Anhydride End Groups Research Articles

Ultrastrong, Ductile, Tear- and Folding-Resistant Polyimide Film Doubly Reinforced by an Aminated Rigid-Rod Macromolecule and Graphene Oxide.

As a high-performance polymer with exceptional mechanical, thermal, and insulating properties, polyimide (PI) has been widely used as flexible circuit substrates for microelectronics, portable electronics, and wearable devices. Due to the growing demand for further thinning and lightweighting of electronic products, PI films need to have further enhanced mechanical properties. Traditional nanofiller-reinforced PI films often exhibit reduced ductility and limited improvements in strength. Therefore, it remains a challenge to simultaneously improve the strength and toughness of PI films while preserving their ductility. In this study, we report an exceptionally strong and ductile PI doubly reinforced by one-dimensional rigid-rod para-aramid, poly(p-aminophenylene aminoterephthalamide ((NH2)2-PPTA), and two-dimensional graphene oxide (GO) nanosheets. The amino side groups of (NH2)2-PPTA react with the anhydride end groups of PI, forming covalent bonds. At a (NH2)2-PPTA content of only 0.4 wt %, the (NH2)2-PPTA/PI film displays significantly enhanced mechanical properties. When 0.4 wt % of GO is added together with (NH2)2-PPTA, the tensile strength, tensile toughness, and strain at break reach 284.8 ± 5.3 MPa, 277.9 ± 7.6 MJ/m3, and 132.6 ± 3.8%, which are ∼178, ∼312, and ∼51% higher, respectively, than those of pure PI. Moreover, the doubly reinforced PI film also exhibits a 206% increase in tear strength and significantly enhanced folding resistance. The dual reinforcement of PI with (NH2)2-PPTA and GO improves the mechanical properties more efficiently than any single reinforcing agents previously reported and overcomes the disadvantage of most inorganic nanofillers that reduce ductility.

Highly transparent triethoxysilane-terminated copolyimide and its SiO2 composite with enhanced thermal stability and reduced thermal expansion

A highly transparent and colorless copolyimide was synthesized to contain electron withdrawing sulfone and fluorine groups. Then, the triethoxysilane terminal groups were introduced by reacting the anhydride end groups of the polymer with (3-aminopropyl)-triethoxysilane. Based on the triethoxysilane-terminated copolyimide, a series of composites of the copolyimide (PI6FDA-TFDB-mBAPS(Si)) with inorganic SiO2 network was successfully fabricated in order to satisfy the requirements for transparent insulators with high thermal stability. Because the hybrid with inorganic SiO2 networks, the composite (PI6FDA-TFDB-mBAPS(Si)_SiO2) can complementarily improve the thermal resistant drawbacks of organic systems. As a result, the composite films exhibit small values of the coefficient of thermal expansion (CTE) with the increasing SiO2 content. The coefficient of thermal expansion (CTE) of the hybrid PI6FDA-TFDB-mBAPS(Si)_SiO2-40% film is 14.4ppm°C−1 in the temperature range from 80 to 170°C. Compared to a value of 34.7ppm°C−1 for the pristine PI, a 57% reduction is achieved for the composite. The composite possesses the glass transition temperature (Tg) of 276.0°C and shows good optical transmittance of 94% at the wavelength of 450nm. The incorporation of cross-linked SiO2 networks by using the triethoxysilane-terminated PI preserves the high transparency and enhances the thermal stability for the composite films. Due to these optimized properties, the composite can show potential applications in the micro-flexible transparent electronic devices such as transparent insulating panel of advanced transparent display devices and transparent flexible circuit board.

Low dielectric and thermally stable hybrid ternary composites of hyperbranched and linear polyimides with SiO2

