In situ EPR and Raman spectroscopy in the curing of bis-methacrylate–styrene resins

Abstract

The curing of bis-methacrylate–styrene resins initiated by the cobalt catalyzed decomposition of cumyl hydroperoxide is monitored at ambient temperatures in situ by EPR and Raman spectroscopy.

The Mechanism of Inhibition of Pyruvate Formate Lyase by Methacrylate

“…Inclusion of an additional 1 H did not statistically improve the simulation fit, as judged by the residuals and the HFC confidence intervals of the additional nuclei. The spectrum is consistent with a C2· methacryl radical, which has been reported previously, , but where the radical has minimal electron density overlap with the second methylene 1 H of C3. No change in the G· signal was observed at any time for C 418 S or C 419 S (Supporting Information Figure S5).…”

Activation of alkyl hydroperoxides by manganese complexes of tmtacn for initiation of radical polymerisation of alkenes

“…4) initiated by catalytic or thermal decomposition of cumene hydroperoxide can be determined in situ by Raman spectroscopy, manifested in the change in intensity of the alkene stretching bands, as well as other changes in the spectrum characteristic of the loss of conjugation that accompanies polymerisation. 14 The time dependence of alkene conversion/polymerisation during curing of BADGE-MA/styrene mixtures initiated with cumene hydroperoxide with either 1, or 2b as catalyst, Fig. 4 shows that both catalysts provide for sigmoidal shaped reaction profiles 36 as observed for the standard catalyst Co(II)(2-ethylhexanoate) 2 .…”

“…24 The composition of the resin used should be considered in light of earlier studies where carboxylic acids were required to form, e.g., 2b, from 1. 15,23 The BADGE-MA crosslinking monomer, used here, was prepared earlier with known composition 14 and has an acid value that equates to ca. 0.1 molal acid content, mostly methacrylic acid from the synthesis, which provides carboxylato ligands for the manganese complexes studied here.…”

“…It should be noted that although EPR spectroscopy at 77 K is generally useful in the study of manganese complexes, the complexes 1, 2b and 2a are EPR silent, and the EPR signals expected for Mn(II) complexes of tmtacn, 16 are overwhelmed by the organic radicals present in cured resins. 14…”

“…2,10 The current drive to replace cobalt due to concerns over safety presents the challenge to find catalysts that can activate alkyl hydroperoxides in the currently used alkene resin formulations with the same curing profile (delay before onset of autoacceleration 11 to allow for application) as obtained with cobalt. 2,3,12–14…”