Some applications of photoluminescence for

Transcription

1 Some applications of photoluminescence for probing polymer relaxation processes Part 2 p1 Teresa DibZambonAtvars Instituto de Química Universidade Estadual de Campinas Campinas, São Paulo, Brasil tatvars@iqm.unicamp.br Summer School - Stereochemical Aspects of Novel Materials, UCSB, august 14-27, 2005

2 Slide 1 p1 ro prpg, 7/2/2005

3 outline Polymer systems and morphology Polymer motions, phase transitions and polymer relaxation processes Photoluminescence spectroscopy and polymer relaxation processes fluorescence phosphorescence quenching processes time resolved spectroscopy Luminescence in polymers Non-fluorescent polymers (host-guest systems) Polymers modified with luminescent groups Intrinsically luminescent polymers Conjugated luminescent polymers Electroluminescence and photoluminescence Summer School - Stereochemical Aspects of Novel Materials, UCSB, august 14-27, 2005

4 Types of luminescent polymers : 1. nonfluorescent polymers (host-guest systems) Amorphous materials Semicrystalline polymers How the guest interacts with the polymer? Which site is the guest sensing?

5 Guest in semicrystalline polymers Surface of a lamellae Interfase between amorfous and crystalline phase Amorphous region

6 Probing orientation in stretched materials Molecules changes from one site to other and can be preferentially oriented in the stretching direction They can sense the new environment

7 Relaxation processes in oriented polymers Talhavini et al. Polymer, 1986

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9 Relaxation processes associated with the interface crystalline amorphous interface are more defined There is a larger population of anthracene molecules located in the interface compared with non-stretched material α-relaxation process Talhavini, et al, Polymer 1986

10 How important is the distance for a guest sensor? Pyrene in LDPE and some coplolymers with vinyl acetate (EVA) I I /I III ratio changes Lifetimes also change

11 Linear correlation with lifetime and I I /I III ratio because the random distribution of the polar groups

12 1 st (open) and 2 nd run (dark) Yamaki, Eur. Polym. J., 2002

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14 First (dark) and second (open) scans

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16 Naylons = condensation of an amide a carboxylic acid Naylon-6,6 Poly(caprolactone) Naylon-6,9 constant Naylon-6 Naylon-6,10 Naylon-11 Naylon-6,12

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18 Photophysical properties of pyrene in naylons Poly(caprolactam) ns Naylon ns Naylon-11 Naylon-6, ns 250 ns Decrease of the polarity Naylon-6, ns Naylon-6, ns Naylon-6, ns

19 Polymers modified with luminescent groups Will sense the environment around the molecule More sensivity to the motions involving the segments where they were bonded Selective attachment should enhance the sensitivity and coupled motions can be analyzed.

20 Polyethylene and vinyl acetate copolymers modified with pyrenyl groups Weiss, et al., 1992

21 Selective attachment Relaxation processes will be associated with these groups Not observed Yamaki, et al., Photochem. Photobiol. Sci

22 8000 a. 30 K Relative intensity (a.u.) K Pyrene as a guest in LDPE Wavelength (nm) b. Relative intensity (a.u.) K 410 K pyrenyl attached to LDPE Wavelength (nm)

23 1,0 a. 1,0 b. 0,8 0,8 Normalized intensity 0,6 0,4 0,2 T γ T g (β) T m Normalized intensity 0,6 0,4 0,2 T β T β T g T α 0, Temperatura (K) 0, T ( K ) Normalized and integrated fluorescence intensities versus temperature for pyrene (n) and 1-pyrenyl groups ( ) in (a) LDPE and (b) PVAC.

24 Schur, Weiss et al., Macromolecules, 2003

25 Weiss et al., Macromolecules, 2003

26 Intrinsically luminescent polymers: poly(2- vinyl naphthalene) Poly(2-vinyl naphthalene) Cruz, et al. J. Appl. Polym. Sci. 2001

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29 Intrinsically luminescent polymers: Deus, Akcelrud, et al. Chem. Phys. 2004

30 Deus, Akcelrud, et al. Chem. Phys. 2004

31 Deus, Akcelrud, et al. Macromolecules 2004

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33 Conjugated luminescent polymers O n * * O Poly(2-methoxy-5-(2-ethylhexyloxy)-p-phenylene vinylene) MEH-PPV

34 Steady-state fluorescence emission Blue shift Increase of intensity Cossiello, et al. Macromolecules 2005

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36 DMTA data Arrhenius plots

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38 Relaxation processes Techniques DMTA TSC Fluorescence β-relaxation T = 210 ± 10 K Ea = 29.1 kj mol -1 K -1 T = 210 ± 10 K Ea = 22.5 kj mol -1 K -1 T = 220 ± 10 K α-relaxation T = 330 ± 10 K Ea = 85.4 kj mol -1 K -1 T = 310 ± 10 K Ea = 62.4 kj mol -1 K -1 T = 320 ± 10 K Cossiello et al. Macromolecules, 2005

39 Molecular Motions by 13 C NMR Bloise, et. al. Phys. Rev. B. 2005

40 Bloise et al. Phys. Rev. B, 2005

41 Conclusions from 13C RMN Carbons 11, 12, 13, 14, 15, 16, and 17 gain mobility after the β-relaxation process

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44 Implications of the relaxation processes on the electroluminescence properties

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46 Electroluminescence and photoluminescence poly(9,9-(di-n,n-octyl-fluorene)) Winokur et al. Phys. Rev. B. 2003

47 Spectral profiles and condensed medium

48 Spectral profiles and condensed medium

49 Spectral profiles and condensed medium

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51 Relaxation process and spectral broadening Brown, et.al. J. Polum Sci. Polym. Phys. Ed. 2004

52 Martins, et. Al. J. Phochem. Photobiol. A Chem. 2002

53 Thank you! Fred Miguel Jennifer Summer School - Stereochemical Aspects of Novel Materials, UCSB, august 14-27, 2005