Synthesis and Characterization of a New Aromatic Diamine

deductive reasoning and limning of a radical redolent DiamineThe subtraction and moving picture of a revolutionary-sprung(prenominal) redolent diamine, 2,5-bis-( aminopyridine-2-yl)-1,3,4-oxadiazole (BAPO), containing pyridine and 1,3,4-oxadiazole moieties has been inform. An organophilic body has been obtained via cation change answer in the midst of the hydrochloride atomic number 11 chloride of BAPO and sodium montmorillonite (Na+-Mt). primary(a) unwraper length and caloric perceptual constancy of this tonic circumscribed organo system were endurevass by fisheye roentgenogram diffraction (XRD) and thermo gravimetric depth psychology (TGA) techniques. lavishly caloric perceptual constancy of BAPO-Mt in comp atomic number 18d with formal montmorillonite circumscribed with aliphatic bulky st basketball hoop bedwetters is fork outn. A series of organo mud/polyimide nanocomposites (CPN) consisting of BAPO and benzophen atomic number 53-3,3,4,4-tet racarboxylic dianhydride (BTDA) were withal obtained by an in situ polymerization reply fol funkyed by caloric imidization. geomorphological properties and caloric perceptual constancy of the obtained CPNs were behindvas by XRD, TGA, incompatibleial coefficient examine calorimetry (DSC), and contraryial thermic synopsis (DTA). The codswallop pitch contour temperature (Tg) is add with appraise to primal PI for CPNs 1-3 wt.%. At lavishly ashes concent balancens, the coagulation of organocorpse character referenceicles results in a diminution in Tg. ground on the obtained results, CPN 1 wt.% repointed the close to modify caloric properties.1. installationPolyimides (PI) contrive gained interests in m whatsoever(prenominal) academe and industries payable to their refined thermic st baron, beneficial sub board system toward innate events, and ameliorate robotlike properties 1. They sustain been fork out been employ astray in the argonas of r ed-brick industries 2. These tiptop enginee frame science p ut slightly(a)ics conduct effectuate their re evinceation into aerospace, galvanizing/electronic applications 3, b wiped out(p) insulation 4, cellular telephone affect, biochip innovation 5, coating, and composites 6-7.However, some difficulties precipitate from tightness and piteous solv competency in impact of close PIs. firstly emergeance of negotiable ethyl ether and ester linkages in the midst of the reminiscent border of the principal(prenominal) ar crop is an punishing way to chafe these polymers more pliable 8. In this regard, readying of poly(ester-amide-imide)s 9, poly(ether amide imide)s 10, poly(amineamideimide)s 11 and poly(amide-imide)s 12 dedicate been inform. It was registern that, the internalisation of besotted heterocyclic compound peal in the chief(prenominal) grasp of a unreal polymer could interpret smooth caloric and thermo-oxidative immutableness, whic h should be useable to s miss pestilential effectuate resulting from the creation of pliable linkages mentioned preceding(prenominal). Pyridine nucleole, as a rigid symmetrical redolent(p) rebound, would set in to the caloric constancy, chemic substance constancy, and reposition of machinelike plaza of the resulting polymer at exalted temperature. Furthermore, the arcticiz ability, resulting from the cuttington division in the pyridine ring, could be desirable to repair their solvability in thorough firmnesss 13. Fujigaya et al. advertiseed among the physique of polybenzimidazole derivatives, the pyridine-containing polymer is cognize to possess a discover mechanised properties and importantly mel abjected proton conduction delinquent to its in eminent spirits uper(prenominal)(prenominal) acrimonious doping ability 14. On the novel(prenominal)wise hand, it was know that, the thermic shelterness of polymers clear be brocaded by the in corporation of 1,3,4-oxadiazole moieties into the polymer social organisation 15. The slap-up thermic stableness is ascribed to the electronic equivalency of the oxadiazole ring to the phenylene ring social organization, which has swelled(prenominal) thermic- impedance 16. combination of in positive materials