Synthesis of a novel polyester building block from pentoses by tin-containing silicates

12 Pages·2016·0.82 MB·English

by  S. G. Elliot

RSC Advances
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Synthesis of a novel polyester building block from
ce. pentoses by tin-containing silicates†
n
M. Lice Citethis:RSCAdv.,2017,7,985
4:42 Aported San. Gd.EE.lTlioaat,rancinCg.*Aandersen,b S. Tolborg,ac S. Meier,c I. Sa´daba,a A. E. Daugaardb
2n
2:U
023 1n 3.0 Wereportherethedirectformationofthenewchemicalproducttrans-2,5-dihydroxy-3-pentenoicacid
d on 3/4/2Attributio umalskeinatlhgi-yfSlrnee-esBtceeortanfdraoistmiothnepsecinnattmoalseyetssht.auUnsoninldgaetrttoienpm-tcipmoenirstaeatduinricenosgnindsiitltihicoeantrsea,snagayesie1cl4da0toa–fly138st30s%.(cid:1)CTish.aeTchhpeireohvdiegudhc.etPstuisyriifiefoeldrdmstaerradensfuo-n2ud,n5ed-r
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y 2017. DoCreative Co RADceOccIee:pi1vt0ee.dd10123289tth/hcN6Noroavv2ee6mm7b0be8erdr22001166 aeinsvpteersrotdiignuactttehdecoupnsotianlyigneisnttregiflrufubonarccoktaibocoenntaiecl.gaTrnohhueypdsrreiodaceritgiavinintaydtionthgfiotfhlr–oeeminnectrocarnhpseo-mr2ai,ts5et-rddy,ihotylhedufirsnoxialylun-3sdt-rphaetyindntrgeonxthoyleicmpaoocitieedtniemtisaelwthfoaysrl
ara www.rsc.org/advances functionalisingthenewco-polymers.
4 Januunder
n 0ed Introduction indicating that it may be developed as a useful material in the
ed ocens packaging materials segment.6 Ethylene glycol itself can be
Publishcle is li Tbeheenempaerrtgiceunlcaerloyfsbuiocc-beasssfeudlcihnetmheicaalreparoodfupcotslyfersotmersmugaatersrihalass. pofrosdourbceitdolininvayriieoldusswofayuspfotori3n7s%tan1c4eobrydciraetcatllyyticfrohmydrgolguecnoasetioinn
Article. This arti Sanimdpdleiaplocolyheostlse,rbsuucilhdinagsbllaocctkicsianccidlu,dseuhcycdinroicxyaacciiddsa,nddiac1i,d3s- cyioemldbsinoaft3io5n–7w5i%th.1r5,e16trIon-aalddoilffceor-ecnattaclyastatslystuicchapapsrtouancghstuesninsagltasciind
ss propyleneglycol.Thesebuildingblockscanbeproducedfrom catalysis,sorbitolcanbedehydratedtogiveisosorbide.Thisdiol
e
Acc sugars by fermentation or chemocatalysis.1–3 While fermenta- has been successfully polymerised with different dicarboxylic
en tion has been the preferred method, research aimed at trans- acidsresultinginnewtypesofpolyestermaterials,someofwhich
p
O forming sugars into polyester building blocks using chemo- have already become commercial products.6,7 Adipic acid is
catalytic processing has proliferated during the last decade.4–9 accessiblefromglucoseintwostepsbycatalytichydrogenationof
These activities are driven partly by the prospect of chemo- glucaricacid.17Racemicmethyllactatecanbemadedirectlyfrom
catalysis offering cost advantages over fermentation, but also C6 sugars in yields up to 75% using tin-containing silicates as
bytheprospectofgainingaccesstochemicalproductsthatare catalysts.18Lacticacidisanestablishedpolyesterbuildingblock
inaccessiblebyfermentation.Polyesterbuildingblocksthatare used in the production of poly(lactic acid) which has become
accessible in few steps from sugars using chemo-catalysis widely used as a bio-based polyester material within the pack-
include 2,5-furandicarboxylic acid, ethylene glycol, adipic agingmaterialssegment.19Thenewestandleastknownmember
acid,isosorbide,lacticacidand2-hydroxy-3-butenoicacid. ofthisgroupismethylvinylglycolate(MVG),whichcanbemade
2,5-Furandicarboxylic acid is accessible via acid catalysed directly from C6 sugars in yields up to 20% as a co-product to
dehydrationoffructose,followedbyoxidation.10–12When2,5-fur- methyllactateandfromC4sugarsinyieldsupto60%.8,20–22Dueto
andicarboxylic acid is polymerised with ethylene glycol, poly- itschemicalsimilaritytolacticacid,MVGcanbeco-polymerised
ethylenefuranoateisformed.13Thispolyesterhasbeenshownto with lactic acid to produce a co-polyester having pendant vinyl
have favourable barrier properties compared to PET plastics, groupsthatallowforpostfunctionalisation.23Here,wereportthat
pentose sugars can be converted into a new activated polyester
buildingblock,trans-2,5-dihydroxy-3-pentenoicacidmethylester
aHaldorTopsøeA/S,HaldorTopsøesAll´e1,2800-Kgs.Lyngby,Denmark.E-mail:esta@
(DPM),inonestepusingtin-containingsilicatesascatalysts.We
topsoe.dk
havefurthermoreisolatedgramquantitiesofDPMandweshow
bDanish Polymer Centre, Department of Chemical and Biochemical Engineering
TechnicalUniversityofDenmark,Sølvtosplads,2800-KgsLyngby,Denmark the successful co-polymerisation of DPM and ethyl 6-hydrox-
cDepartmentofChemistry,TechnicalUniversityofDenmark,Kemitorvet,2800-Kgs. yhexanoate (E6-HH) using enzymatic polymerisation. The co-
Lyngby,Denmark polymers can be functionalised by thiolation or acetylation of
†Electronic supplementary information (ESI) available. See DOI: theolenandhydroxylmoiety,respectively.
10.1039/c6ra26708d
Thisjournalis©TheRoyalSocietyofChemistry2017 RSCAdv.,2017,7,985–996 | 985
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The catalytic conversion of sugars to lactic acid derivatives most studied tin-containing silicate is Sn-Beta, inwhich tin is
using tin-containing silicates has been reported for all simple incorporated into a framework of silica having the *BEA
monosaccharides.20,21,24,25 The rst report was related to triose topology.Sn-Betaisoenreportedasbeingasuperiorcatalyst
sugars in water and methanol and later reports described compared to other tin-containing silicates for these reac-
similarchemistryoccurringforhexoses,tetrosesandpentoses. tions.18,30,31,37,38Currently,thissupposedsuperiorityofSn-Betais
The product selectivity varies, depending on the length of the not well understood, especially under operando conditions.
