untitled Thermom polymers complex Sohail Saee a Department of C b Institut für Anorg c National Enginee *Corresponding a fax: +92.51.92500 ARTICLE INFO Received: 23 June Received in revis Accepted: 20 Sep Online: 31 March KEYWORDS Amino‐thiourea d Metal‐containing Dynamic mechan Differential scann Thermogravimet DGEBA 1. Introductio Thermally for use in com supersonic air major synthet polymers. Inc chains offers a polymers. The leads to ther properties an Routes to such additives 1‐3 8, and the use The last app enhance the t metal‐contain producing epo and high therm temperatures Various m copper, and n epoxy oligome from metal c Thiourea deri transition m containing an resin curing a containing epo mechanic s from dig es eda,*, Naghm Chemistry, Research rganische und Analy ering & Scientific C uthor at: Departme 081. E‐mail address ORMATION e 2010 ed form: 19 Augus tember 2010 h 2011 derivatives g epoxy polymers nical analysis ning calorimeter tric analysis on y stable, high‐p mposite structur rcraft and reus tic efforts is in corporation of a possibility to e synthesis of m rmally stable m nd thus offers h polymers incl , synthesis of m e of metal‐cont roach has rec thermal stabilit ing epoxy pol oxy polymers w mal stability as [11,12]. metal complex ickel can be us ers. The cross‐l omplexes with ivatives are w metals. Compl amino functio agents 13. It oxy polymers p E ISSN 2153‐ Europ J al studies glycidyl e mana Rashida h Complex, Allama I ytische Chemie, Tec Commission, P.O.Box ent of Chemistry, R s: sohail262001@ya st 2010 performance re res on aerospa sable launch ve the field of he transition me access new us metal‐containin materials with s various pote ude the use of m metal containin aining cross‐lin ceived attentio ty of the epoxy lymers allows with good mec s well as achiev xes such as t ed as cross‐link linking agents c h O‐, N‐ or S‐c well known ch exes of thio onality are also has been foun possess high str European Journa Europe 2249 (Print) / IS DOI:10.515 pean Jo Journal home s of therm ether of bi a, Peter Jone Iqbal Open Univers chnische Universitä x 2801, Islamabad, Research Complex, A ahoo.com (S. Saeed ABSTRACT New thermally by curing digly Characterizatio elemental anal epoxy/thiourea calorimetry. Th properties of th glass transition Introduction of polymers with thermal stabilit The copper‐con (24:100) show 6080 MPa at 12 esins are requ ce vehicles suc ehicles. One of eat‐resistant ep etals into poly seful heat‐resis ng epoxy polym good mechan ential applicati metal complexe ng epoxy resins nking agents 9, on in attempts y polymers. Us the possibility chanical proper ving low proces those of titani king agents for can also be der containing liga elating agents ourea derivat o known as ep nd that the me rength and ther al of Chemistry 2 ean Journal of Ch SSN 2153‐2257 55/eurjchem.2.1 ournal o epage: www.e mally stab isphenol A esb and Rizw sity, Islamabad‐440 ät Braunschweig, P Pakistan Allama Iqbal Open d). stable epoxy po ycidyl ether of on of the meta lysis and mass a metal compl his method is b he resulting meta n temperature, t f metal ions, es good thermal st ty compared to t ntaining epoxy ed a 2.6% weig 25 oC, which is co uired ch as f the poxy ymer stant mers nical ions. es as s 4‐ ,10. s to se of y of rties sing ium, r the ived ands. for tives poxy etal‐ rmal stab glass vehi T best synt appl as ep to p ethe com tran thiou liter inve cont thiou meta DGE 2. Ex 2.1. D equi obta chem thioc meth 2 (1) (2011) 77‐8 hemistry (Online)  2011 1.77‐82.183 of Chem eurjchem.com le metal‐c A and am wan Hussain 000, Pakistan Postfach, Braunschw University, Islamab olymers containi bisphenol A (D al complexes w spectrometry. ex ratio was based on the se al‐containing ep thermal stability pecially the cop tability and mec the DGEBA‐DDM polymer obtain ght loss after he omparable to the ility and can be s‐reinforced p icles [14]. The thiourea‐b t known classes thesized. These lications, such a poxy resin cros prepare polyme er of bisphenol mplexes. Surpri sition metal c ureido)carbony ature for epox estigates the s taining epoxy urea metal com al complexes a EBA to yield the xperimental Materials and Diglycidyl ether ivalent weight ained from Bak micals used, cyanate, ethy hane (DDM), h 82 1 EURJCHEM mistry m containin mino‐thiou nc weig, D‐38023, Germ bad‐44000, Pakista ing copper and GEBA) with am was carried