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H.Švajdlenková 1, O.Šauša 2, M.Iskrová 2, V.Majerník 2, J.Krištiak 2 and J.Bartoš 1 1 Polymer Institute of SAS, Dúbravská cesta 9, 845 41 Bratislava 45,

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Presentation on theme: "H.Švajdlenková 1, O.Šauša 2, M.Iskrová 2, V.Majerník 2, J.Krištiak 2 and J.Bartoš 1 1 Polymer Institute of SAS, Dúbravská cesta 9, 845 41 Bratislava 45,"— Presentation transcript:

1 H.Švajdlenková 1, O.Šauša 2, M.Iskrová 2, V.Majerník 2, J.Krištiak 2 and J.Bartoš 1 1 Polymer Institute of SAS, Dúbravská cesta 9, Bratislava 45, Slovakia 2 Institute of Physics of SAS, Dúbravská cesta 9, Bratislava 45, Slovakia On the relationships between guest molecule dynamics and free volume in a series of small molecular and polymer glass-formers by means of E S R and P A L S techniques PPC 10, Smolenice, Slovakia 2011

2 Introduction and motivation The structural - dynamic state of condensed materials can be measured 1)directly, i.e. by i n t e r n a l structural and dynamic probe techniques XDNS DS such as X-ray diffraction (XD) and scattering (NS,... ), or relaxation (DS,... ) and NMR nuclear resonance (NMR,... ) techniques, respectively 2)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 electron spin resonance E S R 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 P A L S via the annihilation behavior by means of P A L S The actual questions: E S RP A L S -What are the relationships between the E S R and P A L S responses ? P A L S -What is the role of free volume detectable by P A L S in the spin probe dynamics ?

3 E S R - E S R - spin probe method Energy MSMS MIMI ΔEΔE +1/2 -1/2 B=0 B0B0 Magnetic field fine splitting hyperfine splitting Nitroxide - type spin probes: TEMPO Resonance condition and selection rules:    0 : ΔE = hν = g e  e B ext M S = ± 1/2 and  M S = 1 M I = -1, 0, +1 and  M I = 0 B0B0 ESR ESR follows the dynamics of magnetization of spin system M in static magnetic field B 0 (  0 =  B 0 ) making precession motion with angle frequency ω (ω/2  ~ 9 GHz) V probe W V probe W = 170 Å 3 => R probe W,eq R probe W,eq = 3.43 Å

4 E S R E S R spectral evolution of TEMPO The spectral evolution from b r o a d triplet ( 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 s l o w regime f a s t regime

5 E S R A. E S R spectral evolution and analysis methods: The f i r s t quantitative measure of the spin probe reorientation dynamics:  spectral parameter of mobility: 2A ZZ’ (T) ESR 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 ESR the basic characteristic ESR temperature: T 50G - a c c e l e r a t i o n s within s l o w or/and ESR f a s t regime at further characteristic ESR temperatures: e.g. T X1 s,Azz, T X2 s,Azz and T X1 f,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 E S R E S R : molecular vdW-bonded glass-formers System T g, K T 50G, K T 50G /T g Pc DEP m-TCP DGEBA Empirical findings: 1) T 50G > T g and 2) T 50G  (1.1 – 1.25) T g T 50G

8 P A L S P A L S : molecular vdW-bonded glass-formers τ 3 (T 50G ) = 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 E S R : molecular H-bonded glass-formers System T g, K T 50G,K T 50G /T g PG DPG TPG m-TOL GL Empirical findings: 1) T 50G > T g and 2) T 50G  (1.3– 1.5) T g T 50G

11 P A L S P A L S : molecular H-bonded glass-formers τ 3 (T 50G ) = 2.20 ± 0.15 ns

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

13 E S R E S R : polymeric glass-formers System T g, K T 50G,K T 50G /T g c-t-1,4 PBD PPG c-1,4-PIP PIB PVME Empirical findings: 1) T 50G > T g and 2) T 50G  (1.1– 1.3) T g T 50G

