Electrochemically and electrochromically stable polyimides bearing tert-butyl-blocked N,N,N′,N′-tetraphenyl-1,4-phenylenediamine units

A new class of electrochemically active polyimides with di-tert-butyl-substituted N,N,N′,N′-tetraphenyl-1,4-phenylenediamine units was prepared from N,N-bis(4-aminophenyl)-N′,N′-bis(4-tert-butylphenyl)-1,4-phenylenediamine and various aromatic tetracarboxylic dianhydrides via a conventional two-step procedure that included a ring-opening polyaddition to give poly(amic acid)s, followed by chemical or thermal cyclodehydration. Most of the polyimides are readily soluble in many organic solvents and can be solution-cast into tough and amorphous films. They had useful levels of thermal stability, with relatively high glass-transition temperatures (276-334 °C), 10% weight-loss temperatures in excess of 500 °C, and char yields at 800 °C in nitrogen higher than 60%. Cyclic voltammograms of the polyimide films cast on the indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at 0.70-0.74 V and 1.05-1.08 V vs. Ag/AgCl in acetonitrile solution. The polyimide films revealed excellent stability of electrochromic characteristics, with a color change from colorless or pale yellowish neutral form to green and blue oxidized forms at applied potentials ranging from 0.0 to 1.3 V. These anodically coloring polymeric materials exhibited high optical contrast of percentage transmittance change (Δ%T) up to 44% at 413 nm and 43% at 890 nm for the green coloration, and 98% at 681 nm for the blue coloration. After over 50 cyclic switches, the polymer films still exhibited good redox and electrochromic stability.     

Green electroluminescent polyfluorenes containing 1,8-naphthalimide moieties as color tuner

A series of copolymers (CNPFs) containing low-band-gap 1,8-naphthalimide moieties as color tuner was prepared by a Yamamoto coupling reaction of 2,7-dibromo-9,9-dioctylfluorene (DBF) and different amount of 4-(3,6-dibromocarbazol-9-yl)-N-(4′-tert-butyl-phenyl)-1,8-naphthalimide (Br-CN) (0.05-1 mol% feed ratio). The light emitting properties of the resulting copolymers showed a heavy dependence on the feed ratio. In photoluminescence (PL) studies, an efficient color tuning through the Förster energy transfer mechanism was revealed from blue to green as the increase of Br-CN content, while in electroluminescence (EL) studies, the color tuning was found to go through a charge trapping mechanism. It was found that by introduction of a very small amount of Br-CN (0.1-0.5 mol%) into polyfluorene, the emission color can be tuned from blue to pure green with Commission International de l'Echairage (CIE) coordinates being (0.21, 0.42) and (0.21, 0.48). A green emitting EL single-layer device based on CNPF containing 0.1 mol% of Br-CN showed good performances with a low turn-on voltage of 4.2 V, a brightness of 9104 cd/m², the maximum luminous efficiency of 2.74 cd/A and the maximum power efficiency of 1.51 lm/W. To further improve the EL performances through balancing the charge trapping process, a copolymer (BCNPF05) derived from 0.5 mol% of a triarylamine-containing 4-{3,6-bis-[4″-(4?-bromophenyl-p-tolyl-amino)-phenyl]-carbazol-9-yl}-N-(4′-tert-butyl-phenyl)-1,8-naphthalimide (Br-BCN) and 99.5 mol% of 2,7-dibromo-9,9-dioctylfluorene was also prepared. As expected, a single layer EL device based on BCNPF05 exhibited better performances with a brightness of 14228 cd/m², the maximum luminous efficiency of 4.53 cd/A and the maximum power efficiency of 1.57 lm/W.     