out Determination studied by m earch for the m poxy polymers w y, tensile streng pper ion, into th chanical propert M (DDM: 4,4’‐dia ned at a mole ra eating at 400 °C e epoxy‐DDM sy e used for indus plastic springs ased metal com s of complex, si metal complex as catalysis, as ss‐linking agent ers through a c A (DGEBA) wit isingly, to the complexes of yl]benzoate hav xy cross‐linking synthesis and polymers by c mplexes. The am are expected t rmally stable ep d characterizat r of bisphenol‐A 280 g/eq an kelite® AG thro 4‐nitrobenz yl p‐aminoben hydrazine mon ng epoxy urea meta many an. Tel.: +92.51.925 nickel ions have mino‐thiourea m t using infrared of the optimum eans of differe maximum enthal were investigated gth, and viscoela he polymer ma ties. The polyme aminodiphenylm atio of copper c and had a stor ystem. strial productio s for large‐lo mplexes repres ince the ligands xes are stable a O2‐storage dev ts [13]. Thus, it curing reaction th new thioure e best of our ethyl 4‐[3‐(4‐ ve not been de g agents. The properties of curing DGEBA mino functional to undergo a poxy polymers. tion A (DGEBA), EPR nd solid conten ough procurem oyl chloride, nzoate, 4,4’‐di ohydrate, palla al 0081; e been prepared metal complexes. d spectroscopy, m value of the ential scanning lpy change. The d with respect to astic properties trices produced er showed good methane) system complex:DGEBA rage modulus of on of one‐plate oaded motor ent one of the s can be easily nd have many vices [15] and t is of interest n of diglycidyl a‐based metal r knowledge, aminophenyl) scribed in the present work f new metal‐ with amino‐ groups in the reaction with . R 05322, epoxy nt 100%, was ment. The other , ammonium aminodiphenyl adium‐charcoal d . , e g e o . d d . A f y s r m l l 78 Saeed et al. / European Journal of Chemistry 2 (1) (2011) 77‐82 (10 %) of analytical grade from Merck were used as received. All other reagents and solvents were of analytical grade and used without further purification. The 1H NMR and 13C spectra were recorded in DMSO‐d6 solvent on Jeol ECS‐400 and 300 MHz spectrophotometers using tetramethylsilane as an internal reference. The apparent resonance multiplicity is described as s (singlet), br s (broad singlet), d (doublet), dd (doublet of doublets), t (triplet), q (quartet) and m (multiplet). Infrared measurements were recorded in the range 400‐4000 cm‐1 on a Spectrum 2000 spectrometer by Perkin Elmer. Elemental analysis was carried out using a Perkin Elmer CHNS/O 2400. Obtained results were within 0.4% of the theoretical values. FAB MS were obtained on a Finnigan MAG 90 mass spectrometer using glycerol as a matrix. Thin layer chromatography (TLC) analyses were carried out on 5×20 cm plates coated with silica gel GF254 type 60 (25‐250 mesh) using an ethyl acetate‐petroleum ether mixture (1:2) as solvent. The cross‐linking reaction of DGEBA with the metal complexes was investigated with FT‐IR spectrophotometer using KBr pellets. Glass transition temperatures of metal‐containing epoxy polymers were obtained on differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA). The dynamic mechanical analysis was performed with a Diamond DMA provided with bending mode of deformation with a 50 mm span length. Samples used were in the shape of rectangular strips with dimensions of 50×10×2 mm. The tests were carried out at frequency of 1 Hz and a heating rate of 2 oC/min in a temperature range from 27 to 250 oC under inert atmosphere. Thermal stability of the polymers was determined using TGA by heating the polymer samples under nitrogen atmosphere and recording their weight losses. Moisture absorption was measured according to ASTM D570‐63 standard. Rectangular shaped samples having dimensions 10×10×2 mm were dried under vacuum at 120 oC for 24 h until trace water had been expelled, then after cooling to room temperature the samples were weighed and placed in 100 oC boiling water for 6 h and weighed again. Tensile testing was performed on an Instron model 4301 according to ASTM D638 standard. 