Structure Analysis of Poly(propylene-β-d oxide) by Proton Nuclear Magnetic Resonance Spectroscopy

Abstract

Pmr Structure Analysis of Poly(propylene oxide) 459 should be the most probable of the pentads deriving from BAA triads. Similar observations can be made for every peak in the spectrum; again, the observed frequences correspond to the calculated pentad sequences with higher ethylene content. Owing to the low number of transients presently used we think that an analysis at even lower vinyl acetate content is possible; experiments on polymers containing a very small amount of each monomer are in progress.Another interesting result is given by the spectrum of the copolymer with 0.18-mol fraction vinyl acetate obtained using a solid sample (Figure 4). Fine structure is present similar to that obtained with the same sample in benzene solution. The carbonyl signal (not shown in Fig-ure 4) appears to be shifted in respect to the corresponding signal in solution, respectively at 11.2 and 24.8 ppm, showing the shielding effect of the aromatic solvent. Other chemical shifts appear unaffected. Further experiments on solid samples are in progress. Although this result must be considered in greater detail, the possibility of obtaining data for such a polymer in the solid state is evident. Aknowledgment. This work was sponsored by the Consiglio Nazionale delle Ricerche. The authors thank Dr. F. Wehrly of Varían for running the spectra.

Conformational Analysis of Poly(propylene oxide) and Its Model Compound 1,2-Dimethoxypropane

“…The fractions obtained from the MO data are comparable with the previous results.11 Both studies have estimated the conformational stability of bond b to be in the order g+ > t > g-. This tendency can be confirmed from NMR data reported by Hirano et al 54 and Oguni et al 55 It can be concluded that, in terms of the bond conformation, the previous and present studies have reached almost the same solution. For the conformational energies, however, these two studies have given different conclusions; Abe et al have suggested that the g+ preference of the C-C bond is due to the attractive firstorder a interaction, while the present MO calculations indicate that the gauche oxygen effect arises from the attractive C-H"*0 interactions (aq, aq, and y).…”

Stereoselective Epoxide Polymerization and Copolymerization

“…Jedlinski used 13 C NMR spectroscopy to examine the microstructure of poly­(propylene oxide) obtained from Al­(O i Pr) 3 and Al­(O i Pr) 3 /ZnCl 2 systems and to investigate modes of epoxide ring opening. The 13 C NMR spectrum of poly­(propylene oxide) synthesized using Al­(O i Pr) 3 displayed a significant number of regioerrors . By contrast, poly­(propylene oxide) synthesized using Al­(O i Pr) 3 /ZnCl 2 had a 13 C NMR spectrum consistent with that of a regioregular (HT only) polymer.…”

Cationic Polymerization of 1,2-Epoxypropane by an Acid Exchanged Montmorillonite Clay in the Presence of Ethylene Glycol

“…Effect of catalyst proportion upon the viscosimertic molecular weight. According to the work published by Oguni et al [38] and Ishimori et al [39] The signals of protons in the groups underlined in reaction (2) are to close to the corresponding signals from the chain, therefore hydroxyl end-groups were converted into the ester groups by reaction with trifluoroacetic anhydride. Thus, fourfold excess of (CF 3 CO) 2 O was added directly to the NMR tubes containing solution of PPO diol.…”