Copolymers chemical shifts

Fig. 9. Postulated complete triad assignment of the a-CHj resonance in DMF at 100 °C for MMA-MAA copolymers. Chemical shifts given in cps from TMS at 220 MHz...

Serial number Mole fraction of styrene in copolymers Chemical shift of different triads ... 

Figure 7.6 Chemical shift (from hexamethyldisiloxane) for acrylonitrile-methyl methacrylate copolymers of the indicated methyl methacylate (Mj) content. Methoxyl resonances are labeled as to the triad source. [From R. Chujo, H. Ubara, and A. Nishioka, Polym. J. 3 670 (1972).]...

In the past, ionomers have generally consisted of 10-12 mole percent of ions and it is our intention to be consistent with the corresponding random ionomers previously discussed in the literature. In addition to gel permeation chromatography (GPC), H and 3C NMR can readily be utilized to verify the relative amount of monomer successfully incorporated into the block copolymer. For example, the composition of a PMMA-PTBMA diblock can be verified by H NMR ratioing the methyl ester integration (3.5 ppm) to the t-butyl ester integration (1.36 ppm). Figure 1 depicts the t-butyl ster chemical shift which appears reproducibly at 1.J6 ppm. C or FTIR can be utilized in certain instances when H NMR chemical shifts overlap. For... 

The analysis of 1H NMR spectra of aliphatic and aromatic polyanhydrides has been reported by Ron et al. (1991), and McCann et al. (1999) and Shen et al. (2002), and 13C NMR has been reported by Heatley et al. (1998). In 1H NMR, the aliphatic protons have chemical shifts between 1 and 2 ppm, unless they are adjacent to electron withdrawing groups. Aliphatic protons appear at about 2.45 ppm when a to an anhydride bond and can be shifted even further when adjacent to ether oxygens. Aromatic protons typically appear with chemical shifts between 6.5 and 8.5 ppm and are also shifted up by association with anhydride bonds. The sequence distribution of copolymers can be assessed, for example in P(CPH-SA), by discerning the difference between protons adjacent to CPH-CPH bonds, CPH SA bonds, and SA-SA bonds (Shen et al., 2002). FTIR and 111 NMR spectra for many of the polymers mentioned in Section II can be found in their respective references. 

An important first step in interpreting the C-13 spectra is to distinguish a-carbons from 3-carbons, i.e. methine from methylene. Observation of multiplicity when the proton decoupler is off is one way, but this is not always easy if the lines are broadened by chemical shift multiplicity. Measurement of has been used for this purpose since the 3-carbon with two bonded protons relaxes about twice as fast as the a-carbon with only one. A very positive way is by deuterium labelling. In Fig. 3 is shown the main-chain 25 MHz carbon spectrum of two styrene-S02 copolymers containing 58 mol% styrene, or a ratio of styrene to SO2 of 1.38 (7 ). In the bottom one, 3,3-d2-styrene has been used, cind all the 3-carbon resonances are distinguishable from the a-carbon resonances since the presence of deuterium has eliminated their nuclear Overhauser effect because of this eind the deuterium J coupling ( 20 Hz), they are markedly smaller eind broader than the a-carbon resonances. 

Main Chain Carbon Chemical Shifts in Styrene-SO>> Copolymers... 

Chemical Shifts of Hydrogenated 1,4-Po1.ydimethy1butadiene Compared to those of cis-2-Butene-Ethy1ene Alternating Erythrodiisotactic Copolymer... 

C NMR chemical shifts expected for the carbon atoms in propylene-vinyl chloride (P - VC) copolymers of low propyiene content are calculated as a function of copolymer stereosequence. Mark s conformational model of P - VC copolymers (C 004) Is coupled with the y gauche effect, which results in upfield chemical shifts for those carbon atoms in a gauche arrangement with carbon or chlorine substituents in the y position, to calculate the 13C NMR chemical shifts of the carbon atoms in the vicinity of a propyiene unit surrounded by vinyl chloride units. Agreement of the calculated chemical shifts and those which are observed is excellent. 

From Mark s RIS model for ethylene-propylene copolymers (J. Chem. Phys. 1972, 57, 2541) it is determined that P(t) = 0.380, P g+) = 0.014, and Pig") = 0.606 in 2,4-dimethylhexane (2,4-DMH). Using this RIS model, furthermore, for all the branched alkanes considered whose isopropyl groups are separated by at least one methylene carbon from the next substituted carbon and the RIS model developed by Asakura et at. (Makromol. Chem, 1976, 177, 1493) for head-to-head polypropylene to treat 2,3-dimethyl pentane, AS s are calculated for a large number of branched alkanes. The agreement between the observed and the calculated nonequivalent 13C NMR chemical shifts is quite good, including the prediction that separation of the isopropyl group from the next substituted carbon by four or more methylene carbons removes the nonequivalence. 

The reaction of acrylamide copolymers and taurine was studied at temperatures between 125° and 200° C, reaction time 2-7 hours, and taurine charge 10-100 mol% based on polymer. The substituted amide formation was determined by NMR and colloid titration. The C-13 NMR of the product exhibits carbonyls consistent with the formation of a secondary amide. The spectrum also exhibits two new methylene signals for the incorporated taurine at chemical shifts slightly different from the starting taurine. Additionally, the chemical shifts for the signals of taurine are pH dependent, whereas little change in chemical shift is observed for the signals of the incorporated taurine. The presence of sulfonate incorporated into the polymer was detected and quantitatively determined by colloid titration at pH 2.5. 

Addition of DPP to growing MPP at 60° C produced still another type of copolymer. Solvent-cast films of this material are transparent. The copolymer does not crystallize on heating, forms stable solutions in m-xylene, and has a single glass transition, at 190°C. The thermal behavior is similar to that of a random copolymer, but the NMR spectrum (Figure 7) is more nearly that expected of a block copolymer. The methyl proton peak is rather sharp with the chemical shift expected for... 

Table II. Chemical Shifts of Methyl Protons in DMP—DPP Copolymers...

C-NMR spectroscopy has also been used to investigate the composition of DADMAC copolymers [38, 45-47]. Copolymers with acrylamide (AAM) have been extensively studied. Based on the chemical shifts in the 13C-NMR spectra of the homopolymers of DADMAC [17-19] and AAM [48-50], the copolymer spectra can be analyzed. Specifically from two likely chad structures (m/r) in PAAM and six different diad structures (r/m, c/t) in PDADMAC, eight different diad structures can be expected for the copolymers. A detailed NMR analysis has therefore been carried out in order to determine the copolymer compositions. The reactivity ratios obtained were found to be in good agreement with the results from other methods, such as potentiometric titration or elementary analysis, provided that the DADMAC in the copolymer was below approximately 70% [38]. 

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