The Radiation Chemistry of Organized Systems:

Transcription

1 The Radiation Chemistry of rganized Systems: Basic Studies and Implications Vladimir Feldman Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation

2 utline Background and motivation: concept of molecular organization Experimental approaches and methods Intermolecular complexes: modeling the first step Polymers: effect of molecular packing Crown ethers: effect of steric configuration and hostguest interactions Interpolyelectrolyte complexes: controlled assembling of metal nanoparticles Conclusions and outlook

3 Background and motivation: molecular organization and radiation chemistry Ionizing radiation is rather a scalpel than a bludgeon Common reasons for selectivity: - inhomogeneous energy deposition - selective localization of primary events - selectivity of secondary radical reactions Knowing molecular structure and chemical composition is not enough to predict the effect molecular organization is important Self-organization and forced organization (e.g., orientation, application of high pressure, etc.) Driving forces for self-organization at molecular level: - weak non-covalent interactions - ionic interactions - guest-host interactions rganized systems: from simplest binary complexes to micelles and biopolymers

4 Experimental approaches and methods Modeling the first step: matrix isolation at low and ultra-low temperatures (down to 5 K) Characterization of weak interactions: FTIR spectroscopy Irradiation: X-rays, gamma-rays and e-beam in various experimental configurations (low-temperature matrices, films and solutions at room temperature) Identification of the radiation-induced intermediates: EPR and optical spectroscopy Characterization of the radiation-induced structural changes: XRD, TEM and other methods

5 The role of weak intermolecular interactions: 2 /C 2 /Ng system Formation of C radicals correlates with the concentration of C 2 2 complexes Spectroscopic evidence for intermolecular complexes in matrices S.V. Ryazantsev and V.I. Feldman, J. Phys. Chem. A, 2015, 119, 2578 ther recent works on radiation-chemistry of weak complexes in matrices: S.V. Kameneva et al., J. Chem. Phys., 2016, 145, ; V.I. Feldman et al., Rad. Phys. Chem., 2016, 124, 7

6 Effect of molecular packing in polymers: polystyrene Pre-existing benzene ring dimers act as hole traps due to lower IP Isotactic polysyrene R Formation of dimeric radical cations is an important factor of the radiation resistance of polystyrene ( ).+ no damage Particularly high yield of dimeric radical cations is observed in isotactic polystyrene (A.A. Zezin, V.I. Feldman, Dokl. Chem., 2004, 394, 26) R

7 Effect of stereoisomerism, ionic and guest-host interactions: crown ether complexes with metal Cis-syn-cis-DC18C6 T m = С A - Me 2+ A - cations Free dicyclohexano-18-crown-6 (DC18C6) is most suitable host-ligand for radioactive 90 Sr binding Effect of stereoisomerism on radiolysis? Complex formation leads to Macrocycle conformation changes C- bonds elongation Me 2+ coordination by both -atoms of CE and anion Cis-anti-cis-DC18C6 T m = С Does the nature of cation and anion in CE complexes affect the radiation stability? A - Me 2+ A -

8 Crown ethers: effect of stereoisomerism Me 2+ Cis-syn-cis-DC18C6 МеCl 2 Radiolysis of free DC18C6 Macrocycle destruction occurs in reactions of primary radical cations C C()= Me 2+ Cis-anti-cis-DC18C6 МеCl 2 Radiolysis of complexes Macrocycle destruction occurs in reactions of primary radical cations and in post-irradiation processes C C()= +. Ratio of macrocycle cleavage yields: G anti /G syn = 1.4 Ratio of macrocycle cleavage yields: G anti /G syn = 2 Cis-syn-cis-isomer has a higher radiation resistance to macrocycle cleavage at early and post-irradiation stages of radiolysis..a. Zakurdaeva, S.V. Nesterov, V.I. Feldman. Rad. Phys. Chem., 2017, 130,

9 Crown ethers: effect of metal cation inclusion I. Free crown ether CE CE + + e C 2 Ċ + R + CE + + CE 2 C C()= + C 3 C 2 R e CE + CE + C 2 Ċ + 2 CE+ (C 6 9 ) + 2 II. Macrocyclic complex with metal chloride B Me 2+ Cis-syn-cis-DC18C6 МеCl 2 Me 2+ = Ca 2+, Sr 2+, Ba C 2 C 2 A C 2 C 2 Ba 2+ Inclusion of metal ion into macrocyclic cavity initiate a new channel of macrocycle cleavage at post-irradiation stage. C 3 C 2 C 2 C 2. A. Zakurdaeva, S.V. Nesterov, V. I. Feldman. Rad. Phys. Chem., 2013, 87, Ba 2+

