Spontaneous molecular orientation of polyimides induced by thermal imidization (4): Casting- and melt-induced in-plane orientation

Optically transparent aromatic poly(ester imide)s with low coefficients of thermal expansion (1). Self-orientation behavior during solution casting process and substituent effect

“…However, chemical imidization of TA-TMHQ/TFMB swept away a reputation as a "worthless material" as stated above; the curve (3C) represents that the PEsI chains for TA-TMHQ/TFMB can highly align along the film plane just by drying at 60 C for 2 h. Then, the halfdried PEsI film obtained probably undergoes additional orientational enhancement by fully drying it on the substrate at 250 C owing to an expected apparent stretching effect concomitant to a slight thickness decrease as mentioned later. This hypothesis is based on our previous observation; i.e., melt-induced in-plane orientation behavior by annealing above the T g on the substrates for s-BPDA/TFMB [36]. Indeed, the substrates must play a great role when annealed at 250 C in the present case; if the substrate was removed after drying at 60 C for 2 h, the half-dried TA-TMHQ/ TFMB PEsI film most likely suffers somewhat orientational relaxation by heating at 250 C (3C′) as suggested from the fact that CTE ¼ 13.0 ppm K À1 in case of heating on the substrate and CTE ¼ 22.3 ppm K À1 off substrate for TA-25DBHQ(70); PMDA(30)/ TFMB copolymer.…”

“…However, in this work we tried to find out some common feature between them from the viewpoint of "molecular mobility" during the film formation processes. Our previous studies revealed that the degree of in-plane orientation is affected by some structural factors (backbone linearity/stiffness) and processing conditions (heating rate, film thickness, solvents and amounts of residual solvents in PAA films) during thermal imidization [31,36]. It is accepted that the residual amide solvents behave as a plasticizer [38].…”

Novel Poly(benzoxazole-etherimide) Copolymer for Two-Layer Flexible Copper-Clad Laminate

“…Such an orderly arrangement was expected to improve the mechanical strength, heat resistance, and thermal stability of PI films. [8,11,12] …”

“…The key strategy for reducing the CTE values is to choose PI systems consisting of rod-like backbone structures. [8,11,12] However, PIs with rigid rodlike conformations usually have inherently poor adhesion properties. [13,14] To balance the thermodimensional stability and good adhesion properties, blending a rodlike polymer system with a flexible polymer is an approach to obtain such a combination of desired properties.…”

Polymer/organosilica nanocomposites based on polyimide with benzimidazole linkages and reactive organoclay containing isoleucine amino acid: Synthesis, characterization and morphology properties

“…Among a large number of PIs which have been so far studied from both academic and industrial viewpoints, aromatic PIs are the most reliable heat-resistant polymers, which have combined excellent properties, i.e., high glass transition temperatures (T g ), high resistance to chemicals and radiations, relatively low dielectric constants, and good mechanical properties [3][4][5]. Beyond excepted advantages of such materials, PIs have limitations in processability and solubility that caused recently significant synthetic efforts through the synthesis of new diamine or dianhydride monomers.…”