Controlled Molecular Weight Polyimides from Poly(amic acid) Salt Precursors

Highly Macroporous Polyimide with Chemical Versatility Prepared from Poly(amic acid) Salt-Stabilized High Internal Phase Emulsion Template

Macroporous polymers have gained significant attention due to their unique mass transport and size-selective properties. In this study, we focused on Polyimide (PI), a high-performance polymer, as an ideal candidate for macroporous structures. Despite various attempts to create macroporous PI (Macro PI) using emulsion templates, challenges remained, including limited chemical diversity and poor control over pore size and porosity. To address these issues, we systematically investigated the role of poly(amic acid) salt (PAAS) polymers as macrosurfactants and matrices. By designing 12 different PAAS polymers with diverse chemical structures, we achieved stable high internal phase emulsions (HIPEs) with >80 vol % internal volume. The resulting Macro PIs exhibited exceptional porosity (>99 vol %) after thermal imidization. We explored the structure-property relationships of these Macro PIs, emphasizing the importance of controlling pore size distribution. Furthermore, our study demonstrated the utility of these Macro PIs as separators in Li-metal batteries, providing stable charging-discharging cycles. Our findings not only enhance the understanding of emulsion-based macroporous polymers but also pave the way for their applications in advanced energy storage systems and beyond.

The block copolymer shuffle in size exclusion chromatography: the intrinsic problem with using elugrams to determine chain extension success

Is an increase in hydrodynamic volume always expected in block copolymer synthesis? Why SEC is sometimes not the last word.

Preparation and characterization of high-performance polyamic acid salt hydrogel in aqueous solution

Herein, we report an easy-to-prepare polyamic acid salt (PAAS) hydrogel with multiple functionalities including rapid self-healing, stimuli-responsive properties, and conductivity. This study describes a method for synthesizing PAAS hydrogel in aqueous solution. Phenylenediamine and 3,3′,4,4′-biphenyltetracarboxylic dianhydride were used to prepare a hydrogel with a fully aromatic backbone via gradual polymerization. It is possible to use the gel in the field of biomaterials in the absence of organic solvents. The prepared hydrogel was characterized using Fourier-transform infrared spectroscopy and dynamic rheometry. The gel has good toughness and the storage modulus and tensile stress are, respectively, about 0.25 and 0.45 MPa. Our study may pave the way for the manufacture of PAAS hydrogel, which may promote the development of hydrogel materials.

3D Printing All-Aromatic Polyimides Using Stereolithographic 3D Printing of Polyamic Acid Salts

Polyamic acid (PAA) salts are amenable to photocuring additive manufacturing processes of all-aromatic polyimides. Due to an all-aromatic structure, these high-performance polymers are exceptionally chemically and thermally stable but are not conventionally processable in their imidized form. The facile addition of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to commercially available poly(4,4'-oxydiphenylene pyromellitamic acid) (PMDA-ODA PAA) afforded ultraviolet curable PAA salt solutions. These readily prepared solutions do not require multistep synthesis, exhibited fast gel times (<5 s), and rendered high G' gel-state moduli. Vat photopolymerization 3D printing afforded self-supporting organogels. Subsequent thermal treatment rendered the cross-linked PAA precursor to all-aromatic PMDA-ODA polyimide. This fast and facile strategy makes PMDA-ODA polyimides accessible in three dimensions and offers impact on aerospace or automotive technologies.

Counterion-Induced Control of the Colloidal State of Polyamic Acid Nanoparticles for Electrophoretic Deposition

Optimizing the colloidal state of polyamic acid (PAA) nanoparticles is essential for achieving a uniform and high-performance polyimide coating by electrophoretic deposition (EPD) on metal substrates of various shapes. In this paper, we report two important roles of the counterions in the formation of PAA colloids for EPD, which, to date, have not been recognized. First, when tertiary alkyl amines are used to neutralize PAA, the polarity of neutralizing counterions determines the size and stability of the PAA colloidal particles. The polarity can be finely tuned by using two different tertiary alkyl amines containing polar and nonpolar groups and adjusting the molar ratio. Depending on the polar/nonpolar ratio, various states of PAA colloids were obtained, including dissolved state, stable colloid, and aggregates. Second, we observed that the confined counterions inside PAA nanoparticles can act as an imidization catalyst during the thermal annealing process. It is revealed that some fraction of the counterion species, mostly having nonpolar groups, is not drawn toward the counter electrode and remains inside the PAA nanoparticles during the EPD process. Optimizing the polarity eventually allowed us to form uniform EPD coatings with high dielectric strengths.