10 A - Me 2+ Crown ethers: effect of anion A - Crown ether (CE) 18C6 Me 2+ = Sr 2+, Ba 2+ A - = BF 4-, PF 6 - and N 3 - Direct action on CE: CE CE + + e CE + + CE C 2 Ċ + R + 2 CE + + CE C C()= + C 2 5 R e CE+ CE + C 2 Ċ + 2 Direct action on anion: XF n - /\/\/\ XF n + e XF n - + e XF n F - XF n XF n-1 + F Indirect Action on CE: F + CE C C 2 + F Basic Intermediates C C ( 90%) + C C()= ( 10%) Direct action on CE: CE CE + + e CE + + CE C 2 Ċ + R 2 + Direct action on anion: N 3 N 3 + e N 3 + e N 3 2 Basic intermediates N 3 2- (>85%) + C C 2 (<15%) While nitrate anions protect the crown ether up to 40 kgy, radiolytic products of halogenous anions promote additional destruction channels.a. Zakurdaeva, et al. Rad. Phys. Chem, 2015, 115,

11 Interpolymer and interpolyelectrolyte complexes: films, ultrathin coatings and suspensions C C C C interpolymer PAA - PVT interpolyelectrolyte PAA - PEI N 2 N 2 N 2 N 2 Cu 2+ Cu 2+ _ + N N N N C C C Cu 2+ C - Triple interpolyelectrolyte -metal complexes (TIMC) - stable, swellable films with readily adjustable content of metal ions (up to wt %) [see A.B. Zezin, V. B. Rogacheva, V.I. Feldman, P. Afanasiev, A.A. Zezin, Adv. Colloid Interface Sci., 2010, 158, for more details]

12 The radiation-induced preparation of metal nanoparticles: a mechanistic overview General scheme for aqueous solutions 2 e - aq,., 3 +, 2,.. + C 3 C 2 C. 3 C + 2 Ме n+ + e - aq Ме(n-1)+... Me 0 Ме n+ + R. Ме (n-1)+ + R + Me 0 + Me n+ Me n+ 2 Me p+ k (p<k) nanoparticles For review: Belloni, J.: Catal. Today,113 (2006)141; Ershov, B.G.: Russ. Chem. Rev., 66 (1997) 103 Specific features of the radiation-induced reduction of metal ions in polyelectrolytes: - inhomogeneous dose distribution (particularly, for X-rays) - involvement of additional reaction channels - diffusion restrictions and size selection

13 Nanocomposites prepared by radiationchemical method from organized systems Cotton fibers with NP-filled coatings Polymer films with NPs Tuning the size and spatial distribution of nanoparticles in a polymer matrix due to variations of system composition, radiation type and dose rate Zezin A.B., Rogacheva V.B., Feldman V.I., Afanasiev P., Zezin A.A.: Adv. Colloid. Interface Sci. 158 (2010) 84; Feldman V.I., Zezin A. A., Abramchuk S. S., Zezina E. A.: J. Phys. Chem. C 117 (2013) 7286

14 Formation of copper nanoparticles in irradiated suspensions: self-organization and generation of spatially ordered structures nanoparticle fraction, % PAA-PAAm 0.05 М PAA 0.05 М PVIM 0.02 М Cu 2+ p= Nanoparticle diameter, nm Bakar A., De V. V., Zezin A. A., Abramchuk S. S., Guven., Feldman V. I. :Mendeleev Communs. 2012, 22,. 211.; Bakar A., Guven., Zezin A. A., Feldman V. I. : Rad. Phys.Chem., 2014, 94, 62 PAA-PVIM 0.05 М PAA 0.05 М PVIM 0.01 М Cu 2+ p=2.4 D. Dagas et al., manuscript in preparation

15 Conclusions and outlook Molecular organization controlled by relatively weak interactions is crucial for the radiation chemistry of a wide variety of different systems Implications: novel approaches to radiation stability and radiation modification may be based on the molecular organization concept Prospective applications: - development of radiation-resistant sorbents and extraction systems - stabilization and sensitization of polymers without chemical modification - fabrication of different-type metal-polymer nanohybrides for various purposes (sensors, bactericide films, catalysts ) - nanolithography - and more utlook: we still need to learn more, but we can start developing technologies now

16 Acknowledgements Research team (major contributions) Dr. A.A. Zezin Dr. S.V. Nesterov Dr..A. Zakurdaeva Dr. E. V. Saenko Dr. E.S. Shiryaeva Dr. D. A. Tyurin PhD students: S. V. Ryazantsev S. V. Kameneva Collaborations: Institute of Synthetic Polymeric Materials of RAS, Moscow, Russia Prof. lgun Güven (acettepe University, Ankara, Turkey) Support from: Russian Foundation for Basic Research Russian Science Foundation

17 13 th International Symposium on Ionizing Radiation and Polymers (IRaP 2018) IRaP 2018 is to be held in Moscow region, Russia on August 26-31, 2018 (exact location to be confirmed before September 1, 2017) Conference chair: Prof. Vladimir Feldman Detailed information is coming soon Welcome to Moscow in 2018 (and at any other time)!