In situ monitoring of sorption and drying of polymer films and coatings: self-referencing, nearly temperature-independent fluorescence sensors

Sorption and drying processes were monitored in situ in polymer films by a fluorescence rotor probe, 4-tricyanovinyl-[N-(2-hydroxyethyl)-N-ethyl]aniline (TC1), a solvatochromatic fluorescence probe, 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS), and pyrene. Taking advantage of an intensity ratio to monitor sorption, these fluorescence probes were found to serve as self-referencing sensors of water sorption in polyvinylacetate, with DANS being the most sensitive followed by TC1 and pyrene. Additionally, the shapes of the emission spectra (and thus intensity ratios) for TC1 and DANS were independent of temperature over a range of reasonable expected use temperatures. Covalent attachment of these fluorescence dyes was shown to enable the determination of sorbate levels within particular layers of multilayer films or coatings. Finally, these probes were also shown to provide sensitivity to desorption or drying of both water and organic sorbates.     

Synthesis, characterization and liquid-crystal-aligning properties of novel aromatic polypyromellitimides bearing (n-alkyloxy)biphenyloxy side chains

Novel aromatic polypyromellitimides bearing (n-alkyloxy)biphenyloxy side chains were prepared by two-step polycondensation of 1,4-phenylenediamine (PDA) and biphenyl-4,4′-diamine (BZ) with 3,6-bis[4′-(n-alkyloxy)biphenyl-4-oxy]pyromellitic dianhydrides (C_mB-PMDAs, m = 6, 8, 10, 12), which had been synthesized by the nucleophilic substitution of N,N′-diphenyl-3,6-dibromopyromellitimides with sodium 4-(n-alkyloxy)biphenoxides. Inherent viscosities of the poly(amic acid)s were in the 0.26-0.62 dL/g range. Poly{1,4-phenylene-3,6-bis[4′-(n-alkyloxy)biphenyl-4-oxy]pyromellitimide}s (C_mB-PPIs) and poly{4,4′-biphenyl-3,6-bis[4′-(n-alkyloxy)biphenyl-4-oxy]pyromellitimide}s (C_mB-BPIs) obtained in films by thermal imidization of the corresponding poly(amic acid)s were characterized by FT-IR spectroscopy and elemental analysis, and their crystalline structure and thermal properties were measured and discussed with respect to the side chain length. After the polyimide films were surface-treated by rubbing with velvet fibers, standard liquid crystal (LC) cells containing 4-cyano-4′-n-pentylbiphenyl (5CB) were fabricated and their LC-aligning properties were investigated in terms of pretilt angle. The pretilt angles were remarkably affected by side chain length and on surface of the polyimides with m = 6 and 8 LCs aligned parallel to the rubbing direction while on surface of the polyimides with m = 10 and 12 they aligned nearly or completely vertical to the rubbing direction.     

Gas foaming of segmented poly(ester amide) films

Biodegradable segmented poly(ester amide)s, based on dimethyl adipate, 1,4-butanediol and N,N′-1,2-ethanediyl-bis[6-hydroxy-hexanamide], with two distinct melting transitions were gas foamed using carbon dioxide (CO₂). Polymer films were saturated with CO₂ at 50 bar for 6 h after which the pressure was released. The samples were immersed in octane at the desired temperature after which foaming started immediately. Just above the lower melt transition the polymers retain adequate mechanical properties and dimensional stability, while the chain mobility increased sufficiently to nucleate and expand gas cells during the foaming process. In this way semi-crystalline poly(ester amide)s can be gas foamed below the flow temperature.Two poly(ester amide)s with 25 mol% (PEA2,5-25) and 50 mol% (PEA2,5-50) of bisamide segment content were foamed at 70 and 105 °C, respectively. The storage modulus (G′) of both pure polymers at the onset foaming temperature is 50-60 MPa. Closed-cell foams were obtained with a maximum porosity of ∼90%. The average pore size of PEA2,5-25 ranges from 77 to 99 μm. In contrast, the average pore size of PEA2,5-50 is in between 2 and 4 μm and can be increased to 100 μm by lowering the CO₂ saturation pressure to 20 bar. The porosity of PEA2,5-50 foams using this saturation pressure decreased to 70%.     

