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Luminescent Conjugated Polymers for Staining and Characterization of Amyloid Deposits 331

O O
H H
C O – C O –
H N + H N +
H H
H H
O O O
–
O C N
H 3 C O +
N Cl –
CH 3
S n S n S n S n
PTAA POWT POMT PTMI
O O
H H
–
C O O C
H N + N + H
H H
H H
O O O O
–
O C C O –
S S
S S n S S

tPTAA tPOWT
FIGURE 9.1 Chemical structures of some anionic, cationic, and zwitter-ionic
luminescent conjugated polymers that have been used for staining and
characterization of amyloid fi brils.

the polymers be compatible with an aqueous environment. This can
be achieved by adding ionic substituents on the polymer backbone.
To achieve excellent LCPs, e.g., polymers exhibiting fluorescence
with high quantum efficiency, a polymer backbone consisting of sub-
stituted thiophene rings or fluorene building blocks is preferable, as
photoluminescence in conjugated polymers requires a non degener-
ated ground state. A wide range of water-soluble LCPs have been
reported, 1–14 and some examples are shown in Fig. 9.1. The functional
groups of the conjugated polymers, being anionic or cationic at differ-
ent pH values, make these polymer derivatives suitable for forming
strong polymer complexes with negatively or positively charged bio-
molecules, such as DNA or proteins. In addition, the ionic groups are
able to create versatile hydrogen bonding patterns with different
molecules, which might be necessary to achieve specific interactions
with different biomolecules.

9.2.2 Optical Properties
The optical processes in conjugated polymers are highly influenced
by the conformation of the polymer backbone and the separation and