Miscibility behavior and reequilibration of binary poly(amic acid) mixtures

Abstract

Five poly (amic acid) solutions based on PMDA‐PDA, PMDA‐ODA, PMDA‐6F, ODPA‐ODA, and 6FDA‐ODA were prepared in N‐methylpyrrolidone at a polymer concentration of ca. 10 wt %. From these five poly (amic acid) solutions, six different binary blends were prepared: PMDA‐PDA/PMDA‐ODA, PMDA‐PDA/PMDA‐6F, PMDA‐ODA/6FDA‐ODA, PMDA‐ODA/ODPA‐ODA, PMDA‐PDA/ODPA‐ODA, and PMDA‐PDA/6FDA‐ODA. These blends were then characterized with respect to miscibility in the ternary state (polyamic acid‐1/polyamic acid‐2/N‐methylpyrrolidone), the condensed state (ca. 70 wt % polymer), and the fully imidized state. All blends except for PMDA‐PDA/PMDA‐6F yielded homogeneous mixtures in the ternary solution of 10 wt % polymer concentration. The PMDA‐PDA/PMDA‐6F mixture eventually became homogeneous after 10 days of mixing at room temperature. Upon solvent evaporation (condensed state) and full cure (imidized state) two blends incorporating ODPA‐ODA as one of the components exhibited apparent miscibility as evidenced by optical microscopy. The remaining blends exhibited large‐scale phase separation upon solvent evaporation with no significant differences in the overall morphology between the condensed and imidized state. However, as in the case of the PMDA‐PDA/PMDA‐6F ternary system, the morphology in the condensed and imidized state was strongly dependent on the mixing time of the precursor poly(amic acid) components; the phase‐separated domain size decreased with increasing mixing time, eventually leading to complete miscibility. These results are discussed with respect to the proposed “polymer‐monomer” reequilibration reaction as well as its implications with respect to the preparation of polyimide molecular composites.

Synthesis and characterization of fully rodlike poly(4,4?-biphenylene pyromellitimide)s with various short side groups

“…However, in the DMTA measurement, the ␤-relaxation of the PMDA-PDA polyimide was detected to be very weak or almost not detectable below 500°C, 13,14 indicating that the large-amplitude main-chain motions necessary for ductile deformation are restricted very much in the PMDA-PDA polyimide. In contrast, the PMDA-BZ exhibited a slightly enhanced ␤-relaxation below approximately 300°C, 18,48 indicating that the main chain motions, including the aforementioned rotational motions of phenylene rings, are allowed in the PMDA-BZ polyimide.…”

“…9 -11 This statement can be extended for aromatic polyimides with relatively high T g s, which are in the glassy state or the semicrystalline state. In general, semirigid and flexible aromatic polyimides exhibit very broad ␤-relaxations over the range of Ϫ100 to 330°C, depending upon the polymer flexibilities, [13][14][15][16][17][18][19][20][21] as follows: the ␤-relaxation temperature (T ␤ ), which is the temperature at the peak maximum of ␤-relaxation spectrum, is in the range of 42-230°C, depending upon the polymer flexibilities. In general, a higher chain flexibility gives a lower T g as well as a lower T ␤ .…”

Adhesion of poly(4,4′-oxydiphenylene pyromellitimide) to copper metal using a polymeric primer: Effects of miscibility and polyimide precursor origin

“…However, this polyimide is known to have a poor adhesion to the polymer itself as well as to metals and substrates which are used together in the fabrication of microelectronic devices [6][7][8][9][10][11][12][13][14] . In particular, the polyimide exhibits a very poor adhesion to copper metal, so that the polyimide film is easily delaminated from the copper when it is overcoated on copper metal [6][7][8][9][10][11][12][13][14] . Furthermore, its poly(amic acid) precursor was found to react with copper metal during the imidization process, consequently generating copper oxide particles which diffuse into the polyimide film [12][13][14] .…”

Synthesis and Curing Behaviors of Polyisoimide Oligomers with Ethynyl End Groups

“…3,4 폴리이미드 제조 시 가장 널리 이용되고 있는 전구체 고분 자는 다이아민과 다이안하이드라이드로 합성되는 폴리아미드 산인데, 중합 방법이 간단하다는 장점이 있으나 폴리아미드 산의 분자량 및 용액점도는 공기 중에 포함된 습기 및 온도 변화 등에 의하여 민감하게 변하므로, 운송 및 보관 시에 항 상 냉장상태를 유지해야 하는 불편함이 있고, 또한 실제 사 용할 때 시간에 따른 용액 점도의 변화로 인해 가공조건을 수시로 조절해야 하는 단점이 있다. 5,6 또한 폴리아미드산을 이용한 가공공정 중에는 부산물로 H 2 O가 생성되며 이는 기 공생성의 원인이 되어 최종제품의 물성저하를 초래할 수 있 다. 7,8 반면, 폴리아미드산으로부터 화학적인 탈수 반응에 의해서 제조되는 폴리아이소이미드는 열만 가하면 휘발 성분의 부산 물을 생성하지 않고 바로 폴리이미드로 전환된다( Figure 1).…”