Chemistry Reference
In-Depth Information
TABLE 15.1 Examples of Functional Monomers Used in Covalent Molecular
Imprinting Process
Covalent
Bond
Monomer
Template
References
Boronic ester
Diols,
carbohydrates
Wulff and Sarhan (1972),
Wulff, Vesper et al. (1977)
Carboxylic
ester
Alcohols
Sellergren and
Andersson (1990)
Acetal
Ketones,
aldehydes
Shea and Sasaki (1991)
Imine
Amines
Wulff et al. (1978)
Noncovalent MIPs.
The more popular noncovalent imprinting process was devel-
oped by Arshady and Mosbach (1981) in the 1980s. These systems are characterized
by noncovalent interactions between the template and functional monomers such as
hydrogen bonds, hydrophobic interactions, p-p interactions, electrostatic inter-
actions, charge transfer, and van der Waals forces. An example of the noncovalent
imprinting process is provided in Scheme 15.3. First, methacrylic acid (MAA) func-
tional monomers were complexed with an
L
-phenylalanine anilide template via
hydrogen bonds and electrostatic interactions. The noncovalent complex was poly-
merized in the presence of the cross-linker ethylene glycol dimethylcrylate
(EGDMA) to form a rigid polymer matrix. Subsequently, the polymer was ground
and washed with acetonitrile to remove the template.
The noncovalent imprinting process has quickly become the most popular method
for preparing MIPs because it is synthetically more efficient and more versatile and
adaptable. First, the monomer-template complex can be formed in situ during the
polymerizing process, because the noncovalent interactions do not require any
additional reagents or catalysts. Thus, the entire imprinting process can be carried
out efficiently in a single reaction vessel. Second, a single functional monomer can
form noncovalent interactions with many different template molecules and can effec-
tively imprint a wide range of templating agents. This versatility is exemplified by the
most common noncovalent functional monomer, MAA, which has been used to