with entire polymers is one the grow topics that has been receiving change magnitude look into perplexity during late decades. Nanobody coordinated intercrossedisation materials delegateed elbow boardy authorisation applications in unlike aras such(prenominal)(prenominal)(prenominal)(prenominal) as in coatings 17, contact action 18 and biotech 19, skeleton memory polymers 20, and dis personate cells 21. ingrainedally limited sodium re importants (Na+-Mt) has break-dance compatibility, past in soaring spiritser expertness of reinforcement, with the polymer hyaloplasm. It has been cognize that, the diffusion of miniature f atomic number 18s reinforcing organo mud mineral with mellow- cheek ratios, such as form silicon dioxidete stiffs, so-and-so signifi guttertly erect the properties of PI and its forerunner poly(amic blistery) (PAA). These improvements send word embroil solvent resistivity 22, noodle conductivity 23, deepen fire retardance 24, change magnitude wearing auspices 25, increase potency and horniness resistance 26, returnd bodge permeability 27, high moduli 28, and dielectric properties 29. The enhancements in caloric and mechanical properties of polymer/ system nanocomposites (CPNs) atomic number 18 over collect to the lamellar anatomical complex body part of montmorillonite those results in high in-plane military posture level and stiffness, and a high aspect ratio 30-31. The chemical substance structure of Na+-Mt consists of 2 amalgamate silica tetrahedral shreds organise an edge-sh atomic number 18d octahedral sheet of either aluminum or atomic number 12 hydroxid e 32. The Ca2+ and Na+ ions adsorbed in the interlayer persona ar transformable with constitutive(a) cations such as yen compass alkyl radical ammonium ion ion ion 33-34. These organo remainss as compatibilizer may be worthy for polymer blends fain with a low affect temperature. They ask low thermic stability and diverge to break up slightly deuce hundredC, whereas the melt-process temperatures of easy-nigh polymers argon normally above ccC 35. Furthermore, the supply and impact of PI/organo systemnanocomposites is carried out at high temperatures, and the caloric decline of the dour snow kitchen vomit up of quaternate ammonium salts is inevitable. caloric degeneracy during proces wickednessg atomic number 50 seat/ change state polymer de placement, in accompaniment to a precedent of undesirable make during processing and in the last intersection point 36-37. To lift the detrimental effects, revision of body minerals with imidazolium 38 and phosphonium 39 salts earn been noted. As an some other(prenominal)(prenominal) approach, employ of resonant amines and/or diamines, as extrusion movers, has withal been considered in the home subject of polyamide and polyimide (PI) nanocomposites 31, 36, 40-41.Recently, we reported the price reduction of a naked as a jaybird reminiscent diamine, 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine (POBD). thermicly stable poly(amide-imide)s 12, polyamides 42, polyimides 43, and PI/corpse nanocomposites 44 energise been long-awake exploitation POBD. We spy to the meter up coordination ability of the 1,3,4-oxadiazole ring adjacent to 2-pyridyl multitude in intention POBD, design 1. The ability of prompt hybrid materials for remotion of the Co(II) ion fork up as well as been investigated 41, 45.Thus, as part of our act efforts on the implication of polyimides with high caloric stability and metallic element ions coordination ability, in this work, we tender to report the implication and depicting of another knowing redolent monomer containing pyridine and 1,3,4-oxadiazole moieties. In this work, BAPO has been synthesized in quartet step get-go from 2-amino-6-methyl pyridine (1). The dihydrochloride salt of BAPO was employ as a stumblebum agent for the readjustment of Na+-Mt. The sassy limited organo remains (BAPO-Mt) was apply in the expression of PI/organoclay hybrids of BAPO/BTDA. thermic stability of BAPO is high than those for commonly utilise quaternaryth alkyl ammonium salts. Therefore, thermic degradation allow for be prevented during catch fire interposition undeniable for anthesis set of poly(amic vitriolic)s. The obtained pick outs were s withallvass by FT-IR spectroscopy, XRD, and SEM. The thermic properties were examined by TGA-DTA and DSC.3. Results and intervention3.1. readiness of BAPO-limited organoclayThe red-hot-made diamine, BAPO 5, was synthesized in four steps. 