sugarmolecule.Triosesformexclusivelylactateswhiletetroses Recent work aimed at elucidating the catalytic functioning of
leadtohighyieldsofMVG.Pentosesandhexosesformmultiple Sn-BetaincludesDFTcalculations,FT-IR,TPRand119Sn-NMR
e. products,dependingamongstotherfactorsonthepresenceof spectroscopy.39–44 Despite it being a crystalline material, the
nc co-solutesinthereactionmedium.Recentlywehaveshownthat preparation method oen greatly inuences the catalytic
M. Lice trans-2,5,6-trihydroxy-3-hexenoic acid methyl ester (THM) is performance. Two principally different preparation methods
4:42 Aported sfoilrimcaetedsinasyicealdtaslyosfts15a–n1d8%infrthome ahbesxeonsceesoufsiandgdteidn-ccoon-stoaliuntiensg. acorendnitoiornmsaullsyinugshedyd,rodirueocrticsaycnitdheassismiunnedraelrisihnygdarogethnetr[mSnal-
2n
023 12:n 3.0 U Twhaesidreeancttiioendapsatthhweainytewrmasedeilautceidreastepdonasnibdle3f-odretohxeygfolurmcoastoionne BBeettaa (zHeoTl)i]teanwdithsyantthinessisoubrycepo[Ssnt-tBreeatatm(PeTn)t].oTfhaedSenal-uBmetain(aHteTd)
d on 3/4/2Attributio ofufrftWuhriesalhpderreoerdicvuoactntivtaiennsu.d2e6oofurreelaxtpeldoralatciotonnoefscahnedm5o--hcaytdarloyxtiycmseutghayrl fitseypwdiicdffiaelcflyeuclcttost.noTsiinisnctsoloropafdolrianartggesehuhipgyhdteorro2pl%ohaodabirniecgtcsyrpoyifscttaainlllsy.45oeSfmn3p-–Bl5oeytmeamd(P,wTas)itiihst
wnloademmons ppraottceersnsinemg,etragkeisngbatsheedseornepthoretspriniotrorceopnosritdsercaotniosnis.tiAngproofdtuhcet mumadineatferdo.mThaepSanr-eBnettaA(lP-BTe)tcaryzsetaollitseizewihsicihnhheraistedbefernomdethale-
DoCo homologous series of a-hydroxy esters: THM from hexoses, parentmaterialandisoenintherangeof0.2–1mmindiam-
017. ative MVG from tetroses and methyl lactate from trioses. From this eter.Thematerialcontainsmanydefects,causingittobemore
y 2Cre trend, a similar C5 product can be predicted for pentoses hydrophilicthantheSn-Beta(HT).Severaldifferentmethodsof
n 04 Januared under a (prSeacctheibnelmtelyeeids1t)ee.nrTtihveiesrdspioarmondouoncfgt,ttrDraiPhnsMy-d2,r,o5is-xdytiphheeyndatracontxiovyia-c3te-apdceinadnteddneorbiiivcoactaoivcmeids- ieenmxccophrlaopnyogereda4t7isnaugncdhtiranesuivnxatpoinoutihsr-oepphrdaoespaeylludamelpcionohsaitotelidowni,zt4he6oasliottleiindassraetlat.t4be8eiionng
d oens formedfromxyloseinwater.29Here,weverifythatthisproduct, We synthesised Sn-Beta (HT) and Sn-Beta (PT) with a tin
Publishecle is lic DxyPloMse,,islyixnodseeeadnfdorrmibeodsei.nTyhieisldsnodfiunpgstoho3w3%sthfraotmtinth-ceopnetnaitnoisnegs caonndteonttheorf 1L.e2w5i–s1.a5c%idiacloBnegtsaidzeeooltihteesr.tiTnh-ceosentaminaitnergiaslislicwaeteres
Article. This arti sdielihcyadterastidoinssploafysaugraermsatorkaaffbloerdabiniltietyrmtoedciaartyalbys,ge-ucnosnasteucruattievde ttehseteadiminofthideepnrtoifdyuinctgioanctiovfitDyPpMattferronmsaxnyldosoeptiinmmiseinthgatnhoelDwPitMh
s a-keto-aldehydeswhichareconvertedintotheb,g-unsaturated yield.
s
ce a-hydroxyesterendproducts(Scheme1).
c
A
n Tin-containing silicates are solid Lewis acid materials that Experimental
e
p are capable of activating carbonyl groups in small molecules
O
andcatalysesimpletransformations.ExamplesincludeBaeyer– Catalystsynthesis
Villiger oxidation, Meerwein–Ponndorf–Verley–Oppenauer Sn-,Zr-,Ti-andAl-Beta(Si/M¼150)viahydrothermalsynthesis
redox reactions, monosaccharide isomerisation, aldol- and were prepared by modifying the route described by Valencia
retro-aldolreactionsandcertaindehydrationreactions.30–36The etal.45,49InatypicalSn-Beta(Si/Sn¼150)synthesisprocedure,
30.6 g of tetraethyl orthosilicate (Aldrich, 98%) was added to
33.1 g of tetraethylammonium hydroxide (Sigma-Aldrich, 35%
inwater)undercarefulstirring((cid:3)60min),andtin(IV)chloride
pentahydrate(Aldrich,98%)dissolvedin2.0mLofdemineral-
isedwaterwasaddeddropwise.Themixturewasthenletostir
for several hours. Finally, 3.1 g hydrouoric acid (Fluka, 47–
51%) in 1.6 g of demineralised water was added. All samples
werethenhomogenisedandtransferredtoaTeon®-container
placed in a stainless steel autoclave. The samples were then
incubated at 140 (cid:1)C for 14 days. The solid was recovered by
ltration and washed with demineralised water, followed by
dryingovernightat80(cid:1)Cinair.Theorganictemplatecontained
withinthematerialwasremovedbyheatingthesampleat2(cid:1)C
min(cid:4)1to550(cid:1)Cinstaticairandmaintainingthistemperature
for6h.
Zr-Beta(Si/Zr¼150)andAl-Beta(Si/Al¼150)zeoliteswere
Scheme1 Formationofhomologousa-hydroxyesterproductsfrom
C –C sugars catalysed by tin-containing silicates. The reaction is preparedbytheaforementionedprocedure,exchangingthetin
3 6
applicablebothtoaldosesandketoses. sourcewithzirconylchlorideoctahydrate(Sigma-Aldrich,98%)
986 | RSCAdv.,2017,7,985–996 Thisjournalis©TheRoyalSocietyofChemistry2017
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Paper RSCAdvances
or aluminium chloride hexahydrate (Fluka, $99%), respec- in60gofdemineralisedwater.Thesolutionwasthenstirredfor
tively. Furthermore, Al-Beta was incubated for only 5 days at 2 h. To the synthesis mixture 18.0 g of tetraethyl orthosilicate
140 (cid:1)C. For Ti-Beta (Si/Ti ¼ 150), tetraethyl orthotitanate (98%,Aldrich) wasaddedfollowed bytin(IV)chloridepentahy-
(Aldrich)wasrstdissolvedinamixtureofhydrogenperoxide drate(Aldrich,98%)dissolvedin2.0gofdemineralisedwater.
and water and then used in a similar fashion as the metal Themixturewasthenstirredfor24hat40(cid:1)Candthentrans-
source.SnO -Beta(Si/Sn¼200)wassynthesisedusingtinoxide ferred to a Teon®-lined autoclave and heated to 100 (cid:1)C for
2
(Aldrich, <100 nm) as the tin source. Purely siliceous Beta (Si- 24h.Thesolidwasrecoveredbyltration,washedwithample
Beta)waspreparedbyomittingtheadditionofametalsource. waterandthencalcinedat550(cid:1)Cfor6hours.
e. Sn-Beta (Si/Sn ¼ 125) via post-treatment was prepared
nc according to a modication of the procedure described by Catalystcharacterisation
4:42 AM. ported Lice Hu12ma.m5in,maNtoeHnd4d+b-fyeotrtmrael).a4t7wmCaesonmtcamwlcietirhncei1ad0l azgteoo5lf5it0ceo(cid:1)nBCceetanfot(rrZae6teodlhysntai,ntrSdiic/Adaelcai¼dl- sCoartpatliyosnt acnhdarIaCctPe-rOisEaSt.ioPnowwdaesrXp-erarfyodrmifferdactbioynX(RXDRD, )BpEaTt,terNn2s-
2n of the prepared and calcined samples were measured on an
023 12:n 3.0 U (aStig8m0a(cid:1)-CA.ldTrihceh,s$ol6id5%w)apserregcroavmeroefdzeboyliteltBraettiaopno,wwdaesrhfeodr1a2nhd aXr'Peaertanddiffpraocrteomvoeltuemr (ePhmileiapssu)ruesminegntCsuw-Kearerapderiafotiromne.dSuursfaincge
Downloaded on 3/4/2Commons Attributio A5dircmaarlgdtlipicerooidrinfceoheagtfhdtn,e1a19(2t1s58e5o05%d.l0i(cid:1))FdCb(cid:1)o.wyCrAfaoitsfrnhoecd1irrsi2ipts6hpisheeouhnalr)ivt.pnmeodTwdpsherceieeta,nngltdcneiwiensanaas(teItliIeudom)rmncae(hgpit5nhlar.o7aoiorn5tcdie.deodmselsoLz,(ge0)tyoh.1alewni2ts8dieathgmwa,dapaSdslieeSgtdihmw/Seatannos- mwtsmauaiuernsnflaettcidcspae)lou.cisuaTnirlnhtaegeNtaet2tdhaoaentbdadBysloEtsrpThupoemrtrifetoae-ncptseh/lidoozateedrsmeoaaanrenptd(ahtSiltoBoyhsEdneeT)roumnsoi(icQfnarngutohapAtenhoutrestaeoacAsvmhuoorprtlouoblmesmasoeuerwbt(oIV3anmsmssatioocrtrubioc)---
017. ative Sn-MFI (Si/Sn ¼ 100) was prepared following a procedure wS3araen.dThTeabchlearSa1c.t†erTihsaetieolnemreesnutlatlscaoremsphooswitnioinnothfethEeSIp,rFeipga.rSe2d,
y 2Cre described by Mal et al.50 In a typical synthesis, tin(IV) chloride materials was measured using inductively coupled plasma-
n 04 Januared under a paAlelidnsretiadchhwy)a.dtTreahrtieasn(mAdliadxdrtuidcrehed,wt9oa8s1%5t)h.6ewgnaossftditreirstersdaoelfvtoherdyl3io0nrmt5hiongs.iolAifcadeteremw(9ain8rd%esr-,, amtoomdeilcOepmtiimssaio3n00s0p(eVcatrrioasncoVpiysta()I.CP-OES) on a PerkinElmer
d oens 13.4goftetrapropylammoniumhydroxide(40%,AppliChem)in Catalytictests
ec
s Article. Publish This article is li 11satrud63ab0.dn4ses(cid:1)egdfCqe.orufTfroeedhrndeet2mlsytdooinlaaueynatsriaoaTulndiensddewiodetanirswo®sntat-hataleieltnrinc6ew0dlceaosganausdodttifiodtricerdolideannmvasge.nifTndoahernsret2dai0rlsirossheyledi.nddTtfhohwwreeaas1stgiesherrele,dcawwonaaavdsst- I>1(Bn98i90o.at8ma%ggte)y,)op.3fiNc6ca0oaltmsapelgyexscp(ti2eaw.rl4iemprmreeemncatado,udl)te4ixod.y0nltososgweae(m5rSeiemgttmahLkaaegn-nlAoallstdosr(iamScvhiiogc,mird>oa9wm-9Aa%olvdie)srtaivucnihradel,
ces eredbyltration,washedwithamplewateranddriedovernight or oxygen. The reaction vessel was heated under stirring (600
n Ac at80(cid:1)Cfollowedbycalcination(2(cid:1)Cmin(cid:4)1,550(cid:1)C,6hdwell rpm)for2hinaBiotageInitiator+microwavesynthesiser.Aer
pe time)toobtainthenishedmaterial. cooling, samples were retrieved and analysed. In some experi-
O
Sn-MCM-41 (Si/Sn ¼ 200) was prepared according to the ments, an alkali salt co-solute was added by replacing the
appropriate portion of the methanol solvent with a 1.0 mM
methoddescribedbyLietal.51Inatypicalsynthesis,26.4gof
tetraethylammonium silicate (Aldrich, 15–20 wt% in water, standard solution of potassium carbonate (Sigma-Aldrich,
$99.99%) was slowly added to a solution of 13.0 g of hex- $99.0%)inmethanoltoobtainthedesiredconcentration.
