Upload
ahava
View
48
Download
0
Tags:
Embed Size (px)
DESCRIPTION
(b). (a). I n. I w. Figure 1. Typical ESR spectra of spin probe in NR:. Figure 4. ESR spectra of spin probe diffusing in NR irradiated with 300 kGy. The probe incorporation temperatures were: (a) 4 °C and (b) 24 °C. Spectra were measured at 19 °C. narrow (T > T g ) broad (T < T g ) - PowerPoint PPT Presentation
Citation preview
ESR - Spin Probe Method in Studying Crosslinked Elastomers:an Effect of the Probe Incorporation Temperature
M. Didović1, D. Klepac1 and S. Valić1,2
1 University of Rijeka, School of Medicine, Braće Branchetta 20, Rijeka, 51000, Croatia2 Rudjer Bošković Institute, Bijenička 54, Zagreb,10000, Croatia
spin probe:
EXPERIMENTAL
4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl
Objective
. N
OH
O
natural rubber (NR) latex – 62 wt.% of dry matter
(The Rubber Research Institute of India)
natural rubber latex containing 62 wt.% of dry matter was irradiated with different total irradiation doses of 200 kGy and 300 kGy
irradiated NR latex was deluted by ammonia solution (0.6 wt.%) up to 25 wt.% of solid content
~1mm thick NR films were prepared by removing the liquid phase at room temperature
spin probe was incorporated in NR samples by swelling the samples in the probe solution at 4 °C, 16 °C, 24 °C and 37 °C. The solvent was toluene.
solvent was slowly removed by evaporation; all samples were then annealed at 60 °C for 72 hours
ESR spectra were recorded on Varian E-109 ESR spectrometer equipped with Bruker ER 041 XG microwave bridge and Bruker ER 4111 VT variable temperature unit
To investigate the influence of the temperature of spin probe incorporation process on the shape of ESR spectra.
the shape of ESR spectra of the spin probe in heterogeneous systems, as shown for NR, depends on the probe incorporation temperature
the increase of the probe incorporation temperature results in a higher amount of the broad component
higher probe incorporation temperature allows probe molecules to diffuse into the higher density regions of the matrix and consequently leads to the restriction in probe dynamics
L. J. Berliner, Spin Labeling: Theory and Applications Vol 1. and Vol 2., Academic Press, 1976.
Z. Veksli, M Andreis, B. Rakvin, ESR spectroscopy for the study of polymer heterogeneity, Prog Polym. Sci. 25 (2000) 949-986.
Figure 5. Schematic representation of the spin probe incorporation process at (a) 4 °C and (b) 37 °C in NR matrix
(a) (b)
Figure 4. ESR spectra of spin probe diffusing in NR irradiated with 300 kGy. The probe incorporation temperatures were: (a) 4 °C and (b) 24 °C. Spectra were measured at 19 °C.
Figure 3. ESR spectra of spin probe diffusing in NR irradiated with 200 kGy measured at 0 °C. The probe incorporation temperatures were: (a) 16 °C and (b) 24 °C.
Figure 2. ESR spectra of spin probe diffusing in nonirradiated NR measured at -10 °C. The probe incorporation temperatures were: (a) 4 °C, (b) 24 °C and (c) 37 °C.
Sample
Temperature of
measurement / ºC
Temperature of probe
incorporation / ºC
In/Iw
NR 0 kGy -10
4 1.61
24 1.35
37 1.15
NR 200 kGy 016 2.47
24 2.32
NR 300 kGy 194 20.9
24 15.1
Table 1. Intensity ratios of the narrow (In) and broad (Iw) components of ESR spectra shown in Figures 2-4.
Figure 1. Typical ESR spectra of spin probe in NR:
a) narrow (T > Tg)b)broad (T < Tg)c) bimodal (T≈T5mT)
Iw
In
Materials and Methods
References Conclusions
Results
17th European Symposium on Polymer Spectroscopy, September 9th to 12th, 2007 in Seggauberg, Austria