A hydroxyl-terminated hyperbranched polyimide was synthesized via the A2 + B3 reaction between dianhydride and triamine monomers. The hydroxyl groups at the peripheral positions were then introduced by modification of the anhydride end groups via a reaction with 4-aminophenol. Based on the hydroxyl-terminated hyperbranched polyimide, HBPIBPADA-TAP(OH), we successfully fabricated hybrid ternary composites, which were comprised of a linear polyimide (PI6FDA-APB), HBPIBPADA-TAP(OH), and an inorganic SiO2 component. The material was designed to satisfy the requirement for cutting-edge insulators with a low dielectric constant and a high thermal stability. Because of the appropriate choice of the hybrid ternary composite systems with HBPIBPADA-TAP(OH) and inorganic silica, it is sensible to improve the dielectric properties and thermal resistant properties of unary systems or improve the disadvantages of the dielectric and optical properties of binary systems. For an optimized composition, the dielectric constant (Dk) of the PI6FDA-APB–HBPIBPADA-TAP(OH)-30%–SiO2-20% composite reaches the lowest value of 2.24 at 100 kHz. Research also showed that the optical transparency is significantly improved with the increase of the HBPIBPADA-TAP(OH) content in the composite. Compared with the binary linear PI 6FDA-APB–SiO2 composite, the transmittance increases from 1% to 75% at the wavelength of 450 nm. The incorporation of SiO2 can preserve the good thermal properties of the hybrid composites containing HBPIBPADA-TAP(OH). By adding 10% of HBPIBPADA-TAP(OH) to the PI6FDA-APB–SiO2-20% system, the coefficient of thermal expansion of the hybrid ternary composite is 20.9 ppm °C−1 in the temperature range from 100 to 150 °C, which is significantly lower than that of the linear polyimide (37.1 ppm °C−1 for PI6FDA-APB). Because of these optimized properties, hybrid ternary composites have the potential for use in applications in the micro-electronic insulator fields, such as interlayer dielectrics of advanced electronic devices.

Comparison of Photooxidation and Thermal Oxidation Processes in Poly(ether imide)

Thermal oxidation and photooxidation processes occurring in poly 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride−1,3-phenylendiamine copolymer (ULTEM), were investigated and compared. The study aimed at finding possible differences in the oxidation pathways of this complex polymer by using the analytical power of MALDI techniques. ULTEM films were subjected to photooxidation by exposure at 60 °C in a UV accelerated chamber (Q-UV Panel) in atmospheric air, and the oxidative process was followed as a function of the exposure time. Relevant structural information on the photooxidized ULTEM species was extracted from the MALDI spectra. These data show the presence of polymer chains containing acetophenone, phenyl acetic acid, phenols, benzoic acid, phthalic anhydride, and phthalic acid end groups. The mechanisms accounting for the formation of photooxidation products of Ultem involve several reactions: (i) photocleavage of methyl groups of the N-methyl phthalimide terminal units; (ii) photooxidati...

New Vistas in Polymer Degradation. Thermal Oxidation Processes in Poly(ether imide)

Poly{2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride−1,3-phenylendiamine} copolymer (ULTEM) was subjected to thermoaging in an attempt to determine the structure of the species formed during oxidative degradation. The oxidative process was followed as a function of exposure time by using MALDI−TOF MS. Thermal oxidation produces charring after only 15 min and the formation of insoluble residue amounts to 50% after 180 min at 350°C. Highly valuable structural information (including the end groups) was extracted from the MALDI spectra of the thermally oxidized ULTEM soluble samples. Oxidized specimens contained acetophenone, phenylacetic acid, phenols, benzoic acid, bisphenol A, phthalimide, and phthalic anhydride end groups. The mechanisms accounting for their formation involve several reactions: (i) cleavage of the diphenyl ether units; (ii) oxidative degradation of the isopropylidene bridge of BPA units; (iii) thermal cleavage of phenylphthalimide units.

Hydrolytic stability of sulfonic acid-containing polyimides for fuel cell membranes

The long-term stability of sulfonic acid-containing polyimides has been investigated. The hydrolytic degradation of homopolyimide and the block copolyimide comprising 27 mol% of 2,2′-bis(trifluoromethyl)benzidine and 9 mol% ofm-phenylenediamine (BTFMB27mP10[7/(3+1)]), was quantified through viscosity measurements and FT-IR spectroscopic analyses. The viscosity decrease with respect to time and the degradation rate were similar. The degrees of degradation with respect to time under ambient conditions and at elevated temperature in water were monitored by FT-IR spectroscopy. A new absorption peak was observed at 1786 cm−1, which we corresponds to the presence of anhydride end groups formed by hydrolytic scission of the imide rings.

Schottky barrier height at an organic/metal junction: A first-principles study of PTCDA/X(X=Al,Ag)contacts

First-principles calculations within the density-functional theory have been performed for a 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA) molecule deposited on Al(111) and Ag(111) substrates, focusing on the structural and electronic properties. The relatively large interplanar distance between the PTCDA plane and the Al surface, along with the small adsorption energy, suggest the interaction to be pretty weak. Moreover, the analysis of Mulliken population combined with the density of states shows that the main interactions occur in the molecular anhydride end groups, whereas the perylene core is basically unaffected by the Al substrate. Very similar results are obtained for PTCDA deposited on the Ag(111) surface, the interaction being even weaker than with Al, as expected for the less reactive noble metal. As for the technologically important issue of the potential lineup, our results show that the PTCDA/Al contact has a rectifying character, with a p-type Schottky barrier height of about 1.5 eV. This same value is obtained for the PTCDA/Ag contact, irrespective of the interface geometry. This suggests that, irrespective of the underlying metal, the Fermi level is pinned at the same energy position with respect to the PTCDA highest occupied molecular orbital, in excellent qualitative agreement with experimental findings.

