13C–{1H} Nuclear Magnetic Resonance Spectroscopy of Poly(methyl methacrylate)

Abstract

The 13C-{1H} high-resolution nuclear magnetic resonance spectra were measured for poly(methyl methacrylate). The spectra clearly split corresponding to dyad, triad, tetrad, and pentad placements. The relative intensity of every peak for the spectrum of a polymer prepared with 9-fluorenyllithium in tetrahydrofuran/toluene (80/20) at -23°C was reasonably interpreted by the Bernoulli trial model.The nuclear Overhauser effect due to total proton decoupling did not affect the relative intensities among the peaks assigned to chemically equivalent carbons except for the difference in stereochemical configuration. This was confirmed by comparison between the relative intensities of the above-mentioned polymer and by comparison between those of 13 C-{1H} and of 1H resonance of the polymer.The microtacticity determined by 13C-{1H} spectra of a polymer prepared with 9-fluorenyllithium in tetrahydrofuran/toluene (4/96) was fairly well interpreted by the stereoblend model, but by neither first-order nor second-order Markovian model. KEY WORDSPoly(methyl methacrylate) / 13C-{1H} NMR / Stereoblend / Markovian Model/ Bernoullian Model / Nuclear Overhauser Effect /

A cationic bridged zirconocene complex as the catalyst for the stereospecific polymerization of methyl methacrylate

“…g) The agreement factor is a normalized standard deviation of the measured signal intensities from the calculated signal intensities. [24][25][26][27] The smaller the agreement factor [24] the better the correspondence of the measured pentad distribution with a calculated pentad distribution on the basis of a proposed model. [25][26][27] h) For enantiomorphic site control.…”

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

“…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].…”

Analysis of ?-CH2 signals in the13C NMR spectra of the methyl methacrylate-ethyl acrylate copolymer as a tool for microstructure determination

“…In order to determine precisely the limits of the regions of the three respective diads it is necessary beforehand to examine in detail the spectra of homopolymers to assign the different tetrads. 12,13 However, in the case of PMMA certain tetrads, like MrMmMrM, can be situated in the same place as the signal of the OCH 3 (M) carbons and it was necessary to record the spectrum of isotactic PMMA in order to avoid this ambiguity [ Fig. 1(c)].…”