1 / 23

H.Švajdlenková 1 , O.Šauša 2 , M.Iskrová 2 , V.Majerník 2 , J.Krištiak 2 and J.Bartoš 1

On the relationships between guest molecul e dynamics and free volume in a series of small molecu lar and polymer glass-formers b y means of E S R and P A L S techniques. H.Švajdlenková 1 , O.Šauša 2 , M.Iskrová 2 , V.Majerník 2 , J.Krištiak 2 and J.Bartoš 1

aelan
Download Presentation

H.Švajdlenková 1 , O.Šauša 2 , M.Iskrová 2 , V.Majerník 2 , J.Krištiak 2 and J.Bartoš 1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. On the relationships between guest moleculedynamics and free volume in a series of small molecularand polymer glass-formers by means ofESR and PALS techniques H.Švajdlenková1, O.Šauša2, M.Iskrová2, V.Majerník2, J.Krištiak2 and J.Bartoš1 1Polymer Institute of SAS, Dúbravskácesta 9, 845 41 Bratislava 45, Slovakia 2Institute of Physics of SAS, Dúbravskácesta 9, 845 11Bratislava 45, Slovakia PPC 10 , Smolenice, Slovakia 2011

  2. Introduction and motivation The structural - dynamic state of condensed materials can be measured • directly, i.e. by i n t e r n a l structural and dynamic probe techniques such as X-ray diffraction (XD) and scattering (NS , ... ), or relaxation (DS , ... ) and nuclear resonance (NMR, ... ) techniques, respectively • indirectly, i.e., by e x t e r n a l structural - dynamic techniques such as a) m o l e c u l a r probing the local structure and its fluctuation using stable radical species , the so-called spin probes, e.g. , TEMPO via the reorientation behavior by means of electron spin resonance E S R b) a t o m i c probing the static or/and dynamic free volume using ortho - positronium (o-Ps) probe via the annihilation behavior by means of P A L S The actual questions: • What are the relationships between the E S Rand P A L S responses ? • What is the role of free volume detectable by P A L S in the spin probe dynamics ?

  3. E S R -spin probe method B0 Nitroxide-type spin probes:TEMPO VprobeW= 170Å3=> RprobeW,eq= 3.43 Å ESR follows the dynamics of magnetization of spin systemM in static magnetic field B0 (0 = B0)making precession motion with angle frequency ω(ω/2 ~ 9 GHz) fine splitting hyperfine splitting MI MS 1 +1/2 0 Energy Resonance condition and selection rules:   0 : ΔE=hν = geeBext MS = ± 1/2 and  MS= 1 MI= -1, 0, +1 and MI= 0 -1 ΔE -1 0 -1/2 1 B=0 B0 Magnetic field

  4. E S Rspectral evolution of TEMPO s l o w regime The spectral evolution from b r o a d triplet (70 - 60 G) from spin probes in s l o w motional regime to n a r r o w triplet (40 – 30 G) from spin probes in f a s t motional regime f a s t regime

  5. A. E S Rspectral evolution and analysis methods: The f i r s tquantitative measure of the spin probe reorientation dynamics: spectral parameter of mobility:2AZZ’(T) directly from ESR spectra using WIN-EPR program Features: quasi-sigmoidal dependence with various effects from - s l o w to f a s t regime transition at the basic characteristic ESR temperature: T50G - accelerations withins l o w or/and f a s t regime at further characteristic ESR temperatures: e.g. TX1s,Azz,TX2s,Azz andTX1f,Azz

  6. I. Molecular vdW-bonded glass-formers Propylene carbonate (Pc) Dietyl phthalate (DEP) meta-Tricresyl phosphate (m-TCP) Diglycidyl-ether of bis-phenol A (DGEBA)

  7. ESR:molecular vdW-bonded glass-formers ---------------------------------------------- SystemTg ,KT50G, KT50G/Tg ---------------------------------------------------------------------- Pc 158 194 1.23 DEP 184 230 1.25 m-TCP 205 249 1.22 DGEBA 257 283 1.10 ---------------------------------------------- Empirical findings: 1) T50G > Tgand 2) T50G (1.1 – 1.25) Tg T50G

  8. PALS:molecular vdW-bonded glass-formers τ3 (T50G) =2.28 ± 0.17 ns DGEBA: G. Dlubek et al.: PRE (2006)

  9. II. Molecular H - bonded glass-formers Propylene glycols (PGs) n = 1, 2 and 3 Glycerol (GL) meta – Toluidine (m-TOL)

  10. E S R:molecularH-bonded glass-formers ---------------------------------------------- SystemTg,KT50G,KT50G/Tg ---------------------------------------------------------------------- PG172 248 1.44 DPG 189 250 1.32 TPG 186 247 1.33 m-TOL 187 239 1.28 GL 190 283 1.49 ---------------------------------------------- Empirical findings: 1) T50G> Tgand 2) T50G (1.3– 1.5) Tg T50G

  11. P A L S:molecular H-bonded glass-formers τ3 (T50G) =2.20±0.15 ns

  12. III. Polymer glass-formers H o m o polymers: Diene type: cis-trans-1,4-PBD cis-1,4-PIP Vinyl – and Vinylidene type: PIB PVME H e t e r o polymer: PPG

  13. E S R:polymeric glass-formers --------------------------------------------------- SystemTg,KT50G,KT50G/Tg ------------------------------------------------------------------------------ c-t-1,4 PBD174 224 1.29 PPG 197 242 1.23 c-1,4-PIP 205 251 1.22 PIB 205 263 1.28 PVME250 276 1.11 ---------------------------------------------------- Empirical findings: 1) T50G > Tgand 2) T50G (1.1– 1.3) Tg T50G