2.2. Synthesis 2.2.1. Synthesis of ligand Ethyl 4‐[3‐(4‐nitrophenyl)thioureido)carbonyl]benzoate (HL) was prepared as in our previous work [16‐18]. A solution of 4‐nitrobenzoyl chloride (1.85 g, 0.01 mol) in anhydrous acetone (80 mL) and 3% tetrabutylammonium bromide (TBAB) in dry acetone was added dropwise to a suspension of ammonium thiocyanate (0.76 g, 0.01 mol) in dry acetone (50 mL) and the reaction mixture was refluxed for 45 minutes. After cooling to room temperature, a solution of the corresponding ethyl p‐aminobenzoate (1.65 g, 0.01 mol) in anhydrous acetone (25 mL) was added and the resulting mixture refluxed for 1.5 h. Hydrochloric acid (0.1 N, 400 mL) was added, and the solution was filtered. The solid product was washed with water and purified by recrystallization from an ethanol:dichloromethane mixture (1:2) (Scheme 1). M.p.: 179‐ 180 oC. Yield 91%. IR (KBr pellet, cm‐1): 3350 (free NH), 3201 (assoc. NH), 1691 (C=O), 1735 (C=O ester), 1613 (C=N stretching), 1590 (aromatic C=C). 1H NMR (400 MHz, DMSO‐d6, δ, ppm): 12.56 (1H, br s, NH), 11.61 (1H, br s, NH), 8.23 (2H, d, J=9.1 Hz), 7.82 (2H, d, J=8.0 Hz), 7.66 (2H, d, J=7.9 Hz,), 7.62 (2H, d, J=7.2 Hz), 4.32 (2H,q, ‐CH2), 1.31 (3H, t, ‐CH3, J=7.1 Hz). 13C NMR (300 MHz, DMSO‐d6, δ, ppm): 178.9 (C=S), 168.2 (C=O ester), 165.0 (C=O amide), 145.8, 130.0, 129.2, 126.5, 125.3, 124.1, 121.4, 60.7, 14.1. Anal. Calcd. for C17H15N3O5S (373.38): C, 54.68; H, 4.05; N, 11.25; S, 8.59. Found: C, 54.67; H, 4.06; N, 11.25; S, 8.58. O Cl O2N NH4SCN C O O2N N S C O O2N N S H2N O O CH3 O2N O N H S N H O O CH3 O O H3C NO2 N S N H O O O CH3 O2N N S N H O M O O H3C N S N H O O O CH3 N S N H O M NH2 H2N Reduction M = Cu2+, Ni2+ + + MX Scheme 1 2.2.2. X‐ray structure determination of ethyl 4‐[3‐(4‐ nitrophenyl) thioureido) carbonyl] benzoate (HL) Crystal data: C17H15N3O5S, monoclinic, space group P21/n, a = 4.3449(2), b = 18.7349(5), c = 10.4511(3) Å,  = 93.293(3)°, V = 849.33(5) Å3, T = 100 K, Z = 2, F(000) = 388, Dx = 1.460 g/cm‐1,  = 0.226 mm–1. A yellow plate 0.35×0.15×0.10 mm3 was mounted on a glass fibre in inert oil. Measurements were performed on an Oxford Diffraction Xcalibur E diffractometer with monochromated Mo‐Kα radiation to 2= 30.03°. The data were corrected for absorption using the multi‐scan method. Of 53082 intensities, 4948 were independent (Rint = 0.0348). The structure was refined anisotropically using SHELXL‐97 [19]. The NH hydrogen was refined freely. The methyl group was refined as an idealised rigid groups allowed to rotate but not tip. Other hydrogen atoms were included using a riding model. The final wR2 was 0.0626, with a conventional R1 of 0.0260, for 244 parameters; S = 0.98; max. 0.238 e Å–3. Saeed et al. / European Journal of Chemistry 2 (1) (2011) 77‐82 79 2.2.3. Preparation of the copper and nickel complexes (CuL*2 and NiL*2) 2.2.3.1. Preparation of the copper complex (CuL*2) The complexation of the thiourea derivative was carried out according to the reported procedures [20,21]. To 30 mL of ethanol containing HL (0.01 mol) was added an ethanol solution of CuCl2.2H2O (0.05 mol). The reaction mixture was filtered and left to crystallize by slow evaporation for two weeks. The catalytic reduction of this complex was carried out: CuL2 (0.01 mol), 5 mL hydrazine monohydrate, 70 mL ethanol and 0.03 g of 10 % Pd‐C were transferred into a 250 mL two‐ necked round‐bottom flask and refluxed for 18 h. The reaction was monitored by thin layer chromatography (TLC). After completion, the reaction mixture was allowed to stand for one day and then filtered. The solvent was removed by rotary evaporation under reduced pressure. The copper complex (CuL*2) was obtained as a green solid after two weeks by recrystallization from ethanol (Scheme 1). Yield: 1.50 g (85%). IR (KBr pellet, cm‐1): 3405, 3325 (NH2), 1618 (N‐H bending), 1529 (benzene ring), 1405 (C‐N stretching), 1140 (C=S). MS (FAB, m/z): 803 (M+). Anal. Calcd. for C34H28N6O10S2Cu (802.73): C, 50.8; H, 3.4; N, 10.4; S, 7.9. Found: C, 50.9; H, 3.5; N, 10.1; S, 7.8. 2.2.3.2. Preparation of the nickel complex (NiL*2) To 30 mL of ethanol containing HL (0.01 mol) was added an ethanol solution of NiCl2.6H2O (0.05 mole), followed by NaOAc (0.01 mol) dissolved in ethanol was added, the reaction mixture was stirred at room temperature for 4 h, and filtered to give a light yellowish green solid, which was dried in air. The catalytic reduction of complex was carried out as follows. 