adecyltrimethylammonium bromide (Sigma, $99.0%) dis-
Productanalysisforcatalysttesting
solvedin38.0gofwaterandallowedtostirfor1h.Atthispoint,
tin(IV) chloride pentahydrate (Aldrich, 98%) and hydrochloric Analysisofthereactionmixtureswasperformedusingacombi-
acid(Sigma-Aldrich,min.37%)in2.1gofwaterwasaddeddrop nation of GC-FID, HPLC and 1D and 2D NMR. A Bruker
wisetothesolutionandallowedtostirfor1.5h.Tothissolu- (F¨allanden,Switzerland)AvanceII800MHzspectrometerequip-
tion,12.2goftetraethylorthosilicate(98%,Aldrich)wasadded ped with a TCI Z-gradient CryoProbe and an 18.7 T magnet
and stirred for 3 h. The sample was then transferred to a Tef- (Oxford Magnet Technology, Oxford, U.K.) was used for the
lon®-linedcontainerinastainlesssteelautoclaveandplacedin identication of unknown products. A 7890A Series GC system
apre-heatedovenat140(cid:1)Cfor15h.Thesolidwasrecoveredby (AgilentTechnologies)with aPhenomenex ZebronZB-5column
ltration, washed with ample water and dried overnight at and a FID detector was used for the quantication of glyco-
80 (cid:1)C. The material was nalised by calcination, heating the laldehydedimethylacetal(GA-DMA),methyllactate(ML),methyl
sampleto550(cid:1)Cat2(cid:1)Cmin(cid:4)1instaticairandmaintainingthis vinyl glycolate (MVG), methyl 4-methoxy-2-hydroxybutanoate
temperaturefor6h. (MMHB) and 2,5-dihydroxy-3-pentenoic acid methyl ester
Sn-SBA-15(Si/Sn¼200)waspreparedfollowingthesynthesis (DPM).With theexception ofDPM, commercial standardswere
route described by Ramaswamy et al.52 In a typical synthesis, used for the calibration. DPM was synthesised and puried as
1.0 g of hydrochloric acid (37 wt%, Fluka) in 140 g of demin- describedunder“Isolationoftrans-2,5-dihydroxy-3-pentenoicacid
eralisedwaterwasaddedtoasolutionof8.0gofPluronic®P- methylester(DPM)”andthepurematerialwasusedincalibration
123 (PEG–PPG–PEG polymer, Aldrich, M ¼ (cid:3)5800 g mol(cid:4)1) standards.
w
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RSCAdvances Paper
AnAgilent1200seriesHPLCequippedwithanAminexHPX- a crude brown residue. trans-2,5-Dihydroxy-3-pentenoic acid
87H (BioRad) column (0.004 M H SO , 0.6 mL min(cid:4)1, 65 (cid:1)C) methylesterwasisolatedfromthecrudebydrycolumnvacuum
2 4
using a refractive index and diode array detector was used for chromatography using ethyl acetate/heptane as the eluent,
detectionandquanticationoffurfural,furfuraldimethylacetal typically yielding 2.6 g trans-2,5-dihydroxy-3-pentenoic acid
andotheranalogues.Theaqueousacidiceluenthydrolysesall methyl ester of >94% purity (GC-MS, Fig. S4,† 1H-NMR,
furfural analogues back to furfural, resulting in a collective Fig.S5†).
quanticationofallfuranics(FUR). trans-2,5-Dihydroxy-3-pentenoic acidmethyl ester.1HNMR
One-dimensional 1H NMR spectra were used to quantify 3- (400 MHz, CD OD) d 5.89(dtd, J¼ 15.5, 5.0, 1.4Hz, 1H), 5.72
3
e. deoxy-g-pentonolactones (DPL), 2,4,5-trihydroxy-3-pentanoic (ddt,J¼15.5,5.7,1.7Hz,1H),4.76(s,4H),4.58(ddt,J¼5.7,1.4,
nc acid methyl ester (TPM) and 2,5-dihydroxy-4-methoxy- 1.4Hz,1H),3.99(ddd,J¼5.0,1.6,1.4Hz,2H),3.63(s,3H),3.21
AM. d Lice pentanoic acid methyl ester (DMPM) using the CH3 signal at (p, J ¼ 3.3, 1.6 Hz, 1H). 13C NMR (101 MHz, CD3OD) d 173.2,
4:42 porte 1o.n39repapcmtiofnrommixMtuLreassainremfeertehnacneo.lSapecetrrarewmeorevarlecoofrcdaetdaldysirteacntldy 132.2,126.8,70.9,61.3,51.2.
2n
023 12:n 3.0 U uSppeocntraaddwietiroenroefco1r0d%ed(vo/vn)Da4-BmruetkhearnAolva(CnacembIIrIidsgpeecIstrootompeetse)r. Etrnaznysm-2a,5ti-cdiphoyldyrmoxeyri-3sa-ptieonnteonfoeitchaycli6d-hmydetrhoyxlyhesetxearntooatpeoalyn(Ed6-
2o
d on 3/4/Attributi epfrqreouqtiuopenpnecdrieewssoitonhfana3c.e39s6.4pwTpemrme,ag4sn.u7ep8tp6raenpsdpsmead uBbsBiyOngpprtrehosbeaett.uwrMoateiltoohngaincaoatll HFoHr-ctoh-DePcMo)-polymerisation, 0.40 g (3 mmol) of trans-2,5-
wnloademmons scahmanpnlienlsgo8f0t9h6ecsopmecptlreoxmdeattear.pSopinectstrdauwreinregraencoarcdqeudisaitti3o0n(cid:1)tCimbey detihhyyldr6o-hxyy-d3r-opxeynhteenxaonicoaatceid(Simgmetah-yAlldersitcehr,, 29.70%g) a(1n3dm0.m24olg) ooff
DoCo of 1.02 seconds, employing an inter-scan delay of 10 seconds N435 (Novozymes) was added to a Schlenk tube. The mixture
017. ative andaccumulating16scans. 2w0a0smplbacaerdprinesasnuroeilfobra2thhu,nbdefeorrmebageninegticresdtuircreindgtoat56m0(cid:1)bCarafnodr
ed on 04 January 2censed under a Cre astDipfPsyeMpTcmewtrcoaaetr-ttdhahilnyamlawdtegiudnlarytsachi1loo3sonC1if3adCle2cs12aiHrs(rpoM–ipe1toG3mrCp)oitcHaffonsSadseQbatCumreonpssfdipldae1enu0ctact1hrelea.psawupTnbmheosreemtra1auenHtsredie–cd1re3erCmteloagptiHqiolvouSneyaQentoCdof- a(Td$Snrhi9ooge9fmtu%hrael)a-tr.AnrRal7dte0aerfnrihcidwgh.ae,psTr$arheete9icvoi9apnp.p9irotao%artdta)e5utdeac(cid:1)dntCidnwifniaomcsrvoam3lddc0ieusdmosm,ioaielnrtvteeehf-lddyaonillsioonsllwtoelte(rveSdeetidrdgbamhybinyyad-lsAtrtueorldatcfruttraiiiroochahnnyn-,,.
