13C-NMR study of chlorinated ethylene–vinyl acetate copolymers

¹³C-NMR has been used to analyze the microstructures of a series of experimental chlorinated ethylene–vinyl acetate copolymers (15–56% CI). Previously established line assignments for EVA copolymers and substituent effect parameters for chlorine have enabled us to tentatively assign partial structures up to five carbon atoms in length. The ¹³C-NMR analyses of a commercial vinyl chloride–vinyl acetate copolymer, a commercial vinyl chloride–vinyl acetate–ethylene terpolymer, and a commercial chlorinated polyethylene support the structural assignments. Data obtained for the experimental resins indicate that the acetate groups influence the way in which chlorine is added to the polymer chain. furthermore, the data indicate the acetate groups undergo little, if any, chlorination.     

Block copolymers derived from azobiscyanopentanoic acid. X. Synthesis of silicone–vinyl block copolymers via polysiloxane(azobiscyanopentanamide)s

The synthesis of silicone–vinyl block copolymers has been studied by the use of poly(azo-containing siloxaneamide)s (abbreviated as PASAs), i.e., polysiloxane (azobiscyanopentanamide)s as macroazoinitiators. PASAs with number-average molecular weight of 12000–31000 and with siloxane chain lengths of 250–9800 were prepared by the condensation of azobiscyanopentanoyl chloride and α,ω-bis(3-aminopropyldimethyl)polysiloxanes in equimolar feeds. Several kinds of silicone–vinyl block copolymers were synthesized by radical polymerization of vinyl monomers such as methyl methacrylate, styrene, and vinyl acetate, in the presence of PASA in homogeneous media. The block copolymers with siloxane contents up to 30 mol % were then characterized on the basis of infrared absorption, proton NMR spectra, and gel permeation chromatography.     

Nuclear magnetic resonance studies on microstructure of ethylene copolymers. VII. Proton resonance spectra of hydrolyzed ethylene–vinyl acetate copolymers1

Complete and partial alcoholyses of ethylene–vinyl acetate (E–VA) copolymers yield ethylene–vinyl alcohol (E–VOH) copolymers and ethylene–vinyl acetate–vinyl alcohol (E–VA–VOH) terpolymers, respectively. From the 220-MHz proton NMR spectra of E–VOH copolymers the stereoregular and chemical sequence distributions of the comonomers can be readily determined. Partially hydrolyzed E–VA polymers were acetylated with perdeuterated acetic anhydride. The monomer distributions in the terpolymers were then quantitatively determined by examining the proton spectra of the derived products. It was found that alcoholysis of E–VA polymers occurs preferentially at VA units which have neighboring VA groups.     

Carbon-13 NMR of poly(vinyl acetate) and ethylene–vinyl acetate copolymer

Carbon-13 nuclear magnetic resonance spectra of atactic poly(vinyl acetate) and ethylene–vinyl acetate copolymers are reported and analyzed. Carbon spectra at 22.6 and 62.9 MHz together with use of shift reagents have permitted a more complete assignment than previously reported; in some cases the published assignments are found to be in error.     

Nuclear magnetic resonance studies on microstructure of ethylene copolymers. VI. Carbon-13 spectra of ethylene–vinyl acetate copolymers

The 22.6-MHz Fourier-transform noise-decoupled ¹³C (carbon-13) NMR spectra of several ethylene–vinyl acetate (E–VA) copolymers were obtained. We found that triad information on monomer placement can be deduced from carbonyl resonances, triad and pentad information can be deduced from methine carbon resonances, and triad information is available from the methylene carbon resonances. The random comonomer distributions in E–VA polymerizations were demonstrated up to pentad placements. In addition, the use of model-compound data in the analysis of copolymer spectra was shown.     

Thermal analysis and FT‐IR studies of adsorbed poly(ethylene‐stat‐vinyl acetate) on silica

