Thermomechanical characterization of thermoplastic polyimide to improve the chain interaction via crystalline domains

Abstract

In a previous study on polyimides, we incorporated an aromatic diamine monomer with a methylene linker, 4,4 0 -methylenebis (2,6-dimethylaniline), to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to decrease rigidity. In this report, we explore the behavior of crystalline regions provided by the organized packing of polyethylene oxide into the formerly characterized polymers. The polymers were designed to exhibit thermal properties in between those of conventional aromatic polyimides and polymers with wholly aliphatic ether diamine links, with a target to improve the mechanical characteristics. Through dynamic mechanical analysis and differential scanning calorimetry, it is shown that the incorporation of polyethylene oxide diamine and the removal of methyl pending groups serve to improve the organized packing of the chains. All of this allows for a broader range in tenability of thermal and mechanical properties of the polyimide. Furthermore, the crystalline regions are an important component to maintain the temperature stability of polyimide while maintaining the processability. The polymers are characterized by Fouriertransform infrared spectroscopy, thermomechanical and calorimetric analysis, microhardness measurements, tensile testing, and wide-angle X-ray scattering.

Thermoplastic polyimide with good comprehensive performance based on carbazole groups and short flexible linkages

“…As the ratio of Me‐BiCzDA increases up to 15%, storage modulus decreases exceeding 1000 MPa. The observations demonstrate that the Me‐BiCzDA‐based TPIs, meanwhile, have excellent thermoplastic properties 4,6,12,17 …”

“…The observations demonstrate that the Me-BiCzDA-based TPIs, meanwhile, have excellent thermoplastic properties. 4,6,12,17 Then, thermal mechanical analysis (TMA)is employed to further verify the thermal properties of TPIs (Figure 2A). Corresponding to the DMA results, the Me-BiCzDA-based TPIs (10%-15%) possess lower T g of 341-348 C than the reference PI ODA-PMDA with T g of 369 C (Figure 1B).…”

“…1,2 To overcome this issue, thermoplastic polyimide (TPI) is developed for adhesion application. 1,[3][4][5][6] In general, desirable TPI can be achieved by introducing flexible linkages, 4,[7][8][9] bulky side groups, 10,11 twisted noncoplanar structure [12][13][14][15][16][17] or asymmetric structure, 14,18 or copolymerization. 6,16,18,19 However, too soft linkage would enhance the movability of the polymer chain, leading to poor heat resistance and mechanical properties.…”

“…But its limited thermal stability is not able to meet the requirements of FCCLs applied under extreme conditions 1,2 . To overcome this issue, thermoplastic polyimide (TPI) is developed for adhesion application 1,3–6 …”

Thermoplastic polyimide with low dielectric properties enabled by the 2,2′‐spirobifluorene group

“…1,2 For instance, they can replace of epoxy resins in flexible copper clad laminates, which are able to serve under extreme conditions such as high temperature circumstance. [3][4][5][6] Many efforts have been made to improve the thermoplasticity with storage modulus dropping exceeding 1000 MPa over T g , 5,7,8 including enhancing the flexibility of polymer chains, 5,[9][10][11] weakening intra-/inter-molecular interactions, 7,8,[12][13][14][15][16] and breaking the symmetric structure to some extent. 7,14,17 However, with the increasing demands for electronic devices in high-frequency communication, high-performance TPIs with low dielectric constant (D k )/dielectric loss factor (D f ) at high frequency are also highly desirable.…”