Phenylethynyl-Terminated Imide Oligomer-Based Thermoset Resins

Abstract

Phenylethynyl-terminated imide (PETI) oligomers are highly valued for their diverse applications in films, moldings, adhesives, and composite material matrices. PETIs can be synthesized at varying molecular weights, enabling the fine-tuning of their properties to meet specific application requirements. Upon thermal curing, these oligomers form super-rigid network structures that enhance solvent resistance, increase glass-transition temperatures, and improve elastic moduli. Their low molecular weights and melt viscosities further facilitate processing, making them particularly suitable for composites and adhesive bonding. This review examines recent advancements in developing ultra-high-temperature PETIs, focusing on their structure-processing-properties relationships. It begins with an overview of the historical background and key physicochemical characteristics of PETIs, followed by a detailed discussion of PETIs synthesized from monomers featuring noncoplanar configurations (including kink and cardo structures), fluorinated groups, flexible linkages, and liquid crystalline mesogenic structures. The review concludes by addressing current challenges in this research field and exploring potential future directions.

Keywords: composite material matrix; phenylethynyl-terminated imide oligomer; structure parameters; thermoset resin.

Scheme 7

Chemical structures of PETIs with inorganic hybrid configurations: (A) 0, 1, 2, 3 cis- and/or trans-POSS (reproduced with permission from [29], Copyright 2013, American Chemical Society); (B) PI-mPDA/CB-PEPA blend series (reproduced with permission from [56], Copyright 2017, SAGE Publications).

Scheme 1

Chemical structures of PETIs with isomeric configurations: (A) Oligo-n [3]; (B) PI-n [8]; (C) Oligo-n [33]; (D) Pn and PETI-RTM [34].

Figure 1

Complex viscosity curves: (A) Oligo-n (reprinted with permission from [3], Copyright 2001, SAGE Publications); (B) PI-n (reprinted with permission from [8], Copyright 2015, SAGE Publications); (C) Oligo-n (reprinted with permission from [33], Copyright 2018, Wiley); (D) P4 (reprinted with permission from [34], Copyright 2002, SAGE Publications).

Figure 2

TGA curves: (A) The fully cured Oligo-n and polyimide in air; Oligo-1.5 (— · —), Oligo-10 (– – –), PI (a-BPDA/3,4′-ODA; 4,4′-ODA) (50:50) (——) (reprinted with permission from [3], Copyright 2001, SAGE Publications); (B) Cured PI-6 in air and in nitrogen (reprinted with permission from [8], Copyright 2015, SAGE Publications); (C) The fully cured Oligo-n films in nitrogen (reprinted with permission from [33], Copyright 2018, Wiley).

Scheme 2

Chemical structures of PETIs with kinked configurations: PETI, PE-3F, and PE-6F oligoimides [14].

Figure 3

(A) Viscosity curves of PE-3F oligoimides; (B) TGA curves of PE-3F oligoimides in nitrogen (reprinted with permission from [14], Copyright 2003, American Chemical Society).

Scheme 3

Chemical structures of PETIs with cardo configurations: (A) o-BAFL-n [44]; (B) Oligo-n [45]; (C) PI oligomer/Cardo-HPI blends [43]; (D) B-O-n, F-O-n, B-T-n, F-T-n, B-P-n, and F-P-n [9].

Figure 4

Complex viscosity curves: (A) TriA-PI and o-BAFL series; ((a) TriA-PI (o-BAFL-0), (b) o-BAFL-10, (c) o-BAFL-25, (d) o-BAFL-50) (reprinted with permission from [44], Copyright 2006, SAGE Publications); (B) Oligo-n (reprinted with permission from [45], Copyright 2018, Springer); (C) PI oligomer/Cardo-HPI blends (reprinted with permission from [43], Copyright 2019, Elsevier); (D) F-O-2, F-T-2, F-P-2, B-O-2, B-T-2, and B-P-2 (reprinted with permission from [9], Copyright 2023, Elsevier).