Synthesis and Dielectric Properties of Polyimide-Chain-End Tethered Polyhedral Oligomeric Silsesquioxane Nanocomposites

Nanoporous polyhedral oligomeric silsesquioxanes (POSS) containing amine groups (NH2−POSS) were reacted with poly(amic acid) having anhydride end groups to form porous POSS/polyimide nanocomposites. The van der Waals interaction between tethered POSS molecules is incompatible with the polar−polar interaction of imide segments, resulting in a self-assembled system of zigzag shaped cylinders or lamellas about 60 nm long and 5 nm wide, as determined by transmission electron microscopy. The incorporation of 2.5 mol % nanoporous POSS results in a reduction of the dielectric constant of the polyimide nanocomposite from 3.40 for the pure polyimide to 3.09 without any degradation in mechanical strength.

Photo-oxidation products of polyetherimide ULTEM determined by MALDI-TOF-MS. Kinetics and mechanisms

Poly 2,2-bis4-(3,4-dicarboxyphenoxy) phenylpropane dianhydride-1,3-phenylendiamine copolymer (ULTEM) was subjected to photo aging in the attempt to find evidence on the structure of the species formed in the oxidative degradation. The oxidation was followed as a function of the exposure time by MALDI and SEC/MALDI techniques. The SEC curves showed extensive degradation, with the formation of low molar mass oligomers having different end groups. Valuable structural information on the photo-oxidized ULTEM species was extracted from the MALDI spectra of the photo-oxidized ULTEM. These showed the presence of polymer chains containing acetophenone, phenyl acetic acid, phenols, benzoic acid, phthalic anhydride and phthalic acid end groups. The mechanisms accounting for the formation of photo-oxidation products involve several simultaneous reactions: (1) photo-cleavage of methyl groups of the N-methyl phthalimide terminal units; (2) photoxidative degradation of the isopropylidene bridge of BPA units; (3) photo-oxidation of phthalimide units to phthalic anhydride end groups: (4) hydrolysis of phthalic anhydride end groups. The kinetic behaviour of all the species detected is in agreement with the predictions of the reaction mechanisms hypothesized.

Synthesis and characterization of hyperbranched polyimides with good organosolubility and thermal properties based on a new triamine and conventional dianhydrides

AbstractA triamine monomer, 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB), was synthesized from phloroglucinol and 4‐chloronitrobenzene, and it was successfully polymerized into soluble hyperbranched polyimides (HB PIs) with commercially available dianhydrides: 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). Different monomer addition methods and different monomer molar ratios resulted in HB PIs with amino or anhydride end groups. From 1H NMR spectra, the degrees of branching of the amino‐terminated polymers were estimated to be 0.65, 0.62, and 0.67 for 6FDA–TAPOB, ODPA–TAPOB, and BTDA–TAPOB, respectively. All polymers showed good thermal properties with 10% weight‐loss temperatures (T10's) above 505 °C and glass‐transition temperatures (Tg's) of 208–282 °C for various dianhydrides. The anhydride‐terminated HB PIs showed lower T10 and Tg values than their amino‐terminated counterparts. The chemical conversion of the terminal amino or anhydride groups of the 6FDA‐based polyimides into an aromatic imido structure improved their thermal stability, decreased their Tg, and improved their solubility. The HB PIs had moderate molecular weights with broad distributions. The 6FDA‐based HB PIs exhibited good solubility even in common low‐boiling‐point solvents such as chloroform, tetrahydrofuran, and acetone. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3804–3814, 2002