Publishcle is li xtiyvliotsye.Saanmdpiltessmweertehpylregplyacroesdidbeyscoantdheinghsinregs1olmutLioonftahnedlsteenresdi- y6i2e%ldeydiepldo)l.y(E6-HH-co-DPM)asanorangestickysolid(1.088g,
ss Article. This arti rrseepadecicsttisrooanlvwimenrgiextrutehrceeorudrseeisdnugoltnaanaStpBerreuedskiVedarucAevvaaincnuceuDmII4I-mcHoeDnthcseapnnetocrlat.rtooTmrhaeetnseder 52.8668P5oH,ly1zm7,20e1.r1.6I1HH–)-,pN5oM.l7y9R(E(6d(3-dH0,0HJ¼M-coH1-5Dz.,4P8CM,D)4.C.5Fl83T)-HIdRz,5(0.c9.m177(cid:4)(Hd1))t,,34J4.96¼62,(1d25,9.J4493¼,,
en Acce esaqmuipplpinedgw10it2h4aan9.d41T2m8caogmneptlaexnddaataBrpuokienrtsCirnyotPhreob1HeParnoddi1g3yC, 43..3979(Ht,zJ,¼0.168.6H4)H, 4z.,514.6(4dH, J),¼3.558.5(9t,HJ¼z,80..2236HH)z,,40..1178H(m),,20.2.347(Ht,)J,
p spectral dimensions foracquisitiontimes of292 and 58milli-
O ¼7.47Hz,2.00H),1.58(m,4.13H),1.31(m,2.11H),1.19(t,J¼
seconds, respectively. Spectra were processed with extensive
7.19Hz,0.06H).13C-NMR(75MHz,CDCl )d173.5,172.8,130.0,
zerollinginalldimensionsandintegratedinTopspin3.5. 3
126.7,70.4,67.9,65.9,64.1,34.0,28.3,25.4,24.5.
InsampleswhereDPMorMLwerepresentinlessthan10%,
estimations of DPL, TPM, DMPM, MG and residual substrate
were quantied by a combination of an Agilent 1200 series Triuoroaceticanhydrideestericationofpoly(E6-HH-co-
DPM)
HPLCequippedwithaCarbohydrate(Zorbax)column(60wt%
acetonitrile/water, 0.5 mL min(cid:4)1, 30 (cid:1)C) and two-dimensional In a typical esterication, 63 mgpoly(E6-HH-co-DPM) wasdis-
1H–13CHSQCemployingstandardadditionofxylose.50mLof solved in 0.7 mL D-chloroform (Sigma-Aldrich, 99.8%) and
a 100 mM stock solution in D -methanol was added to the transferredtoaNMRtubeand4dropsoftriuoroaceticanhy-
4
sample and spectra were re-recorded by the aforementioned dride (Sigma-Aldrich, >99%) were added. The mixture was
two-dimensional1H–13CHSQCprocedure. precipitated in cold methanol (Sigma-Aldrich, $99%) and
refrigeratedat5(cid:1)Cfor30min.Themixturewastransferredto
a syringe and ltered using a Teon® syringe lter. The lter
Isolationoftrans-2,5-dihydroxy-3-pentenoicacidmethylester
waswashedwithchloroformandtheliquidwascollected.The
Up-scaled reactions were performed in a 1 liter autoclave solvent was evaporated under ambient conditions and the
(Autoclave Engineers) with mechanical stirring. The autoclave product was dried overnight in a vacuum oven at 30 mbar at
wasloadedwith300gofmethanol,18gofxyloseand4.5gof room temperature, yielding the functionalised polyester (poly-
Sn-Beta(PT)andheatedunderstirringto160(cid:1)Cfor16h.The mer II). Coupling yield was determined by 1H-NMR, based on
autoclavewasallowedtocool,thecatalystwasthenremovedby thechangeinchemicalshioftheprotonsvicinaltothealcohol
ltrationandthereactionmixturewasdriedovernightwith50g groupofDPM.
molecular sieves. The molecular sieves were ltered from the Polymer II. FT-IR (cm(cid:4)1) 3500, 2960, 2864, 1723. 1H-NMR
productmixtureandmethanolwasremovedinvacuoaffording (300 MHz, CDCl ) d 6.11 (dt, J ¼ 15.68, 5.39 Hz, 0.19H), 5.92
3
988 | RSCAdv.,2017,7,985–996 Thisjournalis©TheRoyalSocietyofChemistry2017
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Paper RSCAdvances
(dd,J¼15.61,6.39Hz,0.18H),5.63(d,J¼6.37Hz,0.16H),4.67 evaporate in a closed vessel at room temperature to ensure
(d,J¼5.23Hz,0.28H),4.21(m,0.38H),4.10(t,J¼6.56,1.70H), a slow evaporation of the solvent. The resulting lm was hot-
3.91(t,J¼6.63,0.11H),2.37(t,J¼7.49,2.00H),1.66(m,4.21H), pressedat70(cid:1)Cfor10mintoensureauniform,atlm.
1.39 (m, 2.32H), 1.26 (m, 0.14H). 13C-NMR (75 MHz, CDCl )
3
d 175.8, 175.7, 166.6, 158.9, 149.7 (q), 131.5, 123.2, 113.7 (q), Watercontactanglemeasurements
74.8,68.01,67.9,66.6,65.1,34.3,28.2,25.5,24.6.
A water droplet of 15 mL was placed on the surface with the
needle inside the drop, and the drop was expanded and con-
Thiol–enefunctionalisationofpoly(E6-HH-co-DPM) tractedonthesurfaceofthepolymerlmatarateof2.0mLs(cid:4)1.
ce. For the thiol–ene functionalisation, 15 mg poly(E6-HH-co- All water contact angle measurements were determined as an
AM. d Licen aDnPdM2),.94mdgro(p0s.0o2fmmmerocla)p2to,2a-cdeimticetahcoidxy(-2S-ipgmhean-Aylladcreictohp,h$e9n8o%ne) daviffereargeentopfosthitrioeensmoneatshuerepmoleynmtserosfurtfharceee. different drops at
4:42 porte (Sigma-Aldrich, 99%) was dissolved in 0.6 mL D-chloroform
2:2Un (Sigma-Aldrich,99.8%).ThemixturewastransferredtoaNMR Results and discussion
023 1n 3.0 tyuiebledinangdthirerathdiioatlefdunwcittihonUaVlisleidghpto(llye¼ste3r6(5ponlmym)efrorII3Ic0).mTihne, Identicationoftrans-2,5-dihydroxy-3-pentenoicacidmethyl
2o
3/4/buti conversion of the double bond was determined by 1H-NMR esterandco-products
d on Attri from the signals at 5.97 and 5.79 ppm corresponding to the Thorough analyses of product mixtures from reactions using
7. Downloadeve Commons sfi3nuu4cnb6rc1settaiicotsumnetdai(cid:4)ol1ipns.raePotsiofoelnntyhmceeewdorasofsucIbIaIfrlaueb,rotbbhxoy,enlriddc caainocninddpoferlumynw(eEced6tri-eoHnbpHyarl-eictpody-aeDirtneePdcMFtiTb)o.-ynITRthhoaiestf xitanoydlidtothiisateeilolpyanrspeaevltirhpofeourorssmdluyuebrcdesttpsbroaywrtGteeerCdae-nMrpedrSter.SosHne-an-eBlrtdee.9ot,i2alt5a,w2(n6HadAsTndf)oaeaulhysnysddtishrtaehotfaicotatnhitnaeplayrpdsortddouiwdtciueotrcsnet,
ary 201a Creati awfiothrem1-emnetirocnapedtohpreoxcaendeu,rme,eerxccahpatonegtihnagntohl,e2d-eertihvyalthiseixnagneatgheinotl cmoinxturrmeseduthsiengpre2seDnceheotferDoPnMuclaelaorngs(1iHde–133-Cd)eoxsyp-egc-tpreonstcoonpoy-,
4 Januunder oScrhtehmioep3h.enol respectively, and coupling yields are given in l(aTcPtMon)easnd(D2,P5L-d),ih2y,d4r,5o-xtyr-i4h-ymderothxyopxey-npteanntoaincoiaccaidcidmmeeththyylleesstteerr
ed on 0censed Polymercharacterisation (pDoMrtePdM)f.orThtheesecopnrovderuscitosnaoref htheuxossehsomtoolTogHuMesaonfdth3o-dseeoxrey--
Article. PublishThis article is li NStseppMmeeccRptterrcaorhaswatpureiarnrece-tBeburruasisisknaeetgdriooCnAnDCoChfolp33mo0lao0ysmnuseMcorlslHevawezrnatas.snppdAeescrhsftoriegortnmemrmeoednteenurotcnsleaaaotrf7crTNooeMrosrmleRa- gaNfonlMuraclRoythsnsieospleapcccrottornoocvneseedcrsous.piroFeynowtlolaoosqfwueipnsatengantbtithfloyiissshtehsienedi(,tdSiciacffohlmeewrmbeonirenkti,nr2aeg).acGcoTtCimho,inpsHrpePahrLnoeCadnluasycinsvtidess
ess lation spectroscopy (1H–1H COSY and 1H–13C HSQC spectra). procedure was used for comparing different catalysts, condi-
c
Ac Glass transition temperatures (T ) and melting temperatures tionsandco-solutesandforoptimisingtheyieldofDPM.
