Carbon-13 Nuclear Magnetic Resonance Determination of Monomer Composition and Sequence Distribution in Ethylene-Propylene Copolymers Prepared with a Stereoregular Catalyst System

Kweon

et al. 1996

Polym J

ABSTRACT:The monomer compositions in a series of propylene heterophasic copolymer, propylene random copolymer, propylene random terpolymer and ethylene-propylene-2-ethylidiene-5-norborane (ENB) terpolymer have been determined from 13 C NMR spectra. The simplified and highly resolved 13 C NMR spectra made it possible to assign unambiguously and calculate the monomer compositions. A complete sets of NMR chemical shift assignments and the way to measure the quantity of monomer are newly given in diverse polymers. Furthermore, it is shown that complete dyad, triad, tetrad and pentad distributions can be determined by 13 C NMR spectra. These NMR quantitative analytical determinations for monomer compositions are consistent with those from Infrared spectroscopic data.KEY WORDS 13 C Nuclear Magnetic Resonance / Monomer Composition / Ethylene-Propylene Copolymer / Ethylene-Propylene-Butene-I Terpolymer / Ethylene-Propylene-Diene Terpolymer / It has been demonstrated that carbon-13 nuclear magnetic resonance (1 3 C NMR) is sensitive to monomer sequence structure in high polymers. 1 -8 This technique has been proven quite useful in the determination of polymer compositional studies. 9 -12 13 C NMR spectroscopy is a unique spectroscopic tool in representing copolymer molecular structure because unlike connecting comonomer sequences can be detected independently of like connecting comonomer sequences. Quite often, this structural information is not only limited to just dyad but also includes triad, tetrad, and even pentad connecting sequences. Thus, copolymer structure can be determined with considerable details. 9 -12 The translation of 13 C NMR data to meaningful quantitative terms, however, is not always readily accomplished. The observed spectral information is also related to factors other than the simple comonomer distribution. Configuration and mode of addition can seriously complicate the analysis of copolymer 13 C NMR spectra.The nature of Fourier transform techniques, which are used to acquire the data, requires a relatively detailed knowledge of the relaxation parameters for the particular polymer investigated if the subsequent analysis is to be quantitative and unambiguous. Thus, the choice of pulse delays and possibly, pulse angles are dependent upon the spin-lattice relaxations (T 1 ) of the nonequivalent polymer carbons. 13 -ls In order to get a true equilibrium spectrum, a spectrum is acquired only after a time of approximately 4-5 x T 1 (max.) has elapsed since the last pulse. Thus integrated peak intensities will not be misleading. 6 Another problem of concern is the possibility that different carbons in the same molecule may possess different nuclear Overhauser enhancement (NOE). 16 · 1 7 The concentration of different groups or isomers obtained from the integrated intensities may be seriously affected by such a phenomenon.This problem can be circumvented by the use of inverse -~--------gated decoupling or chemical modification of the sample (addition of paramagnetic reagent). 6 However, both of these te...

Section: Resultsmentioning

confidence: 90%

A 13C NMR Determination for Monomer Compositions in Ethylene–Propylene Copolymers, Ethylene–Propylene–Butene-1, and Elthylene–Propylene–Diene Terpolymers

Kweon

et al. 1996

Polym J

Macro Chemistry & Physics

“…Table 1 (comonomer content 15.2 mol-%). It is possible to determine dyad distribution from methylene data by the following equations: [35] PP ¼ S aa…”

Section: Resultsmentioning

confidence: 99%

Ethylene/4‐Methyl‐1‐pentene Copolymers by a “Constrained Geometry Catalyst”: Advances in ¹³C NMR Assignment

Losio

Boccia

2008

Ethylene/4‐methyl‐1‐pentene (E/4M1P) copolymers were synthesized by [Me2Si(η5‐Me4C5)‐(η1‐N‐tBu)TiCl2] and methylalumoxane (MAO) catalyst (CG) and analyzed by 13C NMR. The low regio‐ and stereoregularity of CG leads to spectral multiplicities which can be ascribed not only to differences in comonomer sequences but also to the presence of regio‐ and stereoirregularities. The tendency of CG to give a nearly random comonomer distribution gives rise to so far undetectable alternating sequences. The complete set of assignments proposed allows a satisfactory characterization of variously microstructured E/4M1P copolymers and the evaluation of the amount of regioirregular sequences in addition to the full determination of dyad and triad copolymer composition.magnified image

“…The pulse interval was 5.2 s, the acquisition time was The mesopentad fraction (mmmm) of PP was determined according to the method reported previously 13,14) . The monomer composition of PE-co-PP was estimated according to standard techniques 15,16) .…”

Section: Characterization Of Resulting Polymersmentioning

confidence: 99%

Synthesis and basic characteristics of polypropene-block-poly(ethene-co-propene) by modified stopped-flow polymerization with an MgCl2-supported Ziegler catalyst

Yamahiro¹,

Mori²,

Nitta³

et al. 1999

Macromol. Chem. Phys.

SUMMARY: A well-defined diblock copolymer, polypropene-block-poly(ethene-co-propene), was synthesized by modified stopped-flow polymerization with an MgCl 2 -supported Ziegler catalyst. The copolymer shows a unimodal gel permeation chromatography (GPC) elution curve without any material in the low molecular weight region. The molecular weight can be controlled by the polymerization time (ca. 0.1 to 0.2 s). Furthermore, the elution pattern by cross fractionation chromatography showed that the block copolymer eluted at each temperature region between 0 8C to 120 8C is composed of a uniform material. After extraction with heptane, the 13 C NMR spectra showed that the signals from poly(ethene-co-propene) remain unchanged in the block copolymer but are absent in a corresponding polypropene/poly(ethene-co-propene) blend. The results of differential scanning calorimetry (DSC) and optical microscopic observation indicate not only the formation of a block copolymer with a chemical linkage between the polypropene block and the poly(etheneco-propene) block, but also the regulation of the crystalline morphology in the block copolymer by changing the composition.