Polymerization of methylmethacrylate monomer in the presence of dithizone and carbazone complexes

Abstract

It has been proved that lead dithizone and carbazone complexes act as adequate initiators for radical polymerization of methylmethacrylate and also as reliable indicators for the free-radical mechanism. Lead dithizone complex, in particular, exhibited the phenomenon of color change during the polymerization process, suggesting the use of this complex as a free-radical indicator and also as a coloring material for acrylic polymers in situ. The color change observed during the polymerization process was attributed to the change in the structure of complex compounds according to a tautomerization mechanism. The presence of lead dithizone and carbazone complexes as initiators exhibited reduced molecular mass compared to those prepared in their absence, indicating their role as regulating agents during the polymerization process. The polydispersity and tacticity parameters were measured through the present work using GPC and 1 H-NMR techniques, respectively. The amorphous nature of polymer chains in both the absence and the presence of the lead dithizone and carbazone was studied using X-ray diffraction, where an increased crystallinity was observed.

Dual-curing resin cement with colour indicator for adhesively cemented restorations to dental tissues: Change of colour by curing and some physical properties

“…Although the exact substances or mechanics causing the color change of the studied cement are not known, this study was undertaken to get more in-depth data on the nature of the color change and its relation to curing. In the field of polymer sciences, it has been shown, that the use of commercially available dyes and certain other reagents can result in a color change during polymerization (Hanna et al, 2001, Masere and Pojman, 1998). For example, the use of lead dithizone or carbazione in poly(methylmethacrylate) (PMMA) results in a color change from red to yellow during the polymerization (Hanna et al, 2001).…”

“…In the field of polymer sciences, it has been shown, that the use of commercially available dyes and certain other reagents can result in a color change during polymerization (Hanna et al, 2001, Masere and Pojman, 1998). For example, the use of lead dithizone or carbazione in poly(methylmethacrylate) (PMMA) results in a color change from red to yellow during the polymerization (Hanna et al, 2001). This was explained by the previous study conducted by Hanna et al, which was mainly because of formation of lead dithizone complex.…”

“…This was explained by the previous study conducted by Hanna et al, which was mainly because of formation of lead dithizone complex. When lead dithizone is present, the PMMA polymerization proceeds by a free radical mechanism and the color change is attributed to formation of azo group by lead dithizone (affected by free radicals) (Hanna et al, 2001). When the polymerization proceeds and all of lead dithizone has reacted, the final color is achieved.…”

Salen Transition Metal Complexes as Catalysts for the Synthesis of Photostable Poly(methylmethacrylate)

“…Metal complex compounds also proved feasible in bulk, solution, and heterogeneous systems and even during grafting of some natural fibers [7][8][9][10][11]. In such systems, the rate of polymerization is usually governed conditionally and kinetically as reported [12][13], affecting the polydispersity of the final polymer and the mode of loss of end groups [14], for mainly refining the polymer specific properties toward more challenging applications.…”