Random Block Copolymers via Segment Interchange Olefin ...
Random Block Copolymers via Segment Interchange Olefin ...
Random Block Copolymers via Segment Interchange Olefin ...
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1442<br />
Figure 2. TEM images of polyethylene/polycarbonate (50:50 wPE/<br />
wPC) material isolated from solution blends. Figure 2a: no<br />
metathesis catalyst added; Figure 2b: benzylidene[1,3-bis(2,4,6trimethylphenyl)-2-imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium<br />
metathesis catalyst added.<br />
phase ordering indicative of a block copolymer. The microphase<br />
separation of these materials is observed for other<br />
base polymer ratios as demonstrated by the TEM<br />
micrograph for a 20:80 w/w, polyethylene/polycarbonate<br />
RBC (Figure 3).<br />
To further establish this micro-phase ordering, the<br />
samples from Figure 2 were analyzed <strong>via</strong> SAXS a technique<br />
diagnostic for this ordering. Figure 4 shows successive<br />
SAXS traces as a function of temperature. The presence of a<br />
discrete scattering peak throughout the temperature range<br />
is indicative of micro-phase separation. The peak position<br />
at 0.1 2u is indicative of an ordered micro-phase separated<br />
block copolymer structure. It is highly unusual for block<br />
copolymer materials to exhibit micro-phase ordering<br />
which persists well into the liquid phase such as displayed<br />
by these RBC materials. The SAXS and TEM data for the<br />
sample without the metathesis catalyst added are<br />
representative of a simple PE/PC blend.<br />
Conclusion<br />
N. L. Wagner, F. J. Timmers, D. J. Arriola, G. Jueptner, B. G. Landes<br />
Figure 3. TEM image of a self-assembled RBC prepared from<br />
segment interchange, 20% polyethylene—80% polycarbonate<br />
(stained dark).<br />
<strong>Segment</strong> interchange <strong>via</strong> olefin metathesis is a new<br />
method for the preparation of RBCs from base polymers<br />
with randomly distributed backbone unsaturation. The<br />
extent of segment interchange (i.e., block lengths and<br />
block distribution) is governed by the degree and<br />
distribution of backbone unsaturation in the base polymers<br />
as well as the extent to which metathesis is allowed<br />
to proceed. When chemically dissimilar base polymers are<br />
used, RBCs form which can display micro-phase ordering<br />
that persist at temperatures well into the melt phase of the<br />
material.<br />
Macromol. Rapid Commun. 2008, 29, 1438–1443<br />
ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/marc.200800344
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