Macromolecules, Vol. 37, No. 7, 2004
Polyolefins 2469
ics involving the crystalline phase essentially do not
show up in the dielectric probe response.
From a systematic study of the effect of probe con-
centration on the dielectric relaxation behavior of three
different polymers we can conclude the following:
(2) Runt, J . P.; Fitzgerald, J . J . Dielectric Spectroscopy of
Polymeric Materials: Fundamentals and Applications; Ameri-
can Chemical Society: Washington, DC, 1997.
(
3) Bottcher, C. J . F.; Bordewijk, P. Theory of Electric Polariza-
tion; Elsevier Scientific Pub. Co.: New York, 1978; Vol. 2.
4) Hill, N. E.; Vaughan, W. E.; Price, A. H.; Davies, M. Dielectric
Properties and Molecular Behaviour; Van Nostrand Rein-
hold: London, 1969.
(
(i) Addition of the dielectric probe DBANS to i-PP,
LDPE, and PS modifies the relaxation behavior of the
polymers by specifically enhancing the strength of the
dielectric glass transition process.
(
5) W u¨ bbenhorst, M.; de Rooij, A. L.; van Turnhout, J .; Tacx, J .;
Mathot, V. Colloid Polym. Sci. 2001, 279, 525-531.
6) McCrum, N. G.; Read, B. E.; Williams, G. Anelastic and
Dielectric Effects in Polymeric Solids; Dover Publications:
New York, 1991.
(
(ii) This “strengthening” is proportional to the mean
probe concentration up to about 0.5 DBANS content in
polyolefins.
(7) Boersma, A.; van Turnhout, J .; W u¨ bbenhorst, M. Macromol-
ecules 1998, 31, 7453-7460.
(
8) Simon, G. P.; Runt, J . P. In Dielectric Spectroscopy of
Polymeric Materials: Fundamentals and Applications; Fitzger-
ald, J . J ., Ed.; American Chemical Society: Washington, DC,
1997; Vol. 1, pp 329-378.
(
iii) The relaxation time of the probe relaxation
coincides well with the mean relaxation time of the
native” polymer within 1 order of magnitude in fre-
quency.
“
(
9) W u¨ bbenhorst, M.; Folmer, B. J . B.; van Turnhout, J .;
Sijbesma, R. P.; Meijer, E. W. IEEE Trans. Dielectr. Electr.
Insul. 2001, 8, 365-372.
(10) Ashcraft, C. R.; Boyd, R. H. J . Polym. Sci., Polym. Phys. Ed.
1976, 14, 2153-2193.
(iv) Glass transition temperatures deduced from the
probe relaxation times are in fair agreement with values
determined from DSC and DMA measurements and are
in line with data reported in the literature. For PS, Tg
values of ∼95 °C were found, while LDPE and i-PP
reveal dielectric Tg’s (τ ) 100 s) that are slightly lower
(
11) Fr u¨ bing, P.; Blischke, D.; Gerhard-Multhaupt, R.; Khalil, M.
S. J . Phys. D: Appl. Phys. 2001, 34, 3051-3057.
12) Hoffman, J . D.; Williams, G.; Passaglia, E. J . Polym. Sci.,
Part C 1966, 173-233.
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101, 788-797.
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15) Fulcher, G. S. J . Am. Ceram. Soc. 1925, 8, 339.
16) Tammann, G.; Hesse, G. Z. Anorg. Allg. Chem. 1926, 156,
245.
(
(
LDPE: -38 °C; i-PP: -16 °C) than corresponding DSC
and DMA data.
(
(
(
Fluorescence spectroscopy revealed that both crystal-
lization and melting of LDPE and i-PP are clearly
detected. The observed changes in probe emission are
explained by migration of probe molecules: from the
crystallizing regions during the crystallization process
or into the melting regions during the melting process.
This probe migration, resulting in effective increases
and decreases of probe concentration during crystal-
lization and melting, respectively, was proven with
dielectric spectroscopy.
(17) Livanova, N. M.; Zaikov, G. E. Polym. Degrad. Stab. 1997,
5
7, 1-5.