14 P A L S : P A L S : polymeric glass-formers τ 3 (T 50G ) = 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 E S R B. E S R spectral evolution and analysis methods: The s e c o n d quantitative measure of spin probe reorientation dynamics:  rotational correlation time:  c (T) from relaxation model of spin system magnetization ESR by simulation of the ESR spectra using Non-linear Least Square Line (NLSL) program (B u d i l et al. 1996) Outputs: -correlation times :  c  ( – s ) and - fractions of s l o w and f a s t spin probes: F s  and F f =1 - F s 

16 ESR data:  c vs. 1/T and F s, F f vs.T 2) T c τ  T C Ff  T 50G Mutual relationships between the t w o measures of spin probe TEMPO mobility: 1) dynamic heterogeneity in cis-1,4-PIP over 80K fromT X1 s = 170K up toT 50G = 250K 3) T X1 f,   T X1 s  T X1 Ff ; T X1 s,   T X2 s  T X2 Ff and T X2 f,   T X1 f but no F counterpart

17 ESRPALS ESR vs. PALS relationships ESRPALS relationships: ESR vs. PALS relationships: T X1 s,A zz and T X1 Fs  T b1,  G T X2 s,Azz and T X2 Ff  T g PALS T 50G and T C Ff  T b1 L and  T b1,  L T X 1 f,Azz  T b2 L and  T b2,  L and m o r e o v e r:  c (T 50G )   3 (T 50G ) Y.Yu: PhD Thesis (2011) LT 9.0

18 PALSfree volume (FV) PALS and free volume (FV) data Standard quantum - mechanical (SQM) model of o-Ps annihilation in spherical hole: [Tao (1972) – Eldrup (1981) – Nakanishi &Jean (1988) ]  3 =  3,0 { 1 – R h /(R h +  R) + (1/2  ).sin[ 2  R h /(R h +  R) ] } -1 where R h – free volume hole radius => V h = (4  /3) R h 3  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 T 50G V TEMPO W appears to be due to the relation V h (T 50G ) = 122 ± 15 Å 3 < V TEMPO W = 170 Å 3 PALS closely related to the local free volume fluctuation as observed by PALS

19 PALS and FVdata: R h n(R h ) T PALS and FV data: R h and n(R h ) vs.T R TEMPO W,eq vs. R h relationships: a c c e l e r a t i o n within the s l o w regime at T X1 s,A ZZ : R W,eq TEMPO -> the h i g h e s t (tail) value of hole volume distribution a c c e l e r a t i o n within the f a s t regime at T X1 f,A ZZ : R W,eq TEMPO -> the m a x i m a l (peak) value of hole volume distribution

20 Summary and Conclusions ESR  The most pronounced effect in the ESR response in a series of small molecular and polymer glass-formers / TEMPO systems, i.e., s l o w to f a s t transition in the spin probe TEMPO mobility at T 50G  ( )T g is characterized by the empirical finding:  3 (T 50G ) = 2.25 ± 0.15 ns corresponding according to the SQM model (Tao – Eldrup - Nakanishi & Jean) to the occurrence of the mean equivalent free volume hole size: V h (T 50G ) = 122 ± 15 Å 3 almost i n d e p e n d e n t 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 ESR PALS  The changes in the smallest spin probe TEMPO dynamics at characteristic ESR temperatures are closely related to the local free volume fluctuation as observed by PALS

21

22 Outline 1. Introduction and motivation 2. Phenomenological and semi-empirical results E S R 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: 2A zz’ (T) and correlation time,  c (T) E S R 2) characteristic E S R temperatures P A L S 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 V h and its distribution n(R h ) from the SQM model P A L S b) characteristic P A L S temperatures E S RP A L S 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

23 Partial summary ESRThe most pronounced effect in the ESR response of the spin system, i.e., s l o w to f a s t transition in the smallest spin probe TEMPO mobility in a series of small molecular and polymer glass-formers at T 50G is characterized by the empirical  3 (T 50G ) finding:  3 (T 50G ) = 2.2 ± 0.4 ns corresponding to the occurrence of the equivalent m e a n free volume hole, V h (T 50G ) = 122 ± 15 Å 3 nearly i n d e p e n d e n t 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 V h (T 50G ) < V TEMPO it may be interpreted as a fluctuation free volume needed for the spin probe transition from s l o w to f a s t motional regime


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