0.01 mol of nickel complex, 5 mL hydrazine monohydrate, 70 mL ethanol and 0.03 g of 10 % Pd‐C was transferred into a 250 mL two‐necked round‐bottom flask and refluxed for 18 h. The reaction was monitored by TLC. After completion, the reaction mixture was allowed to stand for one day and then filtered. The solvent was removed by rotary evaporation under reduced pressure. The nickel complex was obtained as a green solid after one week by recrystallization from an ethanol: dichloromethane (1:2) mixture (Scheme 1). Yield: 1.42 g (83%). IR (KBr pellet, cm‐1): 3405, 3323 (NH2), 1619 (N‐H bending), 1528 (benzene ring), 1403 (C‐N stretching), 1142 (C=S). 1H NMR (400 MHz, DMSO‐d6, δ, ppm): 12.32 (2H, br s, NH), 7.65‐ 7.28 (16H, m, aromatic), 4.26 (4H, m, ‐CH2), 1.27 (6H, m, ‐CH3). MS (FAB, m/z): 801 (M+). Anal. Calcd. for C34H28N6O10S2Ni (800.75): C, 51.0; H, 3.5; N, 10.5; S, 8.0. Found: C, 51.1; H, 3.7; N, 10.5; S, 8.1. 2.3. Preparation of metal‐containing epoxy polymers A mixture of DGEBA and thiourea metal complex was dissolved in acetone at room temperature. Then the solvent was evaporated under vacuum and the blends were placed in the refrigerator before performing the DSC measurement. The mixture was cast into a metal or a silicone mould and crosslinked in a heated air oven (Scheme 2). The cured samples were then cooled slowly to room temperature to prevent cracking. The completeness of the crosslinking reaction was confirmed by the disappearance of the characteristic band of the epoxide groups in DGEBA at 912 cm−1 in the IR spectrum. CH3 CH3 O O O O Heat Metal containing cross-linked epoxy polymers n + O O CH3 N S N H O O O H3C N S N H O M H2N NH2 CH3 CH3 O OH CH3 CH3 O O O O CH3 N S N H O O O H3C N S NH OM N N O O Scheme 2 The crosslinking temperature range for CuL*2 and NiL*2 was 180‐210 °C. When CuL*2 was employed, the crosslinking temperature was 210 °C. The crosslinking time was 2 h at the mole ratios of DGEBA:metal complex (100:24) for the copper complex and 100:31 for the nickel complex. A comparative polymer was prepared by crosslinking of DGEBA with DDM. 3. Results and discussion 3.1. Synthesis and characterization of the ligand and metal complexes The synthetic pathway for the target compounds is outlined in Scheme 1. The use of a phase transfer catalyst (PTC) as a method of agitating a heterogeneous reaction system is gaining recognition [22,23]. In search of improving methods to prepare the target aroyl thiourea by reacting isothiocyanates with nucleophiles, we have found the use of tetrabutylammonium bromide (TBAB) as a PTC can afford aroyl isothiocyanates in good yield. In this communication, we have conducted our reaction using TBAB as a phase transfer catalyst to synthesize the intermediate aroylthiourea. The structure of the free ligand HL is shown in Figure 1. There are three essentially planar regions of the molecule: (i) the ring C11‐16 plus C17, C18, O2, O3, N1 (mean deviation 0.02 Å); (ii) the central thioamide moiety N1, S, C1, C2, C2, O1 (mean deviation 0.04 Å); (iii) the ring C21‐26 plus N3, O4, O5, C2 (mean deviation 0.006 Å). Interplanar angles are 38° from (i) to (ii) and 26° in the opposite sense from (ii) to (iii). Consistent with this, the torsion angles along the chain C12‐C11‐N1‐C1‐ N2‐C2‐C21‐C26 are 36.5 (about C11‐N1), –173.6, –4.3, –176.5 and –24.7°. There is an intramolecular hydrogen bond from N1‐ H1 to O1, with H…O 1.83(2) Å and N‐H…O 146(2)°. The packing diagram (Figure 2) shows that the molecules are connected by three hydrogen bonds [N2‐H02…O2 with H…O 2.55(2) Å, angle 163(1)°; C25‐H25…O2, 2.48 Å, 133°; C15‐H15…O5, 2.51 Å, 152°] to form layers parallel to (010). Curiously, the classical H bond is the longest of the three. 80 Figure 1. Structu 50% probability l Figure 2. Packin indicate hydroge lie in the directi involved in H bon Metal com the reaction o presence of so crystal structu ligands [24‐3 synthesized by and copper co carbonyl] ben catalytic redu groups were catalytic redu phenyl) thio stretching vib associated NH and 1140 cm‐1 IR spectra of compared wit The most strik at ~3200 cm agreement wit complexation for the carbo 1691 cm‐1 in t stretching of frequency upo the deproton stretching vib observed for t which are ob ligands, and unfortunately, unambiguousl The 1H N solution is giv with the struc characteristic 11.61 and 12 179.5 for C= proton signals metal ions as corresponding carbonyl grou ure of the free liga levels. g diagram of HL v n bonds. The appr on [201] and the nds are omitted for mplexes of thiou of metal salts odium acetate. ures of some m 32]. The nicke y a two‐pot rea omplexes of eth nzoate were p uction was ca converted in uction. FT‐IR oureido)carbony brations at 33 H, 1691 cm‐1 fo 1 for thioimides the complexe th the FT‐IR spe king change is ‐1 in the free th both the liga reaction. Anot nyl stretching the FT‐IR spect the carbonyl on complexatio nation induces bration [27,28 the thiocarbony served at appr shift to highe , this vibrat ly. NMR data of t ven in the expe ctural results. broad singlet f 2.56. 