Assignment of the 1H and 13C NMR spectra and stereochemical analysis of radical-initiated poly(1-naphthylmethyl acrylate) and poly[2-(1-naphthyl)ethyl acrylate] (original) (raw)
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The stereochemical structures of poly(pentyl acrylate) (PPA) prepared by solution polymerization is studied by the combination of one and two dimensional NMR spectroscopy. The OCH2, methine, methylene, and the carbonyl carbon resonances are assigned to triad, tetrad and pentad sequences respectively. The polymerization mechanism was studied using the carbonyl and OCH2 resonances. It was found that homopolymerization followed Bernoullian statistics. The various configurational assignments in the aliphatic region were done with the help of inverse HETCOR, inverse HETCOR-TOCSY, homonuclear DQFCOSY experiments.
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Poly(isobornyl acrylate) (PiBA) was prepared by atom transfer radical polymerization (ATRP). Complete characterization of microstructure of PiBA was carried out using one-dimensional [ 1 H, 13 C{ 1 H}] and two-dimensional (HSQC, TOCSY and HMBC) NMR spectra. The methyl, methylene, methine, quaternary and carbonyl carbon resonance signals were found to be sensitive to various configurational sequences. The methine carbon (C 12 ) was assigned up to triad configurational sequences in 13 C{ 1 H} NMR spectrum whereas b-methylene carbon resonances were assigned up to diad configurational sequences. The quaternary carbon in 13 C{ 1 H} NMR spectrum were resolved completely with the help of HMBC NMR spectrum. The stereoregularity of PiBA was found to be random with mm = 20%, mr = 53%, and rr = 27%.
Journal of Polymer Science Part A: Polymer Chemistry, 2009
Terpolymers of acrylonitrile (A), methyl methacrylate (B), and methyl acrylate (M) were synthesized under optimized atom transfer radical polymerization conditions using 2-bromopropionitrile as an initiator and CuBr/dinonyl bipyridine as a catalyst. Variation of the feed composition led to terpolymers with different compositions. Composition of synthesized terpolymers were calculated from quantitative 13 C{ 1 H} NMR spectra. Number average molecular weight and polydispersity index were determined by gel permeation chromatography. The overlapping and broad signals of the terpolymers were assigned completely to various compositional and configurational sequences by correlation of one-dimensional 1 H, 13 C{ 1 H}, and distortionless enhancement by polarization transfer and two-dimensional heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY). 2D HSQC NMR study shows one to one correlation between carbon and proton signals, while 2D TOCSY spectra were used to confirm 1, 2 bond geminal couplings between nonequivalent protons of same methylene group. V
Assignment of finely resolved 13C NMR spectra of polyacrylonitrile
Polymer, 2001
13 C NMR spectra of three poly(vinyl alcohol)s differing in the stereoregularity (atactic, syndiotactic-rich and isotactic-rich) were determined in DMSO-d 6 and D 2 O. The methylene and methine carbon absorptions including so far unassigned ones (mmmr heptad signals in mm-centered region and all heptad signals in mr-centered region) were completely assigned with hexads and heptads, respectively, and the assignments were quantitatively con®rmed for atactic and syndiotactic-rich poly(vinyl alcohol)s. The isotactic-rich polymer showed a discrepancy between the observed and the calculated intensities, assuming the ®rst-order Markov statistics, due to dif®culty in determining its polymerization mechanism. q
Journal of Polymer Research, 2020
This investigation reports the analysis of different microstructures present in poly(methyl methacrylate) (PMMA) using1D and 2D NMR spectroscopy. The PMMA used in this study has been prepared via activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) in DMF at ambient temperature using methyl 2-chloro propionate (MCP) as initiator, CuBr 2 as catalyst in combination with N, N, N´, N´´, N´´-pentamethyldiethylenetriamine (PMDETA) as ligand and ascorbic acid as reducing agent. 13 C NMR, which provides good information about tacticity of a polymer, has been used extensively along with 1 H NMR spectroscopy to extract the information about the different microstructures present in PMMA. Heteronuclear multiple-bond correlation (HMBC), heteronuclear single-quantum coherence (HSQC), and total correlation spectroscopy (TOCSY) were also used to study the position of protons, couplings with carbon etc. in the PMMA.
Macromolecules, 1992
A series of copolymers of ethylene and acrylonitrile, produced by high-pressure free-radical polymerization, were recovered from a reactor in low yields. The copolymers differed by melting points and profiles of the melting point distributions. These were characterized utilizing carbon-13 NMR for the structures and amounts of incorporated acrylonitrile (AN) repeat units. The carbon-13 NMR spectra were consistent with five principal modes of acrylonitrile incorporation. Each of the five different repeat unit structures contained only isolated acrylonitrile units, with only one being a linear -E-AN-E-structural sequence. It represented approximately 65 % of the acrylonitrile incorporation. The remaining structures were rationalized in a common manner by considering variations in the Roedel free-radical "back-biting" mechanism. Similar distributions of these five structures were observed independently of the total level of acrylonitrile. Interestingly, evidence for free-radical chain-transfer reactions involving terminal acrylonitrile units indicated that such reactions occurred to an extent of only about 6-7%. In the residues examined, there were essentially no consecutive sequences of acrylonitrile units, and polyacrylonitrile homopolymeric sequences were detected at only about 1 % .
