Three methacrylate-containing polyimides (Px–MMA; x = 1–3) were prepared from the esterification of hydroxyl-containing polyimides (Px–OH; x = 1–3) with methacrylic anhydride. Px–MMA exhibits active ester linkages (Ph–O–C(=O)–) that can react with epoxy in the presence of 4-dimethylaminopyridine (DMAP), so Px–MMA acted as a curing agent for a dicyclopentadiene-phenol epoxy (HP7200) to prepare epoxy thermosets (Px–MMA/HP7200; x = 1–3) thermosets. For property comparisons, P1–OH/HP7200 thermosets were also prepared. The reaction between active ester and epoxy results in an ester linkage, which is less polar than secondary alcohol resulting from the reaction between phenolic OH and epoxy, so P1–MMA/HP7200 are more hydrophobic and exhibit better dielectric properties than P1–OH/HP7200. The double bond of methacrylate can cure at higher temperatures, leading to epoxy thermosets with a high-T_g and moderate-to-low dielectric properties. Full article

Flexible displays are a systematic revolution in the field of display, in which high-performance and high-barrier polymer substrates are considered to be one of the most important key materials. In this work, high water vapor barrier polyimides containing amide moieties were synthesized via the ternary polymerization of 4,4′-diaminobenzailide (DABA), 4,4′-diaminodipheny ether (ODA), and 3,3′,4,4′-biphenyl-tetracarboxylic acid dianhydride (BPDA) followed by thermal imidization. The relationship between the content of amide moieties and the water vapor barrier property of the prepared polyimides was studied by means of density test, water absorbing test, water contact angle test, water vapor permeation test, fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), thermogravimetry coupled with fourier transform infrared spectrometry (TG-FTIR), wide-angle X-ray diffraction analysis (WXRD), mechanical performance test, etc. The results show that the introduction of amide groups into polyimide (PI) main chains can improve the water vapor barrier properties of the polyimides effectively. The water vapor transmission rate (WVTR) of the polyimide films can be improved from 8.2365 g·(m²·24 h)⁻¹ to 0.8670 g·(m²·24 h)⁻¹ with the increasing content of amide moieties. Full article

In this work, four isohexide-derived isomeric dianhydrides were synthesized through a four-step procedure using isohexide and chloro-N-phenylphthalimides as the starting materials. The one-step solution polymerization of these dianhydrides with petroleum- or bio-based diamines enabled the synthesis of poly(ether imide)s (PEIs), which had viscosities of 0.41 to 2.40 dL∙g⁻¹. The isohexide-derived PEIs were characterized based upon their solubility and their thermal, mechanical, and optical properties. The results showed that most of the isohexide-derived PEIs possessed comparable glass transition temperatures (T_g), tensile strengths, and moduli to petroleum-based PEIs. However, the thermo-oxidative stability of the PEIs was found to be lower than that of the common petroleum-based PEIs. Moreover, the PEIs displayed good optical activity, which originated from their unique chiral isohexide moieties. The isomeric effects of dianhydride monomers on the properties of the resulting PEIs were comparatively studied. The results suggested that the corresponding 4,4′-linked PEIs possessed lower T_g, higher mechanical properties, and higher specific rotations compared to 3,3′-linked polymers. Meanwhile, the polyimides with isomannide residue displayed higher T_g and more specific rotations than the corresponding polymers with isosorbide residue. These results contributed to more restricted rotations of phthalimide segments in 3,3′-linked or isomannide containing polyimides. Full article

In this study, a new diamine monomer, namely 4,4′-diamino-4″-(5H-dibenzo[b,f]azepin-5-yl)triphenylamine, was prepared and polymerized with four kinds of dicarboxylic acids via direct polycondensation reaction resulting in a novel series of soluble and electroactive polyamides (PAs). The tough thin films of all PAs could be solution-cast onto an indium-tin oxide (ITO)-coated glass substrate owing to the good solubility in polar organic solvents. Two pairs of obvious redox peaks for these films were observed in cyclic voltammetry (CV) with low onset potentials (E_onset) of 0.37–0.42 V accompanying with remarkable reversible color changes between light yellow and dark blue. A new absorption peak at around 915 nm emerged in near infrared (NIR) spectra; the increasing potential indicated that PAs could be used as a NIR electrochromic material. Moreover, the PAs showed high coloration efficiency (CE; η) in the range of 190–259 cm² C⁻¹. Full article

Two series of polyamides and polyimides containing bulky trityl-substituted triphenylamine units were synthesized from condensation reactions of 4,4′-diamino-4′′-trityltriphenylamine with various dicarboxylic acids and tetracarboxylic dianhydrides, respectively. The polymers showed good solubility and film-forming ability. Flexible or robust films could be readily obtained via solution-casting. The use of aliphatic diacid or dianhydride reduces interchain charge transfer complexing and leads to colorless polyamide and polyimide films. These polymers showed glass-transition temperatures in the range of 206–336 °C. Cyclic voltammograms of the polyamide and polyimide films displayed reversible electrochemical oxidation processes in the range of 0–1.0 or 0–1.3 V. Upon oxidation, the color of polymer films changes from colorless to blue-green or blue. As compared to the polyimide counterparts, the polyamides showed lower oxidation potentials and thus a higher electrochromic stability and coloration efficiency. Simple electrochromic devices were also fabricated as a preliminary investigation for electrochromic applications of the prepared polymers. Full article