Adsorbed poly(ethylene‐stat‐vinyl acetate) (PEVAc) on fumed silica was studied using temperature‐modulated differential scanning calorimetry (TMDSC) and FT‐IR spectroscopy. The properties of the copolymers were compared with poly(vinyl acetate) (PVAc) and low density polyethylene (LDPE) as references. TMDSC analysis of the copolymer‐silica samples in the glass transition region was complicated for the copolymers because of the ethylene crystallinity. Nevertheless, examination of the glass transition region for small adsorbed amounts of these copolymers indicated the presence of tightly‐ and loosely‐bound polymer segments, similar to other polymers which have an attraction to silica. Compared with bulk polymers with the same composition, the tightly‐bound polymers showed an increased glass transition temperature (T_g) and a loosely‐bound fraction with a lower T_g than bulk. FT‐IR spectra of the surface copolymers indicated that the fraction of bound carbonyls (p) increased as the fraction of vinyl acetate in the copolymers decreased, consistent with the notion that the carbonyls from vinyl acetate preferentially find their way to the silica surface. Spectra from samples with different adsorbed amounts of polymer were used to obtain the amount of bound polymer (M_b) and the ratio of molar absorption coefficients of bound carbonyls to free carbonyls (X). The copolymers had very large p values (up to 0.8) at small adsorbed amounts and dependent on the composition of the polymer. However, an analysis of the bound fractions, based on only the vinyl acetate groups, superimposed the data, suggesting that the ethylene units simply dilute the vinyl acetate groups in the surface polymer. The sample with the smallest fraction of vinyl acetate did not show this behavior and may be considered to be “carbonyl poor.” © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 727–736     

Durable and refreshable polymeric N‐halamine biocides containing 3‐(4′‐vinylbenzyl)‐5,5‐dimethylhydantoin

A novel vinyl‐hydantoin monomer, 3‐(4′‐vinylbenzyl)‐5,5‐dimethylhydantoin, was synthesized in a good yield and was fully characterized with Fourier transform infrared (FTIR) and ¹H NMR spectra. Its homopolymer and copolymers with several common acrylic and vinyl monomers, such as vinyl acetate, acrylonitrile, and methyl methacrylate, were readily prepared under mild conditions. The polymers were characterized with FTIR and ¹H NMR, and their thermal properties were analyzed with differential scanning calorimetry studies. The halogenated products of the corresponding copolymers exhibited potent antibacterial properties against Escherichia coli, and the antibacterial properties were durable and regenerable. The structure–property relationships of the polymers were further discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3348–3355, 2001     

Characterization of copolymers of vinyl acetate with ethyl α-cyanocinnamate

Alternating and random copolymers of ethyl α-cyanocinnamate and vinyl acetate were studied. Infrared, ¹H, and ¹³C spectra of the copolymers are discussed by comparison with a model compounds, poly(vinyl acetate), and various copolymers. The decomposition temperature and T_g of copolymers of various composition, studied by TMA and DSC, increase both with increasing content of ethyl α-cyanocinnamate.     

Reactivity ratios and microstructure determination of vinyl acetate–alkyl acrylate copolymers by NMR spectroscopy

(Vinyl acetate)/(ethyl acrylate) (V/E) and (vinyl acetate)/(butyl acrylate) (V/B) copolymers were prepared by free radical solution polymerization. ¹H-NMR spectra of copolymers were used for calculation of copolymer composition. The copolymer composition data were used for determining reactivity ratios for the copolymerization of vinyl acetate with ethyl acrylate and butyl acrylate by Kelen-Tudos (KT) and nonlinear Error in Variables methods (EVM). The reactivity ratios obtained are r_v = 0.03 ± 0.03, r_E = 4.68 ± 1.70 (KT method); r_v = 0.03 ± 0.01, r_E = 4.60 ± 0.65 (EV method) for (V/E) copolymers and r_v ? 0.03 ± 0.01, r_B ? 6.67 ± 2.17 (KT method); r_v = 0.03 ± 0.01, r_B = 7.43 ± 0.71 (EV method) for (V/B) copolymers. Microstructure was obtained in terms of the distribution of V- and E-centered triads and V- and B-centered triads for (V/E) and (V/B) copolymers respectively. Homonuclear ¹H 2D-COSY NMR spectra were also recorded to ascertain the existence of coupling between protons in (V/E) as well as (V/B) copolymers. © 1995 John Wiley & Sons, Inc.     

