Department of Synthesis and Characterization of Polymers
The aim of the department is to cover completely the expertise in synthesis of polymers using various polymerization techniques including free radical, reversible-deactivation radical and anionic polymerizations. The second object of synthesis represents preparation, spectral characterization and mainly utilization of different fluorescence probes for characterization of polymer microstructure and for polymerization study mechanism. Modification of polymers by grafting, crosslinking and functionalizations and preparation of polymeric and inorganic nanoparticles and hybrids represents another part of synthetic direction. Prepared as well as comercial polymers are characterised by spectral methods (UV-VIS, FTIR, Fluorescence and Raman spectroscopy), thermal analysis (DSC, TGA, chemiluminescence, thermal and photo stability, flammability) and their molar characteristics by advanced HPLC techniques. Electron spin resonance (ESR) and positron annihilation lifetime spectroscopy (PALS) techniques are used for the microscopic structural-dynamic characterization of various pure and composed organic materials.
1. Study and development of reversible-deactivation radical polymerizations and synthesis of functional polymers
2. Inorganic and carbon (nano)particles and hybrids
3. Polymeric (nano)particles, (hydro)gels and (nano)fibres
4. Synthesis and properties of photoactive compounds
5. Synthesis of polymers and polymeric materials from renewable monomers
6. Degradation, stabilization and flammability of polymers
7. Liquid chromatography research for effective separation of macromolecules
8. Structure and physico - chemical properties of polymers
1. Study and development of RDRP and synthesis of functional polymers
Photochemically induced reversible-deactivation radical polymerization
Scheme of photoATRP of methyl methacrylate Development of RDRP is focused on use of photochemistry in initiation and propagation steps of polymerizations. Recently a new variation of atom transfer polymerization technique using only 50-100 ppm of stable complexes of higher oxidation state copper halides as a catalyst was developed and is further studied. In situ reduction of the catalyst can be achieved simply by UV or visible light. The advantage of the photochemically induced ATRP (photoATRP) is the synthesis of well defined polymers at ambient temperature while irradiation significantly increases also the rate constant of polymerization.
In addition to copper halides various other copper compounds such as, low-cost and widely available CuSO4·5H2O or various organic copper compounds (copper acetate, copper triflate, copper acetylacetonate, etc) can be also used as a catalysts in photoATRP. The polymerization rate, as well as control over the molar mass and dispersity of poly(methyl methacrylate), is nearly the same for all of the copper catalysts because in each case the polymerization is controlled by CuBr/CuBr2/L catalytic system formed in situ after the photochemical reduction of the investigated copper catalysts.
Scheme of in situ formation of CuBr/CuBr2/L catalytic system during photoATRP starting from various copper compounds
Proposed simplified mechanism of photoRDRP in the presence of oxygen. PhotoATRP is investigated also in the presence of a limited amount of air. It is expected that first there are cycles of oxidation of CuBr/L by reaction with oxygen and photochemical regeneration of CuBr/L. Subsequently after consumption of oxygen in the system the CuBr/L activates the alkyl halide to initiate the polymerization of MMA. The induction period before starting the polymerization can be shortened by using approximately a 4-fold excess of the TPMA ligand with respect to the copper catalyst. Thus the photoATRP as well as the chain extension polymerization can be successfully performed without the necessity of degassing monomers and solvents. In comparison with ARGET or ICAR ATRP, which can also be run under a limited amount of oxygen, the photoATRP does not need additional chemicals such as reducing agents or sources of radicals. The photoATRP system can have tremendous importance from an industrial point of view because costly, time consuming procedures of removing oxygen from the polymerization mixture can be avoided without losing control over the molecular characteristics of the final PMMA.
Related recent publications:
J. Mosnacek, A. Andicsová-Eckstein, K. Borska „Ligand Effect and Oxygen Tolerance Studies in Photochemically Induced Copper Mediated Reversible Deactivation Radical Polymerization of Methyl Methacrylate in Dimethyl Sulfoxide”, Polym. Chem., Vol. 6, p. 2523-2530 (2015).
J. Mosnáček, A. Kundys, A. Andicsová „Reversible-deactivation radical polymerization of methyl methacrylate induced by photochemical reduction of various copper catalysts”, Polymers, Vol. 6 (10), p. 2862-2874 (2014).
J. Mosnacek, M. Ilcikova „Photochemically Mediated Atom Transfer Radical Polymerization of Methyl Methacrylate Using ppm Amounts of Catalyst”, Macromolecules, Vol. 45 (15), p. 5859–5865 (2012).
Study of livingness and initiation efficiency of various RDRP techniques
Scheme of determination of livingness and initiation efficiency using fluorescently labeled regulators In comparison with living anionic polymerization, termination cannot be entirely avoided in reversible-deactivation radical polymerizations (RDRP, also known as controlled radical polymerizations), so these systems are never living at a level of ionic polymerizations. Study of RDRP is focused on studies of initiation efficiency and livingness of RDRP in dependency on type of polymerization technique and polymerization conditions. The livingness is studied using LC LCD technique of liquid chromatography enabling detection of even very small amount of homopolymer in block copolymers, or using fluorescent initiators and subsequent determination of concentration of fluorescent groups of the initiator bonded in the polymer chains by UV and/or fluorescent spectroscopy. Also combination of these two methods can be used by incorporation of a fluorescent detector to the GPC or HPLC system.
Related recent publications:
Š. Chmela, J. Kollár, Ľ. Hrčková, „Fluorescent dye-labeled TIPNO type regulator for nitroxide mediated reversible-deactivation radical polymerization”, J. Photochem. Photobiol. A Chem., Vol. 307–308, p. 123 – 130 (2015).