13C NMR =O (amide), C s of the ligand s s expected. H g to the proton p. Sa and HL in the crys viewed parallel to roximately horizon diagonal columns r clarity. urea derivatives with thiourea Arslan et al. r etal complexes el and coppe action. In the fi hyl 4‐[3‐(4‐nitro prepared and i arried out. Bot nto amino fun spectrum of yl]benzoate [ 50 and 3201 r the carbonyl s I, II and III, re s show signifi ectra of the cor that the N‐H s ligands disapp nd and comple ther important vibrations. A tra of the ligan l group, which on of the thiou delocalization 8]. The same yl stretching vib roximately 130 er frequency a tion could the ligand obt erimental sectio The 1H NMR s for protons of N showed peaks =S (thioamide hift to lower fie HL shows a p n of the N1‐H g aeed et al. / Euro stal. Ellipsoids rep the b axis. Dashed ntal chains of mol s in [100]. H atom s can be prepare a derivatives in reported a seri s of various thio r complexes irst stage, the n ophenyl)thiour in the second th nitro funct nctional group ethyl 4‐[3‐(4‐ [HL] showed cm‐1 for free and at 1534, espectively. Th cant changes w rresponding lig tretching frequ ears completel x structures an change is obse strong vibratio nd is ascribed t h shifts to h urea ligand bec n of the carb trend is us bration frequen 00 cm‐1 in the after complexa not be assi tained in DMS on and is consi pectrum show N1 and N2 at δ (p at δ (ppm) 1 e), respectively elds upon bindi eak at 11.61 group attached opean Journal of resent d lines ecules ms not ed by n the ies of ourea were nickel eido) step tional s by ‐nitro the e and 1327 e FT‐ when ands. uency ly, in nd the erved on at to the igher cause bonyl sually ncies, e free ation; igned SO‐d6 istent ws the ppm) 169.1, y. All ing to ppm, with 3.2. I func amin in D copp netw curin open amin prim the disa vibr and O‐H appe terti the func epox T nick the from can the form 0532 com cros Sche 3.3. T poly (TGA rate resin stud diffe optim corr nick epox Tg va the m tran from optim the b Two ratio and valu T weig max epox of th (T10) weig of m and calo mea of th and Chemistry 2 (1) Preparation of In a curable m ctional groups w no groups in th DGEBA. Curing per complex a work. While cu ng agent where ns the epoxy ri ne appears in t mary ‐NH2 and IR spectrum ppearance of ations due to c the appearance formation, con earance of an iary C‐N symm primary N‐H ctionality of the xy ring and the The curing me kel metal compl epoxy group o m the epoxy ring then other epo epoxy‐harden mation has occ 22, epoxy resi mplete. These r s‐linked metal eme 2. Thermal Studi Thermal prop ymers were in A) and different of 10 oC/min. n and curing a dy, a dynamic erent ratios. Fr mum ratio v responds to the kel and coppe xy/metal comp alues. It is expe maximum value sition tempera m which it can b mum ratio valu best optimum o different ways o value; the co for the maxim uable approach. The results of ght loss below ximum degradat xy polymers lie he polymers wa ), maximum de ght at 500 oC as metal‐containing was calculat rimetry. Resid asured and was hermogravimet DDM‐epoxy po (2011) 77‐82 f metal‐contain mixture of DGE which undergo he metal compl of DGEBA, EP at 215 oC pr uring, the epox eby the ‐NH2 fun ing of the epox the final netwo epoxide groups of the cure asymmetric ycloxirane at 9 e of a strong ab nfirming the op absorption ba etric stretching group were o e curing agent reaction was co echanism of D exes is propose of DGEBA by th g openings to g oxy groups. Fro ers, it can b curred and rea in and the me reactions occur l‐containing ep ies by DSC and perties of th nvestigated by tial scanning ca In order to ev agent necessar study was ca om these data values are 10 e maximum valu er complexes. plex curing agen ected that ΔH m e of Tg. Table 1 ature Tg values be confirmed th ue for copper co ratio value for s were used in ombined search mum glass tem f the TGA ana w 300 oC in a tion temperatu s between 400 as also evaluate egradation tem s listed in Table g epoxy polyme ted by mean ual weight los s found in the