Variable-temperature carbon-13 NMR studies of carbonyl motion in solid bisphenol A polycarbonate

Abstract

Variable-temperature 13C NMR spectra of bisphenol-A polycarbonate, isotopically labeled with 13C at the carbonyl position, have been analyzed in terms of local motion of the carbonate group. Slight variation of the observed powder pattern occurred as the temperature was varied from -255 "C to room temperature. Nevertheless, a computer analysis showed that oscillation about the chain axis through a total angle of 40" is consistent with the results. IntroductionBecause bisphenol-A polycarbonate (BPAPC) has an unusually high impact strength, there has been a great deal of interest in the elucidation of its dynamic properties. Nuclear magnetic resonance is one of a number of tools that have been used for this purpose.'

Solid-State NMR Investigation of the Structural Consequences of Plastic Deformation in Polycarbonate. 1. Global Orientational Order

“…27 For the carbonate unit (C1), the y-axis (intermediate shielded) is perpendicular to the C1-O1-O2 plane, whereas the x-axis (most shielded) is aligned with the C1-O1 double bond (Figure 2). This is the inverse of what has been assumed previously, 21,[27][28][29] and corresponds to the revised orientation of the carbonate chemical shielding tensor published recently by Robyr et al 30 At the phenylene site (C2), the z-axis (least shielded) is aligned with the O2-C2 bond, while the x-axis coincides with the normal to the phenylene ring plane (Figure 2).…”

“…For the carbonate unit (C1), the y -axis (intermediate shielded) is perpendicular to the C1−O1−O2 plane, whereas the x -axis (most shielded) is aligned with the C1−O1 double bond (Figure ). This is the inverse of what has been assumed previously, ,− and corresponds to the revised orientation of the carbonate chemical shielding tensor published recently by Robyr et al…”

“…They do not correspond exactly to those indicated in Tomaselli et al, which contains printing errors. On the basis of the accepted value for the isotropic shift of the carbonate site, the above values for δ and η correspond to CSA eigenvalues of σ xx = 84.9 ppm, σ yy = 120.1 ppm, and σ zz = 236.4 ppm for the carbonate site and σ xx = 77.9 ppm, σ yy = 127.2 ppm, and σ zz = 239.9 ppm for the phenylene site.)

2 Ball-and-stick representation of a section of the polycarbonate chain.

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Local order in polycarbonate glasses by 13C{19F} rotational‐echo double‐resonance NMR

“…3(a), bottom]. The presence of many carbonate‐carbon spinning sidebands is consistent with the absence of large‐amplitude motions for the carbonate group 25. Also visible are the natural‐abundance 13 C methyl and quaternary‐carbon peaks at 30 and 42 ppm, respectively.…”

Main-chain reorientation in polycarbonates

“…Only the aromatic carbon dipolar pattern of PK changes significantly with the duration of the carbon spin lock. Dipo-1859 Hz 930 Hz 16 MREV-8 CYCLES JU_Ia.…”