Early-stage phase separation in polyimide precursor blends: an atomic force microscopy study

Abstract

The surface of polyimide precursor blends is studied using atomic force microscopy (AFM). The acid (PAA) and ester (PAETE) precursors in the blends are of the same polyimide. The topographical contrast is due to the complexation of solvent with the acid precursor, causing the latter to swell. Early-stage phase separation prior to impingement is studied for a blend with 20% weight fraction of PAA relative to PAETE. The growth rate of the domains is by nucleation and growth. The PAA-rich discontinuous phase grows at a rate of ~f1 rather than the t1-5, which is usually obtained for surface-induced phase separation.The study also demonstrates the effect of moisture on the acid precursor. It is further shown that due to ~15-fold faster kinetics of imidization of PAA relative to PAETE, the phase-separated topography is maintained even after both precursors convert to the same polyimide.

Atomic Force Microscopic Studies on the Silicone Rubber-Fluororubber Blend Containing Ground Rubber Vulcanizate Powder

“…A TOMIC FORCE MICROSCOPY (AFM) has been applied in the surface analysis of polymeric materials on a nanometer scale [1][2][3][4][5][6]. Haeringen et al have used AFM to investigate the morphology, filler distribution, and adhesion of elastomers using chemically modified tips [7].…”

“…The blends show characteristics of fluororsilicone rubber [11]. Using AFM, Ghosh et al [12] have reported that the surface of the unfilled fluororubber is smooth except for the randomly distributed Ca(OH) 2 particles, which are present in the formulation as potential acid acceptor. Silicone rubber surface, on the other hand, possesses a granular morphology and the blends of silicone rubber and fluororubber are microheterogeneous.…”

Tailoring the surface morphology of polyimide for improved adhesion

“…We note that initially, a.s PAA -» Pl(l), the depth of the dimples is reduced because of CPAARP shrinkage, but the elevation difference is enhanced during the second process of PAETE -^ PI(2). 448 and 6(c) is not as sipiflcant on curing for PAETE-rich blends [38].…”

“…[A blend of x% PAA andyVc = (100 -JC) PAETE is referred to asjc/y.] The minority component (PAA) forms the discontinuous PAA-rich phase (DPAARP) that is elevated with respect to the continuous PAETE-rich matrk (CPATRP) with excess NMP [38]. The uniform size distribution of the DPAARP "mounds" is due to phase separation by spinodal decomposition.…”

Formation of polyimide- Cu complexes: improvement of direct Cu-on-PI and PI-on-Cu adhesion

“…or alloys of these metals is employed as an adhesion-promoting layer [4,5] or a seed layer [6,7]. The application of these adhesion-promoting layers requires deposition equipment and a number of process steps.…”