Two bisimide compounds, TPA–TPDI and NPC–TPDI, consisting of a triptycene core and two triphenylamine (TPA) or N-phenylcarbazole (NPC) end groups were successfully synthesized by the condensation reactions from 1,4-bis(3,4-dicarboxyphenoxy)triptycene dianhydride with 4-aminotriphenylamine and N-(4-aminophenyl)carbazole, respectively. These two monomers could polymerize electrochemically via the oxidative coupling reactions of triarylamine units. The electrochemical and spectroelectrochemical properties of the electro-generated triptycene poly(ether-imide)s (TPA–TPPI and NPC–TPPI) were studied. Both polymers have two colored oxidation states, and TPA–TPPI showed better electrochromic performance than NPC–TPPI. Full article

A novel aromatic diamine monomer, 4-(4-(1-pyrrolidinyl)phenyl)-2,6-bis(4-(4-aminophenoxy)phenyl)pyridine (PPAPP) containing pyridine rings, pyrrolidine groups, and ether linkages, was successfully synthesized using 4-hydroxyacetophenone and 1-chloro-4-nitrobenzene as starting materials by three-step reactions, and then used to synthesize a series of polyimides by polycondensation with various aromatic dianhydrides via a two-step method. The structure of PPAPP was characterized by NMR, FT-IR, and mass spectrometry analysis methods. These polymers showed good solubility in common organic solvents (e.g., NMP, DMF, DMSO, and DMAc) at room temperature or on heating. Moreover, they presented a high thermal stability with the glass transition temperature (T_gs) exceeding 316 °C, as well as the temperature of 10% weight loss ranged from 552–580 °C with more than 67% residue at 800 °C under nitrogen. Furthermore, they also exhibited excellent hydrophobicity with a contact angle in the range of 85.6°–97.7°, and the results of Wide-Angle X-ray Diffraction (WAXD) indicated that all of the polymers revealed an amorphous structure. Full article

It is a great challenge to develop semicrystalline polyimides exhibited significant recrystallization ability and fast crystallization kinetics from the melt. A series of semicrystalline polyimides based on 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and different diamines, including 1,3-bis(4-aminophenoxy)benzene (TPER), 1,4-bis(4-aminophenoxy)benzene (TPEQ), 4,4′-oxydianiline (4,4′-ODA) and 4,4′-bis(4-aminophenoxy)biphenyl (BAPB), end capped with phthalic anhydride were synthesized. Crystallization and melting behaviors were investigated by differential scanning calorimetry (DSC). The polyimide derived from HQDPA/TPER (PI-1) exhibited a glass transition temperature (T_g) at 190 °C and double melting temperatures (T_ms) at 331 °C and 350 °C, and the polyimide derived from HQDPA/TPEQ (PI-2) displayed a T_g at 214 °C and a T_m at 388 °C. PI-1 and PI-2 showed significant recrystallization ability from melt and high crystallization rate by isothermal crystallization kinetics study, while polyimides based on 4,4′-ODA and BAPB lost crystallizability once taken to the melt. These polyimides also exhibited excellent thermo-oxidative stability with 5% weight loss temperature higher than 500 °C and good mechanical properties with tensile moduli of 2.0–3.3 GPa, tensile strengths of 85–105 MPa and elongations at break of 5–18%. PI-1 also possessed outstanding melt flowability with less than 300 Pa·s around 370 °C by rheological measurements. Full article

Phase-separated polymer blend composite films exhibiting high thermal diffusivity were prepared by blending a soluble polyimide (BPADA-MPD) and a bismaleimide (BMI) with needle-shaped zinc oxide (n-ZnO) particles followed by high-temperature curing at 250 °C. Images recorded with a field-emission scanning electron microscope (FE-SEM) equipped with wavelength-dispersive spectroscopy (WDS) demonstrated that the spontaneously separated phases in the composite films were aligned along the out-of-plane direction, and the n-ZnO particles were selectively incorporated into the BMI phase. The out-of-plane thermal diffusivity of the composite films was significantly higher than those of the previously reported composite films at lower filler contents. Based on wide-angle X-ray diffraction (WAXD) patterns and image analysis, the enhanced thermal diffusivity was attributed to the confinement of the anisotropically shaped particles and their nearly isotropic orientation in one phase of the composite films. Full article

