Synthesis and characterization of fully aliphatic polyimides from an aliphatic dianhydride with piperazine spacer for enhanced solubility, transparency, and low dielectric constant

Synthesis of a Novel Rigid Semi-Alicyclic Dianhydride and Its Copolymerized Transparent Polyimide Films' Properties

A new series of colorless polyimides (CPIs) with outstanding thermal properties and mechanical properties were fabricated by the copolymerization of a novel dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2′-bistrifluoromethyl benzidine (TFDB). The novel dianhydride, 10-oxo-9-phenyl-9-(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetraacid dianhydride (3FPODA), possessed a rigid semi-alicyclic structure, –CF₃ and phenyl side groups, and an active carbonyl group. Benefitting from the special structure of 3FPODA, the glass transition temperatures (T_g) of the new CPIs improved from 330 °C to 377 °C, the coefficient of thermal expansion (CTE) decreased from 46 ppm/K to 24 ppm/K, and the tensile strength (T_S), tensile modulus (T_M), and elongation at break (E_B) increased from 84 MPa to 136 MPa, 3.2 GPa to 4.4 GPa, and 2.94% to 4.13% with the increasing amount of 3FPODA, respectively. Moreover, the active carbonyl group of the 3FPODA could enhance the CPI’s adhesive properties. These results render the new dianhydride 3FPODA an ideal candidate monomer for the fabrication of high-performance CPIs.

Synthesis and characterization of an adamantane-based copolyimides with high transparency

In this work, a copolyimide (Co-PI) film with high transparency was prepared by the copolymerization of hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,2′-Bis(trifluoromethyl)benzidine (TFMB) and adamantane-1,3-diamine (DAA). The effects of DAA monomers on the optical, thermal, and mechanical properties of the co-PIs were discussed in detail. We found that the preparation of polyimide (PI) based on the combination of two dianhydrides and two diamines could obtain the co-PI film with excellent comprehensive performance due to the synergy between the -CF3 group, the aliphatic ring and the aromatic structure. Through the structure and composition optimization, the co-PI film with 1.30% DAA (Q3) has a Tg of 374oC, T5 higher than 530oC, T430 of 82% and the tensile strength higher than 145 MPa. These results indicate that the Co-PI films can be successfully utilized in the development of novel heat-resistant plastic substrates for the optoelectronic engineering applications.

Transparent polyimide films with ultra-low coefficient of thermal expansion

According to the application requirements of colorless transparent polyimide (CPI) film for low coefficient of thermal expansion (CTE) in the field of OLED display, the new aromatic dianhydride monomers with amide bond structure were synthesized, namely s-ABDA, i-ABDA, EADA. Furthermore, a series of CPI films were prepared by two-step method from the reaction of as-synthesized dianhydrides with 2.2′-bis (trifluoromethyl) −4.4′-diaminobiphenyl (TFMB) or trans-1.4′-cyclohexanediamine ( t-CHDA). Based on the analysis of performance results, the incorporation of amide group and biphenyl, benzene or ether bond into dianhydride monomer helped this new type of transparent polyimide film with excellent optical properties (T550 nm> 88%), great heat stability (CTE < 4.4 ppm/K; Tg > 314°C; Td5% > 478°C) and good mechanical strength (σ > 208 MPa). The film s-ABDA/TFMB showed ultra-low CTE value at 4.4 ppm/K, aligning with the maximum birefringence, indicating that the role of hydrogen bonding was of great benefit to the regulation of thermal expansion.

Super-heat resistant, transparent and low dielectric polyimides based on spirocyclic bisbenzoxazole diamines with Tg > 450°C

Maintaining ultra-high heat resistance and sufficient colorless transparency at the same time is a challenge for polymer materials because of conflicting design principles, but such materials are urgently needed for...

Crosslinked Fluorinated Poly(arylene ether)s with POSS: Synthesis and Conversion to High-Performance Polymers

This study reports on a series of crosslinked poly(arylene ether)s with POSS in the main chain. The fluorinated and terminated poly(arylene ether)s were first synthesized by the nucleophilic reaction of diphenol POSS and decafluorodiphenyl monomers, including decafluorobiphenyl, decaflurobenzophenone, and decafluorodiphenyl sulfone. They were then reacted with 3-hydroxyphenyl acetylene to produce phenylacetylene-terminated poly(arylene ether)s. The polymers were of excellent processability. When heated to a high temperature, the polymers converted into a crosslinked network, exhibiting a low range of dielectric constant from 2.17 to 2.58 at 1 HMz, strong resistance against chemical solutions, low dielectric losses, and good thermal and hydrophobic properties.