r ric analysis of t olymers is show ning epoxy poly EBA and meta crosslinking re lexes and the e PR 05322, with oduces a thre xy monomer r nctionality of th y monomer. He ork with the dis s from DGEBA, d material, o and symmet 12 and 830 cm bsorption at 34 pening of the e and at 1359 c g; no absorption observed show was used up omplete. DGEBA with th ed to involve a r he hydroxyl gr give secondary a om FT‐IR spect be concluded action between etal complex c r repeatedly to poxy polymers TGA Measurem he metal‐cont thermogravim alorimetery (DS valuate the opt ry for a poster arried out. DSC it can be conc 00/31 and 1 ue of ΔH, respe . The optimu nts were also e maximum value shows the enth for the differe hat 100/24 corr omplex curing a r nickel comple order to find t h for the maxi perature seem alysis showed a nitrogen atm ure (Tmax) for m and 450 oC. Th ed in term of 10 mperature (Tmax e 2. The enthalp ers ranges from ns of differen ss at 500 oC ( range of 31‐41% thiourea metal c wn in Figure 3. lymers l complex, the eactions are the epoxide groups h the nickel or ee‐dimensional eacts with the he curing agent ence, a tertiary sappearance of EPR 05322. In one notes the tric stretching m‐1, respectively 433 cm‐1 due to epoxy ring. The cm‐1 is due to n bands due to wing the ‐NH2 in opening the he copper and ring opening of roups resulting alcohols, which tral analysis of that network n DGEBA, EPR curing agent is o produce the s as shown in ments taining epoxy metric analysis SC) at a heating timum ratio of rior isothermal C was run for cluded that the 00/24, which ectively, for the um values of evaluated from corresponds to halpy and glass ent ratios used, responds to the agent, whereas, ex was 100/31. the best mixing mum enthalpy s to be a very no significant mosphere. The etal‐containing hermal stability 0% weight loss x) and residual py of formation m 500 to 525 J/g ntial scanning R500) was also %. Comparison complex‐epoxy e e s r l e t y f n e g y o e o o 2 e d f g h f k R s e n y s g f l r e h e f m o s , e , . g y y t e g y s l n g g o n y Saeed et al. / European Journal of Chemistry 2 (1) (2011) 77‐82 81 Table 1. ΔH and Tg values for different epoxy/crosslinking combinations. Complexes Ratio epoxy resin: Crosslinking agent ΔH (J/g) Tg (oC) CuL*2 100:22 522.20 140.0 100:23 556.14 142.0 100:24 565.14 142.3 100:25 539.45 141.0 100:26 540.36 140.2 NiL*2 100:29 522.20 138.0 100:30 556.14 140.0 100:31 565.14 141.0 100:32 539.45 139.0 100:33 529.25 139.0 DDM system ‐ ‐ 122.9 Table 2. Thermal stability of the cured metal containing epoxy polymers. Complexes Mole ratio of curing agent: DGEBA T10 (oC)a Tmax (oC)b R500 (%)c CuL*2 100:22 415 471 39.0 100:23 412 473 40.5 100:24 417 475 41.0 100:25 414 473 39.9 100:26 411 470 35.5 NiL*2 100:29 410 452 28.0 100:30 410 455 29.0 100:31 415 459 31.2 100:32 414 459 28.0 100:33 414 455 27.0 DDM system ‐ 380 410 18.0 a Temperature at 10% weight loss. b Maximum degradation temperature obtained from differential curves. c Residual weight at 500 oC. Figure 3. Thermogravimetry of cured polymers. 3.4. Mechanical properties of cured polymers Tensile testing was done on the metal‐containing polymers obtained from metal complex and DGEBA at different molar ratios since these polymers showed good thermal stability. Tensile testing was carried out using an Instron 4301 universal testing machine. Three specimens were cut from each polymer sheet for tensile testing. Results from samples that failed within the grips were excluded. The highest tensile strength was obtained at the mole ratio of ML*2:DGEBA (31:100), which was comparable to the epoxy‐DDM system (Table 3). Increasing the amount of ML*2 in the formulation resulted in a decrease of tensile strength, since the mixture before curing became more viscous and therefore the polymerization was difficult to control. It was found that copper‐containing polymer obtained at the mole ratio of DGEBA:CuL*2 (100:24) possessed high Tg, high tensile strength and good thermal stability which is comparable to the DGEBA‐DDM system. 