Chemistry Reference
In-Depth Information
electropolymerization (Gong et al. 2004), condensation (Asanuma et al. 1997), step
growth (Beinhoff et al. 2006), and metathesis polymerizations (Patel et al. 2003).
Cross-linker.
The cross-linker plays an important role in determining the recog-
nition and material properties of MIPs. MIPs are commonly prepared with a high per-
centage of cross-linking agent, typically 50-80%. These high cross-linking
percentages are required to maintain the structural integrity of the imprinted
binding sites (Biffis et al. 2001). Despite these high cross-linking percentages, the
majority of the template (.90%) can usually be removed because of the macroporous
nature of the polymer matrix (Siemann et al. 1997). The most common cross-linkers
are EGDMA (Vlatakis et al. 1993) and DVB (Fig. 15.1; Wulff and Sarhan 1972;
Sellergren and Andersson 1990). Other cross-linkers include trimethylolpropane tri-
methacrylate (Glad et al. 1995) and N,N
0
-methylenebisacrylamide (MBA; Wang et al.
1997; Suedee et al. 2006). Although the primary role of the cross-linker is to form a
rigid matrix, the cross-linker can also contain recognition groups and thus participate
directly in recognition events. In principle, the recognition groups in the cross-linker
become more rigidly fixed into the polymer matrix and thus can form higher affinity
binding sites. For example, cross-linkers with hydrogen bonding urea (Hall et al.
2003), amide (Sibrian-Vazquez and Spivak 2004), N,N
0
-diacyl-2,6-diaminopyridine
Figure 15.1 Examples of common cross-linkers used in the preparation of molecular
imprinted polymers: ethylene glycol dimethylcrylate (EGDMA); divinyl benzene (DVB),
trimethylolpropane trimethacrylate (TRIM), N,N
0
-methylenebisacrylamide (MBA), and
N,O-bismethacryloyl ethanolamine (NOBE).