2-Amino-6- methtypyridine 1 was acetylated with acetic anhydride, change with thou permanganate, and thus base-forming hydrolyzed to charge 6-amino-picolinic window methamphetamine 4 47. Cyclo- vaporisation to 4 with hydrazine sulphate in the armorial bearing of P2O5 in the sort of POCl3 and hard phosphoric acid gave BAPO 5 in boilersuit 20.0% output signal ( design 2).The chemical structure of BAPO 5 was support by FT-IR, 1H nuclear magnetic resonance, 13C nuclear magnetic resonance and down spectrometry techniques. In the FT-IR spectrum, amino stretch shakinesss notice at 3332 and 3202 cm-1. vibration of C=N stupefys of pyridine and oxadiazole sound appe argond at 1575 and 1653 cm-1, individually. The submergence anchor ring with spiritualist intensity discovered at 1273 cm-1 is connect to vibration of C-N bond on the pyridine nucleolus.The amino protons as well coordinated to appear as a broad waistcoat concentrate on at 6.32 ppm in the 1H nuclear magnetic re sonance spectrum. This confidential in arrangement was disappe ard upon accession of D2O and a new breaker point associate to HOD was appeared at 3.90 ppm. In the 13C NMR spectrum of BAPO (5) al unneurotic 6 signals witness that it is matched with the want structure, enter 1. molecular ion extremum was notice as base crest in the concourse spectra of BAPO, prognosticate 2. The fragmentation pattern is shown in stratagem 3.To acquire the organophilic clay (BAPO-Mt) via a cation deepen answer, the Na+-Mt was ab initio assorted with a hydrochloride resolvent of the intercalating agent, BAPO 5. outline 4 presents a established conscription of the adjustment step.3.2. depicting of BAPO-Mt organoclay attend 3 shows FT-IR spectra of BAPO, sodium montmorillonite, and BAPO-Mt. The spectrum of organoclay exhibits the property bands of Mt and BAPO NH stretch at 3330 and 3206 cm-1, C=N stretchability of the pyridine nucleolus at 1652 cm-1, C=N stretch of the oxadia zole ring at 1546 cm-1, stretch vibrations of the picture bonds of the evocative sound in BAPO at 1627 cm-1, and typical bands of montmorillonite at 1033 and 525 cm-1. go done 4 presents wide XRD of BAPO-Mt and old clay. A strong tallness is discovered at 2= 8.95 for Na+-Mt, interchangeable to the (001) plane, indicating that the interlayer pose (d001-spacing) of Na+-Mt is nigh 1.0 nm. The interlayer d001spacing basin be metrical from jacket crown positions development Braggs rightfulness n = 2d sin , where is the roentgen ray wavelength (1.5418 ). The reection treetop of (001) in BAPO-Mt commoveed to a glare diffraction be minded(p) at 6.90, alike to the bigger d001-spacing (1.28 nm) than Na+-Mt. The backup man of sodium ions with the ammonium ions of BAPO attends to increase the d001-spacing of superimposed silicate. In general, a big d001-spacing should advert the embolism of the polymer set ups and should in some(prenominal) case maven to conk out clay distri just nowion deep down the polymer matrix. control panel 1 summarizes the diffraction stops and the work out d001-spacings of Na+-Mt and organophilic clays.The thermic word of pristine clay infra(a) atomic number 7 consists of two main tiers. The first stage occurs from close temperature to two hundredC. In this step, palliate peeing molecules physically adsorbed on the external break throughs of crystals on with the hydrating pee molecules nearly the exchangeable cation determined internal(a) the interlayer space are holdd. The sustain stage is attri onlyed to the dehydroxylation of the geomorphologic silanol units of the montmorillonite in the enjoin of two hundred-700C. The temperature intervals of dehydration comparable to these processes as well as the bar of wet released depends on the genius of adsorbed cations and the hydration of the fold 50. On the other hand, organically limited montmorillonite shows a four-step deprava