End‐functionalized copolymers prepared by the addition–fragmentation chain‐transfer method: Vinyl acetate/methacrylonitrile system

Copolymers of vinyl acetate and methacrylonitrile were prepared by free‐radical polymerization in the presence of the chain‐transfer agent (CTA) ethyl‐α‐ (t‐butanethiomethyl)acrylate. Molecular weight measurements showed that the chain‐transfer constants increased with the vinyl acetate content of the comonomer mixture, ranging from 0.42 for methacrylonitrile to 6.3 for the copolymerization of a vinyl acetate‐rich monomer mix (89/11). The bulk copolymer composition was not appreciably affected by the amount of CTA used in the copolymerization. The efficiency of the addition–fragmentation mechanism in producing specifically end‐functionalized copolymers was investigated with ¹H NMR spectroscopy. Spectral peaks consistent with all the expected end groups were observed for all comonomer feeds. Peaks consistent with other end groups were also observed, and these were particularly prominent for copolymers made with lower CTA concentrations. At the highest concentrations used, quantitative measurements of end‐group concentrations indicated that 70–80% of the end groups were those expected on the basis of the addition–fragmentation chain‐transfer mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2911–2919, 2001     

Microstructure of vinyl acetate–butyl acrylate copolymers studied by 13C-NMR spectroscopy: Influence of emulsion polymerization process

The compositions and sequence distributions of vinyl acetate–butyl acrylate copolymers obtained with batch and semicontinuous emulsion polymerizations have been studied by ¹H and ¹³C NMR. The batch process gives heterogeneous copolymers while with the semicontinuous one the sequence distribution is statistical. These differences in sequence distributions have been related to the physical properties of the copolymers.     

Sequence distributions of vinyl chloride-vinyl acetate and vinyl chloride-vinyl propionate copolymers

¹³C-NMR spectroscopy was used in a detailed study of vinyl chloride-vinyl acetate and vinyl chloride-vinyl propionate copolymers. The NMR spectra of the methylene carbon region showed three split peaks whose intensities changed with composition of the copolymers. These peaks were assigned to diad sequences and the observed diad concentrations were in good agreement with the calculated concentrations in terms of the random copolymerization theory. For the methine carbon spectra of vinyl acetate or vinyl propionate units in the copolymers the degree of splitting of the signal was improved by the addition of tris(1,1,1,2,2,3,3-heptafluro-7,7-diemthyl-1,4,6-octanedinata)-praseodymium as a shift reagent. Four peaks assigned to the methine carbon were interpreted in terms of triad sequence distribution and tacticity.     

Alternating copolymerization through the complexes of conjugated vinyl monomers–alkylaluminum halides

A vinyl monomer that has the nitrile or carbonyl group conjugated to the C?C double bond, such as acrylonitrile, methyl acrylate, and methyl methacrylate, forms a complex with an alkylaluminum halide, and the complex reacts spontaneously with a hydrocarbon monomer such as styrene, propylene, or ethylene, giving a high molecular weight copolymer. The copolymers always contain the two monomer units in 1:1 ratio. Thus styrene, copolymerized with methyl acrylate or methyl methacrylate in the presence of ethylaluminum sesquichloride in homogeneous toluene solution, gives such an equimolar copolymer regardless of the initial monomer compositions. The NMR spectra of these copolymers are distinctly different from those of the equimolar copolymers obtained with azobisisobutyronitrile as initiator and have simpler and well separated patterns. The copolymers and the corresponding radical copolymers appear to be amorphous, judged by their x-ray diffraction patterns and their differential thermal analyses. Their infrared spectra resemble each other very closely. Hence, the difference in the NMR spectra may be ascribed to the matter of the sequence distribution. The infrared spectrum of ethylene–methyl acrylate copolymer shows no absorption near 720 cm.^?1 due to the methylene sequence arising from ethylene–ethylene linkage. These experimental data lead to the inference that the equimolar copolymers obtained in this work may have an alternating sequence.     

Thermal degradation of vinyl alcohol/vinyl acetate copolymers. III. Study of the reaction products

The thermal decomposition of vinyl alcohol/vinyl acetate copolymers have been studied at p = 10⁻²–10⁻⁴ Torr and T = 0–600°C. The decomposition products (solids, liquids, and gases) have been characterized by infrared (IR) and ultraviolet (UV) spectroscopy, gas chromatography, vapor pressure osmometry, and elemental analysis. It has been ascertained on the basis of the obtained data that the decomposition mechanism of the vinyl alcohol/vinyl acetate copolymers depends on the chemical composition and sequence distribution of comonomers.     