3.5. Moisture absorption behaviour Moisture absorption will increase the dielectric constant of the cured polymer and have a disadvantageous effect on mechanical properties [33]. Furthermore; it will ionize the ionic impurities and thus corrode the integrated circuits. Thus, to obtain a higher performance epoxy polymer, it is necessary to decrease the moisture absorption. The moisture absorption was calculated as percent weight gain: Moisture absorption % = (W/Wo‐1) × 100% (1) where W is the weight of the sample after dipping in 100 oC boiling water for 6 h and Wo is the weight of the sample after placing in vacuum oven for 24 h. Conventionally, the moisture absorption increases as the Tg increases in the cured polymers from novolac type epoxy resin and phenol novolac [34]. However, because of the hydrophobic nature of the thiourea metal complex, the cured polymer exhibited relatively low moisture absorption of 0.851‐0.864 %, compared to that of DDM‐epoxy of 1.250 %. Table 3. Mechanical properties of epoxy polymers obtained from various mole ratios of curing agents and DGEBA. Complexes Mole ratio of curing agent: DGEBA Tensile Strength(MPa) CuL*2 100:22 65 100:23 68 100:24 71 100:25 68 100:26 66 NiL*2 100:29 63 100:30 67 100:31 69 100:32 68 100:33 68 DDM system ‐ 65 3.6. Dynamic Mechanical and Thermal Analysis (DMTA) Dynamic mechanical observations were performed to analyze the dynamic elastic modulus and the occurrence of molecular mobility transitions such as glass transition [35]. The peak temperature of tan delta was taken as the glass transition temperature. Dynamic storage modulus (E´) is the most important property to assess the load bearing capability of a polymer and composite material, which is close to the flexural modulus. The ratio of the loss modulus (E") to the storage modulus is known as a mechanical loss factor (Tan D), damping factor, or dissipation factor. This quantity is the measure of balance between the elastic phase and the viscous phase in a polymeric structure. Tan δ shows very accurately the phase transition temperature, particularly the movement of certain parts of the polymer molecules when it is linearly heated. Loss behaviour of the copper complex, nickel complex and DDM/epoxy formulation is shown in Figure 4a. The DMTA measurement indicated that Tg of the cured polymers from copper and nickel metal complexes/epoxy system are 142.3 and 141 oC, respectively, which are comparatively higher than in the DDM/epoxy system (Tg = 122.9 oC). The tan delta value of the epoxy resin cured with the reference curing agent is higher. This shows that these polymeric materials cured with metal complex curing agents are relatively flexible, which is an essential requirement for the designing and manufacturing of high pressure and high temperature sustainable composite structures. The DMTA curves of storage and loss modulus and tan δ versus temperature for the cured polymers with copper and nickel complex curing agents are shown in Figure 4a‐c. The values of both the storage modulus and loss modulus for cured polymers containing NiL*2 and CuL*2 complexes/epoxy resin, over the range of temperature investigated are substantially higher than those of the DDM‐epoxy sample. For instance, at 125 oC the storage modulus value for the copper complex‐ epoxy sample is 6080 MPa whereas its value for DDM‐epoxy sample is 57.39 MPa at the same temperature. The maximum 82 loss modulus were found to DDM‐epoxy r Figure 4c. Figure 4. Dynam delta; (b) D 4. Conclusion Two new derivative com linking agents nickel comple tensile strengt epoxy polyme system. At 12 complex‐epox epoxy” sample epoxy sample maximum we and nickel com whereas the w same tempera the cured poly be considered These pronou candidate fo composite ma values of copp be 2230 and 2 esin was foun (b mic mechanical pro Dynamic Storage M n w transition m mplexes have be s for an epoxy exes into the th, especially in er, which is com 25 oC, the valu xy” sample is e is 5060 MPa e is 57.39 MP ight loss of the mplex at 400 o weight loss for D ature which ind ymeric materia d as new proces unced favourabl r electronic terials. Sa er and nickel c 100 MPa respe d to be 80.38 (a) b) (c) operty variation wi Modulus; (c) Dynam metal containi een successfully resin. Introduc polymer matr n the case of th mparable to the e of storage m 6080 MPa an a, whereas its v a at the same e cured epoxy oC was 4% and DDM‐epoxy sys dicates the high als. These polym ssable high per le properties m encapsulation aeed et al. / Euro complex‐epoxy ectively while th 8 MPa as show ith temperature (a mic Loss Modulus. ing amino‐thio y prepared as c ction of copper rix results in e copper‐conta known epoxy‐ modulus for “co d “nickel com