Four triphenylpyridine diamines with different substituent structure were successfully synthesized and polymerized to obtained polyimides (PIs) via one-step. The diamines and PIs were characterized by FTIR and 1H-NMR spectra. The aggregated structure of PIs was amorphous by wide angle X-ray diffraction test. The structure of the substituent had an important influence on the properties of PI (such as solubility, thermal stability, optical and mechanical properties). The introduction of tert-butyl group could reduce the solubility in non-polar solvent of PI. In addition, the introduction of hydroxyl group alone could increase the solubility in polar solvent of polymer due to the large polarity of the hydroxyl groups. All PIs exhibited high thermal stability and heat resistance, but the introduction of too much tert-butyl group reduced the thermal stability of PI. The introduction of tert-butyl group could effectively improve the optical properties of PIs. The maximum transmittance of PIs was above 85% (87.2–90.3%).

A new diamine containing hydroxyl and bis-tert-butyl substituted triphenylpyridine units was synthesized and used in the synthesis of polyimides (PIs) via a one-step polymerization. The diamine and PIs were characterized by FTIR and 1H-NMR. The aggregated structure of PIs was amorphous by wide angle X-ray diffraction test and all of them exhibited excellent solubility in most organic solvents. The bis-tert-butyl and triphenylpyridine units endowed PIs excellent thermal stability with 10% weight loss temperatures in the range 493–525 °C and high glass transition temperature in the range 301–344 °C, while the existence of hydroxyl groups provided the possibility for further modification of polymer. The PI membranes had excellent mechanical properties with tensile strength in the range 65–93 MPa. The density of PIs was lower with density in the range 1.266–1.289 g/cm3. It was foreseeable that PIs will greatly promote the applications of heat-resistant and lightweight PI materials in the future.

A new triphenylpyridine-containing aromatic diamine monomer named 4-phenyl-2,6-bis(4-aminophenyl) pyridine was successfully synthesized. A series of polyimides (PIs) with triphenylpyridine moieties were prepared from the newly synthesized diamine monomer via a one-step polymerization with oxydiphthalicanhydride. All the PIs were amorphous and showed excellent solubility in many polar aprotic solvents at room temperature and most of them could afford flexible, transparent, and tough films with good mechanical properties. All the PIs had useful levels of thermal stability associated with high glass-transition temperatures (299–341 °C), 10 % weight-loss temperatures in excess of 537 °C, and char yields at 800 °C in nitrogen higher than 54.9 %.

A new diamine monomer 4-((4-dodecyloxy)phenyl)-2,6-di((4-amino)phenyl)pyridine (DPDAPP) was successfully synthesised and polymerised with 4,4ʹ-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and diamine 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) via the conventional two-step chemical imidisation method to produce a series of various alkyl-chain content polyimides (PIs). X-ray diffraction (XRD), nuclear magnetic resonance spectrometry (1H-NMR) and Fourier-transform infrared spectroscopy (FT-IR) were applied to study the structure of PIs. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to measure the thermal properties. Results show that the solubility of the PIs was significantly improved by the introduction of DPDAPP at low concentration (≤50%). However, with further increasing concentration of DPDAPP, the amount of alkyl-chain increased and then partial crystallisation appeared, resulting in decreased solubility. The glass transition temperature (Tg) and decomposition temperature (Td) of these PIs were above 215°C and 450°C, respectively, which can meet the demands as liquid crystal (LC) alignment layers. Furthermore, the surface of these PIs showed strong hydrophobicity and more stable vertical alignment abilities, and hence the pretilt angle of LC was nearly 90° even with a low content of alkyl-chain.

A novel functional diamine containing triphenylamine moiety and biphenyl as well as a long alkyl chain, 4-dodecyloxy-biphenyl-4′,4′′-diaminotriphenylamine (DBDTA), was synthesized and characterized.

A new triphenylamine-based functional diamine monomer named N, N-bis (4-aminophenyl)-4-(nonyloxy-biphenyl)-4′-aminophenyl ether (N9) was successfully synthesised from cesium fluoride-mediated N,N-diarylation of 4-(nonyloxy-biphenyl)-4′-aminophenyl ether with p-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. A series of polyimides (PIs) with triphenylamine (TPA) moieties were prepared from the newly synthesised diamine monomer, 3,3′-dimethyl-4,4′-methylene-dianiline and 4,4′-oxydiphthalic anhydride through a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. The PIs were completely amorphous and exhibited good solubility in organic solvents. PI films attained from a casting method showed high transmittance above 90% in the wave length range of 400–700 nm and could align liquid crystals vertically before and after rubbing treatment. The PIs derived from N9 exhibited much higher thermal stability compared with the corresponding PIs from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (D12). The results demonstrated that the introduction of TPA units into the polymer backbone could largely enhance the thermal stability of PIs while sustaining its solubility.