Macromolecules, 1998
The effects of the initial monomer concentration, [M]o, and percent conversion on the extent of chain transfer to polymer in free-radical solution polymerization of n-butyl acrylate has been studied. The polymerizations were carried out in cyclohexane at 70°C using 0.1% (w/w) 2,2′-azobis(2-cyanopropane) as initiator and the mole percent branched repeat units (mole percent branches) in the poly(n-butyl acrylate) was determined from unique resonances of branch-point carbons in the 13 C NMR spectra. At [M]o > 10% (w/w) the mole percent branches is independent of [M]o and increases from 0.8 to ∼2.2% as conversion increases from 35 to ∼95%. However, for more dilute solutions, with [M]o e 10% (w/w), the mole percent branches increases as [M]o decreases and is higher than at equivalent conversions for the more concentrated solution polymerizations; e.g., at ∼25% conversion the mole percent branches increases from 2.7% for [M]o ) 10% (w/w) to 5.9% for [M]o ) 3% (w/w). These observations are explained in terms of the ratio of the concentrations of polymer repeat units and monomer in the vicinity of the propagating chain end. In more concentrated solutions, intermolecular chain transfer to polymer dominates because, at all except the lowest percent conversions, the overall polymer repeat unit concentration is sufficient for overlap of individual polymer coils. However, in the dilute solutions the overall polymer repeat unit concentration is too low for overlap of individual polymer coils and intramolecular chain transfer to polymer dominates. Under these conditions, the local polymer repeat unit concentration within the isolated propagating chains is defined by the chain statistics and so is approximately constant, whereas the monomer is distributed uniformly throughout the solution. Thus, for dilute solutions, as [M] o decreases, the probability of chain transfer to polymer (and hence the mole percent branches) increases.
Determination of the Distribution of Acrylic Comonomers in Free Radicals Polymers
Asian Journal of Chemistry, 2013
One of the most common and useful reactions to make polymers is free radical polymerization. This polymerization is used to make polymers from monomers containing carboncarbon double bonds such as acrylates, vinyl monomers, allylic monomers etc. Some acrylate monomers have been used by Voss et al. 1 and Wouters et al. 2 to study the effect of pendant functionality on the thermal and physical properties of polymers obtained by the reversible addition-fragmentation chain-transfer (RAFT) polymerization. The methacrylate copolymers studied by these authors contained n-butyl-methacrylate and methyl methacrylate (MMA) to control the glass transition temperature of the final polymer and a minor fraction of one of the monomers displayed in Fig. 1. These monomers were chosen for their particular interacting capabilities (H-bonding or π-π interaction). In this study, the authors assumed that the distribution of comonomers in the RAFT polymers is random and nevertheless no further investigation was done to prove this supposition. We extended the work of Voss et al. 1 and Wouters et al. 2 by performing free radical copolymerization of monomers 3 and 5 with methyl methacrylate and butyl-methacrylate with the aim to estimate the reactivity ratios, giving though insight in the monomer distribution in the polymer chain. The copolymerizations of monomers 3 and 5 with both methyl methacrylate and butyl methacrylate were carried out. Subsequently, the reactivy ratios are determined and the compositions of the present polymers are presented. 1 H NMR spectroscopy is employed to study the polymer composition.
Polymer Journal, 2005
Compositional variations occurring along the chains in the copolymers of methyl methacrylate (M) and n-butyl acrylate (B) were investigated using 13 C{ 1 H} NMR spectroscopy. Copolymerization of methyl methacrylate and n-butyl acrylate with varying infeed ratio was done using Atom Transfer Radical Polymerization. Copolymer compositions were determined from 1 H NMR spectra. Percentage conversion was studied gravimetrically. Analysis of the variations of methylene dyads fractions and M-and B-centered triad fractions with conversion was done using Distortionless Enhancement by Polarization Transfer (DEPT) experiments to have a better insight to trend followed by the compositional drift with conversion. The experimental results were found to be in good agreement with the simulated data indicating towards the uniformity along the copolymer chains resulting in the formation of gradient copolymers.
Using 1H NMR Spectra of Polymers and Polymer Products To Illustrate Concepts in Organic Chemistry
Journal of Chemical Education, 2017
The use of 1 H NMR spectroscopy to analyze the number-average molecular weight of a methoxy poly(ethylene glycol) (MPEG) and an acetate derivative of this MPEG is described. These analyses illustrate NMR principles associated with the chemical shift differences of protons in different environments, NMR integration, and the effect of the natural abundance of 13 C carbons in a polymer and the resulting low but predictable intensity of the satellite peaks due to 13 C− 1 H spin−spin coupling. Also included in this discussion is an example of end-group analysis of the product of an acetylation reaction. In the discussion of the acetylation product, an 1 H NMR spectrum of a crude product mixture where the small peaks due to end groups can be seen along with a set of impurities due to catalyst, solvents, and byproducts is included because, in practice, chemists often first see these sorts of spectra.