Reversible thickness control of polymer thin films containing photoreactive coumarin derivative units

The reversible control of the thickness of polymer thin films was investigated using (meth)acrylic polymers containing photoreactive coumarin derivative units in the side chain. Coumarin derivative units underwent dimerization and the reverse-dimerization by photoirradiation and were used as a reversible cross-linking point. The homopolymer of 7-methacryloyloxy-4-methylcoumarin (T_g = 194 °C) did not cause changes in film thickness after photoreactions. The homopolymer of 7-(2′-acryloyloxyethoxy)-4-methylcoumarin (AEMC) (T_g = 89 °C) decreased 19% of film thickness by photodimerization and 73% of the decreased thickness was recovered after the reverse-dimerization and the subsequent thermal annealing at 130 °C. The reverse-dimerization of the copolymer of AEMC and n-butyl acrylate (AEMC content = 19 mol%, T_g = 11 °C) resulted in 53% of recovery from the decreased film thickness without annealing. The mobility of polymer main-chain was revealed to be essential factor to change film thickness by photoreactions. Photodimerization of coumarin derivative units in low glass transition temperature (T_g) tended to proceed faster than in high T_g polymers and resulted in larger decrease in film thickness.     

Synthesis and blue luminescence of a soluble newly designed carbazole main-chain polymer

A new electroactive polymer with alternating conjugated-nonconjugated repeating units in the main chain was synthesized by step growth polymerization of α,ω-bis(N-carbazolyl)octane in chloroform solution with excess of iron trichloride, and in the presence of N-ethylcarbazole as a terminating agent. The resulting α,ω-N-ethylcarbazole terminated poly(3,3′-bicarbazyl-N,N′-octylene)s are readily soluble in common organic solvents and have good film-forming capabilities, partly because of the special design of the polymer backbone constituted by stiff bicarbazyl chromophores linked by flexible eight-carbon segments. Soluble materials with molecular weights up to 105 g/mol and polydispersity indices around 3.3 were obtained. Purified samples exhibiting quite low polydispersity indices (in the range 1.5-1.7) can be prepared by a selective fractionation of the crude polymer from benzene/methanol mixtures. Structural analysis of these new ‘stairs-like’ polymers disclosed their well-defined character with an aromatic linkage exclusively at position 3 on the carbazole moieties. Electrochemical studies of polymer films exhibited two reversible redox processes between 0 and 1.5 V vs saturated calomel electrode. The photoluminescence (PL) of the polymer in solution and as cast films revealed an intense blue emission and the same intensity level than that of the N,N′-diethyl-3,3′-bicarbazyl molecule, taken as a model of the aromatic segment of the repeating unit. Such a processable and purifiable polymer with bicarbazyl-isolated fluorophores is quite promising for the fabrication of efficient blue light-emitting devices.     

Synthesis and properties of fluorinated polyimides. 3. Derived from novel 1,3-bis[3′-trifluoromethyl-4′(4″-amino benzoxy) benzyl] benzene and 4,4-bis[3′-trifluoromethyl-4′(4-amino benzoxy) benzyl] biphenyl

Novel diamine monomers, 1,3-bis[3′-trifluoromethyl-4′(4″-amino benzoxy) benzyl] benzene (IV) and 4,4-bis[3′-trifluoromethyl-4′(4-amino benzoxy) benzyl] biphenyl (V) have been synthesized. These monomers lead to several novel fluorinated polyimides on reaction with different commercially available dianhydrides like pyromellatic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA) or 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane (6FDA). The polyimides prepared from above two monomers on reaction with 6FDA are soluble in several organic solvents such as N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMAc) and tetrahydrofuran (THF). The polyimides prepared from PMDA/IV is soluble in DMF and N-methyl pyrollidone (NMP) on heating, whereas V/PMDA is insoluble in all solvents. BTDA/IV polyimide is also soluble in NMP, DMF and DMAc. These polyimide films have low water absorption rate 0.2-0.7% and low dielectric constant 2.74-3.2 at 1 MHz. These polyimides showed very high thermal stability even up to 531 °C for 5% weight loss in synthetic air and glass transition temperature up to 316 °C (by DSC) in nitrogen. All polyimides formed tough transparent films, with tensile strength up to 148 MPa, a modulus of elasticity up to 2.6 GPa and elongation at break up to 31% depending upon the exact repeating unit structure.     