Structure and property relationships in ethylene–vinyl acetate copolymers

The effects of vinyl acetate content on crystallinity of ethylene–vinyl acetate (E/VA) copolymers were investigated by x-ray diffraction and differential thermal analysis (DTA). The values of these parameters obtained from DTA were found to agree quantitatively with data calculated from x-ray, probability equations, and copolymer theory. The melting points of the crystalline copolymers, and the molar amounts of vinyl acetate to produce a completely amorphous rubber corresponds exactly to that predicted by the Flory theory. The random character expected in E/VA copolymers is thereby confirmed. The physical properties of E/VA copolymers of all ranges of compositions and crystallinity were determined. Depending directly upon vinyl acetate content, the copolymers changed progressively from highly crystalline polyethylene to semicrystalline polyethylene, a completely amorphous rubber, a soft plastic with a glass transition near room temperature. Properties which were correlated with copolymer composition include: crystallinity, melting point, density, modulus, tensile strength, glass transition, and solubility. Finally, the effect on crystallinity and physical properties of replacing the acetoxy group in E/VA with the smaller, highly polar hydroxyl group (ethylene—vinyl alcohol copolymer) was also investigated.     

The effect of residual acetate groups on the structure and properties of vinyl alcohol–ethylene copolymers

Vinyl alcohol–ethylene (VAE) copolymers, commercially manufactured by hydrolysis of the corresponding vinyl acetate–ethylene copolymers, can contain small amounts of unhydrolyzed vinyl acetate. This article shows the influence of these residual groups on the structure of the resulting copolymers, studied by nuclear magnetic resonance and wide‐angle X‐ray scattering. Thermal and mechanical properties of these materials were investigated by differential scanning calorimetry, thermogravimetry, drawing behavior, birefringence measurements, and dynamic mechanical analysis. The structure of the copolymers is considerably affected by the volume of the residual acetate groups, bigger than that of the hydroxyl ones, which hinders the crystallization process. In relation to the thermal and mechanical properties, the temperature and enthalpy of melting as well as the Young's modulus and yield stress, decrease as vinyl acetate molar fraction increases. Moreover, the α and β relaxations are shifted to lower temperatures as residual content in the copolymer is raised. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 573–583, 2000     

Synthesis of poly(vinyl acetate)‐b‐polystyrene and poly(vinyl alcohol)‐b‐polystyrene copolymers by cobalt‐mediated radical polymerization

Well‐defined poly(vinyl acetate) macroinitiators, with the chains thus end‐capped by a cobalt complex, were synthesized by cobalt‐mediated radical polymerization and used to initiate styrene polymerization at 30 °C. Although the polymerization of the second block was not controlled, poly(vinyl acetate)‐b‐polystyrene copolymers were successfully prepared and converted into amphiphilic poly(vinyl alcohol)‐b‐polystyrene copolymers by the methanolysis of the ester functions of the poly(vinyl acetate) block. These poly(vinyl alcohol)‐b‐polystyrene copolymers self‐associated in water with the formation of nanocups, at least when the poly(vinyl alcohol) content was low enough. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 81–89, 2007     

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002     

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002     

Synthesis of poly(vinyl acetate)‐graft‐polystyrene by a combination of cobalt‐mediated radical polymerization and atom transfer radical polymerization

Vinyl acetate and vinyl chloroacetate were copolymerized in the presence of a bis(trifluoro‐2,4‐pentanedionato)cobalt(II) complex and 2,2′‐azobis(4‐methoxy‐2,4‐dimethylvaleronitrile) at 30 °C, forming a cobalt‐capped poly(vinyl acetate‐co‐vinyl chloroacetate). The addition of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy after a certain degree of copolymerization was reached afforded 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐terminated poly(vinyl acetate‐co‐vinyl chloroacetate) (PVOAc–MI; number‐average molecular weight = 31,000, weight‐average molecular weight/number‐average molecular weight = 1.24). A ¹H NMR study of the resulting PVOAc–MI revealed quantitative terminal 2,2,6,6‐tetramethyl‐1‐piperidinyloxy functionality and the presence of 5.5 mol % vinyl chloroacetate in the copolymer. The atom transfer radical polymerization (ATRP) of styrene (St) was studied with ethyl chloroacetate as a model initiator and five different Cu‐based catalysts. Catalysts with bis(2‐pyridylmethyl)octadecylamine (BPMODA) or tris(2‐pyridylmethyl)amine (TPMA) ligands provided the highest initiation efficiency and best control over the polymerization of St. The grafting‐from ATRP of St from PVOAc–MI catalyzed by copper complexes with BPMODA or TPMA ligands provided poly(vinyl acetate)‐graft‐polystyrene copolymers with relatively high polydispersity (>1.5) because of intermolecular coupling between growing polystyrene (PSt) grafts. After the hydrolysis of the graft copolymers, the cleaved PSt side chains had a monomodal molecular weight distribution with some tailing toward the lower number‐average molecular weight region because of termination. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 447–459, 2007