Functional Polyesters Prepared by Polymerization of�-Allyl(valerolactone) and Its Copolymerization with�-Caprolactone and �-Valerolactone

BRYAN PARRISH, JENNIFER K. QUANSAH, TODD EMRICK

Department of Polymer Science and Engineering, University of Massachusetts, 120 Governors Drive, Amherst,Massachusetts 01003

Received 27 February 2002; 15 March 2002Published online 00 Month 2002 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/pola.10277

ABSTRACT: We report the ring-opening homopolymerization of �-allyl(valerolactone),compound 2, and its copolymerization with �-caprolactone and �-valerolactone usingstannous(II) catalysis. Although the polymerization of substituted �-valerolactones hasreceived little attention for the preparation of functional polyesters, we found thatcompound 2 may be incorporated in controllable amounts into copolymers with otherlactones, or simply homopolymerized to give a highly functionalized, novel poly(valero-lactone). The presence of the pendant allyl substituent had a substantial impact on thethermal properties of these materials relative to conventional polyesters prepared fromlactones, and most of the polymers presented here are liquids at room temperature.Dihydroxylation of the pendant allyl groups gave polyesters with increased hydrophi-licity that degraded more or less rapidly depending on their extent of functionality.© 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1983–1990, 2002Keywords: polyesters; valerolactone; functional polymer; biodegradable polymer;ring-opening polymerization

INTRODUCTION

Various types of polyesters are interesting forapplications that span the range from thermo-plastics to medicine.1–5 Polyesters based on �-ca-prolactone (CL), lactide, and glycolide are some ofthe degradable polymers relevant in the field ofbiomaterials, for example, in suture, tissue engi-neering, and drug delivery applications. The com-bination of biocompatibility and biodegradabilitywith the physical strength provided by the poly-mer is critical for such applications.6 However,the simplicity of these polyesters presents limita-tions in terms of functionality and physical prop-erties; indeed most of these polyesters are hydro-

phobic solids. Thus, researchers are beginning toexplore structural and chemical modifications ofconventional materials through, for example, thepreparation of highly branched polyesters (e.g.,hyperbranched and dendritic) or by the additionof pendant functionality.7–10 Such branchingand/or pendant functionality may be used to tunephysical and chemical properties, including vis-cosity, solubility, hydrophilicity, adhesion, andblood compatibility.11–13

Although substituted lactones are generally re-luctant to participate in ring-opening polymeriza-tion, particularly homopolymerization, the vari-ety of new lactone polymerization catalysts dis-covered and optimized through the rapidlyadvancing work of several research groups14,15

prompted us to conduct this investigation.Sn(Oct)2 and Al(Oi-Pr)3 are now well known cat-alysts used for the ring-opening polymerization of

Correspondence to: T. Emrick (E-mail: tsemrick@mail.pse.umass.edu)Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 40, 1983–1990 (2002)© 2002 Wiley Periodicals, Inc.

1983

lactones,1,15 and Sn(OTf)2 and Sc(OTf)2 were re-cently used by Moller et al.14 to give polyesterswith very low polydispersities in room tempera-ture polymerizations. In terms of monomer poly-merizability, we were also encouraged by thework of Duda et al.18 who used �-butyrolactone(BL), a monomer that is very stable to conven-tional lactone polymerization conditions, in copo-lymerization reactions with CL.

In this work, we show that �-valerolactone(VL), when allylated � to the carbonyl group, canbe copolymerized with both CL and VL as well assimply homopolymerized under Sn(II)-mediatedpolymerization conditions. These functional poly-mers can be modified to give pendant hydroxylgroups and thus polyesters with more hydrophiliccharacter than their precursors. Subsequently wedescribe our use of Sn(OTf)2 for the ring-openinghomo- and copolymerizations of compound 2, tet-rahydro-3-(2-propenyl)-2(2H)-pyranone, or �-al-lylvalerolactone (AVL), to give functional polyes-ters where the degrees of polymerization (DPs)and polydispersity indices (PDIs) are consistentwith the controlled polymerization character nowwell-established for these catalysts.