A novel vacuum-assisted method for fabricating flexible polyimide foams from 3,3′,4,4′-oxydiphthalic anhydride/4,4′-oxydianiline

In this research, a novel method for fabricating flexible polyimide foams was developed. The foam was derived from the precursor synthesized via esterification of 3,3′,4,4′-oxydiphthalic anhydride and 4,4′-oxydianiline. After drying process, the remaining solvent acted as blowing agent. By adjusting the synthesis condition, low-molecular weight precursor was obtained and can be foamed under environment temperature. With this novel type of precursor and vacuum-assisted foaming process, we could easily obtain any shape of foams, which was easy to process under relatively low temperature. The foam could be imidized later in order to improve mechanical strength. During the imidization process, in situ Fourier transform infrared (FTIR) analysis was applied to analyze the variation of the imidization percentage with time. The density of the foams could be adjusted from 12 to 30 kg m−3 with uniform cell structure. Other properties of foams were also investigated. The glass transition temperature of the precursor was 70°C, which is obviously lower than that of the usual previously reported. The 5% and 10% weight loss temperatures of the finally imidized foam can reach up to 567°C and 593°C, respectively. The foams belong to open cell structure with 98% open cell content. The limiting oxygen index of the foams varied from 38.6 to 41.9, depending on foam densities. The compressive strength of the foam ranged from 30.6 to 90.6 kPa when the density changed from 15 to 28 kg m−3. In addition, the in situ FTIR analysis was applied to analyze the imidization percentage of the foam during imidization process.

Preparation, characterization, and properties of poly(thioether imide)s from isomeric bis(chlorophthalimide)s and bisthiophenols

A series of isomeric poly(thioether imide)s (PTIs) containing thioether linkages were prepared by aromatic nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s (BCPIs) and bisthiophenols. The glass transition temperatures ( Tgs) of the isomeric PTIs were 190–264°C, the 5% weight loss temperature ( T5%) reached up to 441–508°C under nitrogen and 472–520°C in air atmospheres, respectively. It was found that the Tg values of the PTIs from three isomeric BCPIs with the same bisthiophenol increased in the order of 4,4′-BCPI < 3,4′-BCPI < 3,3′-BCPI, while the T5% values gradually decreased in the order of 4,4′-BCPI > 3,4′-BCPI > 3,3′-BCPI. Flexible films that could be cast from the polymer solutions exhibited good mechanical properties with tensile strengths of 91–121 MPa, elongations at break of 8–12%, and tensile moduli of 2.2–2.6 GPa. The minimum melt viscosity of isomeric PTIs decreased with increasing the content of asymmetric 3,4′-substituted phthalimide unit, and the PTI (2c) showed the lowest melt viscosity about 760 Pa·s at 264°C among these isomeric polymers.

Multifunctional, marvelous polyimide aerogels as highly efficient and recyclable sorbents

Novel polyimide aerogels with high absorption capacity and excellent recyclability for oils and organic liquids are fabricated by freeze-drying.