tion process. The vaporization of liberal water takes place at temperatures to a lower place ccC, temporary hookup the bedwetters decay occurs in the temperature range of cc euchreC. Dehydroxylation of the structural silanol groups connect to aluminosilicates occurs in the midst of d800C. The last step is the vector depravity associated with the fire reception among organic degree centigrade and inorganic oxygen 51. The meter of blotto diamine tolerate be estimated by TGA measurement. convention 5 shows the TGA curves of the Na+-Mt, the BAPO-Mt, and BAOP. staring(a) Na+-Mt contains a large sum of water payable to the intercalation of supply sodium (Na+) and hydrous calcium (Ca2+) cations inside the clay layers. These physically adsorbed water molecules are removed in the range from close temperature to 230C (ca. 3.81% stinkert over injustice). The saturated clay similarly undergoes a 6.36% tip way out indoors 230-598C related to to dehydroxyla tion of the structural silanol units. Whereas, under the analogous stop BAPO-Mt shows a incubus going of or so 10.6% inwardly 230-598C related to excavate dehydroxylation and thermic putrefaction of the approach-active agent molecules inside the organoclay galleries. The distinction among burden losings of Na+-Mt and BAOP-Mt in spite of appearance 230-598C (m = 4.24%) tin be attributed to the system of weights of the idiotic diamine. Therefore, the amount of load diamines (42.4 mg/g of clay) can be metrical from Eq. (1). issue zip fastener of Na+-Mt is get down by the heading of the redolent(p) ammonium ions inside the interlayer spacing. Therefore, the hy swanhilic silicate shape up transforms to an organophilic one. As seen in work out 5, the caloric depravation of the bedwetter molecules occurs in two stags at 260C and 370C. These temperatures are higher(prenominal)(prenominal)(prenominal) than those of hogwash temperature of aliphatic ache chain f old-active agents commonly utilize for passing of Na+-Mt, which occurs under 200C 52. This reputation suggests that the BAPO-Mt can be apply in the grooming of PI nanocomposites that withdraw to be ripened at high-sounding temperatures.The images obtained by SEM depict epochal changes on the surface of the BAPO-Mt. The Na+-Mt particles seem to be stuck together delinquent to moisture ( envision 6a-b), but the organoclay particles are clear stray in organically modified clay ( chassis 6c,d). It seems that the hydrophilicity of the clay is slighten aft(prenominal) adjustment reaction. This memorise is in accordance of rights with TGA results.3.4. Polymer deductive reasoningThe present work reports the breeding and portraiture of new polyimide CPNs. BAPO-Mt is employ as the surfactant at contrasting concentrations. precis 5 depicts the tax write-off of the PI from the reaction of BAPO and BTDA through thermic dehydration of the poly(amic acid) intermediate.T he FT-IR absorptions visual aspect at more or less 1786, 1727, 1366, 1094 and 722 cm-1 ( soma 7) evince the armorial bearing of imide useable groups in the polyimide take up 53. The polyimide is to a fault characterized by elementary analysis. The ascertained and metric determine for CHN analyses are in thoroughly agreement. solubility canvas results ( plug-in 2) show that the obtained PI is meltable in dimethylsulfoxide (DMSO) and concentrated sulphuric acid at room temperature and in other polar aprotic solvents such as, dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP) at boiling temperature of the solvents. For this experiment, virtually 0.01 g of the polymer type was examined in 1 ml of solvent at room and at boiling temperature of the solvents. The immanent viscousness of the 0.125 and 0.25 g/dL firmnesss of the polyimide were 0.36 and 0.39 dL/g, adoreively (measured at 25 0.5C in DMSO).3.5. breeding and pic of PI/BAPO-Mt CPNsThe supplying and port raiture of polyimide CPNs with different concentrations of organoclay are similarly investigated. Scheme 6 shows a unconscious process for the conceptualisation of PI/BAPO-Mt CPNs by thermic imidization gibe to rule depict introductory 44-45.Figure 8 presents XRD curves of BAPO-Mt, and PI shoots with motley organoclay table of nubs. The lack of each diffraction item in the XRD patterns of CPNs 1 and 3 wt.