Renewable rosin fatty acid polyesters: the effect of backbone structure on thermal properties

Transcription

1 ie siene Pges Theme Issue Reserh Pper Reeive 19/11/2012 Aepte 20/12/2012 Pulishe online 29/12/2012 Keywors: ftty i/polymeri mterils/renewle resoures/lik hemistry ICE Pulishing: All rights reserve Renewle rosin ftty i polyesters: the effet of kone struture on Perry Wilon M Deprtment of Chemistry n Biohemistry, University of outh Crolin, Columi, C, UA Alexner L. Gullege B Deprtment of Chemistry n Biohemistry, University of outh Crolin, Columi, C, UA Brin C. Beniewiz PhD Deprtment of Chemistry n Biohemistry, University of outh Crolin, Columi, C, UA Chuning Tng PhD* Deprtment of Chemistry n Biohemistry, University of outh Crolin, Columi, C, UA Two novel polyesters were prepre from renewle nturl moleulr iomss stor oil erive ftty i n rosin. Highly effiient monomer syntheses inluing thiol-ene lik hemistry n onenstion polymeriztion tehniques inluing trnsesterifition n yli iene metthesis were rrie out. Their were ompre se on flexile n rigi struturl motifs on the polymer kone. Although liner polymer kone le to the formtion semirystlline polymers, polymers with fuse-ring struture in the kone were morphous. The presene of the rosin moiety in the kone lso resulte in higher glss trnsition temperture ompre with the flexile liner ounterprt. 1. Introution Fossil resoures tht re urrently use for oth energy n hemil proution re of finite vilility. The synthesis of plstis ounts for nerly % of the glol fossil fuel proution Depleting oil reserves ouple with rise in glol energy emns hs le to n inrese interest in the evelopment of energy n mterils erive from renewle resoures. A vriety of green plstis hve een erive from either unnt n low ost nturl polymers suh s ellulose, lignin n hitosn, or nturl moleulr iomss suh s vegetle oil, lti i, ftty i, terpenes n rosin. 9,11,12,19,20 Usully otine iretly from forestry n griulture prouts or y miroorgnism fermenttion, these nturl resoures re importnt euse their erive polymers oul mimi plstis mnufture from petroleum hemils. Among nturl moleulr iomss, ftty is hve shown to e prime resoure for polymer hemistry Derive from stor oil, 10-uneenoi i is one of the most importnt ftty is with flexile, liner struture n n unergo numer of syntheti retions to proue renewle monomers for polymer synthesis. 24,26,2 In ontrst, rosin tht is otine from pine resin is ville with more rigi fuse-ring struture, n n lso unergo pyrmi of retions. 20,28 36 lefin metthesis n thiolene retions re just few exmples of highly effiient retions tht tke vntge of the unsturte terminl olefins to proue vlule monomers With rnge of renewle monomers, it is importnt to unerstn how monomers with ifferent struturl hrteristis ffet the properties of their orresponing renewle polymers. Herein we report the omintion of stor oil erive ftty is n rosin to prepre novel polyesters. ur preliminry im of this stuy is to ompre rigi renewle polyesters erive from ftty is n rosin with those liner flexile polyesters solely erive from ftty is. Polyesters were nlyze y gel permetion hromtogrphy (GPC), nuler mgneti resonne (NMR), ifferentil snning lorimetry (DC) n therml grvimetri nlysis (TGA). 2. Experimentl setion 2.1 Mterils 10-Uneenoi i, 1,2-ethneithiol, triethylmine n Hovey Grus seon-genertion tlysts (igm-alrih, UA), ieti i n ryli i (Aros, UA), 10-uneen-1-ol (Alf-Aesr, UA), titnium (IV) n-utoxie (Ti(Bu) 4 ), oxlyl hlorie (Fisher ientifi, UA) n ethylene glyol (VWR, UA) were purhse from ommeril soures n use s reeive. 2,2 - Azoisisoutryonitrile (AIBN, Alrih) ws rerystllize from methnol efore use. Tetrhyrofurn (THF, Alrih), ihloromethne (DCM, Alrih) n methnol (MeH, Alrih) were refluxe with soium n istille uner nitrogen tmosphere efore use. *Corresponing uthor e-mil ress: tng4@milox.s.eu 96

