Poly(amic acid)s and their ionic salt solutions: Synthesis, characterization and stability study - Polyimides and Other High Temperature Polymers - page 6

2.2.2. Model compounds synthesis and characterization

We believe that the most common possibility of polymer degradation activity
would be in the orthocarboximide (-CO-NH-) region at various parts of the poly-
mer chain, e.g. proximity to the aromatic ring, or the proximity to the (-CH 2 CH 2
CH 2 -Si-O-Si-CH 2 CH 2 CH 2 -) group. Therefore, to understand the viscosity drift
of PAA, Co-PAA and its ionic salt solution [i.e. photosensitive poly(amic acid)
(PDPAA)] upon storage at room temperature, two model compounds, ,

were synthesized whose chemical structures were chosen after careful inspection
of the chemical structure of Co-PAA (Figure 4).
2.2.2. (a) Synthesis of model compound

A and B

(Bisphthalamic acid of
3,3'-dimethyl-4,4'-diaminobiphenyl)

A

The synthesis of model compound A was straightforward. The synthesis scheme

is shown in Figure 5.

Figure 4. Model compounds selected based on the chemical structure of Co-PAA repeat unit.

Figure 5. Synthesis scheme for model compound A.