Handbook of Solvents - George Wypych - ChemTech - Ventech!

690 George Wypych
Figure 12.1.11. Morphological features: starlike and
crew-cut. The bottom drawing illustrates polymer
brush. [Adapted, by permission from G Liu, Macromol.
Symp., 113, 233 (1997).]
Figure 12.1.13. PS-PAA aggregates of different
morphologies depending on its concentration in DMF:
A - 2, B - 2.6, C - 3, D - 4 wt%. [Adapted, by permission,
from L Zhang, A Eisenberg, Macromol. Symp., 113,
221-32 (1997).]
Figure 12.1.12. Morphological features of PS-PAA
copolymer having different ratios of PS and PAA block
lengths: A - 8.3, B- 12, C - 20.5, and D - 50. [Adapted,
by permission, from L Zhang, A Eisenberg, Macromol.
Symp., 113, 221-32 (1997).]
Figure 12.1.14. TEM micrograph of nanospheres.
[Adapted, by permission, from G Liu, Macromol.
Symp., 113, 233 (1997).]
Three major morphological features are under investigation: starlike, crew-cut, and
polymer brushes (Figure 12.1.11). Morphological features have been given nick-names
characterizing the observed shapes, such as “animals” or “flowers” to distinguish between
various observed images. 6 Figure 12.1.12 shows four morphologies of aggregates formed
by polystyrene, PS,-poly(acrylic acid), PAA, diblock copolymers. 1 The morphology produced
was a direct result of the ratio between lengths of blocks of PS and PAA (see Figure
12.1.12). When this ratio is low (8.3), spherical micelles are formed. With a slightly higher
ratio (12), rod-like micelles result which have narrow distribution of diameter but variable
length. Increasing ratio even further (20.5) causes vesicular aggregates to form. With the
highest ratio (50), large spherical micelles are formed. One of the reasons for the differences
in these formations is that the surface tension between the core and the solvent varies
widely. In order to decrease interfacial tension between the core and the solvent, the aggregate
increases the core size. 1 Polymer concentration in solution also affects aggregate for-