Back to Search
Start Over
An Investigation of the Selective Chain Scission at Centered Diels-Alder Mechanophore under Ultrasonication.
- Source :
-
Macromolecules . Feb2017, Vol. 50 Issue 4, p1353-1361. 9p. - Publication Year :
- 2017
-
Abstract
- It is a challenging topic to disconnect a linear polymer selectively at the mechanophore site by an external force in a "cold" fashion. In this work, the effect of the power output of ultrasonication on the selective cleavage at the centered urfuryl-maleimide Diels-Alder (DA) mechanophore of poly(methyl acrylate)s (DA-PMA-a and DA-PMA-b) were quantitatively investigated by comparative study on experimental and simulated chain scission kinetics as well as high-resolution 1H NMR spectroscopy (600 MHz). At low power output of the ultrasonication (2.10 W), DA-PMA-a with Mn of ca. 2Mlim (Mlim, below which no further chain scission was observed) presented a DI (degradation index)-t (sonication time) plot with a turnover point at ca. 1.0 and no clear variation of the molecular weight after the turnover, which met well with the calculated center cleavage mode. At 5.52 W, DA-PMA-a and a poly(methyl acrylate) that contained two centered ester bonds (ester-PMA) presented similar DI-t plots with turnover points less than 1.0 within same sonication times, while poly(methyl acrylate) with fully carbon-carbon chain (PMA) had a turnover at DI value of ca. 0.5. By way of contrast, high power output of the ultrasonication (5.52 W) caused a possible cleavage of ester bonds of DA-PMA-a, which would mask the selective cleavage at the DA site. High-resolution 1H NMR result of DA-PMA-b (115.8 kDa, Mn was slightly higher than 2Mlim) showed that DA conversions were up to 55% under 2.10 W and 38% under 5.52 W. The kinetics from GPC traces and 1H NMR results of DA-PMA-b as well as 1H NMR results of DA-PMA-c (68.4 kDa, Mn was slightly higher than Mlim) under sonication confirmed the observation that low power output favored selective chain scission at DA site. The turnover point in the DI-t plot might be used as characteristic parameter to gauge the selective chain scission at mechanophore site for single mechanophore-centered polymers. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00249297
- Volume :
- 50
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- Macromolecules
- Publication Type :
- Academic Journal
- Accession number :
- 121522405
- Full Text :
- https://doi.org/10.1021/acs.macromol.6b02370