One-Pot Polyimide Synthesis in Carboxylic Acid Medium

The melts of aromatic carboxylic acids such as benzoic acid (BA) at 130–160 °C were shown to be excellent media for the one-pot synthesis of high molecular weight, completely cyclicized polyetherimides (PEIs) from the corresponding diamines and tetracarboxylic acid dianhydrides. According to the data on the cyclodehydratation (CD) kinetics of oligomeric amic acid model compounds, the rate of cyclicization of transient polyamic acids in BA at 140 °C is very high, and the polymer chain growth proceeds via the polyaddition of completely cyclicized PEI oligomers with amino and anhydride end groups. Tetracarboxylic acids in BA at 140 °C were shown to react with aromatic diamines to obtain high molecular weight PEIs as well as the corresponding dianhydrides. The effect of the total concentration of comonomers and the presence of an ‘inert’ diluent on the kinetics of the growth of the inherent viscosity in the polycyclocondensation of diamines and dianhydrides is discussed from the point of view of the mechanism of the process. The prospect of a novel synthetic approach in polyimide synthesis is discussed, including obtaining new homopolyimides based on extremely-low-reactivity monomers; new statistical, regular, alternating copolyimides and block copolyimides; two-component blends with one glass transition point, and PEIs based on AB-type heteromonomers.

Preparation of the anhydride terminated polycarbonate and its reactive compatibilization with polystyrene

Polycarbonate with anhydride end groups (PC-anh) was prepared by the reaction between polycarbonate having hydroxyl end groups (PC-OH) and trimellitic anhydride chloride (TMAC). Hydroxyl or anhydride terminated polycarbonates were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The reaction of PC-anh with polystyrene containing oxazoline reactive groups (RPS) was confirmed not only by the torque measurement during melt blending of these two but also by FTIR spectroscopy of the reactive blend obtained. Polycarbonate (PC) / polystyrene (PS) compatibilized blends were prepared by melt blending along with their reactive counterparts, PC-anh and RPS in the Haake mixer. The morphologies of these blends were examined by the scanning electron microscope (SEM). The compatibilized blends with reactive components showed relatively finer morphologies than the uncompatibilized blend without reactive components. Izod impact strength and rheological property of these blends were also investigated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1338–1347, 2000

Preparation of hydrophobic poly(isobutylene) star polymers with hydrophilic poly(propylene imine) dendritic cores

Poly(propylene imine) dendrimers with amino chain ends have been used for the preparation of hydrophobic star polymers with hydrophilic dendritic cores. The unsaturated end groups of polyisobutylene (PIB) were transformed into reactive anhydride end groups by an “ene” reaction with maleic anhydride, and the resulting functionalized PIB was then reacted with dendrimers to afford dendrimer-PIB star copolymers.

Interdiffusion measurements of modified poly(arylether sulfone)s using nuclear reaction analysis

The interdiffusion and miscibility behavior of three different types of modified poly(arylether sulfone)s with deuterated poly(arylether sulfone) is studied by depth profiling using the nuclear reaction D(3He, α)p. The diffusion coefficients are found to be in the range of 10−15 and 10−14 cm2/s at 195°C. A random copolymer of poly(arylether sulfone) containing 4,4-bis-(4′-hydroxyphenyl)valeric acid units is only partially miscible with deuterated poly(arylether sulfone) when the comonomer content is 8.8 mol %, whereas blends with comonomer contents of 1.7 and 4.5 mol % are miscible as indicated by complete interdiffusion. The transition from miscibility to immiscibility is caused by repulsive interactions of copolymer segments and can be explained in terms of a mean-field theory of random copolymer blends. Also, poly(arylether sulfone)s grafted with 0.4 wt % maleic anhydride or having pyromellitic anhydride endgroups are miscible with deuterated poly(arylether sulfone)s. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2083–2091, 1997

The interfacial reaction of modified poly (arylether sulfone)s and polyaramides

It is shown that a fracture test using an asymmetric double cantilever beam test geometry is a powerful tool to study the effect of interfacial reactions on the improvement of the interfacial fracture toughness (G c ) of immiscible polymer systems. The G c values between a partially aromatic polyamide (PA) and a poly(arylether sulfone) (PSU) can be increased significantly when reactive PSUs are used which are obtained by grafting with maleic anhydride by introducing pyromellitic anhydride endgroups or by introducing carboxylic acid groups via copolymerization. Optical and atomic force microscopy investigations of the fracture surfaces show different failure mechanisms for weak and strong interfaces. For weak interfaces it was possible to determine the crack opening geometry using interference microscopy. For significantly reinforced interfaces rib marking lines on the PSU fracture surface can be observed. X-ray photoelectron spectroscopy (XPS) measurements reveal that with increasing toughness of the interface more and more cohesive failure of the PA occurs. This results in an increasing amount of nitrogen detected on the PSU fracture surface and simultaneously no sulfur is detected on the PA fracture surface.