Novel electrochromic aromatic poly(amine-amide-imide)s with pendent triphenylamine structures

Three new aromatic poly(amine-amide-imide)s (PAAIs) having pendent triphenylamine units were prepared from the phosphorylation polyamidation reactions of a newly synthesized diamine, N,N-bis(4-aminophenyl)-N′,N′-diphenyl-1,4-phenylenediamine, with three imide ring-preformed dicarboxylic acids. These PAAIs had inherent viscosities of 0.54-0.86 dL/g, and they were amorphous and readily soluble in many organic solvents and could be solution cast into transparent, tough, and flexible films with good mechanical properties. They displayed relatively high glass-transition temperatures (279-287 °C) and good thermal stability, with 10% weight-loss temperatures in excess of 522 °C in nitrogen and char yields at 800 °C in nitrogen higher than 67%. The solutions of polymers in NMP exhibited strong UV-vis absorption bands with a maximum around 315 nm. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the PAAIs prepared by casting polymer solution onto an indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at 0.67 and 1.08 V vs. Ag/AgCl in acetonitrile solution. All the PAAIs revealed very stable electrochromic characteristics, changing color from original pale brownish to green, and then to blue at 0.67 and 1.08 V, respectively.     

Synthesis and properties of novel soluble polyimides having a spirobisindane-linked dianhydride unit

A new synthetic procedure was elaborated allowing the preparation of semiaromatic dianhydride. N-Methyl protected 4-chlorophthalic anhydride was nitrated with HNO₃ to produce N-methyl-4-chloro-5-nitrophthalimide (1). The aromatic nucleophilic substitution reaction between 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1-spirobisindane and 1 afforded spirobisindane-linked bis(N-methylphthalimide) (2), which was hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). The latter was polymerized with five different aromatic diamines to afford a series of aromatic polyimides. The properties of polyimides such as inherent viscosity, solubility, UV transparency and thermal stability were investigated to illustrate the contribution of the introduction of spirobisindane groups into the polyimide backbone. The resulting polyimides were readily soluble in polar solvents such as chloroform, THF and N-methyl-2-pyrrolidone. The glass-transition temperatures of these polyimides were in the range of 254-292 °C. The tensile strength, elongation at break, and Young's modulus of the polyimide film were 68.8-106.6 MPa, 5.9-9.8%, 1.7-2.0 GPa, respectively. The polymer films were colorless and transparent with the absorption cutoff wavelength at 286-308 nm.     

Copoly(1,3,4-oxadiazole-ether)s containing phthalide groups and thin films made therefrom

A series of aromatic copolyethers containing 1,3,4-oxadiazole rings and phthalide groups was prepared by nucleophilic substitution polymerization technique of phenolphthalein, 1, or of an equimolecular amount of 1 and different bisphenols 2, such as: 4,4′-isopropylidenediphenol, 4,4′-(hexafluoroisopropylidene)diphenol, 4,4′-(1,4-phenylene-diisopropylidene)bisphenol, 4,4′-cyclohexylidene-bisphenol and 2,7-dihydroxynaphthalene, with 2,5-bis(p-fluorophenyl)-1,3,4-oxadiazole, 3. The polymers were easily soluble in polar solvents such as N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and chloroform and can be cast from solutions into thin flexible films. They showed high thermal stability, with decomposition temperature being above 400 °C. The polymers exhibited a glass transition temperature in the range of 220-271 °C, with reasonable interval between glass transition and decomposition temperature. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz and 20 °C were in the range of 2.98-3.15.     