n g
e (T )wereobtainedusingaDiscoveryDSCfromTAInstruments.
p m
O
Thermalanalyseswereperformedataheatingandcoolingrate Reactionpathwaysforpentoses
of10(cid:1)Cmin(cid:4)1from(cid:4)100to150(cid:1)C.T andT weremeasured
g m In the presence of Lewis acidic silicates, pentose sugars react
attheinectionpointandatthepeaktemperature,respectively.
along three primary reaction pathways leading to a variety of
Fouriertransforminfrared(FT-IR)spectroscopywasconducted
products (Scheme 2). These are grouped accordingly: (1)
onanattenuatedtotalreection(ATR)-FT-IR(ThermoiS50with
formation of methyl glycosides (MG) catalysed by Brønsted
abuilt-indiamondATRwitharesolutionof4cm(cid:4)1)inorderto
acidsintheabsenceofalkalico-solutes;(2)retro-aldolreactions
conrm the presence of functional groups. Molecular weight leadingtoC –C a-hydroxyestersandglycolaldehydedimethy-
3 4
and polydispersities were determined using Size Exclusion
lacetal which are catalysed by Lewis acidic silicates in the
Chromatography(SEC).SECwasperformedinTHFonaVisco-
presence of alkali co-solutes; (3) dehydration via 3-deoxy-
tek GPCmax autosampler equipped with a Viscotek TriSEC
xylosone (3-DX) to give DPM, DPL, TPM, DMPM and furfural
model302tripledetectorarray(RIdetector,viscometerdetector
derivatives(FandF-DMA),catalysedbytin-containingsilicates
and light scattering detectors measuring at 90(cid:1) and 7(cid:1)) and
intheabsenceofalkalico-solutes.
aKnauerK-2501UVdetectorontwoPolymerLaboratoriesPLgel
Thecentralintermediate3-DXcanbetransformedintoDPL
MIXED-Dcolumns.Thesampleswererunataowrateof1mL via a 1,2-hydrideshiofits intramolecularhemiacetal. Xylose
min(cid:4)1 at 35 (cid:1)C and molecular weights were determined from give rise to two different DPL diastereomers that can be dis-
aPScalibration.
cernedbyNMRspectroscopy.Wespeculatethesetobe3-deoxy-
g-D-xylonolactone and 3-deoxy-g-D-lyxonolactone, formed by
Filmcasting racemisation on C in the 1,2-hydride shi step. In an analo-
2
Inatypicalprocedure0.27gof3-polycaprolactone(Perstop,M gous open chain form, 3-DX can react with methanol to form
n
¼ 50000 g mol(cid:4)1) and 0.030 g of poly(E6-HH-co-DPM) was ahemiacetalwhichcanundergoa1,2-hydrideshileadingto
dissolved in 6 mL of tetrahydrofuran. The mixture was trans- TPM. From 3-DX a subsequent dehydration can also occur,
ferred to a Teon® mold and the solvent was allowed to leadingtocis/trans-3,4-dideoxyxylos-3-enone(cis/trans-3,4-DXE).
Thisjournalis©TheRoyalSocietyofChemistry2017 RSCAdv.,2017,7,985–996 | 989
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e.
c
n
M. Lice
Ad
4:42 porte
2n
2:U
023 1n 3.0
2o
3/4/buti
d on Attri
wnloademmons
DoCo
7. ve
01ati
y 2Cre Scheme2 Majorpathways,intermediatesandproductsintheconversionofpentosesbySn-Beta.Compoundabbreviations:3-deoxyxylosone
ara (3-DX), cis-3,4-dideoxyxylos-3-enone (cis-3,4-DXE), trans-3,4-dideoxyxylos-3-enone (trans-3,4-DXE), 2,5-dihydroxy-4-methoxy-pentanoic
4 Januunder dacimidetmhyeltahcyeltaelst(eFr-D(DMMAP),Mg),ly3co-dlaeldoexyhpydenetodnimoleatchtyolneac(eDtaPlL)(,GtAra-nDsM-2A,)5,-mdiheythdyrloxgyly-c3o-psiednetsen(MoiGc),acmidetmhyelthlayclteasteter(M(DL)P,Mm),eftuhryflur4a-lm(Fe)t,hfouxryfu-r2a-l
n 0ed hydroxybutanoate(MMHB),methylvinylglycolate,(MVG)and2,4,5-trihydroxy-3-pentanoicacidmethylester(TPM).
d oens
ec
Publishcle is li The trans-3,4-DXE isomer can undergo reactive esterication products(3:5),whileSn-Beta(PT)resultedinalowerDPMyield
Article. This arti fleuardfuinragl tvoiaDaPMthiwrdhidleehcyisd-r3a,4ti-oDnXEsteips.aInltikereelystipnrgelcyu,r3s-odreofoxyr odfiff2e3r%enc(Teaibslelik1e,leynattrtyri2b)uatanbdleshtoowthede baalloawnecreroaftiBor(ø1n:st2e)d.Tahnids
ss xylosonehaspreviouslybeenreportedasanintermediateinthe Lewis acidity in the two materials. Sn-Beta (PT) contains more
e
c
Ac formationoffurfuralfrompentoses.27,28Inthecurrentstudy,we defects due to being synthesised by a post treatment method,
en oen nd that the yields of furfural derivatives and DPM are likely resulting in a more Brønsted acidic character.39,53 Addi-
p
O correlated, supporting that this is indeed an important inter- tionally, the different preparation methods may lead to
mediateintheformationoffurfuralspeciesusingLewisacidic a different incorporation of tin into the *BEA siliceous
catalysts. This interpretation is furthermore supported by the matrix.39,53,54AnindicationofthedifferentaciditybalanceforSn-
use of the Brønsted acidic Al-Beta as the catalyst, resulting in Beta(HT)andSn-Beta(PT)isseenwhencomparingtheiryields
theformationofonlytraceamountsoffurfuralproducts(1%) ofMGbeing6%and23%,respectively.Ofallthetin-containing
and no detectable DPM. In contrast, Sn-Beta forms 11–17% silicates tested, the small pore Sn-MFI material displays the
furfural products and 23–33% DPM under comparable condi- lowest selectivity towards DPM and dehydration products. The
tions.AsmallamountofDMPMwasalsoobservedasaproduct. main products formed aer two hours are methyl glycosides,
This is likely formed via Michael addition of methanol to 3,4- indicatingthatthepentosesarenotconvertedpreferentiallyvia
DXE,priortoa1,2-hydrideshi,therebybeinganalogoustothe Lewisacidcatalysedpathwaysbutinsteadhavetimetoundergo
formationofMMHBfromtetroses.20,21 acetalisationreactionswhicharetypicallycatalysedbyBrønsted
acids.55Othertin-containingsilicatessuchastheorderedmes-
Testingofdifferentcatalysts oporous materials Sn-SBA-15 and Sn-MCM-41 were also active
forthe formation ofDPM, resultingin yields of12% and 16%
Signicant yields of DPM (10–33%) were obtained only for
yield,respectively.Thesecatalystsallbelongtothegroupoftin-
catalysts containing tin incorporated into a siliceous matrix
containingsilicatesandareallabletoformDPMinsignicant
(Table 1, entries 1–5). A comparison of the yields of products
yields.Incontrast,materialshavingtinoutsideofthesiliceous
obtainedfromxyloseusingthedifferenttin-containingsilicates
matrix,suchasdispersedSnO nanoparticlesonSi-Beta,didnot
is shown in Fig. 1. The products are grouped into the three 2
catalysetheformationofDPMunderthesereactionconditions
categoriesmentionedabove,accordingtotheprimaryreaction
(Table 1, entry 6). This nding highlights the importance of
pathwaysresponsiblefortheirformation.ThehighestDPMyield
successfully incorporating tin in the silicate matrix to obtain
of33%wasobtainedusingSn-Beta(HT)(Table1,entry1)which
catalyticallyactiveheterogeneouscatalysts.