EXPERIMENTAL

General

Allyl bromide, N,N-diisopropylamine, hexameth-ylphosphoramide (HMPA), �-valerolactone, andCL were purchased from Aldrich; n-butyllithiumand Sn(OTf)2 were purchased from Alfa Aesar.Allyl bromide, N, N-diisopropylamine. HMPA,and the lactones were distilled over CaH2 shortlybefore use. Ethanol (EtOH) was refluxed overCaH2 for several hours prior to distillation, andtetrahydrofuran (THF) was distilled over sodium/benzophenone. NMR spectra were recorded onCDCl3 solutions using a Bruker DPX-300 spec-trometer—1H at 300 MHz and 13C at 75 MHz,referenced to residual CHCl3. Molecular weightsand PDIs were measured in THF by gel perme-ation chromatography (GPC) relative to poly-styrene standards [Scientific Polymer Productspeak-average molecular weight (Mp) � 503, 700,1306, 2300, 4760, 12,400, 196,700, and 556,000g/mol] on a system equipped with a (three-columnset (Polymer Laboratories 300 � 7.5 mm, 2Mixed-D, 50 A) and a refractive-index detector(Waters R4010). Melting points were recorded ona PerkinElmer Pyris differential scanning calo-

rimeter under He at a scan rate of 10 °C/min,taking data from the second heating.

�-Allylvalerolactone (2)

A solution of N,N-diisopropylamine (4.6 mL, 33mmol) in THF (300 mL) was stirred under nitro-gen and cooled in a dry ice/acetone bath. n-Butyl-lithium (11.8 mL, 33.0 mmol) was added by sy-ringe, and the resulting solution was stirred for10 min. Then a solution of �-valerolactone (2.8mL, 30 mmol) in THF (30 mL) was added drop-wise over 1 h. This mixture was stirred for 20min, and allyl bromide (3.1 mL, 36 mmol) inHMPA (6.3 mL, 36 mmol) was added dropwise.The reaction mixture was then warmed to ap-proximately �40 °C (dry ice/acetonitrile bath)and stirred for 2 h. The mixture was quenchedwith sat, NH4Cl(aq) (3 mL), and allowed to warmto room temperature. Volatiles were removed byrotary evaporation, and the resulting product wasdissolved in ether, washed with brine, dilutedwith hexane, and washed with brine again. Col-umn chromatography (15% EtOAc in hexane) fol-lowed by Kugelrohr distillation gave the title com-pound as a viscous liquid (2.98 g, 71%).

1H NMR � 5.75 (m, 1H), 5.06 (m, 2H), 4.26 (m,2H), 2.55 (m, 2H), 2.26 (m, 1H), 2.04 (m, 1H), 1.85(m, 2H), 1.54 (m, 1H) ppm. 13C NMR � 174.0,135.2, 117.6, 68.6, 39.4, 35.6, 24.21, 22.0 ppm (inaccord with the literature values19).

General Procedure for Polymerization of Lactones

Glassware was thoroughly flame-dried under astream of N2(g). EtOH (1.7 M in THF) andSn(OTf)2 (3.7 � 10�2 M in THF) were combinedand stirred for 30 min. Monomer was then addedaccording to the desired degree of polymerization(by adjusting initiator/monomer ratio) and com-position (i.e., homo- or copolymer). Polymeriza-tions could be performed neat or as solutions inTHF at room temperature. Molecular weightgrowth was monitored by GPC, and polymeriza-tions were typically run for less than 24 h to reachnearly full conversion. The resulting polymerswere dissolved in THF and precipitated into coldmethanol or hexanes to remove catalyst and re-sidual monomer. Column chromatography or re-peated precipitation could then be used to com-pletely remove traces of residual monomer.

Example Homopolymerization of 2

Compound 2 (2.24 g, 16.0 mmol) was added topreviously stirred EtOH (160 �L, 2.72 � 10�1

1984 PARRISH, QUANSAH, AND EMRICK

mmol) and Sn(OTf)2 (145 �L, 5.37 � 10�3 mmol)solutions. The reaction mixture was stirred atroom temperature for 26 h at which point theresulting polymer was dissolved in THF and ex-tracted by addition to excess hexanes. To removetraces of residual monomer, column chromatogra-phy was performed. The monomer eluted in 15%ethyl acetate, after which the polymer was ob-tained by increasing the eluent polarity to afforda viscous liquid homopolymer 4 (1.49 g, 66%). ThePDI of the isolated polymer was narrowed as aresult of column chromatography. Consequently,the GPC data reported subsequently is that col-lected before this purification—weight-averagemolecular weight (Mw) 5200 g/mol, PDI 1.11.

1H NMR � 5.70 (m, 1H), 5.04 (m, 2H), 4.06 (m,2H), 2.36 (br m, 3H), 1.61 (m, 4H) ppm. 13C NMR� 175.2 (COO), 135.2, 117.2, 64.1, 44.9, 36.6, 28.1,26.6 ppm.