Anomalous molecular orientation of isotactic polypropylene sheet containing N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide

Small amount of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide as a β-form nucleating agent is dissolved beyond 280 °C in a molten isotactic polypropylene (iPP) and appears as needle crystals around at 240 °C during cooling procedure. Further, iPP molecules crystallize on the surface of the needle crystals, in which c-axis of the β-form iPP crystals grows perpendicular to the long axis of the needle crystals. Under flow field at extrusion processing, the needle crystals orient to the flow direction prior to the crystallization of iPP. As a result, c-axis of the β-form iPP crystals orients perpendicular to the applied flow direction with a small amount of α-form iPP. Moreover, the vertical molecular orientation of the extruded sheet sample is responsible for unique mechanical anisotropy; the fracture occurs along the transversal direction.     

Synthesis and properties of organosoluble polyimides based on 2,2′-diphenoxy-4,4′,5,5′-biphenyltetracarboxylic dianhydride

A novel method for the preparation of 2,2′-diphenoxy-4,4′,5,5′-biphenyltetracarboxylic dianhydride have been investigated. This new dianhydride contains flexible phenoxy side chain and a twist biphenyl moiety and it was synthesized by the nitration of an N-methyl protected 3,3′,4,4′-biphenyltetracarboxylic dianhydride and subsequent aromatic nucleophilic substitution with phenoxide. The overall yield was up to 75%. The dianhydride was polymerized with five different aromatic diamines to afford a series of aromatic polyimides. The polyimide properties such as inherent viscosity, solubility, UV transparency and thermaloxidative properties were investigated to illustrate the contribution of the introduction of phenoxy group at 2- and 2′-position of BPDA dianhydride. The resulting polyimides possessed excellent solubility in the fact that the polyimide containing rigid diamines such as 1,4-phenylenediamine and 4,4′-oxydianiline were soluble in various solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide and chloroform. The glass-transition temperatures of the polymers were in the range of 255-283 °C. These polymers exhibited good thermal stability with the temperatures at 5% weight loss range from 470 to 528 °C in nitrogen and 451 to 521 °C in air, respectively. The polyimide films were found to be transparent, flexible, and tough. The films had a tensile strength, elongation at break, and Young's modulus in the ranges 105-168 MPa, 15-51%, 1.87-2.38 GPa, respectively.     

Synthesis, characterization and fluorescence adjustment of well-defined polymethacrylates with pendant π-conjugated benzothiazole via atom transfer radical polymerization (ATRP)

Two compounds containing the benzothiazole moiety, 4-(2-benzothiazole-2-yl-vinyl)-phenyl methacrylate (BVMA) and 2-bromo-2-methyl-propionic acid 4-(2-benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) were synthesized. Atom transfer radical polymerization (ATRP) of BVMA was conducted at 60 °C using BPBVE and CuBr/2,2′-bipyridine (BPY) as initiator and catalyst, respectively. Chain extension with 4-methacryloxy-hexyloxy-4′-nitrostilbene (MHNS) was conducted using PBVMA as the macroinitiator. The homopolymer PBVMA in DMF solution emitted blue fluorescence, and the copolymer PBVMA-b-PMHNS emitted orange fluorescence at about 610 nm due to the intramolecular energy transfer. ATRP of BVMA was also conducted using 2-bromo-2-methyl-propionic acid 4-nitrostilbene-hexyloxy ester (BPNHE) as an initiator. The obtained polymer was characterized via ¹H NMR and the fluorescence intensity was found to change with increasing number average molecular weight (M_n). The polymer with M_n = 15900 emitted white fluorescence in DMF solution.     