Colorless Polyimides Derived from an Alicyclic Tetracarboxylic Dianhydride, CpODA

An alicyclic tetracarboxylic dianhydride having cyclopentanone bis-spironorbornane structure (CpODA) was polycondensated with aromatic dianhydrides to form the corresponding poly(amic acid)s which possessed logarithmic viscosities in the range 1.47–0.54 dL/g. The poly(amic acid) was imidized by three methods: a chemical, a thermal, and a combined chemical and thermal process. In a thermal method, imidization temperature markedly influenced the film quality and molecular weight of the polyimide. When the poly(amic acid) was cured over the Tg of the corresponding polyimide, the flexible polyimide films were obtained and the molecular weights increased several times, which means that the post-polymerization took place. In spite of low-temperature cure below Tg flexible films with the imidization ratio of 100% were fabricated by a combined chemical and thermal imidization technique. The films possessed the decomposition temperatures in a range of 475–501 °C and Tgs over 330 °C. The high Tg results from a dipole–dipole interaction between the keto groups of the polymer chains as well as development of the rigid polyalicyclic unit. The polyimide films exhibited CTE between 17 and 57 ppm/K. All the films fabricated were entirely colorless and possessed the λcut-offs shorter than 337 nm. Notably, the films prepared by a chemical method exhibited outstanding optical properties.

Synthesis and characterization of amide-bridged colorless polyimide films with low CTE and high optical performance for flexible OLED displays

Starting from three novel amide-incorporating dianhydride monomers, we synthesized a series of amide-bridged cPI films that have ultra-low CTE and high Tg due to the formation of hydrogen bonds as well as great optical performance.

Cascade aza-Michael Addition-Cyclizations; Toward Renewable and Multifunctional Carboxylic Acids for Melt-Polycondensation

Although the aza-Michael addition reaction on various unsaturated (di-)carboxylic acids and esters of, for example, itaconic acid, is well-known, the consecutive cyclization reaction has not received much attention in literature. The products of this aza-Michael cascade reaction, being mono- or di-carboxylic acid or ester functionalized N-alkyl-pyrrolidone structures, prove interesting for melt-polycondensation reactions as they exhibit excellent stability at elevated temperatures. In other words, this reaction is a toolbox for the generation of renewable monomers and, in turn, polymers with tunable physiological properties. Therefore, this work provides an overview of the state-of-the-art of the cascade aza-Michael addition-cyclization reactions on biobased unsaturated acids and esters, and their use in polymerization reactions. Furthermore, we extend this overview with the cascade aza-Michael addition-cyclization reaction of trans-trimethyl aconitate with di-amines to form a tetra-functional N-alkyl-bis-(pyrrolidone dimethylcarboxylate), which exhibits excellent thermal stability and could effectively be used as monomer in polycondensation reactions. Importantly, the aza-Michael addition reaction between primary amines and trans-trimethyl aconitate can be considered a click-reaction; it proceeds quantitatively within minutes under ambient conditions and follows the principles of green chemistry.

New transparent and thermally stable cardo poly(ether imide)s derived from 10,10-bis[4-(4-amino-2-pyridinoxy)phenyl]-9(10H)-anthrone

A new diamine bearing flexible ether, rigid pyridine, and bulky anthrone pendent group, 10,10-bis[4-(4-amino-2-pyridinoxy)phenyl]-9(10 H)-anthrone (BAPPA), was prepared in three steps from anthrone. BAPPA was reacted with six conventional aromatic dianhydrides in N, N-dimethylacetamide (DMAc) to form the corresponding new poly(ether imide)s (PEIs) via the poly(ether amic acid) (PEAA) precursors with inherent viscosities ranging from 0.85 dL g−1 to 1.26 dL g−1 and thermal imidization. All the PEAAs could be cast from DMAc solution and thermally converted into transparent, flexible, and tough PEI films with tensile strength of 72.2–112.4 MPa, tensile modulus of 1.8–2.1 GPa, and elongation at break of 10–18%. These PEIs were predominantly amorphous and displayed excellent thermal stability with the glass transition temperature of 290–388°C, the 5% weight loss temperature of 480–514°C, and the residue of 68–43% at 800°C in nitrogen. The PEIs derived from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 4,4′-hexafluoroisopropylidenediphathalic anhydride exhibited excellent solubility in organic solvents such as N-methyl-2-pyrrolidinone, DMAc, N, N-dimethylformamide, pyridine, and even in tetrahydrofuran. Meanwhile, these PEIs also exhibited high optical transparency with the ultraviolet cutoff wavelength in the 374–427 nm range and the wavelength of 80% transparency in the range of 468–493 nm.

