A spectroscopic study of the thermal motion of the ester groups in stereoregular polymethylmethacrylate

Belopolskaya, T. V.; Trapeznikova, O. N.

doi:10.1016/0032-3950(71)90333-9

Cited by 6 publications

(11 citation statements)

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“…The profound influence of temperature on the IR spectra of PMMA in the spectral range under consideration has been observed by many authors, mostly for the band intensities. Substantial downshifts in peak positions were reported by Schneider et al and by Belopol'skaya . According to our data for s-PMMA (Figure a), increasing the temperature from 25 to 175 °C causes a downshift of 3−4 cm -1 for the bands located in the room-temperature spectrum at 1149, 1193, and 1242 cm -1 and of 7 cm -1 for the band at 1272 cm -1 .…”

Section: Resultssupporting

confidence: 81%

“…The corresponding van't Hoff plots (Figure ) reveal for each polymer a single linear dependence in the whole range of measured temperatures. The temperature-induced intensity transfer between the two peaks was reported both by Havriliak 27 and Belopol'skaya . The latter author observed the phenomenon down to −173 °C for both polymers, while Havriliak could see it for s-PMMA (i-PMMA was not studied) only above T g .…”

Section: Resultsmentioning

confidence: 68%

“…We adopt the strategy of the already mentioned studies of Havriliak 27 and Belopol'skaya. 28 However, contrary to these previous works, the precision of derived spectroscopic information in the current study is incomparably higher because of the use of computerized FTIR instrumentation and modern methods of quantitative bandfitting analysis in combination with the recent IR and ab initio data for simple esters. As a result, new features in the temperature dependence of component bands in the 1050-1300 cm -1 region are revealed, and for the first time, an unambiguous structural assignment of the bands is achieved.…”

Section: Introductionmentioning

confidence: 67%

“…Here, we report variable-temperature FTIR measurements made on amorphous films of isotactic and syndiotactic PMMA polymers, combined with a detailed analysis of the temperature dependence of integrated band intensities in the region 1050−1300 cm -1 . We adopt the strategy of the already mentioned studies of Havriliak 27 and Belopol'skaya . However, contrary to these previous works, the precision of derived spectroscopic information in the current study is incomparably higher because of the use of computerized FTIR instrumentation and modern methods of quantitative band-fitting analysis in combination with the recent IR and ab initio data for simple esters.…”

Section: Introductionmentioning

confidence: 99%

“…Seven component bands were identified, and four of them were grouped in pairs (1172/1192 and 1238/1268 cm -1 ) and assigned to different rotational isomers of the ester group. Some years later, Belopol'skaya and Trapeznikova 28 applied the approach of Havriliak and Roman both to s-PMMA and i-PMMA and expanded the temperature range below room temperature. The two pairs of peaks isolated by Havriliak and Roman in s-PMMA were found also in i-PMMA.…”

Section: Introductionmentioning

confidence: 99%

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Conformation-Sensitive Infrared Bands and Conformational Characteristics of Stereoregular Poly(methyl methacrylate)s by Variable-Temperature FTIR Spectroscopy

2002

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Variable-temperature FTIR measurements were performed on amorphous films of isotactic and syndiotactic PMMA, followed by a detailed analysis of the temperature dependence of integrated band intensities for C−O stretching modes in the region 1050−1300 cm-1. The use of computerized FTIR instrumentation and modern methods of quantitative band-fitting analysis in combination with the recent IR and ab initio results for simple esters allowed us to achieve, for the first time, the unambiguous conformational assignment for the ester bands of PMMA. This, in turn, enabled reliable IR spectroscopic determination of conformational energies for the PMMA backbone and the ester side group. The backbone conformational characteristics for i-PMMA and s-PMMA are found to be closely similar (in the staggered bonds approximation); the trans−trans state is strongly preferred over the trans−gauche state in both polymers, and the preference is only slightly higher for s-PMMA. At the same time, the two stereoregular forms appear markedly different in the conformational characteristics of ester side group. The minimum energy conformation of the ester moiety is trans in i-PMMA but cis in s-PMMA. Moreover, the absolute value of the conformational energy difference between the cis and trans states is 1.84 kcal/mol for i-PMMA, compared with only 0.46 kcal/mol in s-PMMA. Besides, the FTIR data shows that the ester groups of i-PMMA do not contribute to the glass transition, whereas those of s-PMMA form intermolecular associates (presumably, by carbonyl−carbonyl dipole interactions) and, in this way, elevate the glass transition temperature relative to that expected from the backbone conformational energy alone. This finding discards the thesis of O'Reilly and Mosher (Macromolecules 1981, 14, 602) that the Gibbs−DiMarzio theory fails to explain the difference in T g between i-PMMA and s-PMMA.

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 68%