Application of 13C magnetic resonance spectroscopy to the determination of the tacticity of stereoregular poly (methyl methacrylate)

Peat, I. R.; Reynolds, William F.

doi:10.1016/s0040-4039(01)84627-x

Cited by 97 publications

(38 citation statements)

References 8 publications

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“…Then the spectrum can be simulated assuming Lorentzian lineshape. Assignment of the lines found in this way is in accordance with those from the literature [9,10].…”

Section: Syndiotactic Pmmasupporting

confidence: 89%

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by ¹³C NMR spectroscopy

1999

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IntroductionIn our previous paper [1] we have shown that it was possible to assign individual configurational sequences of poly(methyl methacrylate), PMMA, up to the heptad level. The method was based on the deconvolution of the carbonyl signal in the 13 C NMR spectrum by means of the algorithm of maximum likelihood [2] and then by comparison of the intensities of the individual lines with those calculated according to 1 st order Markov statistics. However, in the case of a copolymer, due to the complexity of the spectrum this method permitted only assignment of the predominating sequences as it was shown for the copolymer of methyl methacrylate and ethyl acrylate [3], PMMA/EA. Based on these first results we have developed a new method of incremental calculation of chemical shifts of the carbonyl signal for different configurational-compositional sequences at triad and pentad level. Therefore, having both intensities and respective line positions, we were able to simulate the 13 C NMR carbonyl signal for this copolymer [4]. Now, we would like to test if this incremental method is applicable to describe the carbonyl signal observed in the 13 C NMR spectrum of the model homopolymer, PMMA. ExperimentalPredominantly syndiotactic PMMA was synthesized by free radical polymerization. The methyl methacrylate monomer was placed in a double-coated reactor under nitrogen and then heated up to 78°C with azobisisobutyronitrile (AIBN) as radical initiator. Predominantly isotactic PMMA was prepared by anionic polymerization under argon atmosphere at -78°C in a mixture of toluene and tetrahydrofuran as a solvent, according to the method described previously [5], using fluorenyllithium as the initiator.The 100 MHz 13 C NMR spectra were recorded on a Bruker DRX 400 for 5 w. % solutions in CDCl 3 at 40°C. In order to obtain quantitative spectra a gated decoupling sequence was applied even though the nuclear Overhauser effect does not influence the carbonyl signal [6] and the time delay between the pulses has to be set at least 5 times greater than the longest relaxation time. Since T 1(C=O) ≅ 3 ÷ 6 sec, the delay was set to 30 sec [7]. A reasonable signal to noise ratio was attained after about 1200 scans. The quantitative nature of the spectra was verified by comparison of the intensities for the C=O, α-CH 3 and α-C signals. Results and discussion Syndiotactic PMMAIn the previous publication [4] we have shown that the 13 C NMR chemical shifts for different configurational sequences of PMMA/EA observed in the carbonyl signal can be described in an empirical manner. For example, the positions of the two symmetric methyl methacrylate triads can be calculated as: Sciences, Institute of Coal Chemistry, ul. Sowinskiego 5, Poland Abstract -A method of incremental calculation of chemical shifts in the 13 C NMR spectra for different configurational-compositional sequences, developed for copolymer of methyl methacrylate and ethyl acrylate, PMMA/EA, has been applied to poly(methyl methacrylate) samples of different tacticity. The numer...

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“…Then the spectrum can be simulated assuming Lorentzian lineshape. Assignment of the lines found in this way is in accordance with those from the literature [9,10].…”

Section: Syndiotactic Pmmasupporting

confidence: 89%

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by ¹³C NMR spectroscopy

1999

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“…The a-CH 3 group is present in the chemical structure of both mesomeric units, but, for PMMA 8 (M in Figure 2), this group gives three resonances at 17.58, 18.75, and 21.73ppm from tetramethylsilane (TMS), assigned to iso (mm), hetero (mr+rm), and syndiotactic (rr) triads in order of increasing field. 9 The a-CH 3 group of PLMA also shows three resonance signals at 17.81, 19.45, and 21.61 ppm from TMS, assigned to mm, mr + rm, and rr tactic triads in order of increasing field, since these values are close to those reported for the resonance of the a-CH 3 in PMMA. 8 -10 The 60).…”

Section: Resultssupporting

confidence: 64%

Microstructural Analysis of Methyl Methacrylate-Lauryl Methacrylate Copolymers Using 13C NMR Spectroscopy