also resulted in the highest ratio of DPM to total dehydration
990 | RSCAdv.,2017,7,985–996 Thisjournalis©TheRoyalSocietyofChemistry2017
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Paper RSCAdvances
Table1 Conversionofxyloseusingavarietyofcatalystsa
Retro-aldol Dehydration
Carbon
XYL, MG, GA-DMA, ML, MVG, MMHB, DPL, TPM/DMPMb, FURc, DPM, Total, balance,
Entry Catalyst % % % % % % Total,% % % % % % %
1 Sn-Beta(HT) n.d. 4 2 14 2 <1 19 10 13 11 33(3) 68 90(4)
2 Sn-Beta(PT) n.d. 23 3 11 <1 <1 15 6 9 17 23(1) 55 93(3)
3 Sn-MFI <1 30 6 17 1 <1 24 3 3 10 11(1) 27 82(5)
e. 4 Sn-MCM-41 n.d. 23 4 12 <1 <1 18 6 14 20 16(1) 57 98(5)
c
n 5 Sn-SBA-15 <1 32 6 11 <1 <1 18 3 10 18 12(1) 42 92(6)
M. Lice 6 SnO2-Betad 53 42 2 <1 <1 <1 3 1 2 1 <1 6 104(7)
Ad 7 Ti-Beta <1 48 7 11 3 <1 22 4 7 5 <1 16 86
24:42 nporte 89 ZArl--BBeettaa <61 3892 1n2.d. 1n0.d. 2n.d. <n1.d. 205 2n.d. 2n.d. 14 n<1.d. 19 8793(1)
2:U
023 1n 3.0 1101 SBil-aBnekta 1838 462 5<1 <21 <<11 <<11 18 n2.d. n3.d. <31 n<1.d. 18 9761(1)
2o
3/4/buti aAllreactionsemployedthestandardreactionconditions:360mgxylose(8.3wt%),4gmethanol,180mgcatalyst,2h,160(cid:1)Cand600rpmstirring.
d on Attri RpreoadcuticotnssawreerperpoevrifdoerdmiendTinabtrlieplSi2ca.tnes.da.n¼dsntoatnddaertdecdteedvi.aRtieofnesrotofthScehleamstedi2giftoarrepgroivdeunctinapbabrreenvitahteisoinssf.obrDCPomMb;fiunleldvayliueeldssan(cdardbeovnia%tio)nosff2o,r4a,5ll-
wnloademmons tfruirhfyudrarolxdyi-m3-eptehnytlaancoeitcala.cdidDmispetehrsyeldesStnerOa2nndan2o,5p-darihtiycdlersoxoyn-4S-mi-Beethtao.xy-pentanoicacidmethylester.cCombinedyields(carbon%)offurfuraland
DoCo
7. ve
01ati
y 2Cre lactates.20 The formation of DPM, in contrast, occurs via
4 Januarunder a athdeitffiner-ceonnttraeiancitniognsipliactahtwesa.yTthheastaimsseetermenindgwlyasonrelypocratteadlyfsoerdthbey
n 0ed formation of THM from hexoses using the same types of
d oens materials.26 The highly Brønsted acidic Al-Beta was found to
ec
Publishcle is li cwohnivcehrtisxiynloascecoinrdtoanmceetwhiytlhgplyrceovisoiduesswnditihngas.h56igNhosfeolremctaivtiiotyn,
Article. This arti odfetDecPtMedw(caas.1o%bs)e.rved, while small amounts of furfural were
s We would like to draw attention to the yields of furanic
s
e
cc products and DPM in the comparison of Zr-Beta and Ti-Beta
A
n with all the tin-containing silicates. Low yields of furanic
e
Op products (4–5%) are observed for the zirconium and titanium
materials while all tin-containing silicates form substantially
higher yields (10–20%). This observation supports the afore-
mentionedhypothesis,thatthemajorityofthefuranicproducts
isformedviaa3-DXrouteforthetin-containingsilicates.The
inabilityofthetitaniumandzirconiummaterialstocatalysethe
formationof3-DXfromxylosethusalsopreventsasubstantial
co-productionoffuraniccompounds.
Fig. 1 Product distribution of tin-containing silicates based on data
from Table 1. Reaction conditions: 0.360 g xylose, 0.180 g catalyst, Effectofreactionparametersandco-solutesforDPM
4.0gmethanol,160(cid:1)C,2hours. formationusingSn-Beta
The catalyst screening claried that Sn-Beta gives higher DPM
yields than other tin-containing silicates. We therefore assessed
The purely siliceous material Si-Beta did not catalyse the thereactionparametersindetailusingSn-Beta(HT)asthecata-
formation of signicant amounts of DPM, and the main lyst.Tothisend,wevariedthereactiontemperature(140–180(cid:1)C),
productobservedwasMG(Table1,entry10).Catalystshaving the catalyst to substrate ratio (0.125–1.0), the concentration of
othermetalsthantinincorporatedintotheframeworksuchas xylose in the reaction solution (8.3–23 wt%) and examined the
titanium, zirconium and aluminium did not form signicant effect of adding alkali co-solutes in the form of potassium
yieldsofDPMfromxyloseeither(Table1,entry7–9).However, carbonate.Furthermore,wetestedifotherpentosescouldbeused
both Ti-Beta and Zr-Beta gave appreciable yields of retro-aldol forDPMformation.Fromthesestudies,itwasdeducedthathigh
products (22–25%), which is in accordance with previous catalysttosubstrateratiosandtheabsenceofalkalico-solutesare
reports of these materials being active for the formation of importantparameterstoobtainhighyieldsofDPM.
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TheeffectofreactiontemperatureontheyieldofDPMwas 0.5.Surprisingly,increasingtheconcentrationdidnotlowerthe
insignicantandsimilaryields(31–34%)wereobtainedinthe yieldofDPMandusinga23wt%solutionofxyloseinmethanol
temperature range of 140–180 (cid:1)C (Table S4†). The reaction gaveasimilaryieldof32%asan8.3wt%solution(TableS3†).
temperatureeffectappearedtobemorepronouncedforyields Finally,twootherpentoses(riboseandlyxose)weretestedas
ofotherreactionproducts,withhighertemperaturesfavouring substrates and found to give DPM yields of 30% and 31%,
retro-aldol products (9% difference) and lower temperatures respectively(TableS3†).
favouringfuranics(8%difference).
