Poly(amic acid)s and their ionic salt solutions: Synthesis, characterization and stability study - Polyimides and Other High Temperature Polymers - page 3

Figure 1. Poly(amic acid) and its photosensitive formulation (PDPAA) having photosensitive terti-
ary amines containing acryloyl groups for negative acting type system, and photolithography proc-
essing steps.
NMR studies were carried out on model compounds both in the absence and
presence of added water at room temperature using 1 H NMR.
Any changes, whether increase or decrease, in molecular weights, bulk and in-
herent viscosities and acid number during storage will highlight the degradation
path of PAA, Co-PAA and Co-PDPAA. Therefore, we have monitored molecular
weights by gel permeation chromatography (GPC) [a.k.a. size exclusion chroma-
tography], bulk and inherent viscosities by viscometry and acid number by poten-
tiometry, as a function of storage time. This study will help to understand what
type of reaction is taking place predominantly at the storage temperature which
accounts for the degradation of Co-PAA and Co-PDPAA. In addition, rheological
behaviour of Co-PAA and Co-PDPAA in solution was also investigated as a func-
tion of shear rate and temperature. We have determined the rate constants at vari-
ous temperatures from the activation energy using the Arrhenius equation for vis-
cous flow of BTDA and BPDA based Co-PAA and Co-PDPAA. Also, we have
investigated the thermal stability behaviour of Co-PAA and Co-PDPAA using a
thermogravimetric analyzer (TGA) and the results are reported here.
2. EXPERIMENTAL
2.1. Materials
Phthalic anhydride (PA) was purchased from BDH Laboratory, London, UK;
BPDA and BTDA were obtained from Chriskev Co., USA; (3,3'-dimethyl ben-
zidine) i.e. (o-TDA) was received from Wakayama Seika Kogyo Co. of Japan;