Macromolecules, Vol. 38, No. 6, 2005
Facile Synthesis of Poly(methylhydrogenosiloxane)s 2235
Figure 7. Raw SEC traces of PMHS extracted from a model
experiment without neutralization and as a function of time:
(
s) 1 day, (- -) 5 months, (- - -) 10 months.
The PMHS stored in gel conditions exhibits a molar
mass distribution that spreads with time because of very
few condensation reactions (Figures 7 and 3a). However,
the PMHS oil remains a sol, i.e., keeps entirely soluble
in toluene for more than 10 months. The surfactant is
easily removed by several washings with water prior
to (immediate) polymer use.
In conclusion, this article shows a reliable, fast, and
cheap way to prepare and store PMHS homopolymers
in a range of molar masses between 10 and 30 kg/mol,
with a small content of small cycles and macrocycles,
and no significant gel content. These polymers may be
used to prepare all kinds of side chain modified polysi-
Figure 6. Physical gelling of PMHS in the presence of 2 (run
1
0, Table 1). (a) (left) Elastomeric gel obtained after emulsion
breaking; (right) liquid oil after solvent treatment (see text
for detail). (b) DSC chromatograms of the gel during the first
temperature rise (solid curve) and second temperature rise
(
g
dashed line). The glass transition (T ) -139 °C) is observed
in both scans, whereas the gel transition (Tgel ) 75 °C) shows
1
loxanes. Particularly in our group, they are about to
up only on the first scan.
be used in the generation of highly grafted silicones.
Low volume samples were easily extracted after neutra-
lization and rapidly injected in SEC for characterization,
but the liquid oil eventually evolves to a transparent
insoluble gel only after 1-2 days. On the other hand,
the neutralization of the full volume of the miniemulsion
is less straightforward, and the polymer material was
often found cross-linked, even before being extracted
from water.
Acknowledgment. F.G. thanks Drs J.-J. Robin and
F. Guida-Pietrasanta for their suggestions on the manu-
script and Dr. M. In for his helpful expertise on physical
chemistry related to “exotic” surfactants.
References and Notes
(1) Boutevin, B.; Guida-Pietrasanta, F.; Ratsihimety, A. In
Silicon-Containing Polymers; Jones, R. G., Ando, W., Cho-
jnowski, J., Eds.; Kluwer Academic Publisher: Dordrecht,
2000; pp 79-112.
(2) Eaborn, C. Organosilicon compounds; Buttherworths Pub.
Ltd.: London, 1960.
An easy way to store linear PMHS after emulsion
breaking is depicted now. First, any trace of bases has
to be avoided during the sample treatment to prevent
cross-linking reaction. Breaking the emulsion without
neutralization nor addition of alun salt (which is slightly
basic) allows one to isolate the polymer and still to avoid
parasite hydrolysis/condensation. Second, the polymer-
ization reaction has to be carried out using the surfac-
tant 2. The small content of this solid (thus nonvola-
(
3) Cancou e¨ t, P.; Daudet, E.; H e´ lary, G.; Moreau, M.; Sauvet,
G. J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 826-836.
(4) Feng, S.; Cui, M. React. Funct. Polym. 2000, 45, 79-83.
(5) Nakamura, G.; Nishimori, T. Block Hydrogen-modified sili-
cone and process for producing the same. EP0786488 A2, July
30, 1997.
(
6) Servaty, S.; K o¨ hler, W.; Meyer, W. H.; Rosenauer, C.; Spick-
ermann, J.; R a¨ der, H. J.; Wegner, G. Macromolecules 1998,
31, 2468-2474.
1
8
tile) diacid trapped in the PMHS indeed acts as an
organogelator; in other words, it considerably depresses
the rates of side reactions by implementing a high
viscosity in the oil. A photograph of the elastomeric gel
observed after emulsion extraction is given in Figure
(
7) Keiichi, A.; Petroff, L. J.; Feng, Q. J. High molecular weight
alkylmethyl-alkylaryl siloxane terpolymers having low SiH
content and methods for their preparation. US6211323, Apr
25, 2001.
(8) Maisonnier, S.; Favier, J.-C.; Masure, M.; H e´ mery, P. Polym.
Int. 1999, 48, 159-164.
6
a (left-hand side). Evidences for physical, rather than
(9) Gaboyard, M.; Hervaud, Y.; Boutevin, B. Phosphorus, Sulfur
chemical, gelling are given by two indubitable facts: (1)
Silicon 2002, 177, 877-891.
The clear gel transition (Tgel) observed by DSC (Figure
(
(
10) Schulz, P. C.; Abrameto, M.; Puig, J. E.; Soltero-Martinez,
F. A.; Gonzalez-Alvarez, A. Langmuir 1996, 12, 3082-3088.
11) Walde, P.; Wessicken, M.; R a¨ dler, U.; Berclaz, N.; Conde-
Friebos, K.; Luisi, P. L. J. Phys. Chem. B 1997, 101, 7390-
6
b), only on the first temperature rise. Passing above
the Tgel, the network is broken and has no time to form
again before the second scan (5 min between the two
1
7397.
0 min analyses). (2) The gel readily dissolves in
(
12) Minardi, R. M.; Schulz, P. C.; Vuano, B. Colloid Polym. Sci.
1998, 276, 589-594.
dichloromethane or toluene, and after evaporation
quick enough to avoid any redistribution reactions by
(13) Gaboyard, M.; Jeanmaire, T.; Pichot, C.; Hervaud, Y.; Boutevin,
(
B. J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 2469-
the still active acid catalyst), the sample goes through
an oily stage (Figure 6a, right-hand side) before it
2480.
(
14) Senhaji, O.; Robin, J. J.; Achchoubi, A.; Boutevin, B. Macro-
mol. Chem. Phys. 2004, 205, 1039-1050.
1
9
gradually “freezes back”.