2 2.2 Chrteriztion 1 H-NMR spetr were reore on Bruker ARX300 n ARX400 spetrometers. The hemil shifts were reore in ppm (δ) reltive to tetrmethylsilne. GPC ws performe t room temperture on Vrin system equippe with Vrin 390-LC multi etetor n Vrin 290 pump injetion moule. The olumns were PLgel MIXED-BL (300 5 mm, with pility to hrterize moleulr weight in the rnge of 500 to g/mol) from Polymer Lortories. HPLC-gre THF ws use s eluent t flow rte of 1 ml/min. mples were filtere over mirofilter with pore size of 0 2 μm (Nylon, Millex-HN 13 mm yringes Filters, Millipore, UA). GPC ws lirte using polystyrene s stnrs. Fourier trnsform infrre spetrometry (FTIR) ws onute on himzu 8400 FTIR spetrometer. Therml trnsitions were reore using DC on TA Q200 lorimeter in temperture rnge from 0 to 100 C t heting rte of 10 C/min uner ontinuous nitrogen flow. All the t were ollete uring the seon heting proess fter ooling t 10 C min 1 from 100 C. The verge smple mss ws out 5 mg, n the nitrogen flow rte ws 50 ml/min. TGA ws operte on TGA Q500 pprtus (TA instruments), rmping from 30 to 600 C t rte of 10 C/min, n mintine t 600 C for 5 min uner nitrogen gs t flow rte of 100 ml/min. 2.3 ynthesis of 6,6 -(ethne-1,2- iylis(sulfneiyl))ihexnoi i To 50 ml roun ottom flsk, 10-uneenoi i (20 00 g, mol), 1,2-ethneithiol (3 0 ml, mol) n AIBN (40 mg, mol) were e. While uner ontinuous flow of nitrogen, the flsk ws ple into prehete oil th set t 80 C. After 12 h the retion ws stoppe n white soli ws oserve. The finl prout ws then rerystllize from THF n white rystlline mteril (86% yiel) ws otine. Mp 115 C; 1 H-NMR (300 MHz, DM F-, δ): (s, -CH2-); (t, -CH2-); (t, -CH2C), (ro, -CH2CH2CH2-). IR (net): m 1 (H strething); m 1 (CH strething); m 1 (C= strething). 2.4 ynthesis of iester monomer imethyl 6,6 - (ethne-1,2-iylis(sulfneiyl))ihexnote A solution of 6,6 -(ethne-1,2-iylis(sulfneiyl))ihexnoi i (33 90 g, mol) in THF (200 ml) ws introue into roun ottom flsk uner nitrogen. xlyl hlorie (20 ml, mol) ws slowly e to the ove mixture t 0 C for 1 h. The mixture ws llowe to ret for 24 h t room temperture. After 24 h, the solvent n ny unrete oxlyl hlorie were remove y vuum istilltion. The prout ws issolve in THF (50 ml) n ple in roun ottom flsk uner nitrogen. A seon mixture ompose of triethylmine (25 ml, mol), methnol (15 ml, mol) n THF (300 ml) ws ple in seprte roun ottom flsk uner nitrogen. The ii solution ws slowly e to this mixture t 0 C for 1 h. The retion ws run t room temperture for 24 h. The flsk ws opene n the finl prout ws preipitte in MeH s n off white rystlline mteril (92% yiel). Mp 59 C; 1 H-NMR (300 MHz, CDCl 3, δ): (s, CH3-); (s, -CH2-); (t, -CH2-); (t, -CH2C), (ro, -CH2CH2CH2-). IR (net): m 1 (CH strething); m 1 (C= strething). 2.5 ynthesis of ftty i n rosin-se monomer Arylopimri i (APA) ws synthesize oring to the literture. 30 APA (2 5g, mol) ws mixe with THF (50 ml) n introue into roun ottom flsk uner nitrogen. xlyl hlorie (2 3 ml, mol) ws slowly e to the ove mixture t 0 C for 1 h. The mixture ws llowe to ret for 24 h t room temperture. After 24 h, the solvent n ny unrete oxlyl hlorie were remove y vuum istilltion. The prout ws issolve in THF (50 ml) n ple in roun ottom flsk uner nitrogen. A seon mixture ompose of triethylmine (2 2 ml, mol), 10-uneen-1-ol (5 5 ml, mol) n THF (50 ml) ws ple in seprte roun ottom flsk uner nitrogen. The APA solution ws slowly e to this mixture t 0 C for 1 h. The retion ws run t room temperture for 24 h. The monomer ws purifie y sili gel olumn hromtogrphy (:1 hexne: iethyl ether) to yiel olorless liqui (44% yiel). 1 H-NMR (300 MHz, CDCl 3, δ): (s, -CHCH2-); (s, -CCH-); (, CH2CH-); (, -CH2), (s, -CHC-); (s, -CHC-); (s, -CH2CH-) (ro, -CH2CH2CH2-). IR (net): m 1 (CH lkene strething); m 1 (CH strething); m 1 (C= strething) m 1 (C=C strething); m 1 (C strething). 2.6 Melt polymeriztion of iester monomer Before polymeriztion, the iester monomer ws rie t 80 C for 2 h. The iester (8 08 g, mol), ethylene glyol (1 09 g, mol) n Ti(Bu) 4 (12 0 mg, mol) were ple in three-nek roun ottom flsk. The flsk ws then equippe with istilltion rm, nitrogen outlet n stir ro. The stir ro ws tthe to n overhe mehnil stirrer n the stir rte ws mintine t 60 rpm for the urtion of the polymeriztion. A vuum pump ws onnete to the istilltion n severl nitrogen purges were onute using Firestone vlve. ne the retion vessel h een purge, temperture ws slowly inrese until the monomers melte. A vuum ws pplie n grully inrese throughout the polymeriztion until finl vuum of 25-mm Hg ws rehe. Temperture ws grully inrese throughout the retion until finl temperture of 200 C ws otine. At this point, the retion ws stoppe n the polymer solution ws llowe to slowly ool to room temperture. The polymer ws then issolve in DCM n preipitte into MeH. 1 H-NMR (300 MHz, CDCl 3, δ): (s, -CH2-); 9