High optical transparency, low dielectric constant and light color of novel organosoluble polyamides with bulky alicyclic pendent group

Novel optically transparent, low dielectric and highly organosoluble alicyclic polyamides derived from bulky alicyclic diamine containing trifluoromethyl group on either side, 1,1-bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl]-4-tert-butylcyclohexane (BTFAPBC), were prepared. The polyamides were obtained in almost quantitative yields and showed inherent viscosity values between 0.55 and 0.72 dL g⁻¹ in DMAc solution. Most of the polyamides showed excellent solubility in polar solvents such as N-methyl-2-pyrrolidinone (NMP), N,N′-dimethyl acetamide (DMAc), N,N′-dimethyl formamide (DMF), pyridine, cyclohexanone, γ-butyrolactone and chloroform. The cut-off wavelength for polyamides ranged from 350 to 388 nm. Polyamides with alicyclic tert-butylcyclohexyl cardo and trifluoromethyl substituents exhibited low dielectric constants ranging from 3.29 to 3.98 (at 100 Hz) compared with commercially available polyamides [Amodel^®, 4.2-5.7 at 100 Hz]. Polyamides showed glass transition temperatures in the range of 244-266 °C and possessed a coefficient of thermal expansion (CTE) of 60-75 ppm °C⁻¹. Thermogravimetric analysis data showed that the polyamides were stable up to 430 °C and the 10% weight loss temperature was found to be in the range of 437-466 °C in nitrogen atmosphere. The polyamide films had a tensile strength in the range of 66-103 MPa, elongation at break in the range of 5-8%, and tensile modulus in the range of 1.5-2.2 GPa. Due to their properties, the polyamides could be considered as engineering plastic and photoelectric materials.     

Synthesis and properties of novel poly(aryl ether ketone)s containing both diphenyl moiety and amide linkages in the main chains

New monomers, 4,4′-bis(4-phenoxybenzoyl)diphenyl (BPOBDP) and N,N′-bis(4-phenoxybenzoyl)-p-phenylenediamine (BPBPPD), were conveniently synthesized via simple synthetic procedures from readily available materials. A series of novel poly(aryl ether ketone)s containing both diphenyl moiety and amide linkages in the main chains were prepared by electrophilic Friedel-Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of BPOBDP and BPBPPD, over a wide range of BPOBDP/BPBPPD molar ratios, in the presence of anhydrous AlCl₃ and N-methylpyrrolidone (NMP) in 1,2-dichloroethane (DCE). All the polymers are semicrystalline and had remarkably increased T_gs over commercially available PEEK and PEKK due to the incorporation of the diphenyl moiety and amide linkages in the main chains. The polymers with 40-60 mol% BPBPPD had not only high T_gs of 183-189 °C, but also moderate T_ms of 314-328 °C, which are very suitable for the melt processing. These polymers had tensile strengths of 107.4-111.5 MPa, Young's moduli of 2.20-2.45 GPa, and elongations at break of 11.3-13.5% and exhibited high thermal stability and good resistance to organic solvents.     

Thickness-dependent crystal orientation in poly(trimethylene 2,6-naphthalate) films studied with GIWAXD and RA-FTIR methods

The thickness dependence of the crystal orientation of poly(trimethylene 2,6-naphthalate) (PTN) films was clearly demonstrated using the methods of two-dimensional grazing incidence wide angle X-ray diffraction (2D GIWAXD) and grazing incidence reflection absorption FTIR (RA-FTIR) spectroscopy. The 2D GIWAXD results showed that for films thicker than 200 nm, the “c” axis (main chain direction) and “b” axis of crystal unit cell are almost parallel to the sample surface, whereas for thin films the “c” axis is preferentially perpendicular to the film plane in the crystalline phase of isothermally crystallized PTN films. The anisotropic orientation of the naphthalene rings in the isothermally crystallized PTN film was also confirmed. By analyzing the relative absorbance of the parallel band (1602 cm⁻¹) to the one of perpendicular band (917 cm⁻¹), the thickness dependence of the crystal orientation suggested by the GIWAXD results was also confirmed. Furthermore, the naphthalene rings in the isothermally crystallized thick films were found to lie flat on the film plane. The chain orientations derived from the GIWAXD and RA-FTIR results in this work were found to be consistent with the “flat-on” and “edge-on” lamellar orientation for the thin and thick films, respectively, which has previously been reported in many polymer systems.     