Chemistry, diffusion, and electronic properties of a metal/organic semiconductor contact: In/perylenetetracarboxylic dianhydride

We present a photoemission investigation of the interface between In and 3, 4, 9, 10 perylenetetracarboxylic dianhydride (PTCDA). The interfacial region is very wide due to an anomalously fast diffusion of In into the organic layer. In also reacts with the anhydride end groups of the molecules. The absence of metal clustering, which permits diffusion, is believed to be due to the ionization of In and ion–ion repulsion in the PTCDA matrix. Finally, the ohmicity of the In/PTCDA contact is attributed to reaction-induced electronic gap states created throughout the wide interfacial region upon formation of the interface. This study provides the first direct correlation between chemistry and electronic properties of a metal contact on an organic molecular semiconductor.

Amine-activated color in anhydride functional styrene/acrylic copolymers

Anhydride functional copolymers, usually prepared from maleic anhydride, styrene and acrylic monomers, are an increasingly important group of co-reactants for polyol and epoxide crosslinked coatings. Aliphatic tertiary amines, the preferred catalysts for crosslinking, generate strong colors when they are added to many of the polymers. Color formation was investigated using tristimulus colorimetry to determine the influence of composition of the anhydride copolymer and the process for copolymer preparation. A structural feature of the copolymers, tentatively identified as unsaturated anhydride end groups from termination by disproportionation, and residual maleic anhydride were found to be major contributors to amine-activated color. Partial hydrolysis of the polymer moderates color development, but increases solution viscosity. Acid level increases and anhydride content decreases as more n-butyl methacrylate is included in the copolymers, possibly because water is formed during the initiation process with this monomer.

Polyimidizations from acylated diamines and dianhydrides

Imide ring formation upon heat treatment of diacylated diamines and dianhydrides was shown to be highly efficient. Evidence to support this conclusion was obtained from thermal gravimetric analyses, differential scanning calorimetry and infra-red spectroscopy. Equimolar mixtures of diacylated diamines and dianhydrides form eutectic mixtures, which quantitatively eliminate the corresponding acid to form imides. Besides the possibility of polyimidization, the reaction of acylated amino end-groups with anhydride end-groups was demonstrated to be useful for chain extension by post-heating a lower-molecular-weight polyimide based on pyromellitic dianhydride (PMDA) and 4,4′-aminodiphenyl ether (ODA). Advantages gained by this technique are narrower molecular-weight distributions and higher-solids poly(amic acid) solutions with lower solution viscosities, which allow more facile fabrication into useful articles.

Telechelic polyisobutylene with unsaturated end groups and with anhydride end groups

Anhydride terminated polyisobutylene (PIB) oligomers were synthesized in a one- or two-step process from chlorine terminated oligomers. In the one-step process, chlorine functional oligomers were just heated in the presence of maleic anhydride (MA) for 12 h at 190°C without a catalyst. In the two-step process, the chlorine end functional groups were first converted by selective dehydrochlorination to isopropenylpoly-isobutylene end groups with t-BuOK in refluxing tetrahydrofuran during 16 h. In a second step, MA was coupled to the PIB with unsaturated end groups by reacting the oligomer with MA for 12 h at 190°C. These reactions could be followed by i.r. and n.m.r. The PIB-MA obtained had a functionality between 30% and 100%. In order to study the formation of amine functionalities, the PIB-MA was reacted with diamines. The coupling gave an imide bonding.

Study of the synthesis of poly(isobutylene‐b‐amide‐11) by polycondensation of α,ω‐dianhydride oligoisobutylene with α,ω‐diamino oligoamide‐11. I. Study of amine–anhydride and amide–anhydride reactions on low molecular weight models and on oligomers and polymers

AbstractThe side reactions connected with the polycondensation of α,ω‐diamino oligoamides and α,ω‐dianhydride oligoisobutylenes are studied on low and high molecular weight models. Models for amine and anhydride end groups are dodecylamine and (2‐dodecene‐1‐yl) succinic anhydride, respectively; their reaction is studied in the bulk (170°C) and in solution (142, 152, and 162°C); the products are analyzed by 1H‐, 13C‐, and 1H‐13C‐NMR and GPC. Some of these products and the junctions between the blocks are prepared independently. Models of amide groups in the chain are N‐dodecyldodecanamide and N‐dodecyloctadecanamide; their reaction with anhydride model results in cleavages with formation of imide groups. The results obtained from low molecular weight models are confirmed by studies on oligomers. They show unambiguous by that crosslinking which accompanies the block polycondensation originates from the reaction of amino‐end groups with the intermediary acid groups resulting from the amine‐anhydride reaction.