Preparation, characterization, and properties of poly(thioether ether imide)s from isomeric bis(chlorophthalimide)s and bis(4-mercaptophenyl) ether

A series of isomeric poly(thioether ether imide)s (PTEIs) containing both thioether and ether linkages were prepared by aromatic nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s (BCPIs) with bis(4-mercaptophenyl) ether (BMPE). The inherent viscosities of synthesized polymers were found in the range of 0.41–0.86 dL g−1 in N-methyl-2-pyrrolidone at 30°C. The glass transition temperature ( Tg) of the isomeric PTEIs were 210–242°C and increased by increasing the content of 3-substituted phthalimide unit in the polymer backbone. The 5% weight loss temperature values reached up to 525–539°C under nitrogen and 523–534°C in air atmospheres, respectively, which indicated this kind of polyimide possessed excellent thermal stability. Flexible films could be cast from the polymer solution. The PTEI films exhibited moderate mechanical properties with tensile strengths of 106–127 MPa, elongations at break of 8.6–11.5%, and tensile moduli of 2.2–2.8 GPa, respectively. Dynamic mechanical thermal analysis results illustrated that the storage moduli ( E′) of PTEI (a–e) almost completely maintained at about 2.3 GPa before reaching the corresponding Tg. It is noted that the minimum melt viscosity of isomeric PTEIs (a′–e′) decreased by increasing the content of unsymmetrical 3,4′-substituted phthalimide unit in the polymer main chain.

Otimização da interface/interfase de compósitos termoplásticos de fibra de carbono/PPS pelo uso do poli(ácido âmico) do tipo BTDA/DDS

No presente trabalho duas técnicas de manufatura de compósitos termoplásticos estruturais são investigadas: a de moldagem por compressão a quente convencional e a de pré-impregnação via suspensão polimérica. A primeira consiste na impregnação do reforço via polímero fundido; enquanto que a segunda faz uso de suspensões poliméricas aquosas, onde a impregnação do reforço ocorre pelo contato deste com a suspensão aquosa de partículas da matriz polimérica. Esta técnica combina a matriz polimérica em pó com um outro polímero formador da suspensão, um poli(ácido âmico - PAA), sendo que os dois polímeros são simultaneamente depositados sobre o reforço, durante a impregnação. Este mesmo PAA, em uma segunda fase do processo, é convertido termicamente em uma poliimida (PI) podendo formar uma região de interfase entre o reforço e a matriz polimérica. Este trabalho tem como objetivo a síntese e a caracterização de um PAA, à base de BTDA/DDS, e a avaliação de sua influência na formação da região de interfase em compósitos de poli(sulfeto de fenileno) (PPS)/fibras de carbono. Resultados de DSC e TG mostram o sucesso da síntese do PAA e de sua conversão em PI, esta com estabilidade térmica até 396 °C. O compósito processado pela técnica de suspensão polimérica apresenta resistência ao cisalhamento interlaminar (56,3 MPa) 12,6% superior ao compósito obtido por moldagem por compressão a quente convencional (50,0 MPa). Estes resultados são confirmados por análises das superfícies de fratura, que mostram que o uso do PAA melhora a interfase do PPS/fibra de carbono.

Síntese de um poli (ácido âmico) para aplicação como interfase em compósitos termoplásticos de alto desempenho

O objetivo do presente trabalho é apresentar a síntese de um poli (ácido âmico) (PAA) a ser utilizado como formador de interfase no processamento de compósitos termoplásticos de alto desempenho. Os materiais compósitos termoplásticos constituídos de um reforço rígido e de uma matriz dúctil têm as suas propriedades mecânicas fortemente dependentes do mecanismo de transferência de carga fibra/matriz. Por esse motivo, a região da interface/interfase nos materiais compósitos possui um papel fundamental nas propriedades finais do material. O PAA surge como uma alternativa para melhorar a adesão fibra/matriz na região interfacial em compósitos de alto desempenho, constituídos de matrizes termoplásticas, reforçadas com fibras de carbono ou vidro. O PAA é utilizado na forma de sal, na preparação de suspensões poliméricas de matrizes termoplásticas. O PAA estudado neste trabalho foi sintetizado utilizando-se os reagentes BTDA e DHPr. Em seguida, o PAA foi convertido em PI por imidização em solução. Análises por FTIR mostram o sucesso da síntese do PAA e da sua conversão em PI. As técnicas de DSC e TGA determinaram as temperaturas de transição vítrea (~213 °C) e de decomposição (~310 °C), respectivamente. Estes resultados motivam a utilização do PAA/PI como formador de interfase na obtenção de compósitos termoplásticos com temperaturas de processamento abaixo de 310 °C.