Polyimides (PI) with different side chains in structure were synthesized by copolycondensation of pyromelliticmdianhydride (PMDA) with 3,5-diamino-(4′-methane acid hexyl ester) phenyl-benzamide (C6-PDA), (4-butoxybiphenol)-3′, 5′-diaminobenzoate (C4-BBDA) and 3, 5-diamino-benzoic acid decyl ester (C10-DA) named PI-PDA, PI-C4, PI-DA, respectively. The lengths of side chains of PI-PDA and PI-DA are as similar as that of PI-C4. Through the pretilt angle tests it is demonstrated that neither the structure of side chains nor the rubbing process could make an obvious difference on vertical alignment property when the lengths of the side chains are similar, standing at around 1.6 nm. The measurement of surface energy of PI surfaces further proved this result. The result of the X-ray photo-electron spectroscope measurement indicated that the side chains of PIs stretched out from the polymer bulk phase and accumulated on the surface.

Novel functional diamine, 6-hexyloxy-naphthalen-3′,5′-diaminobenzoate (N6) containing a rigid naphthalene unit, was molecularly designed and successfully synthesized. PIs (polyimides) were obtained by copolymerization of N6, 3,3′-dimethyl-4,4′-methylenediamine (DMMDA) and 4,4′-oxydiphthalic anhydride (ODPA). The structures of the intermediates, diamines and PIs were confirmed by FT-IR and 1H NMR spectra. All PIs obtained could be dissolved in polar aprotic solvents and low-boiling-point solvents. PI (polyimide) films attained using a casting method showed favorably high transmittance above 95% in the wave length range of 400–700 nm and could align LCs vertically before and after rubbing treatment. PI–N6 derived from N6, DMMDA and ODPA exhibited a much higher temperature at a 5% weight loss (T5) compared with the corresponding PI–C6 from 4-hexyloxy-biphenyl-3′,5′-diaminobenzoate (C6). For PI–N6, the weight ratio of the side chains was smaller than that of PI–C6, but a much higher T5 was attained. The results demonstrated that the introduction of a naphthalene unit into the side chain could effectively improve the thermal stability of PI without sacrificing its solubility. Moreover, the outstanding thermal stability of the PIs was explained in a preliminary manner by the imidization reaction mechanism.

A new diamine with a tert-buty-substituted triphenylpyridine unit was synthesized and used in the preparation of polyimides via a one-step polymerization. The polyimides are completely amorphous and exhibit good solubility in organic solvents. As a result of the presence of bulky substituents and rigid triphenylpyridine units, the final polyimide products have high glass transition temperatures (up to 365 degrees C) and good thermal stability with 10% weight loss temperatures in the range 538-563 degrees C. Triphenylpyridine units and tert-butyl groups might play a key role in improving the solubility of the polyimides while maintaining high glass transition temperatures and good thermal stability. The polyimide films had good mechanical properties.

A functional diamine, 3, 5-diamino-N-(2-octyl-1, 3-dioxoisoindolin-5-yl) benzamide (D8) containing imide unit and an assistant diamine monomer 4,4'-dimethyldiphenylmethane (DMMDA) were molecularly designed and synthesized successfully. Polyimides (PIs) containing asymmetric units in the main chain and imide pendant groups were prepared with the copolymerization of DMMDA, D8 and commercial aromatic dianhydride 4, 4-oxydiphthalic (ODPA) by chemical imidization. Five PIs were obtained by controlling the mole ratio of diamines and dianhydride. The structures and properties of the resulting co-condensation type PIs were characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and ultraviolet analysis (UV-Vis) etc. The PIs obtained were favorably soluble in aprotic polar solvents, such as N-methylpyrrolidone (NMP) and N,N-dimethyl form amide (DMF), and even in common organic solvents such as tetrahydrofunan (THF) and trichloromethane (TCM). The molecular weights of the soluble copolyimides obtained were high and influenced by the mole ratio of the functional diamine monomers. The molecular weights of PIs decreased with the increment of D8. Creasable PI films could be attained by casting from PI solutions. The liquid crystals (LCs) alignment ability of PI films was investigated and the pretilt angles were measured by the crystal rotation method using a pretilt angle tester. It was observed that the pretilt angle increased with the increasing content of functional diamine D8. When the content of D8 was greater than 20%, the PIs obtained high pertilt angles above 89 degrees even after five-times rubbing and showed outstanding rubbing-resistant ability. Moreover, the transmittances of the PIs were more than 80%, and their glass transition temperatures were above 260 degrees C. This kind of PIs containing imide side chains could be promising materials in vertical-alignment-mode LC displays.