Colorless Semi-Alicyclic Copolyimides with High Thermal Stability and Solubility

A series of colorless copolyimide films with high thermal stability and good solubility are synthesized from (trifluoromethyl)biphenyl-4,4’-diamine (TFMB) with different 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) to 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane (6FDA) dianhydride mole ratios through one-pot solution polycondensation. These copolyimide films exhibit excellent optical transparency (T₄₀₀ > 90% and λ₀ ~305–333 nm) with a thickness of 15 μm and good solubility in most organic solvents. The excellent optical properties are mainly attributed to the low inter- and intra-molecular charge transfer interactions due to the alicyclic structure and the strong electronegative CF₃ groups. The glass transition temperature increases from 332 to 352 °C with increasing HPMDA content in the copolymers, while the thermal decomposition temperature is improved with increasing 6FDA content. These results indicate that the copolyimide films can be successfully utilized in the development of novel heat-resistant plastic substrates for the optoelectronic engineering applications.

Polyimide/mica hybrid films with low coefficient of thermal expansion and low dielectric constant

Polyimide (PI)/mica hybrid films were successfully prepared by in situ condensation polymerization method, in which the mica particles were modified by coupling agent γ-aminopropyltriethoxy silane (APTS) to strengthen the interaction between the mica particles and PI matrix. The morphology, structure, thermal and mechanical properties as well as dielectric properties of PI films were systematically studied via Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR spectrometer), Thermal gravimetric analysis (TGA), tensile experiments, Thermal mechanical analyzer (TMA), impedance analyzer, etc. The results indicated that the mica particles were dispersed homogeneously in PI matrix, leading to an improvement of the mechanical property, thermal stability and hydrophobicity. It was novel to notice that hybrid films exhibited low coefficient of thermal expansion (CTE) and low dielectric constant simultaneously. The CTE and dielectric constant of hybrid film dropped to 25.36 ppm/k and 2.42 respectively, in the presence of 10 wt% mica into polyimide matrix.

Novel copolyimides containing 1,4:3,6-dianhydro-d-mannitol unit Preparation, characterization, thermal, mechanical, soluble, and optical properties

In order to obtain colorless and soluble polyimide films, a dianhydride containing 1,4:3,6-dianhydro-d-mannitol unit, 2,5-bis(3,4-dicarboxyphenoxy)-1,4:3,6-dianhydromannitol dianhydride (IMDA) was synthesized. And a series of copolyimides were prepared from IMDA, 1,2,4,5-benzenetetracarboxylic anhydride (PMDA), and 4,4′-oxydianiline by adjusting the mole fraction (between IMDA and PMDA) of IMDA from 0% to 100%. It was found that the solubility as well as the transmittance of the copolyimide films enhanced with the increased content of IMDA. Especially, when the content of IMDA was 60% or more, the copolyimides were readily soluble in common polar solvents and could afford flexible, tough, and colorless films with transparency up to 84% at 450 nm, which may be ascribed to the incorporation of the relatively twisted and flexible 1,4:3,6-dianhydro-d-mannitol units into the backbone of copolyimides. Additionally, the influence of IMDA on the thermal, mechanical, and morphological properties of copolyimides was investigated.

Synthesis and properties of soluble aromatic polyimides from novel 4,5-diazafluorene-containing dianhydride

A dianhydride monomer containing 4,5-diazofluorene was synthesized, and the corresponding organo-soluble polyimides exhibited good comprehensive properties.

Colorless polyimides derived from 2R,5R,7S,10S-naphthanetetracarboxylic dianhydride

Colorless polyimides with excellent thermal and mechanical properties were developed from 2R,5R,7S,10S-naphthanetetracarboxylic dianhydride, and their properties were systematically compared with those based on 1S,2R,4S,5R-cyclohexanetetracarboxylic dianhydride.

Synthesis of novel biobased polyimides derived from isomannide with good optical transparency, solubility and thermal stability

Novel biobased polyimides with good optical transparency and combined properties were synthesized from biomass isomannide-derived diamines and/or dianhydrides, thus providing a new approach to develop sustainable materials of high performance.