3 2 2 8 (s, -CH2-); (t, -CH2-); (t, -CH2C), (ro, -CH2CH2CH2-). 2 H 6 2. ADMET polymeriztion of rosin-ftty i monomer Rosin ftty i monomer (0 2 g, mol) ws ple in roun ottom flsk n purge with nitrogen for 10 min. Hovey Grus tlyst (2 3 mg, mol) ws e to the flsk n the temperture ws rise to 80 C while uner onstnt flow of nitrogen. After 1 h, 5 ml solution of ethyl vinyl ether in THF ws e to the flsk. The finl polymer ws otine y preipitting in ol methnol. 1 H-NMR (300 MHz, CDCl 3, δ): (, -CHCH2-); (s, -CH2-); (s, -CHC-); (s, -CHC-); (ro, -CH2CH2CH2-). 3. Results n isussion 3.1 ynthesis n polymeriztion of iester monomer heme 1 shows the synthesis of stor oil erive ftty i se monomer. The ril ition of thiols to terminl lkenes is well-estlishe n effiient lik retion. 41 Using slight exess of ftty i to thiol, the intermeite ii ws otine in high yiel (86%) fter rerystlliztion. The ii ws further onverte to iester y esterifition with methnol. The monomer ws hrterize y 1 H-NMR spetrosopy, s shown in Figure 1. The ispperne of the terminl lkene peks onfirme high onversion of lkene to thioether. In ition, the emergene of the thioether peks t 2 5 n 2 ppm further inite tht the lik retion ws highly effiient. The esterifition of the ii with exess MeH proue the finl iester monomer in high yiel (92%) fter rerystlliztion. The emergene of the methyl ester pek t 3 ppm ws n inition of suessful esterifition. The next step ws to polymerize the iester monomer s shown in heme 1. Meier et l. polymerize vegetle oil se monomers y onenstion polymeriztion. 39,42,43 In the urrent work, ethylene glyol ws hosen s omonomer in orer to proue polyesters y onenstion polymeriztion. The tlyst utilize for the polymeriztion ws Ti(Bu) 4 ue to its ommeril vilility n high effiieny in polymerizing liphti polyesters. 44 The mount of tlyst ws vrie from 2 mol% to 4 mol%, while the 2 mol% proue the est results. 1 H-NMR nlysis of the finl polymers, shown in Figure 2, onfirme the suessful polymeriztion, s inite y the ispperne of the methoxy pek t 3 ppm n the pperne of the ethyl ester pek t 4 2 ppm. The numer verge moleulr weights (M n ) of the polyesters were etween g/mol, epening on the molr rtio of strting monomers (Figure 3). These polyesters were soli mterils n h olor rnging from light rown for the H 6 6 MeH 6 6 low moleulr weight to lk for the high moleulr weight. The olor of the polymers is most likely euse of the presene of the titnium se tlyst. 3.2 ynthesis n polymeriztion of rosin ftty i se monomer heme 2 shows synthesis of iene monomer erive from ftty i n rosin. APA ws synthesize n purifie oring to the literture. 30 The esterifition retion etween the ii n the unsturte ftty lohol ws onfirme y 1 H-NMR (Figure 4). The ispperne of the H pek t 3 6 ppm n the emergene of new ester pek roun 4 0 ppm s well s the vinyl protons t 4 9 n 5 8 ppm inite the suessful esterifition. Ayli iene metthesis (ADMET) polymeriztion ws use to prepre polymers. 21,22,24,25 Both Grus seon genertion n Hovey Grus seon genertion tlysts were use; however, the Hovey Grus tlyst provie etter results, inluing fst retions n higher moleulr weight. As shown in Figure 4, 1 H-NMR spetrum of the finl polymer isplye loss of the terminl lkene pek t 4 9 ppm, whih ws expete for n ADMET polymeriztion. The finl polymer ws rk rown, stiky mteril with moleulr weight tht vrie from 4000 to 9200 g/mol, epening on the monomer to tlyst rtio (Figure 3). 3.3 Therml properties of polyesters DC ws use to exmine the of polymers with liner flexile kone n polymers with ulky fuse- H H 6 6 H heme 1. ynthesis n polymeriztion of stor oil erive se monomer. H H n 98