(
18) This dipole moment was calculated with the ChemBats3D
software package from Cambridge Software using the AM1
method in combination with a closed cell wave function and
Mulliken charges.
(19) Luckhorst, G. R.; Veracini, C. A. The Molecular Dynamics of
Liquid Crystals; Kluwer Academic Publishers: Dordrecht,
1
994.
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973, 69, 1050.
22) Shears, M. F.; Williams, G. J . Chem. Soc., Faraday Trans. 2
973, 69, 608.
Fluorescence measurements on a paraffin oil model
system showed a red shift in emission upon increasing
the probe concentration, in particular between 0.5% and
(
1
(
(
1
% probe content. The magnitude of this red shift is
1
similar to the shift that was found with real-time
fluorescence measurements for crystallizing i-PP and
LDPE samples containing 0.5% DBANS. This shows
that changes in local probe concentration during crys-
tallization is the major contributor to the spectral
changes that occur in these crystallizing polyolefins.
Using higher probe concentrations in i-PP and LDPE,
above 0.5% m/m, leads to dramatic decreases in fluo-
rescence quantum yield, which seriously decrease the
reliability and accuracy of the fluorescence measure-
ments. For these samples, upon decreasing the temper-
ature, blue shifts in emission are observed at lower
temperatures, and these blue shifts are attributed to
probe aggregation caused by phase separation of the
probe from the polymer or crystallization of the probe.
23) Davies, M.; Hains, P. J .; Williams, G. J . Chem. Soc., Faraday
Trans. 2 1973, 69, 1785.
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25) Thurau, C. T.; Ediger, M. D. J . Chem. Phys. 2002, 116, 9089-
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099.
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26) Thurau, C. T.; Ediger, M. D. J . Chem. Phys. 2003, 118, 1996-
2004.
(
(
27) Hains, P. J .; Williams, G. Polym. Bull. (Berlin) 1975, 16, 725.
28) Several other rigid D-π-A molecules have successfully been
applied as dielectric probes.
29) Loutfy, R. O. Macromolecules 1981, 14, 270-275.
(30) van Ramensdonk, H. J .; Vos, M.; Verhoeven, J . W.; Mohl-
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mann, G. R.; Tissink, N. A.; Meesen, A. W. Polymer 1987,
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51-956.
31) Paczkowski, J .; Neckers, D. C. Macromolecules 1992, 25,
48-553.
32) J ager, W. F.; Volkers, A. A.; Neckers, D. C. Macromolecules
(
(
(
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5
1
995, 28, 8153-8158.
33) J ager, W. F.; Lungu, A.; Chen, D. Y.; Neckers, D. C.
Ack n ow led gm en t. Piet Droppert (DRS measure-
ments) and Ben Norder (DSC and DMA experiments)
are gratefully acknowledged for assisting with the
experiments.
Macromolecules 1997, 30, 780-791.
34) Vatanparast, R.; Li, S. Y.; Hakala, K. Macromolecules 2000,
3
3, 438-443.
(35) J ager, W. F.; Norder, B. Macromolecules 2000, 33, 8576-
582.
36) Peinado, C.; Salvador, E. F.; Catalina, F. Polymer 2001, 42,
815-2825.
37) J ager, W. F.; Sarker, A. M.; Neckers, D. C. Macromolecules
999, 32, 8791-8799.
38) Levenberg, K. Q. Appl. Math. 1944, 2, 164.
8
(
(
(
Su p p or tin g In for m a tion Ava ila ble: Figures of DSC, and
DMA, for LDPE, i-PP, and PS. This material is available free
of charge via the Internet at http://pubs.acs.org.
2
1
Refer en ces a n d Notes
(39) Marquardt, D. J . Soc. Indust. Appl. Math. 1963, 11, 431.
(
40) J ager, W. F.; van den Berg, O. In ACS Symposium Series;
Belfield, K. D., Crivello, J . V., Eds.; American Chemical
Society: Washington, DC, 2003; Vol. 847, pp 426-436.
(
1) Kremer, F.; Sch o¨ nhals, A. Broadband Dielectric Spectroscopy;
Springer-Verlag: Berlin, 2003.