This paper reviews the development of new high-temperature polymeric materials applicable to plastic substrates in image display devices with a focus on our previous results. Novel solution-processable colorless polyimides (PIs) with ultra-low linear coefficients of thermal expansion (CTE) are proposed in this paper. First, the principles of the coloration of PI films are briefly discussed, including the influence of the processing conditions on the film coloration, as well as the chemical and physical factors dominating the low CTE characteristics of the resultant PI films to clarify the challenges in simultaneously achieving excellent optical transparency, a very high T_g, a very low CTE, and excellent film toughness. A possible approach of achieving these target properties is to use semi-cycloaliphatic PI systems consisting of linear chain structures. However, semi-cycloaliphatic PIs obtained using cycloaliphatic diamines suffer various problems during precursor polymerization, cyclodehydration (imidization), and film preparation. In particular, when using trans-1,4-cyclohexanediamine (t-CHDA) as the cycloaliphatic diamine, a serious problem emerges: salt formation in the initial stages of the precursor polymerization, which terminates the polymerization in some cases or significantly extends the reaction period. The system derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) and t-CHDA can be polymerized by a controlled heating method and leads to a PI film with relatively good properties, i.e., excellent light transmittance at 400 nm (T₄₀₀ = ~80%), a high T_g (>300 °C), and a very low CTE (10 ppm·K⁻¹). However, this PI film is somewhat brittle (the maximum elongation at break, ε_{b max} is about 10%). On the other hand, the combination of cycloaliphatic tetracarboxylic dianhydrides and aromatic diamines does not result in salt formation. The steric structures of cycloaliphatic tetracarboxylic dianhydrides significantly influence the polymerizability with aromatic diamines and the CTE values of the resultant PI films. For three isomers of hydrogenated pyromellitic dianhydride, the steric structure effect on the polymerizability and the properties of the PI films is discussed. 1,2,3,4-Cyclobutanetetracarboxylic dianhydride (CBDA) is a very unusual cycloaliphatic tetracarboxylic dianhydride that is suitable for reducing the CTE. For example, the PI system derived from CBDA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) yields a colorless PI film with a relatively low CTE (21 ppm·K⁻¹). However, this PI is insoluble in common organic solvents, which means that it is neither solution-processable nor compatible with the chemical imidization process; furthermore, the film is somewhat brittle (ε_b < 10%). In addition, the effect of the film preparation route on the film properties is shown to be significant. Films prepared via chemical imidization always have higher optical transparency and lower CTE values than those prepared via the conventional two-step process (i.e., precursor casting and successive thermal imidization). These results suggest that compatibility with the chemical imidization process is the key for achieving our goal. To dramatically improve the solubility in the CBDA-based PI systems, a novel amide-containing aromatic diamine (AB-TFMB), which possesses the structural features of TFMB and 4,4′-diaminobenzanilide (DABA), is proposed. The CBDA(70);6FDA(30)/AB-TFMB copolymer has an ultra-low CTE (7.3 ppm·K⁻¹), excellent optical transparency (T₄₀₀ = 80.6%, yellowness index (YI) = 2.5, and haze = 1.5%), a very high T_g (329 °C), sufficient ductility (ε_{b max} > 30%), and good solution-processability. Therefore, this copolymer is a promising candidate for use as a novel coating-type plastic substrate material. This paper also discusses how the target properties can be achieved without the help of cycloaliphatic monomers. Thus, elaborate molecular design allows the preparation of highly transparent and low-CTE aromatic poly(amide imide) and poly(ester imide) systems. Full article

Nanostructured polymers (NSPs) are polymeric materials in the size of nanoscale, normally consisting of nanoparticles, nanofibers, nanowires, nanospheres and other morphologies. Polymer nanoparticles (PNPs) can be fabricated either by physical methods (i.e., solvent evaporation, nanoprecipitation, salting out) or by direct nanosynthesis, using micro- or nanoemulsions with nanoreactor compartments to perform polymerization. Polymer nanofibers (PNFs) can be produced via various techniques and the most commonly used approach is electrospinning, whereby a charged solution of a polymer when exposed to an opposite high electric field is pulled into long thin nanofibers. NSPs in general exhibit enhanced properties such as excellent structural and mechanical properties, making them promising candidates for some particular building applications. A variety of PNFs have been developed and used for noise and air pollution filtration. Moreover, PNFs can also be fabricated with phase change materials which are usually employed for thermal energy storage in construction industry. In this review, we will summarize the morphologies and nanosynthesis methods of NSPs, in particular, PNPs and PNFs. In addition, representative NSPs mainly used in construction are introduced for building applications. Full article

We describe herein the state of the art following the last 8 years of research into aromatic polyamides, wholly aromatic polyamides or aramids. These polymers belong to the family of high performance materials because of their exceptional thermal and mechanical behavior. Commercially, they have been transformed into fibers mainly for production of advanced composites, paper, and cut and fire protective garments. Huge research efforts have been carried out to take advantage of the mentioned characteristics in advanced fields related to transport applications, optically active materials, electroactive materials, smart materials, or materials with even better mechanical and thermal behavior. Full article