Chemistry Reference
In-Depth Information
Figure 5.4 Examples of charged coulombic moieties employed for side chain functionali-
zation of polymers.
polymerization of charged monomers. For example, Langsdorf et al. (1999, 2001)
reported the ROMP of both positively and negatively charged cyclooctatetraenes
using a tungsten-based Schrock catalyst (Fig. 5.4a and b).
Barrett and colleagues (2005) polymerized a positively charged norbornene
monomer using Grubbs' second-generation ruthenium catalyst (Fig. 5.4f and g).
Nair and Weck (2007) also polymerized positively charged norbornenes using
Grubbs' third-generation catalyst (Fig. 5.4e). They reported 100% conversions in
less than 1 h with the polymers exhibiting a low polydispersity index of 1.2-1.3.
Unfortunately, the polymerizations of charged monomers are mostly uncontrolled,
preventing the easy formation of block copolymers. Fang and Kennedy (2002)
circumvented this problem by using a postpolymerization method to introduce the
charge species onto one or more blocks of block copolymers that were synthesized
using ATRP (Fig. 5.4c and d).
5.3. NONCOVALENT MULTIFUNCTIONALIZATION OF THE SIDE
CHAINS OF POLYMERIC SCAFFOLDS
The previous section described the supramolecular side chain functionalization of
polymers based on a single recognition motif. However, biological systems use a
wide variety of noncovalent interactions such as hydrogen bonding, metal coordi-
nation, and hydrophobic interactions in an orthogonal fashion to introduce function,