A series of polyimides (PIs) with various side-chain structures were prepared via copolymerization of pyromellitic dianhydride, 3,3-dimethyl-4,4-methylenediamine and three functional diamines: 4-(4-octyloxybenzoyloxy)biphenyl-3,5-diaminobenzoate (C8-BPDA), 4-octyloxybiphenyl-3,5-diaminobenzoate (C8-PDA) and 4-(4-butoxybenzoyloxy)biphenyl-3,5-diaminobenzoate (C4-BPDA). PIs derived from C8-BPDA and C4-BPDA exhibited excellent rubbing resistance in comparison with PI from C8-PDA and the pretilt angle could be controlled over 89 degrees after rubbing. Thermogravimetric analysis showed that the thermal degradation of PIs under nitrogen atmosphere occurred above 320 degrees C, and PI derived from C8-BPDA showed the best thermal stability. Wide-angle X-ray diffraction patterns indicated an amorphous morphology of the PIs, and the PIs also had outstanding solubility in polar aprotic solvents. The resultant PI films were light colored and maintained high transparency in the visible light region. By increasing the rigidity of side-chains, the rubbing resistance and the thermal stability of PIs could be promoted at the same time. (c) 2012 Society of Chemical Industry

Two functional diamines, octyl-4-(3,5-diaminobenzamido)benzoate (O8, containing phenyl rings) and 3,5-diamino-N-(2-octyl-1,3-dioxoisoindolin-5-yl)benzamide (D8, containing a phthalimide ring), were designed and successfully synthesized. Two kinds of PIs were obtained by copolymerizing 3,3′-dimethyl-4,4′-methylenediamine (DMMDA), 4,4′-oxydiphthalic anhydride (ODPA), and D8 or O8. All of the PIs possessed excellent solubility. The PI films exhibited high transmittance, and were able to align liquid crystals (LCs) vertically. In contrast to the PIs generated from O8 (PI-O8), PIs created from D8 (PI-D8) were able to align LCs vertically even after rubbing, and also exhibited better thermal stability. The temperature at which 5 % of the weight of PI-D8 was lost (T 5) was higher than that for PI-O8. The results showed that the introduction of imide groups to the side chain improved the thermal stability and rubbing resistance of PIs without sacrificing their solubility and transmittance.

A novel diamine with a side-chain containing naphthalimide ring and non-polar alkyl end group, N-octyl-4-(3,5-dinitrobenzoyl)-amido-1,8-naphthalimide (N8), was synthesised and its chemical structure was confirmed by FTIR (fourier transform infrared) spectroscopy and nuclear magnetic resonance spectroscopy (1H-NMR). Then, a new family of polyimides (PIs) containing naphthalimide unit in the side-chains has been successfully synthesised by reaction of 4,4′-oxydiphthalic anhydride (ODPA) and 3,3′-dimethyl-4,4′-methylenediamine (DMMDA) with the novel functional diamine N8. The obtained polymers showed excellent solubility in a broad range of solvents, including tetrahydrofuran. Thermal properties of polymers were good enough to permit the use of these PIs on liquid-crystal displays (LCDs) applications. Alignment films obtained by casting offered outstanding rubbing-resistant ability, meanwhile kept the pretilt angle high above 89°. The PI seems to be prospective materials for alignment layers in LCDs.

4-dodecyloxy-phenyl-4′,4″-diaminotriphenylamine(DPDTA) containing triphenylamine were successfully synthesized.Polyimides(PIs) containing triphenylamine units in the main chain were synthesized with the co-condensation of DMMDA,DPDTA and aromatic dianhydride 4,4′-oxydiphthalic anhydride(ODPA) by thermal imidization.The structures of the PIs were confirmed by FT-IR.The alignment behavior of PIs as liquid crystal alignment layers was also examined with polarized optical micrograph(POM).The properties of the PIs were characterized by TGA,UV-Vis and DSC etc.It was found that side chain density of PIs had important influence on properties of liquid crystal alignment film.Before rubbing,PI containing 25% DPDTA could induce uniform vertical alignment and a pretilt angle of 89.7°.The liquid crystal was not aligned on the surface of PI film which contained 10% DPDTA without the rubbing treatment.After the rubbing process,the pretilt angle of liquid crystal was 2.4,when PI film contained 25% DPDTA and the pretilt angle of liquid crystal was 1.8°,when PI contained 10% DPDTA.The transmittances of the PIs in 500～800 nm wavelengths are more than 80%,and their glass transition temperatures are above 230 ℃.