Color lightness and highly organosoluble fluorinated polyamides, polyimides and poly(amide-imide)s based on noncoplanar 2,2′-dimethyl-4,4′-biphenylene units

A new diamine monomer containing noncoplanar methyl substitution, 2,2′-dimethyl-4,4′-bis(2-trifluoromethyl-4-aminophenoxy)biphenyl (DBTFAPB) was successfully synthesized and used in the preparation of a series of polyamides and polyimides by direct polycondensation with various aromatic dicarboxylic acids and tertacarboxylic dianhydrides. A new noncoplanar dicarboxylic acid monomer containing noncoplanar methyl substitution, 2,2′-dimethyl-4,4′-bis(2-trifluoromethyl-4-trimellitimidophenoxy)biphenyl (DBTFTPB) was also successfully synthesized by refluxing the diamine, DBTFAPB, with trimellitic anhydride in glacial acetic acid. A series of new poly(amide-imide)s were prepared directly from DBTFTPB with various diamines in N-methyl-2-pyrrolidinone (NMP). All the polymers exhibited excellent solubility in solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, tetrahydrofuran (THF), cyclohexanone and γ-butyrolactone at room temperature or upon heating at 70 °C. Inherent viscosities of the polymers were found to range between 0.60 and 1.34 dL g⁻¹. Gel permeation chromatography (GPC) of the polymers showed number-average and weight-average molecular weight up to 7.3×10⁴ and 17.9×10⁴, respectively. These polymers showed that the glass transition temperatures were between 230 and 265 °C, and the 10% mass loss temperatures were higher than 460 °C in nitrogen atmosphere. All the polymers could be cast into flexible and tough films from DMAc solutions. They had a tensile strength in the range of 82-124 MPa and a tensile modulus in the range of 1.9-2.9 GPa. These polymers exhibited low dielectric constants ranging from 2.87 to 4.03, low moisture absorption in the range of 0.29-3.20%, and high transparency with an ultraviolet-visible absorption cut-off wavelength in the 347-414 nm range.     

Purple red and luminescent polyiminoarylenes containing the 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) chromophore

New DPP-containing polyiminoarylenes were prepared from 1,4-diketo-2,5-dihexyl-3,6-di(4′-bromophenyl)pyrrolo[3,4-c]pyrrole and various arylamine derivatives using palladium-catalyzed amination reactions. The arylamine comonomers were aniline (ANI), t-butylaniline (TBA), 2-aminoanthracene (AAN), 1-aminopyrene (APY) and N,N′-diphenyl-p-phenylenediamine (PDA). Purple red polymers with good solubility in common organic solvents and molecular weights between 4.4 and 35.8 kDa were obtained. Polymer solutions were readily fluorescent with quantum yields between 19 and 62%, while solution-cast films only showed a weak fluorescence. All polymers exhibit low band gaps of approximately 1.9 eV. Cyclovoltammetric studies indicate quasireversible oxidation for polymers with TBA, APY and PDA as comonomer units, and quasireversible reduction for the polymer with AAN comonomer unit. Polymers with APY and PDA comonomer units are electrochromic and can be switched between red in the neutral and greenish grey in the oxidized state.     

Template copolymerisation of N-isopropylacrylamide with a cationic monomer: influence of the template on the solution properties of the product

A copolymer containing 91 mol% N-isopropylacrylamide (NIPAM) units and 9 mol% N,N-(dimethylaminopropyl)methacrylamide (MADAP) units, copolymer II, was prepared using polyacrylate chains as a template for the positively charged MADAP units. The properties of this product were compared to the properties of a similar copolymer (copolymer I) prepared in the absence of the template. The molar mass of copolymer II was found much higher than that of copolymer I. Moreover, the cloud point of copolymer II is closer to the cloud point of the homopolymer poly(N-isopropylacrylamide) at various pH conditions, indicating that copolymer II contains longer NIPAM-sequences than copolymer I. This explanation is further supported by the fact that copolymer II forms stronger, more compact and more hydrophobic hydrogen-bonding interpolymer complexes with polyacrylic acid at low pH, as it was revealed by viscometry, fluorescence and turbidity studies.