  14. P A L S:polymeric glass-formers τ3(T50G) = 2.14 ± 0.19 ns PIB : D.Kilburn, G.Dlubek et al.: Macrom.Chem.Phys.(2006) c-1,4-PIP: Y.Yu: PhD Thesis (2011)

  15. B. E S Rspectral evolution and analysis methods: • The s e c o n dquantitative measure of • spin probe reorientation dynamics: •  rotational correlationtime:c(T) • from • relaxationmodel of spin system magnetization • by simulation of the ESRspectrausing • Non-linear Least Square Line (NLSL) program • (B u d i l et al. 1996) • Outputs: • correlation times : c ( 10 -6– 10 -11 s )and • - fractions of s l o w and f a s t spin probes: • Fs  <1;0> and Ff=1-Fs <0;1>

  16. ESRdata: cvs. 1/Tand Fs ,Ffvs.T Mutual relationships between the t w o measures of spin probe TEMPO mobility: 1) dynamic heterogeneity in cis-1,4-PIP over 80K fromTX1s =170K up toT50G= 250K 2) TcτTCFfT50G 3) TX1f,TX1s TX1Ff;TX1s,TX2sTX2Ff andTX2f, TX1fbut no F counterpart

  17. ESR vs. PALSrelationships ESRvs. PALSrelationships: TX1s,AzzandTX1Fs Tb1,G TX2s,Azzand TX2FfTgPALS T50G and TCFf Tb1Land Tb1,L TX1 f,AzzTb2LandTb2,L LT 9.0 and moreover: c(T50G)  3 (T50G) Y.Yu: PhD Thesis (2011)

  18. PALS and free volume (FV) data Standard quantum-mechanical (SQM) model of o-Psannihilation in spherical hole: [Tao (1972) –Eldrup (1981) –Nakanishi &Jean (1988)] 3= 3,0{ 1 – Rh/(Rh+ R) + (1/2).sin[ 2Rh/(Rh+ R) ] }-1 where Rh – free volume hole radius => Vh= (4/3)Rh3 3,0 andR - empirical parameters Usually, the SQM model used in the sense of equivalent m e a n free volume size: => the s l o w to f a s t transition of the smallest spin probe TEMPO at T50G appearsto be due to the relation Vh(T50G)= 122 ± 15 Å3 < VTEMPOW= 170 Å3 closely related to the local free volumefluctuation as observed byPALS

  19. PALSand FVdata: Rhandn(Rh)vs.T RTEMPOW,eq vs. Rh relationships: a c c e l e r a t i o n within the s l o w regime atTX1s,Azz: RW,eqTEMPO->the h i g h e s t (tail) valueof hole volume distribution a c c e l e r a t i o n within the f a s t regime at TX1f,AZZ: RW,eqTEMPO-> the m a x i m a l(peak) value of hole volume distribution

  20. Summary and Conclusions • The most pronounced effect in the ESR response in a series of small molecular and polymer glass-formers / TEMPOsystems, i.e., s l o wtof a s t transition inthe spin probe TEMPOmobility at T50G(1.1 -1.5)Tgis characterizedby the empirical finding: 3 (T50G) =2.25 ± 0.15ns corresponding according to the SQM model (Tao – Eldrup - Nakanishi & Jean) to the occurrence of the mean equivalentfree volume hole size: Vh(T50G) = 122 ± 15 Å3 almost independent of the intra-molecular structure (topology,rigidity) as well as of the type of inter-molecular (vdW- or H-bonding) interactions between the matrix constituents, being a characteristic of the given spin probe TEMPO • The changes in the smallest spin probe TEMPOdynamics at characteristic ESR temperatures are closely related to the local free volumefluctuation as observed byPALS

  21. Outline 1. Introduction and motivation 2. Phenomenological and semi-empirical results E S R responses on a series of amorphous glass-forming systems of various intra-molecular chemical structure (topology, rigidity) and inter-molecular physical interactions a) two measures of spin probe (TEMPO) dynamics: spectral parameter of mobility: 2Azz’(T) and correlation time, c (T) 2) characteristic E S R temperatures P A L S responses on the same glass-formers a) ortho-positronium(o-Ps) lifetime3(T) and dispersion 3(T) ; mean free volume Vhand its distribution n(Rh)from the SQM model b) characteristic P A L S temperatures 3. General relationship between the E S R and P A L S parameters i.e. between molecular and atomic e x t e r n a l probing of the organic matter 4. Summary and Conclusion

  22. Partial summary • The most pronounced effect in the ESR response of the spin system, i.e., s l o wtof a s t transition in the smallest spin probe TEMPOmobility in a series of small molecular and polymer glass-formers at T50Gis characterizedby the empirical 3 (T50G) finding: 3 (T50G) =2.2 ± 0.4 ns corresponding to the occurrence of the equivalent m e a n free volume hole, Vh(T50G) = 122 ± 15 Å3 nearlyindependent of the chemical structure, i.e. topology(molecular vs. macromolecular) and rigidity (rigid vs. flexible) of the matrix constitutents as well as of the type of inter-molecular (H - or vdW - bonding) interactions between the matrix constituents Since Vh(T50G) < VTEMPOit may be interpreted asa fluctuation free volume needed for the spin probe transition from s l o w to f a s t motional regime

More Related