. High damping (tan δ) values were found with the CGC copolymers at temperatures below 0 °C. In oscillatory rheological analysis, compared to the linear EBI counterparts, the LCB CGC copolymer melts showed higher zero shear activation energies, broader plateaus of δ and larger elastic contributions, which are essential characteristics of LCB polymers. It was found that the long chain branching was the determining factor in controlling rheological properties of the polymer melts while the short chain branching from propylene incorporation played a decisive role in affecting dynamic mechanical properties. This work represents the first rheological evidence of LCB in EP copolymers synthesized with CGC.     

Water-soluble Copolymers of N-vinylpyrrolidone and Vinyl Acetate: Synthesis, Characterization, and Monomer Reactivity at High Conversions

Homogeneous copolymers of N-vinylpyrrolidone (VP) and vinyl acetate (VA) which form clear aqueous solutions were prepared by free radical polymerization in a solution of isopropanol alcohol, using 2,2-azobisisobutyronitrile as an initiator. They were characterized by FTIR, ¹H-NMR, and element analysis studies. The reactivity ratios of the monomer were computed by the Extended Kelen–Tüdós method at high conversions, using data from both ¹H-NMR and elemental analysis studies. The reactivity ratios of VP and VA in a homogenous copolymer were observed to be very different from that of a heterogeneous copolymer. Additional information was obtained by finding out the sequence length distribution for copolymers.