Nanocomposites and nanomaterials

Positronics in contemporary nanocomposites science and engineering:  the case of polymer-filler dimethacrylate-based dental restoratives
Shpotyuk Olha1, Ingram Adam2, Filipecki Jacek3, Shpotyuk Oleh3,4 
1 Danylo Halytsky Lviv National Medical University
69, Pekarska str., 79010, Lviv, Ukraine
2 Opole University of Technology
75, Ozimska str., 45370, Opole, Poland
3 Jan Dlugosz University in Czestochowa
13/15, al. Armii Krajowej, 42201, Czestochowa, Poland
E-mail: j.filipecki@ujd.edu.pl
4 O.G. Vlokh Institute of Physical Optics
23, Dragomanov str., 79005, Lviv, Ukraine

Possibilities of positron annihilation lifetime (PAL) spectroscopy applied to characterize peculiarities of microstructure changes in atomic-deficient subsystem under light-curing are studied at the example of commercial dimethacrylate-based dental restoratives such as Charisma, Dipol and ЭСТА-3. The algorithm to treat PAL data for such polymer/filler nanocomposites within three-state mixed trapping model evolving competitive channels of positron and positroniun Ps states referred to as the x3-x2-CDA (coupling decomposition algorithm) [1] is examined. In loosely-packed nanocomposites, Ps decaying takes place in intrinsic holes of polymer matrix, and free positron trapping occurs in filler sub-system, specifically in interfacial voids between filler particles and filler particles contacting with surrounding. Under photopolymerization, fragmentation of intrinsic holes in polymer dominates over enhanced trapping of positrons in filler since filler-particles assemblies get more tightly covered by polymer owing to disappearing of interfacial voids. In densely-packed nanocomposites, where positron trapping in interfacial voids at the surface of agglomerated filler particles takes minor role, the polymerization-driven fragmentation of Ps-decaying holes causes stress inside monolith filler assemblies, resulting in disappearing of some interparticulate traps.

1.	Shpotyuk O., Filipecki J., Ingram A., Golovchak R., Vakiv M., Klym H., Balitska V., Shpotyuk M., Kozdras A. Positronics of subnanometer atomistic imperfections in solids as a high-informative structure characterization tool // Nanoscale Res Lett.-2015.-10.-P. 77-1-5.