Figure 5

TGA curves: (A) Oligo series in nitrogen (reprinted with permission from [45], Copyright 2018, Springer); (B) Cured PI/Cardo-HPI thermosets in nitrogen (reprinted with permission from [43], Copyright 2019, Elsevier); (C) Thermosetting polyimides in nitrogen (reprinted with permission from [9], Copyright 2023, Elsevier).

Scheme 4

Chemical structures of PETIs with asymmetric configurations: (A) Oligo-s–a1–9 and Oligo-bt–a1–9 [48]; (B) PMDA/p-ODA/PEPA imide oligomer [10]; (C) PETI-H, PETI-F, PETI-3F, and PETI-P [46].

Figure 6

Complex viscosity curves: (A) Oligo-s–a1–9 (reprinted with permission from [48], Copyright 2006, Elsevier); (B) Uncured PMDA/p-ODA/PEPA imide oligomers (n = 1–10) (reprinted with permission from [10], Copyright 2012, Elsevier); (C) PETI-H, PETI-F, PETI-3F, and PETI-P (reprinted with permission from [46], Copyright 2023, Elsevier).

Figure 7

TGA curves: Cured PETI-H, PETI-F, PETI-3F, and PETI-P resins (reprinted with permission from [46], Copyright 2023, Elsevier).

Scheme 5

Chemical structures of PETIs with fluorinated units in main chains: (A) AFR-PEPA-N [16]; (B) PI-n [50]; (C) PETI-O, PETI-F, and PETI-P [51].

Figure 8

Complex viscosity curves: (A) PI-n (reprinted with permission from [50], Copyright 2006, Elsevier); (B) PETI-O, PETI-F, and PETI-P (reprinted with permission from [51], Copyright 2021, MDPI).

Figure 9

TGA curves: Cured PETI-O, PETI-F, and PETI-P in nitrogen (reprinted with permission from [51], Copyright 2021, MDPI).

Scheme 6

Chemical structures of PETIs with flexible units in main chains: (A) PI-n [11]; (B) Oligo-n [52]; (C) o-O-n, o-T-n, and o-p-n [12]; (D) Oligo-n [13].

Figure 10

Complex viscosity curves: (A) PI-n (reprinted with permission from [11], Copyright 2007, Elsevier); (B) Oligo-n (reprinted with permission from [52], Copyright 2018, Springer); (C) o-O-n, o-T-n, and o-p-n (reprinted with permission from [12], Copyright 2019, SAGE Publications); (D) Oligo-n (reprinted with permission from [13], Copyright 2016, SAGE Publications).

Figure 11

TGA curves: (A) Oligo-n (reprinted with permission from [52], Copyright 2018, Springer); (B) o-p-n (reprinted with permission from [12], Copyright 2019, SAGE Publications); (C) Oligo-2 and Oligo-5 (reprinted with permission from [13], Copyright 2016, SAGE Publications).

Figure 12

Viscosity curves: (A) Steady shear viscosity dependence on shear rate for uncured oligomides at 250 °C (reprinted with permission from [29], Copyright 2013, American Chemical Society); (B) PI-mPDA/CB-PEPA blend series (reprinted with permission from [56], Copyright 2017, SAGE Publications).

Figure 13

TGA curves: (A) Mass loss profiles [solid lines] and their first derivatives [dashed lines] for all oligomers in nitrogen (reprinted with permission from [29], Copyright 2013, American Chemical Society); (B) Cured PI-mPDA/CB-PEPA blend series in nitrogen (reprinted with permission from [56], Copyright 2017, SAGE Publications).

Scheme 8

Chemical structures of PETIs with liquid crystalline mesogenic configurations: LC-PI series (reprinted with permission from [58], Copyright 2021, American Chemical Society).

Figure 14

TGA curves: LC-PI series (reprinted with permission from [58], Copyright 2021, American Chemical Society).