The proton resonance spectra of poly‐α‐methylstyrenes

Abstract

The proton resonance spectra of a number of poly-a-methylstyrenes have been measured, and from them it is possible to measure the relative amounts of the isotactic, syndiotactic, and heterotactic forms. Polymers prepared by means of cationic catalysts are found to be the most stereoregular, whereas catalysts which with other monomers give stereoregularity do not do so with a-methylstyrene. In all the polymers the syndiotactic placement seems to be favoured over the isotactic. The irregular behaviour is thought to be associated with the considerable steric strain in the polymer. ZUSAMMENFASSUNG:Die Spektren der Protonenresonanz einer Anzahl von Poly-a-methylstyrolen wurden gemessen, und mit Hilfe dieser Spektren kann man die relativen Anteile der isotaktischen, syndiotaktischen und heterotaktischen Formen messen. Es zeigt sich, daB die mittels kationischer Katalysatoren hergestellten Polymere am stereospezifischsten sind, wogegen Katalysatoren, die bei anderen Monomeren eine Stereospezifitat ergeben, dies beim a-Methylstyrol nicht erreichen. Bei allen Polymeren scheint die syndiotaktische gegeniiber der isotaktischen Anordnung bevorzugt z u sein. Es wird angenommen, daB das unregelmaDige Verhalten mit der erheblichen sterischen Spannung im Polymeren zusammenhiingt.

Carbon‐13 nuclear magnetic resonance spectroscopy of polystyrene and poly‐α‐methylstyrene

“…Considering the discussion of the polymerization mechanisms of polya-methylstyrene, however, we can support the assignment first reported by BROWNSTEIN et al 13), because the microtacticities of poly-a-methylstyrene used in this paper could be described by BERNoULLIan statistics. I n many cases35141), the microtacticities of vinyl polymers whose polymerization mechanisms can be described b y BERNoULLIan statistics are rich in syndiotactic diads.…”

“…The methyl protons of poly-cc-methylstyrene are split into three peaks which seem to be due to three different configurations. These three methyl peaks were assigned to isotactic, heterotactic, and syndiotactic triads in the order of increasing field strength by BROWNSTEIN et al 13). SAKURADA et ~1 .…”

The NMR of Polymers

“…As Brownstein and his co-workers [215] showed, in the NMR spectrum of poly-a-methylstyrene the signal of the a-methyl group is sensitive to the stereochemical configuration. This group lies between two phenyl nuclei and its diamagnetic screening depends on the structure of the polymer.…”

“…Analysis of the NMR spectra of samples of poly-O!-methylstyrene (see Chapter ill) showed [212,215] that a Ziegler catalyst and butyllithium do not lead to the formation of a stereoregular polymer; syndiotactic poly-O!-methylstyrene may be obtained with a cationic catalyst. According to data obtained by Sakurada and his co-workers [594], the degree of isotacticity of poly-O!-methylstyrene changes with the catalyst in the series Fig.…”

Partitioned partial least squares regression with application to a batch fermentation process

“…But, there are only few reports in the literature of production of syndiotactic‐rich Pα‐MeSts. Brownstein et al30 and Matsugama and Kunitake8 reported the synthesis of syndiotactic‐rich PαMeSts via the cationic polymerization using Lewis acids at −78 °C. However, no information was provided on whether the polymerization was controlled or not.…”