Ozonolysis of polybutadienes with different microstructure in solution

Abstract

ABSTRACT:The reaction of ozone with 1,4-cis-polybutadiene and polybutadiene having the following linking of the butadiene units: 1,4-cis (47%), 1,4-trans (42%), 1,2 (11%) was investigated in CCl 4 solution. It was found out by means of IR-spectroscopy and 1 H-NMR spectroscopy that the basic ozonolysis products of both elastomers are ozonides and aldehydes. The aldehyde:ozonide ratio was 11 : 89 and 27 : 73 for E-BR and BR, respectively. In addition, epoxide groups were detected, only in the case of BR, and their yield was about 10% of that of the aldehydes. On the basis of BR ozonolysis it was established that the ozonide yield from 1,4-trans units is about 50%. By using the aldehyde yields, an evaluation was made of the efficiency of ozone degradation of the two polybutadienes, according to which the respective value of BR is considerably higher than that of E-BR. A reaction mechanism is proposed, which explains the formation of the identified functional groups and the differences in the ozone degradation of the studied elastomers.

Ozone and its Reactions with Diene Rubbers

“…The mentioned differences in the aldehyde yields indicate that, according to IR-analysis, the degradation efficiency of the BR solutions is greater. The 1 H NMR spectroscopy provides much more opportunities for identification and quantitative determination of functional groups, formed during ozonolysis of polybutadienes [32]. Fig.…”

“…In this case the area of the signals is widened, most probably due to the presence of ozonide signals of the 1, 2-monomer units [20]. The basic route of the reaction -the formation of normal ozonides does not lead directly to a decrease in the molecular mass of the elastomer macromolecules, because the respective 1,2,4-trioxolanes are relatively stable at ambient temperature (by analogy with Scheme 1 of polyisoprenes, see below) [31,32]. The most favorable conditions for ozone degradation emerge when the cage interaction (Scheme 1, reaction 3) does not proceed.…”

“…The amount of aldehyde groups is usually used for evaluation of the intensity and efficiency (number of chain scissions per molecule of reacted ozone) of ozone degradation of elastomers. In this case it should be taken into account that the dominant route of degradation leads to the formation of 1 mole of aldehyde from 1 mole of ozone [32].…”

The Effect of 1,2- and trans-1,4-Units on Ketonization of Polybutadienes by Nitrous Oxide

“…Oxidative chemical degradation requires the use of specific oxidizing agents such as potassium persulfate, periodic acid, ozone, and others. ,− In addition, the indicated methods often involve several chemical steps. For instance, the direct ozonolysis of polydienes leads to the formation of FLRs that contain various functional groups (aldehyde, ketone, carboxylic, hydroxyl, hydroperoxide, and ozonide). − Therefore, an additional chemical treatment (e.g., reduction) is needed for their conversion into a certain type of functional group. − …”

Thermal rearrangement study of low molecular weight polybutadiene

“…Several phenomena of degradations which affect microstructure of PBD chains have been studied among them ultrasonic [1], ultra violet [2,3], ozone [4], pressure [5] in the presence of other parameters such as oxygen [6][7][8] can be cited. One of the most important parameter affecting PBD microstructure is heating under anaerobic conditions [9][10][11][12][13][14][15][16][17].…”