In this study, 4 hyperbranched polyimides(HBPI) s with intrinsic viscosities in the range0.15-0.95 dl g-1 and good film forming properties were prepared using 4 anhydrides and 1 tetramine monomer, and then were applied as LC alignment layers. The results showed the HBPIs had excellent performance for LC alignment, and the pretilt angles were all above 2°. UV-Vis spectra showed that HBPIs had excellent transmittance and the minimum transmittance in the 400nm was still more than 90%.The results of TGA showed that the HBPIs had good thermal stability, with T5being as high as 362℃ and T10390℃. The glass-transition temperatures(Tg) s of the HBPIs were all above 175℃.

A novel functional diamine(H8-c) with thick ring and long alkoxy was synthesized from 3,5-dinitrobenzoyl chloride,estradiol and 1-Bromooctane.A polyimide(PI),applied in liquid crystal(LC) vertical orientation agent,was prepared from p-phenylenediamine(PDA),1,2,3,4-cyclobutanetetracarboxylicdianhydride(CBDA) and H8-c.The PI possessed excellent vertical alignment for nematic LC.The vertical alignment of LC cell which was kept at 120 ℃ for 12 h was still stable.It could be seen that the thermal stability of the vertical alignment of LC was excellent.The temperature at 5% weight loss of the PI(T5) is as high as 400 ℃ in nitrogen.The temperature at 10% weight loss of the PI(T10) is as high as 480 ℃ in nitrogen.The PI film exhibited high transparency(95%) at wavelengths above 400 nm.

A series of functional diamines, with various side chain structures and length, were designed and synthesised. Four polyimides (PIs) were copolymerised from pyromelitic dianhydride, p-phenylenediamine and four functional diamines. The conformation of the side chains on the surface of PI film was investigated through X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared dichroic spectroscopy. The results showed that the side chains on the PI film surface aligned outwards in the polymer bulk phase before rubbing. It was found that the length and the contents of the side chains influenced the conformation of the side chains. The interaction between the liquid crystals (LCs) and the side chains on the PI film surface induced the LCs to align vertically.

Several hyperbranched polyimides (HBPIs) were applied in liquid crystal (LC) alignment layers and exhibited outstanding performance for LC alignment. The maximum pretilt angle was above 8°, and the minimum pretilt angle was 4.2°. The results of atomic force microscope measurement disclosed that a lot of grooves were aligned parallel to the rubbing direction and found that the grooves were not main factor for LC alignment. The LC alignment and pretilt angles are unambiguously associated with the intrinsic HBPI chemical structures. The results of thermal gravimetric analysis and ultraviolet–visible spectra showed that the HBPIs had good thermal stability and excellent transmittance. T5 and T10 were higher than 360°C and 400°C, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

Polyimides(PI) were synthesized from 3-carboxylmethylcyclopentane-1,2,4-tricarboxylic(TCA),4,4'-diaminodiphenyl methane(MDA) and long alkyloxy side-group-containing diamine 4-dodecyloxy-biphenyl-3',5'-dinitrobenzoate(DBPDA) by one-step method.Their properties such as solubility,optical transparency and alignment ability were studied.All PIs were organosoluble.They exhibited high transparency at wavelengths 400 nm～700 nm(>90%).The resultant PI films induced excellent uniform vertical alignment of liquid crystal.Even after the rubbing process,the PI films still exhibited good features as the alignment layers with pretilt angles of above 89°.

The first series of polyimides with different ratio of side chain were copolymerized from 4-octyloxy-biphenyl-3,5-diaminobenzoate(C8),3,3′-dimethyl-4,4′-methyl-enedianiline(DMMDA) and 4,4-oxydiphthalic(ODPA) via one-step method.The effect of the diamine content of these PIs on their solubility,alignment,pretilt angle and thermal stability was investigated.Similarly,the second series of polyimides with different main chain were copolymerized from C8,DMMDA and different dianhydrides which include ODPA,pyromellitic dianhydride(PMDA),3,3′,4,4′-dibenzophenonetetracarboxylic dianhydride(BTDA) via one-step method.The effect of dianhydride structure on the solubility and thermal stability was explored.