Ithadpreviouslybeenshownforhexosesthatalkalico-solutes
e. signicantly diminish the yield of THM and furanic products, Polymerisationpotential
c
n leadingto increasedyieldsofretro-aldolproducts, from 30%in InordertoevaluatetheusefulnessofDPMasanovelpolyester
M. Lice theabsenceofalkalito75%inthepresenceof0.065mMofadded monomer, and having shown that DPM can be formed in
4:42 Aported pthoetacsosniuvmerscioarnboofnpaeten.1t8osWese(Fnigd.t2h),aitllaunstarnatailnoggothuasteoffpetcitmeaxlisytiselfdosr aDcPcMeptwaabslepyeierflodrsm(aebdovaet3la0r%ge),rtshceasleyn(t1hLes).isDaunedtpoutrhiecasitmionploerf
2n
023 12:n 3.0 U obfyDICPPMmreeaqsuuirreemaesntrtisctthcaotnatrboalcokfgarolkuanlidcaolnkatalimleinvealnotfs.1W.3ewftopupnmd seyxnptehnesseisofroautleowoefrSonv-eBreatlal D(PPTM), tyhieisldc.aFtarolymsttwhaesseulsaerdgea-tsctahlee
d on 3/4/2Attributio nwaatsTinhpgerefcrsaoetmnatlyteshvteetnobosurunobsdsieltirrcaa“ttaeelkrgaaltlaiisosfwrweaaesr”ev.caorniedditfiroonms,0p.o1s2s5ibtoly1o.0riogni- DpexrPpeMperairmewdeansitnss,ay2cnc.t6ehpegtsaiosbfeled$.a9mH4%oauvinpntugsr,ewsh(eaosbweencsatimtmheaattiendDtePbreMyst1eHcda-NninMibRtes)
wnloademmons wcoenigshtatntbaatsi8s.,3wwth%ilexylkoeseep.iInngterethsteingsluyb,satrsattreongcodnecpeenntrdaetniocne ubyseSaeslsaapnodlycmo-ewrobrukielrdsinthgabtloMckV.GItchanasbperecvoi-opuosllyymbeereisnedshwowitnh
DoCo on catalyst loading was found, as selectivity towards DPM lactic acid with a 1,2-linkage to afford a polyester material
017. ative increasedsignicantlyfromacatalysttosubstrateratioof0.125 having pendant vinyl groups available for post functionalisa-
y 2Cre (19%DPM)upto0.5(34%DPM)(TableS4†).Theformationof tion.23Additionally,ithasrecentlybeenreportedthatMVGcan
4 Januarunder a rweittrho-ainldcorelapserdodcuacttaslyfsotlltoowesdubtshtreatoeppraotsioitseftrroemnd,adceocmrebaisninedg vbiea caomnveetrattehdesiinstroeadcitmioent.h57y,5l8(TEh)-i2s,5n-edwihypdrorodxuychtehx-a3s-eanlesodiboaeteen,
n 0ed yieldof32%atacatalysttosubstrateratioof0.125tojust15% successfully co-polymerised with lactic acid.57 In contrast to
d oens ataratioof1.0. MVG, DPM contains both a secondary and a primary alcohol,
Publishecle is lic wasThteeseteffde,ctkoeefpthinegxytlhoeseccaotanlcyestnttroatsiuobnsitnrattheerraetaiocticoonnmstaixntturaet wtohpicohorprseevleencttisvitthyecuosnetroofl.clHasoswiceavlepr,oelynmzyemrisaatitciopnoclyamtaelyrsistsatdioune
s Article. This arti mmpreoimtnhoaomrdysearnsp.d5e9r,s6m0ecitoEnspdpoaelcryyimaalellycrioshathotielosneennoazfbylmseusecthhseehlseipcgethicvliyitycfusbnynectttwhioeenseainsl
s
ce of functional linear polymers that cannot be prepared using
c
A
n chemo-catalysis.61,62 Unfortunately, homo-polymerisation of
e
p DPM was unsuccessful and resulted only in the formation of
O
oligomers. As an alternative to homo-polymerisation, co-
polymerisations wereconducted usingthe commerciallyavail-
able monomer ethyl 6-hydroxyhexanoate (E6-HH) as shown in
Scheme 3. Polymerisation of pure E6-HH affords poly-
caprolactone (PCL) which is a linear and biodegradable poly-
ester produced on industrial scale. Co-polymerisation with
DPM could be envisaged to be a useful way to modify the
propertiesofPCL.ThisapproachincorporatesDPMintolinear
polymers with a linear 1,5-linkage, leaving the secondary
alcoholandolenmoietiesavailableforpost-functionalisation
(Scheme3,polymerI).
Theenzymaticco-polymerisationsbetweenDPMandE6-HH
wereperformedat60(cid:1)Cinbulkmonomerinaccordancewith
the general procedure described in the Experimental section.
TheNMRspectrumoftheresultingpolymer(Fig.3)showsthat
that the vinylic hydrogen atoms from DPM are present, while
thealcohol,alkeneandesterfunctionalgroupswereconrmed
byFT-IRspectroscopy(Fig.S6†).
Fig.2 ProductdistributionatdifferentalkaliconcentrationsusingSn-
The polymer synthesis procedure was varied to study the
Beta, based on data from Table S5.† Reaction conditions: 0.360 g
xylose,0.180gSn-Beta(HT,Si/Sn¼150),4.0gmethanol,160(cid:1)C,2 effects of feed ratio and polymerisation time on the resulting
hours.YieldsofTPMandDMPMandDPLarenotincludedinthisgraph. polymers. Polymerisation time was studied by conducting co-
RefertoScheme2forabbreviations. polymerisation experiments using a DPM to E6-HH molar
992 | RSCAdv.,2017,7,985–996 Thisjournalis©TheRoyalSocietyofChemistry2017
View Article Online
Paper RSCAdvances
testedreactiontimesreasonabledegreesofpolymerisation(M
w
¼10000–12350gmol(cid:4)1)andpolydispersityindices(PDI¼2.1–
2.5) were obtained, comparable to typical results from enzy-
maticpolymerisationofmonomerscontainingbothsecondary
andprimaryalcohols.61,62
These ndings clearly showed that DPM was more chal-
lenging to polymerise than E6-HH, which was also evident by
DPM being unable to homo-polymerise. Nevertheless, DPM
e. should become incorporated at longer polymerisation times
c
n andhigherDPMfractionsinthefeed(Table2).
M. Lice A study of varying the feed ratio of E6-HH to DPM from
Ad
4:42 porte athmeocola-rporalytmioeorfi0n.c2r2eatose0d.6w6itshhoinwcerdeathseadttrhaetioco.nTtheinstleoafdDtPoMfuinll
2n
023 12:n 3.0 U itnimcoerspoorfa7ti2onhoafnDdPMmoilnetcoultahrercaoti-opsolaymboevres 0a.t4p4o.lDymesepriitseatfiuonll
2o
d on 3/4/Attributi Scheme 3 Enzymatic co-polymerisation of DPM and ethyl 6- 0imn.6oc6olermcpuoolrlaaartriworaentiigoho,tfrsesoDpfPeoMcnt,ilvyet4lhy5.e0sM0eoalnpedcouly3lma7r0e0wriegsiagmthiootsnl(cid:4)sa1bforoevrseu01l.0t4e40d0a0nindg
017. Downloadeative Commons ashounynpddeprofosoxusryebmhdseeliyxsqaourneecopncarutetresfeou(nEnn6tcee-tdiiHothiHnnea)rtluihscseaaitnrsibogconhCn.eamTonhfedetidfhoaerreaocanllcaettarfiiiortncynit.cicomafoliptiehatesieestB,hbio(CulstAoLc-naBlny) mogabottTela(cid:4)dhin1ebeadtyshfDeoorSrbmCstahelraevnspeedrdocpsowhe-iprottohwieleys0dm.o2egf2rliaasmlsalstotilhtoarenarsncr.soai-ttpiiooonlyDmtPeMemrspceworuearltdeurinensovte(sTbtgie)-
y 2Cre between (cid:4)49 (cid:1)C to (cid:4)56 (cid:1)C, which is typical for aliphatic poly-
n 04 Januared under a eTdsehtteeerrmsmeailnntidendgcottonembrepme4sra2tt.h8uer(cid:1)eC(eTaxminb)dlaetTnm0a.1tdu2ercmereooalfastrehdreawtpiioothloymfinDecrPrMecahsawiinangs.
d oens content of DPM to 7.5 (cid:1)C at 0.66 molar ratio DPM. The incor-
ec
Publishcle is li ptoo-rcahtaioinnpoafcDkPinMgcreleqaurilryepdrfeovrenthtsetphoelyrmegeurlatorictyryasntadllcilsoes,ethcehraeibny-
Article. This arti redTuhciensgetihneitimaleslttiundgietsemclpeaerrlaytusrheo.wthatDPMcanbesuccess-
s fully polymerised with other similar monomers thereby
s
ce providing access to functional polymers. Furthermore, the
c
A
n degreeofincorporationmaybeusedtomanipulatethephysical
pe Fig.3 1HNMRassignmentoftheco-polymerproduct,poly(E6-HH- propertiesoftheco-polymer.
O
co-DPM),fromTable2entry4.