value for the D e temperature. resins with co d 4.5%, respect tem was 20% a h thermal stabil meric materials formance mate make it an attra applications opean Journal of resin hat of wn in a) Tan ourea cross‐ r and good aining ‐DDM opper mplex‐ DDM‐ The opper ively, at the ity of s may erials. active and Ackn W Com Dyn tech Supp C data via data Crys 1EZ, Refe [1]. [2]. [3]. [4]. [5]. [6]. [7]. [8]. [9]. [10]. [11]. [12]. [13]. [14]. [15]. [16]. [17]. [18]. [19]. [20]. [21]. [22]. [23]. [24]. [25]. [26]. [27]. [28]. [29]. [30]. [31]. [32]. [33]. [34]. [35]. Chemistry 2 (1) nowledgement We are thank mmission, Islam amic Mechanic hniques (TGA & plementary ma CCDC‐765775 c a for this paper www.ccdc.cam a_request@ccdc stallographic D , UK; fax: +44(0 erences Lin, K. F.; Wang, Lin, K. F.; Shu, W Lin, K. F.; Shu, W Anand, M.; Sriva Anand, M.; Sriva Anand, M.; Sriva Anand, M.; Sriva A30, 5435‐5446 Anand, M.; Sriva Kurnoskin, A. V. V. Inf. Bull. Khim Kurnoskin, A. V 599. Chantarasiri, N. 2031‐2038. Chantarasiri, N.; R.; Wannarong W Saeed, S.; Rahid, o1871. Kurnoskin, A. V N. P.; Cheremis processing techn Parshall, G. W.; I (1992), p. 155, 1 Saeed, S.; Rahid, 2010, 45, 1323‐ Saeed, S.; Rahid, Chem. 2010, 8(3 Saeed, S.; Rashi o2106‐o2106. Sheldrick, G. M. A Zhang, Y. M.; Pa 1663‐1670. Ozer, C. K.; Arsla 62, 266‐276. Wei, T. B.; Chen 1151. Illi, V. O. Tetrahe Arslan, H.; Külcü 819. Mansuroghu, D. 2008, 61, 3134‐ Binzet, G.; Arsla 2006, 59, 1395‐ Ugur, D.; Arslan, Emen, M. F.; Ars 2005, 79, 1615‐ Arslan, H.; Yesilk Eur. J. Chem. 201 Saeed, S.; Rashid 205. Saeed, A.; Mumt Saeed, S.; Rashid 1(3), 221‐227. Boinard, P.; Ban 2229. Ogata, M.; Kinjo, Lee, J. Y.; Jang, J.; 6121‐6126. (2011) 77‐82 t kful to Nation abad, Pakistan cal Analyzer ( DSC) free of co aterial contains the su r. These data ca m.ac.uk/data_re c.cam.ac.uk, or ata Centre, 12 0)1223‐336033 W. H. Polym. Comp W. Y.; Wey, T. L. Poly W. Y.; Wey, T. L. Poly astava, A. K. Polym. astava, A. K. Angew astava, A. K. J. Appl. astava, A. K. J. Mac 6. astava, A. K. Polyme ; Kanovitch, M. Z.; m. Prom. SEV. 1990 V. JMS Rev. Macrom ; Sutivisedsak, N.; ; Tuntulani, T.; To W. Eur. Poly. J. 200 , N.; Tahir, A.; Jone . Metal‐containing sinoff, P. N., Edito nology. New York: Ittel, S. D. In: Hom 177, 239. , N.; Jones, P. G.; Ali 1331. , N.; Jones, P. G.; Hu 3), 550‐558. d, N.; Hussain, R.; Acta Cryst. 2008, A ang, H. X.; Cao, C.; an, H.; Vanderveer n, J. C.; Wang, X. C edron Lett. 1979, 2 ü, N.; Flörke, U. Tr . S.; Arslan, H.; K ‐3146. an, H.; Külcü, N.; F ‐1406. , H.; Külcü, N. Russ. slan, H.; Külcü, N.; ‐1626. kaynak, T.; Binzet, 10, 1(1), 1‐5. d, N.; Ali, M.; Hussa taz, A.; Flörke, U. Eu d, N.; Ali, M.; Huss nks, W. M.; Pethri , N.; Kawata, T. J. Ap ; Hong, S. M.; Hwan nal Engineerin for providing DMA) and Th ost. upplementary c an be obtained equest/cif, or by contacting T Union Road, C . p. 1995, 16(4), 269 ymer 1993, 34(2), ymer 1993, 34(10) Eng. Sci. 1997, 37 w. Makromol. Chem. Polym. Sci. 1994, cromol. Sci., Pure A er 1993, 34(13), 28 Ilyin, V. M.; Gusev, , 6, 25‐29. mol. Chem. Phys. 1 Pouyuan, C. Eur. ongraung, P.; Seang 00, 36, 695‐702. s, P. G. Acta Cryst. 2 g epoxy polymers. ors. Handbook of Marcel Dekker, 19 ogeneous catalysis i, M.; Hussain, R. Eu ussain, R.; Bhatti, M ; Jones, P. G. Acta A64, 112‐122. Wei, T. A. J. Coord r, D.; Binzet, G. J. C C. Synth. Commun 20, 2431‐2435. ransition Met. Che Külcü, N.; Flörke, U Flörke, U.; Duran, . J. Coord. Chem. 20 Flörke, U.; Duran G.; Emen, F. M.; Fl ain, M. Eur. J. Chem ur. J. Chem. 2010, 1 ain, M.; Jones, P. E ick, R. A. Polymer ppl. Polym. Sci. 199 ng, S. S.; Kim, K. U. g & Scientific the facilities of ermal analysis rystallographic d free of charge by e‐mailing The Cambridge Cambridge CB2 9‐275. 277‐288. ), 2162‐2168. 7(1), 183‐187. . 1994, 219, 1‐10. 51(2), 203‐211. Appl. Chem. 1993, 860‐2864. L. L.; Bekeshko, V. 996, C36(3), 457‐ Poly. J. 2001, 37, gprasertkit‐Magee 2009, E65, o1870‐ In: Cheremisinoff, f applied polymer 996. p. 726‐742. s Wiley, New York ur. J. Med. Chem. M. H. Cent. Eur. J. Cryst. 2009, E65, d. Chem. 2008, 61, Coord. Chem. 2009, . 1996, 26, 1147‐ m. 2003, 28, 816‐ U. J. Coord. Chem. N. J. Coord. Chem. 006, 32, 669‐675. , N. Polish J. Chem. lörke, U.; Külcü, N. m. 2010, 1(3), 200‐ 1(2), 73‐75. Eur. J. Chem. 2010, r 2005, 46, 2218‐ 93, 48, 583‐587. Polymer 1998, 39, c f s c e g e 2 , . ‐ , e ‐ , r k , , , ‐ ‐ . . . . ‐ , ‐ ,