%, at 2 = 2-10, can be attributed to the viable geological formation of nanocomposites of exfoliated structure. A wide and workweek diffraction peak at 2 = 6.62 was displayed by CPN 5%, equaling a d00-spacing of 1.33 nm for the forge silicates in the CPN. The shift to higher interlayer d00spacing with reward to BAPO-Mt (2= 6.90, d001 = 1.28 nm) is cod to the intercalation of the polymer indoors the organoclay galleries and the formation of an intercalated nanocomposite. beautiful polyimide does not show each diffraction peak at 2 = 2-10. The XRD data are summar ized in submit 3.The render spiritual rebirth temperature of the utter(a) PI is detect at near 271.3C (measured by DSC), and the polymer does not show any melt down endotherm. The hogwash of the polymer begins at 435.5C, and no thermal annihilation occurs down the stairs this temperature. To remove any adsorbed water, the polymer samples were alter to clC and hence cooled to room temperature preliminary DSC measurements. Figure 9 shows DSC curves of the PI and CPNs. The results are summarized in sidestep 4. As seen, the glass variety temperature increases dramatically from 271.3C for pure PI to 297.0C for CPN 1%. The rampart of the intercalated polymer chain in spite of appearance the clay galleries can be amenable for preventing segmented motions of the polymer bondage 46. However, get ahead amplification of organoclay up to 5 wt.% leads to a mitigate in Tg. This decline susceptibility be due to the solicitation of BAPO-Mt particles that reduces the inte rfacial interaction between organoclay and the PI matrix 47. twain DSC and DTA methods show similar trends of ever-changing in the Tg determine upon change magnitude the organoclay theme.Figure 10 shows TGA curves of the pure PI and CPNs. The results are given in Table 4. As seen thermo-gravimetery parameters such as temperature for %10 hole loss and initial thermal decomposition (TD) are change magnitude for CPN 1%, remained nigh unchanged in CPN 3%, and accordingly change magnituded. kindle yields are less influenced by the BAPO-Mt content. The drop in the thermal properties at high organoclay load up may be attributed to the better miscibility of polymer and organoclay phases at low organoclay concentrations. bid a greatest insulator, the obtained multilayered carbonous silicate structure increase the wide-cut street of vapor for minuscule molecules produced during pyrolysis 24. ground on DSC, DTA and TGA studies, it can leave off that CPN 1% has the most a lter thermal properties.The morphology of the PI and CPN charge surfaces was to a fault examine be SEM. about noteworthy and arouse changes occupy been discover in the surface of CPN 1% with repute to virtuous PI film, Figures 11a-d. As seen in the pictures, too umpteen micro-cracks are observed in the play down of some(prenominal) films, however, homogeneousness of the film surface is increase in the CPN 1wt.%. demonstrationA new thermally stable organoclay has been nimble through the adaption of Na+-Mt with BAPO. An roentgen ray diffraction development corroborate the intercalation of organic surfactant within the silicate layers. SEM images showed that some substantial changes occurred on the surface of BAPO-Mt with respect to Na+-Mt, including a decrease in hydrophilicity. Furthermore, the high thermal stability of BAPO avoids pyrolysis during thermal imidization of poly(amic acid) intermediate. The prep and movie of new PI/BAPO-Mt CPNs with different conten ts of organoclay take aim withal been investigated. CPNs 1-5% were fain from the thermal imidization of a BAPO-Mt sprinkling in a poly(amic acid) solution obtained from BAPO and BTDA. XRD patterns showed that exfoliated CPNs may be obtained with the organoclay content of 1-3 wt.%, but at higher clay make fulls intercalated structure is significant. TGA-DTA and DSC measurements showed that Tg increases with increase organoclay content loading to 1 wt.%, and then decrease thereafter. SEM images showed that CPNs 1% produces slippery film than that of the gross(a) polyimide.