4 H Chemil shift (ppm) 2 1 Figure 1. 1 H-NMR spetr of 10-uneenoi i n imethyl 6,6 - (ethne-1,2-iylis(sulfneiyl))ihexnote monomer. NMR, nuler mgneti resonne. 6 6 n Chemil shift (ppm) 2 1 Figure 2. 1 H-NMR spetrum of ftty i se polymer. NMR, nuler mgneti resonne. 99

5 Cstor oil se polyester Rosin/ftty i se polyester RI intensity (ritrry unit) M n = g/mol PDI = 2 32 RI intensity (ritrry unit) M n = 9200 g/mol PDI = Retention time (min) Retention time (min) Figure 3. GPC tres of ster oil erive polyesters n rosin ftty i se polyesters. GPC, gel permetion hromtogrphy. CH H CH APA ADMET n heme 2. ynthesis n polymeriztion of rosin ftty i se monomer. ring kone. As shown in Figure 5, three enothermi melting point (T m ) in the rnge of 30 0 C ws oserve for liner flexile polyesters. The presene of the T m oserve inite the polyesters erive from stor oil re semirystlline. This is onsistent with previous reports. 42,43 However, for the rosin ftty i se polyesters, DC nlysis revele no melting trnsitions. The lk of melting trnsitions for these polyesters inite tht they re morphous polymers. ur work suggeste tht the ulky fusering rosin moiety isrupts the pking of the liner lkyl group in the kone, resulting in morphous polymers. The glss trnsition tempertures (T g ) t 5 C were oserve for the rosin ftty i polyesters. Although no ler T g ws oserve for liner stor oil erive polyesters, Meier et l. reporte T g s low s 68 C for rnhe polyester with the rm hins similr to our polymers. The shrp ifferene etween these two polyesters inite tht the rottion rrier of ulky rosin moiety signifintly inreses the T g. TGA for the stor oil se polyesters isplye therml stility up to ~250 C, ove whih rpi therml egrtion ws oserve, s shown in Figure 6. TGA of the more rigi rosin ftty i se polyesters showe therml stility up to ~300 C. This my inite tht therml stility of polyesters n e inrese y inluing more rigi nturlly ourring strutures. The therml 100

6 n e f g g e f Chemil shift (ppm) 2 1 Figure 4. 1 H-NMR spetr of rosin ftty i monomer n polyester. NMR, nuler mgneti resonne Temperture C Figure 5. DC thermogrms (seon heting yle) of polyesters: (left) stor oil se polymer (M n = g/mol); (right) rosin ftty i se polymer (M n = 9200 g/mol). DC, ifferentil snning lorimetry Temperture C