Sannigrahi

Garnaik

1998

Polym J

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ABSTRACT:13 C NMR spectra (75.5 MHz) of methyl methacrylate (M}-lauryl methacrylate (L) copolymers prepared by group transfer polymerization (GTP) were analyzed for sequence distribution and relative stereochemical configuration of monomer units along the macromolecular chains. The concentrations of M-and L-centered triads, determined experimentally from ix-CH 3 and C=O resonance signals, were in good agreement with those calculated statistically, taking into consideration the terminal copolymerization model and Bernoullian distribution of stereoregularity, with the statistical parameters P,i determined from the reactivity ratios rM= 1.38±0.11 and rL =0.68 ±0.10 and the coisotacticity parameters uMM=0.24, uLL =0.27, O"ML =O"LM=O"* =0.30. KEY WORDSGroup Transfer Polymerization / 13 C Nuclear Magnetic Resonance / Polymer Microstructure / Methyl Methacrylate / Laury! Methacrylate / (l-Methoxy-2-methyl-l-propenyl)oxytrimethylsilane / Tetrabutylammonium Bibenzoate / Tetrahydrofuran / Group Transfer Polymerization (GTP) makes possible the synthesis of random and block copolymers with good control of molecular weight and distribution. Copolymers of methyl methacrylate (MMA) with higher alkyl methacrylates, such as lauryl methacrylate (LMA) exhibit interesting properties on account of their comblike structures. Controlled synthesis of such polymers is not possible by anionic techniques since living anionic polymerization of alkyl methacrylates is feasible only below -50°C in tetrahydrofuran (THF), under which condition LMA has no solubility in the solvent. Thus, GTP is the only available synthetic method for preparing narrow molecular weight distribution random and block copolymers of MMA and LMA. We recently reported the preparation of random copolymers of MMA and LMA spanning a wide composition range. 1 13 C NMR spectroscopy is useful for the analysis of chemical structure, morphology, orientation and molecular dynamics of a polymer chain 2 all of which have an effect on material properties. The properties of a copolymer depend both on the chemical nature of the repeating units and on their arrangement within the polymer chain.Detailed microstructural analysis of acrylic ester copolymers synthesized by GTP has not been reported in the literature. This paper examines the detailed microstructure of these copolymers using 13 C NMR spectroscopy. EXPERIMENTAL CopolymerizationThe copolymers ofMMA and LMA with varying feed compositions were prepared by using (l-methoxy-2-methyl-1-propenyl)oxytrimethylsilane (MTS) and tetrabutylammonium bibenzoate (TBABB) as a initiator and catalyst in THF at room temperature. 1 Precipitation in methanol and evaporation of solvent gave the random 1 To whom correspondence should be addressed. 340copolymers. The conversions of these copolymers were restricted to a low range as described in Table I. 13 C NMR Spectra Measurements 13 C NMR spectra were recorded at 75.5 MHz (Bruker MSL-300) spectrometer at 393 K. The sample concentration was 15% w/vin 1,2,4-trichlorobenzene. C 6 D 6 (10%) was used ...

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“…19 The tacticity of poly[(S)-MAP] has been evaluated from the 13 C-NMR signals of methyl group, which displays two resonances located at 19.9 and 17.4 ppm, assigned to mr and rr heterotactic and syndiotactic triads, respectively. 20 The probability of formation of a meso dyad m (P m ) can be calculated from the ratio of peak areas (mr/rr), which corresponds to 2P m (1-P m )/(1-P m ), 2 i.e., to the ratio between the probabilities of formation of mr and rr triads. A value of 0.26 is thus found for P m .…”

Section: Synthesis and Characterization Of Poly[(s )-Map] And Poly[(smentioning

confidence: 99%

Synthesis and chiroptical properties of optically active photochromic methacrylic polymers bearing in the side chain the (S)-3-hydroxypyrrolidinyl group conjugated with thetrans-azoaromatic chromophore

Angiolini

Caretti

Giorgini

et al. 1999

J. Polym. Sci. A Polym. Chem.

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Novel optically active polymethacrylates, namely poly[(S)‐3‐methacryloyloxy‐1‐(4‐azobenzene)pyrrolidine] and poly[(S)‐3‐methacryloyloxy‐1‐(4′‐nitro‐4‐azobenzene)pyrrolidine], have been synthesized by radical polymerization of the corresponding monomers, prepared in turn through a synthetic route preserving the asymmetric center by any racemization reaction. These homopolymers are characterized by the presence in the side chain of an optically active pyrrolidinyl ring linked to the trans‐azoaromatic system through the nitrogen atom. The optical activity of the polymers in solution appears much higher than that observed with the low molecular weight models, purposely synthesized for comparison. Circular dichroism spectra of the synthesized products demonstrated that, in solution, the macromolecules assume highly homogeneous conformations with a prevailing chirality to a larger extent with respect to analogous systems previously investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3257–3268, 1999

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Application of 13C magnetic resonance spectroscopy to the determination of the tacticity of stereoregular poly (methyl methacrylate)

Cited by 97 publications

References 8 publications

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by ¹³C NMR spectroscopy

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by ¹³C NMR spectroscopy

Microstructural Analysis of Methyl Methacrylate-Lauryl Methacrylate Copolymers Using 13C NMR Spectroscopy

Synthesis and chiroptical properties of optically active photochromic methacrylic polymers bearing in the side chain the (S)-3-hydroxypyrrolidinyl group conjugated with thetrans-azoaromatic chromophore

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Application of 13C magnetic resonance spectroscopy to the determination of the tacticity of stereoregular poly (methyl methacrylate)

Cited by 97 publications

References 8 publications

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by 13C NMR spectroscopy

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by 13C NMR spectroscopy

Microstructural Analysis of Methyl Methacrylate-Lauryl Methacrylate Copolymers Using 13C NMR Spectroscopy

Synthesis and chiroptical properties of optically active photochromic methacrylic polymers bearing in the side chain the (S)-3-hydroxypyrrolidinyl group conjugated with thetrans-azoaromatic chromophore

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Incremental method for determination of sequence distribution of poly(methyl methacrylate) by ¹³C NMR spectroscopy

Incremental method for determination of sequence distribution of poly(methyl methacrylate) by ¹³C NMR spectroscopy