Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride

1982 ◽  
Vol 15 (4) ◽  
pp. 1150-1152 ◽  
Author(s):  
Masahiro Kakugo ◽  
Yukio Naito ◽  
Kooji Mizunuma ◽  
Tatsuya Miyatake
Keyword(s):  
Sequence Distribution ◽  
Ethylene Propylene ◽  
Monomer Sequence ◽  
Titanium Trichloride

Monomer Sequence Distribution in Ethylene—Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Model

1978 ◽  
Vol 51 (2) ◽  
pp. 149-167
Author(s):  
C. J. Carman ◽  
R. A. Harrington ◽  
C. E. Wilkes
Keyword(s):  
13C Nmr ◽  
Probability Model ◽  
Reaction Probability ◽  
Probability Method ◽  
Nmr Spectrum ◽  
Methine Carbon ◽  
Ethylene Propylene ◽  
Monomer Sequence ◽  
Ethylene Propylene Rubber

Abstract One can measure r1r2 for an ethylene—propylene rubber by determining composition and χ, the ratio of contiguous to isolated propylene units. Our previous determination of χ depended on measuring methine carbon resonances in a 13C NMR spectrum. The χ method based solely on methine peak area measurements is inaccurate. This is not because the χ method is theoretically unsound, but because it is impossible to accurately extract the methine areas, necessary to calculate χ from the complex 13C NMR spectra of ethylene—propylene rubbers. The presence of inverted propylene produces ambiguity in a portion of the methine region. This means the methine areas can be used only to calculate a maximum and minimum boundary for r1r2. Another difficulty in using only methine areas to determine χ arises at propylene levels less than 35 wt%, because the methine areas for contiguous propylene triads become very small and are overlapped by strong resonances from long methylene sequences. We have developed a reaction probability method which accurately accounts for all the resonance areas in a 13C NMR spectrum of an ethylene—propylene rubber instead of restricting the analysis to the tertiary carbon areas. The reaction probability method produces a complete calculated 13C NMR spectrum as a best fit to the observed spectrum. The deduced probabilities provide the following derived quantities: (1) “r1r2”, a measure of monomer sequence randomness, (2) the distribution of methylene sequence lengths, (3) composition, (4) amount of propylene inversion. The probabilities can be used to directly calculate “r1r2”. Or alternatively, the probabilities can be used to calculate the methine carbon areas including the separation of the ambiguous methine area into contiguous and isolated contributions. These areas calculated from the probabilities can then be used to determine χ and the resultant r1r2. The two values for r1r2 are in good agreement, lending credence to the probability analysis. The composition derived from probabilities agrees with other analytical methods such as proton NMR and infrared. The limitation of the method is that we cannot accurately determine the percent propylene inversion. We can only conclude that in the majority of the copolymers of 20 to 60 wt% propylene that we have studied, the concentration of inverted propylene is significant and is between 10 and 40% of the total propylene present. Propylene enriched in carbon-13 could be used to prepare copolymers and perhaps resolve this uncertainty.

Monomer Sequence Distribution in Ethylene Propylene Elastomers. I. Measurement by Carbon-13 Nuclear Magnetic Resonance Spectroscopy

1971 ◽  
Vol 44 (3) ◽  
pp. 781-804 ◽  
Author(s):  
C. J. Carman ◽  
C. E. Wilkes
Keyword(s):  
Chemical Shifts ◽  
Catalyst System ◽  
Reactivity Ratio ◽  
Sequence Length ◽  
Copolymer Composition ◽  
Resonance Spectroscopy ◽  
Sequence Distribution ◽  
Ethylene Propylene ◽  
Average Value ◽  
Monomer Sequence

Abstract The carbon-13 chemical shifts of ethylene propylene copolymers were found to be very sensitive to monomer sequence distribution. Methylene resonances were interpreted in terms of methylene sequence length and tertiary carbon resonances were interpreted in terms of propylene centered pentad sequences. Propylene inversion was detected and measured quantitatively in the spectra. A formula was derived for calculating r1·r2, which is independent of monomer feed, and which is based on measuring contiguous and isolated propylene sequences in the copolymer. The interpretations are shown to be consistent for copolymers containing 26, 34, and 62 mole% propylene. The r1·r2 products were determined for each of these polymers. Calculation of copolymer composition based on the 13C chemical shift assignments gave excellent agreement with the compositions as determined by infrared and 1H NMR. A formula was derived, based on copolymerization theory, for calculating the reactivity ratio product, r1·r2, directly from the copolymer composition (% ethylene) and the ratio of contiguous to isolated propylene sequences. Using this formula an average value for r1·r2=0.42±0.02 was determined for the copolymers made with vanadium acetylacetonate-diethylaluminum chloride catalyst system.

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