7 Weight % Weight % Temperture C Temperture C Figure 6. TGA thermogrms of polyesters (left) stor oil se polymer (M n = g/mol) n (right) rosin ftty i se polymer (M n = 9200 g/mol). TGA, therml grvimetri nlysis. M n (g/mol) T m T g T 5 T 10 Cstor oil se polyesters C N/A* 249 C 264 C Rosin ftty i se polyesters 9200 N/A 5 C 303 C 331 C *Implies tht this is typilly oserve for ftty i se polyesters. T 5 : Temperture t 5% weight loss; T 10 : Temperture t 10% weight loss. Tle 1. Properties mesure for vegetle oil n stor oil se polymers. properties otine for oth stor oil n rosin ftty i se polyesters re summrize in Tle Conlusion In onlusion, we evelope metho for the onversion of nturlly ourring stor oil erive ftty is n rosin into useful monomers for the preprtion of polyesters. Thiol-ene hemistry ws use for the stor oil se monomer synthesis with high yiel. The resultnt flexile stor oil se polyesters prepre y onenstion polymeriztion re semirystlline polymers with moerte moleulr weights. A more rigi rosin ftty i se monomer ws synthesize in high yiel n susequently polymerize y ADMET tehnique. In ontrst, these polyesters re ompletely morphous with higher glss trnsition temperture n inrese therml stility. The inorportion of rigi nturl iomss with liner flexile moleules oul le to polymers with ifferent, expning potentil pplitions for ftty i erive polymers. Aknowlegements This stuy ws supporte y Deprtment of Agriulture NIFA uner the Awr n Ntionl iene Fountion uner the Awr DMR REFERENCE 1. The Tehnology Romp for Plnt/Crop-Bse Renewle Resoures 2020: Renewles Vision 2020, Exeutive teering Group, DE n UDA, U Biose Prouts: Mrket Potentil n Projetions Through 2025: ffie of the Chief Eonomist, ffie of Energy Poliy n New Uses, U Deprtment of Agriulture, Biermnn, U.; Friet, W.; Lng,.; Lühs, W.; Mhmüller, G.; Metzger, J.; Rüsh gen. Kls, M.; häfer, H.; hneier, M. New syntheses with oils n fts s renewle rw mterils for the hemil inustry. Angewnte Chemie Interntionl Eition 2000, 39, k, M. Chemil syntheses of ioegrle polymers. Progress in Polymer iene 2002, 2, Meking,. Nture or petrohemistry? Biologilly egrle mterils. Angewnte Chemie Interntionl Eition 2004, 43, Rgusks, A.; Willims, C.; Dvison, B.; Britovsek, G.; Cirney, J.; Ekert, C.; Freerik, W.; Hllett, J.; Lek, D.; Liott, C.; Mielenz, J.; Murphy, R.; Templer, R.; Tshplinski, T. The pth forwr for iofuels n iomterils. iene 2006, 311,

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9 3. Hoyle, C. E.; Bowmn, C. N. Thiol ene lik hemistry. Angewnte Chemie Interntionl Eition 2010, 49, Hérisson, P.; Chuvin, Y. Ctlyse e trnsformtion es oléfines pr les omplexes u tungstène. II. Téloméristion es oléfines yliques en présene oléfines yliques. Mkromolekulre Chemie 191, 141, Türünς,.; Firus, M.; Klein, G.; Meier, M. A. R. Ftty i erive renewle polymies vi thiol-ene itions. Green Chemistry 2012, 14, Trzskowski, J.; Quinzler, D.; Bährle, C.; Meking,. Aliphti long-hin C 20 polyesters from olefin metthesis. Mromoleulr Rpi Communition 2011, 32, Lowe, A. B. Thiol-ene lik retions n reent pplitions in polymer n mterils synthesis. Polymer Chemistry 2010, 1, Kol, N.; Meier, M. A. R. Monomers n their polymers erive from sturte ftty i methyl esters n imethyl ronte. Green Chemistry 2012, 14, Türünς,.; Meier, M. A. R. Ftty i erive monomers n relte polymers vi thiol-ene (lik) itions. Mromoleulr Rpi Communition 2010, 31, Krihelorf, H. R.; Behnken, G.; hwrz, G. Teleheli polyesters of ethne iol n ipi or sei i y mens of ismuth roxyltes s non-toxi tlysts. Polymer 2005, 46, WHAT D YU THINK? To isuss this pper, plese emil up to 500 wors to the mnging eitor t gmt@iepulishing.om Your ontriution will e forwre to the uthor(s) for reply n, if onsiere pproprite y the eitor-inhief, will e pulishe s isussion in future issue of the journl. ICE iene journls rely entirely on ontriutions sent in y professionls, emis n stuents oming from the fiel of mterils siene n engineering. Artiles shoul e within wors long (short ommunitions n opinion rtiles shoul e within 2000 wors long), with equte illustrtions n referenes. To ess our uthor guielines n how to sumit your pper, plese refer to the journl wesite t 104