NMR spectrum of a copolymer

Figure 10. Proton NMR spectrum of a copolymer obtained at —78°C the measurement was made in Freon 113 at 50°C...

The proton NMR spectrum of a copolymer obtained at — 78°C is shown in Figure 10. Two triplets of equal intensity centered at 5.93 and 7.62r were observed. There is no other resonance for this sample. On the basis of proton NMR spectra of model compounds (5), these two triplets may be assigned to two CH2 groups, as shown below. 

The interpretation of the NMR spectrum of a copolymer in terms of its structure is easiest when its monomer units differ considerably in electronegativity, when no asymmetric atoms are present and when the resonance of the nuclei studied is not complicated by spin-spin interactions. When these conditions are met, sharp, intense, easily resolved signals are obtained and the spectrum is easily studied. Copolymers of isobutylene with vinylidene chloride meet all these requirements and the methylene resonance (Fig. 1) of such copolymers consists of a series of well resolved lines that afford information about diad and tetrad distri-... 

The NMR spectrum of a copolymer of trimer 4 (n = 2) and EA from a eopolymerization in benzene solution taken to low conversion (<10%) is shown in Figure 2. The copolymer was purified by several precipitations from light petroleum and the absence of unreacted trimer confirmed by GPC. The spectrum exhibits signals at 5 5.5 and 6.2 ppm for the terminal olefinic protons and at 6 3.9-4.2 ppm and 3.5-3.8 ppm for the methyleneo of EA and methoxy of trimer respectively. The latter two signals provide an estimate of the ratio of trimer to EA in the copolymer while the small signal at 6 3.72 ppm confirms the presence of a carbonicthoxy group attached to a double bond. 

As an example, an NMR spectrum of a 1,3-dioxolane-/3-propiolactone copolymer, obtained by using a boron-fluoride catalyst, is shown in Fig. 1101. The 1,3-dioxolane (DOL) homopolymer spectrum contains two singlet peaks of area 1 2 numbered 1 and 5, whereas the spectrum of the 0-propiolactone (PL) homopolymer contains two triplet peaks of area 1 1 numbered 2 and 6. Variation of initial feed ratios disclosed that peaks 1,3 and S are associated with the DOL units and that... 

Figure 10. 300 MHz IH-NMR spectrum of a deuterobenzene solution of an equimolar copolymer of 5-methyl-l,4-hexadiene and 1-hexene prepared with a EttAlCl/ S-TiCl, catalyst at 0°C in pentane solvent.

When the NMR spectrum of a 30% (w./v.) solution of peroxide in toluene was recorded at 34°C., absorption was observed between 8 2.74 and 5.46. There were seven main resonances, all multiplets, which were interpreted in terms of aliphatic hydrogen shifted by oxygen. Resonance from ethylenic hydrogen amounted to only a fraction of a proton. However, the sample darkened while in the instrument and probably decomposed extensively. When the spectrum of a solution of peroxide prepared by oxidation to 10.4 mole % was recorded using a cold probe at —35°C. a different picture was obtained. There was complex absorption from both ethylenic and saturated hydrogen which was interpreted as arising from a mixture of 1,2 and 1,4 oxygen copolymers in an approximate jatio of 1 to 2. In this sample the residual chloroprene amounted to 0.15% of the monomer units in the peroxide and dimers of chloroprene to 0.6% of the peroxide. 

In the 13 C NMR spectrum of a statistical copolymer of monomers Mi and M2 four groups of olefinic peaks may be seen, corresponding to M1M1 and M2M2 dyads, and... 

Figure 2. The 13C NMR spectrum of a 50/50—styrene/ethyl acrylate copolymer prepared using a conventional uniform monomer feed process...

Figure 11.27 29Si-NMR spectrum of a silphenylene-siloxane block copolymer (67 mol % DMS), observed at 59.6 MHz [29]...

Fig. 29. Proton NMR spectrum of the copolymer latex (in CDC13) for a mole feed ratio of methacrylic acid to styrene of 0.12, internal phase ratio 0.93, AIBN 0.3 g, SDS 0.4 g and water 3 ml, polymerized first for 12 h at 40 °C. After this polymerization, additional water (twice as much as the weight of the emulsion) was added into the tubes, then polymerization continued for 2 days...

FIGURE 7-45 H NMR spectrum of a methyl methacrylate/hexyl methacrylate copolymer. 

Accordingly, we will just show one example where NMR spectroscopy has been employed successfully to study copolymer sequences. Figure 7-50 shows the 60 MHz H NMR spectrum of a vinylidine chloride-co-isobutylene (VDC-co-EB) copolymer containing 70 mole % VDC. Also included in the figure are the spectra of pure PVDC [denoted (A)] and pure PEB (B) in the same region. Note that both VDC and IB fall under the category of monomers of the type CH CX2. 

Revisit the proton NMR spectrum of a methyl methacrylate-co-hexyl methacrylate copolymer shown in Figure 7-45. The areas of the lines at 3.6 and 3.9 ppm were determined to be 36.9 and 61.3, respectively. How much hexyl methacrylate was incorporated into the polymer ... 

FIG. 17. NMR spectrum of a bisphenol A polycarbonate-polydimethylsiloxane block copolymer with average silicone block length Hpoms = 10. (85)... 

Kunitake and Tsukino ( 0 also used 13c NMR to determine ring size in the copolymer, but they calculated chemical shifts by extrapolating published data on simpler cyclic compounds. By this method they concluded that a copolymer prepared in chloroform contained only tetrahydrofuran rings. However, their published spectrum of the copolymer contained the same peak B as ours, and therefore the copolymer must consist of both five- and six-membered rings. The spectrum of a copolymer prepared in acetone-carbon disulfide was too poorly resolved to show peak B, but Kunitake and Tsukino estimated the polymer to contain about 90% tetrahydropyran rings. 

Figure 1. Solid state NMR spectrum of a melamine formaldehyde crossllnked acrylic copolymer coating. The static magnetic field Is 7.0 T and the spinning rage Is S.OKHz Chemical shifts and assignments are given In Table I and features marked with an asterisk are resolved spinning side bands.

Even mixed polylactide/polyglycollide copolymers can be characterized by NMR spectroscopy [2]. Figure 3-11 shows the H NMR spectrum of a polylactide/glycollide copolymer. By comparing the integral areas it is possible to determine the ratio of both monomer units. 

Figure 3-12 C NMR spectrum of a polylactide/glycollide copolymer, 75 MHz, ultra high resolved carbonyl region, "SSL".

In the case of the p-pinene/isobutene combination initiated with EtAlCl2, the H-NMR spectrum of the copolymer showed an almost equal incorporation of the monomers and a high level of alternation [36]. 

The potential use of H NMR to estimate the amount of ethylene in a PE/ PP-copolymer is rather exciting because the time needed to acquire a H NMR spectrum is of the order of minutes compared to C NMR which needs hours. Figure 2 shows a typical NMR spectrum of a PP/PE copolymer and suggests that four regions (A-D) can be clearly separated. 

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