Post-functionalisation
ratioof0.22andvaryingthereactiontimes(Table2,entries2– Post-functionalisationofpolymersoffersthepossibilitytotailor
4). The shortest polymerisation time of 18 h resulted in the
theirproperties. TheDPM containingco-polymers were tested
incorporation of approximately 55% (0.12 molar ratio) of the
for their ability to undergo functionalisation of the a-hydroxyl
DPM from the feed into the co-polymer. By increasing the and olenic groups (Scheme 3). Functionalisation of the a-
polymerisation time to rst 42 h and subsequently to 72 h, hydroxyl groups of DPM was performed using triuoroacetic
incorporation was increased to 77% (0.17 molar ratio). At all
anhydride (TFA), a highly reactive reagent widely used in
Table2 Enzymaticco-polymerisationofE6-HHandDPMa
Entry Timeh FeedMRb Prod.MRb,c T d,(cid:1)C T d,(cid:1)C M e,gmol(cid:4)1 M e,gmol(cid:4)1 PDIe
g m n w
1f 18 0 0 (cid:4)60.2 48.9 3600 4700 1.3
2 18 0.22 0.12 (cid:4)49.3 42.8 5150 10050 2.1
3 42 0.22 0.14 (cid:4)49.3 42.5 4490 10750 2.4
4 72 0.22 0.17 (cid:4)50.0 34.2 5000 12350 2.5
5 72 0.44 0.44 (cid:4)55.5 15.1 1900 4500 2.4
6 72 0.66 0.66 (cid:4)52.3 7.5 1760 3700 2.1
aAllreactionswereperformedat60(cid:1)Candthepressurewasheldat200mbarfor2hwhereaeritwasreducedto5mbarinaccordancewith
optimisationsperformedwithE6-HH(seeESI).bMolarratio(MR)listedasDPM/E6-HH[molmol(cid:4)1].cDeterminedby1HNMR.dDetermined
byDSC.eDeterminedbySECinTHFusingPSstandards.fUsingonlyE6-HHasmonomer.
Thisjournalis©TheRoyalSocietyofChemistry2017 RSCAdv.,2017,7,985–996 | 993
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RSCAdvances Paper
hydroxyl labelling of polymers, allowing for clear detection of Table3 Advancingandrecedingwatercontactanglemeasurements
functionality by NMR analysis.63,64 The structure of the TFA forPCL,PECD–PCLandPECD(TFA)–PCLfilmsa
modiedco-polymer(Scheme3,polymerII)wasveriedby1H
Film AdvancingWCAdeg RecedingWCAdeg
NMR(seeexperimentalsection“Thiol–enefunctionalisationof
poly(E6-HH-co-DPM)”),showingthatfullfunctionalisationwas PCLb 90(1) 46(1)
achieved. PCL 85(2) 46(2)
Additionally, thiol–ene chemistry was used to demonstrate PECD–PCLc 75(1) 38(2)
thereactivityoftheintra-chainalkene.23Thiol–enechemistryis PECD(TFA)–PCLd 93(2) 36(2)
ce. awell-establishedprotocolforfunctionalisationofpolymersby amAelalswuraetemrecnotnstaocfttahnrgeelesdi(ffWeCreAn)twderroepdsetaetrmdiiffneerdenatspavoesriatigoenssoofnthtrheee
n formation of alkyl sulphides via reaction of a thiol and an
M. Lice alkeneusingradicalchemistry.65,66Here,aphotoinitiator(2,2- ppoarlyemntehressuisr.facbeWaCnAdsvtaanludeardfodrevPiaCtLionfsroomfthleitelarasttudrieg.6i8tacreThgievenlimn
4:42 Aported dwiimtheathsoexleyc-2ti-ponheonfytlhaicoeltocpomhepnoounned,sD(SMchPAem) ew3a)stousileldusttroagteeththeer cToFnAtafuinnecdtio1n0awlist%edppoollyy((EE66--HHHH--ccoo--DDPPMM))..dThe lmcontained10wt%
2n
023 12:n 3.0 U potTenhteiaflufnocrtpioonsat-lpisoaltyimoneriosfatDioPnMfusnucbti-ounnaitlsisaintiotnh.e thiol–ene
Downloaded on 3/4/2Commons Attributio bh3fpeox,eoilnptllpwyoedmorweeilermyieennmrdegenu3sdrtu0psismboIasniwItnnIiaadtifuss–uheen1)end.c0dtet0sPitd%oeoyonriouemarclbldoiislnsineoanevlbtgdueioorbtnnshiuidl.eoistinphTynr,ihgogoiwthfoo1ielntt–Hshhetiennctaetohfennuendrvnseecliarett1csiiaHetoisiosn–otnw1an3sli(sCittSsehcevrihdiNancerMatmichelolRdeey- crppWeohocC-lopeyAbd(oEiilucyn6imp-gtHyWetHoor,fC-9cwtAo3hh-(cid:1)weDi,caPwhslMhmnsi)hocdtohreuawsiffeesuedtleoctexttethdphdaeeitcfnrtteohuadmenofrsbriiyonnlsemectneriedmniainnsticehgsreeisinantcisoltitlh-nhpaegeomltayuphdmohevrieahpirnnhy.acdTiitlrnheiocdge-.
017. ative polymer materials in DMSO and chloroform prevented Bsuortfhacreespurltospeshrtoiews tohfatththeetchoi-npolylmmerbliesnadb,leantodmthoadtifypothste-
y 2Cre conclusive studies of the regioselectivity inthe thiol–ene reac- modication of the co-polymer permits exploitation of the
n 04 Januared under a gtmiroaenrcsi.anpgWtoreeetafhogauennnotdsl,t(mhScaahtkeiimnngepia3tr,tpiocpusosllaiybrmlemerteorIcIfIaubpl–tlcyo)accowenteivrceeratecffitdheecatiinvnde- fulmnctbiolennadlsg.roupsforfurthermodicationofthesurfaceofthin
d oens chain double bond, clearly demonstrating the polymers high
Article. PublisheThis article is lic ptcaooloirsthreaeantsvitopeianoalnnifdnoiarntphgfpuerpnopecxontiildmoyemnanatetelrilasyoalkb1tie0sone-nfero.vsle.Id6nd7-lTchohhweareeeirnhinriageilhaskceettnhixvteuiestsnyaetcrxooetfmreafspoutranidmrceitnadiotaentrdoy- CIbtinunoi-tlchdoneinnctcgaulibrunrlieosnncgiktossDintluPicdMayt,ecswaneashbacevaestaysnlyhtshotsewsniinsethdyiaeftlrdothsmeupnpeontvoetol3sp2eo%slyuewssiitntehgr
s andunderlinesthepotentialofin-chainalkenesforpreparation
ces offunctionalpolymers. xylose concentrations of 23 wt%. This approach provides
c
A a simple and low cost route from a plentiful and sustainable
n
e feedstock to an intriguing chemical product. Future improve-
p
O Co-polymerblendswithpolycaprolactoneinthinlms mentstotheDPMsynthesismayencompasswaystosuppress
theformationoffuranicsorofretro-aldolproducts,ortobetter
The prepared co-polymers have a high structural similarity to
control the formation of ester products from 3-DX. DPM has
PCLandthereforeblendsbetweensomeoftheco-polymersand
PCL were investigated. PCL oen nds uses in biomedical beenshowntobeaninterestingmonomerforthepreparation
of functional polyesters in co-polymerisation with E6-HH.
devices, where control of surface properties and functionality
Enzymatic polymerisations were effective for the synthesis of
are highly desired properties and therefore simple blending
the highly functional polyesters with 0.17 to 0.66 molar ratio
couldbeaninterestingapplicationofthenewco-polymers.
Three different lms consisting of pure PCL, a PCL blend content of DPM. The co-polymers could easily be post-
with10wt%poly(E6-HH-co-DPM)(PECD–PCL)andaPCLblend functionalised using either TFA or thiol–ene chemistry to
with 10 wt% triuroacetic acid functionalised poly(E6-HH-co- extend the potential applications of these co-polymers. As an
DPM) (PECD(TFA)–PCL) were prepared by solvent casting and example,simpleblendswithPCLwereinvestigatedanditwas
hot-pressing. The prepared lms were investigated by water shown howtheco-polymer couldbeusedtoaffectthe surface
propertiesofthepolymerlm.
contactangle(WCA)measurementstodeterminetheimpacton
The chemoenzymatic approach described herein thus
surfacepropertiesoftheblend(Table3).
ThepurePCLlmhadanadvancingWCAof85(cid:1),whichwas enables future bio-reneries to better utilise pentoses from
reduced to 75(cid:1) by blending with the DPM co-polymer. This hemicellulose-containing biomass, providing the chemical
industrywithnewtypesofinterestingpolymerbuildingblocks.
shows the impact of the free hydroxyl groups from the co-
polymer, andcouldbeexploited toincreasethehydrophilicity
ofthethinlm.ThiswascorroboratedwiththerecedingWCA, Acknowledgements
which is reduced by almost 10(cid:1) for the blend, indicating the
presence of more polar groups in the system. Conversely, We gratefully acknowledge funding by the Bio-Value platform
blending PCL with the triuroacetic acid functionalised (biovalue.dk) under the SPIR initiative by The Danish Council
994 | RSCAdv.,2017,7,985–996 Thisjournalis©TheRoyalSocietyofChemistry2017