Example Copolymerization of 2 with CL:Copolymer 5c

Compound 2 (0.84 g, 6.0 mmol) and CL (0.23 g, 2.0mmol) were added to a solution of EtOH (80 �L,1.3 � 10�1 mmol) and Sn(OTf)2 (70 �L, 2.7 � 10�3

mmol) for polymerization of a 75:25 CL:AVL mo-lar feed mixture. This was stirred at room tem-perature for 24 h, then dissolved in THF, andadded to excess hexanes. The extracted polymerwas purified by column chromatography as forhomopolymer 4 to afford copolymer 5c (1.00 g,93%)—Mw 6600 g/mol, PDI 1.15.

1H NMR � 5.71 (m, CH2OCH), 5.08 (m,CH2OCH), 4.06 [m,OCH2AOO(AVL,CL)], 2.33 (brm. OCAOCHO, CAOCHCH2CHACH2, andCAOCH2O), 1.62 (m, CH2 AVL,CL), 1.35 (m, CH2 CL)ppm. 13C NMR � 175.2 (br, CAOAVL), 173.8 (br,CACL), 135.2, 117.6, 64.0, 44.8, 36.5, 34.4, 28.8,28.6, 26.5, 26.0, 24.9 ppm.

Example Copolymerization of 2 with VL:Copolymer 7c

Compound 2 (0.28 g, 2.0 mmol) and �-valerolac-tone (0.60 g, 6.0 mmol) were added to a solution ofEtOH (80 �L, 1.3 � 10�1 mmol) and Sn(OTf)2 (70�L, 2.7 � 10�3 mmol) for polymerization of a75:25 VL:AVL molar feed ratio. The mixture wasstirred for 24 h, at which time the polymer wasisolated by dissolution in THF and addition toexcess cold methanol. Residual monomer was re-moved by column chromatography as for ho-

mopolymer 4 to afford copolymer 7c (0.72 g,82%)—Mw 8300 g/mol, PDI 1.13.

1H NMR � 5.70 (m. CH2ACH), 5.03 (m,CH2ACH), 4.08 (m, OCH2OO), 2.38 (br m, CAOCHO, CAOCHCH2CHACH2, and CAOCH2),1.68 (m, CH2 VL, AVL) ppm. 13C NMR � 175.2 (br,CAOAV), 173.7 (br, CAOVL), 135.2, 117.6, 64.0,44.8, 36.5, 34.1, 28.6, 28.5, 26.5, 21.8 ppm.

Dihydroxylation of Copolymer 5c

Copolymer 5c (0.50 g, 7.5 � 10�1 mmol allyl func-tionality), containing 21% incorporation of 2, wasstirred in acetone (4 mL). To this mixture wasadded a 50 wt % solution of NMO (0.18 g, 7.5� 10�1 mmol) in H2O. A 1 wt % solution of OsO4(0.19 g, 7.5 � 10�3 mmol) in H2O was then added,and the mixture was stirred at room temperaturefor 24 h. The resulting viscous liquid was washedwith water and brine, precipitated into hexanes,and then dried over MgSO4. Volatiles were re-moved by rotary evaporation to yield a viscousliquid (0.51 g, 87%)—Mw 6800 g/mol. PDI 1.13.

1H NMR � 4.02 (m, 2H), 3.65 (m, 2H), 3.40 (m,1H), 2.69 (br, 1H), 2.51 (br, 1H), 2.29 (m, 2H), 1.59(m, 4H), 1.35 (m, 2H). Fourier transform infrared� 3457 (OOH), 1725 (CAO) cm�1.

RESULTS AND DISCUSSION

The ability to perform ring-opening polymeriza-tion chemistry depends critically on monomerring size.20,21 In the case of polyesters preparedfrom lactones, the particular lactone used impactsnot only the polymerization rate but the thermaland degradation properties of the polymer. Asexpected, on the basis of the ring stability, BL isdifficult to homopolymerize under most condi-tions, whereas VL and CL can be homopolymer-ized using the metal-mediated controlled poly-merization techniques mentioned previously.

Molander and coworkers19 previously synthe-sized lactones functionalized with allyl groups � tothe carbonyl as intermediates in their studies ofintramolecular Barbier cyclizations. This � methyl-ene group is susceptible to functionalization un-der anionic conditions because of the enhancedacidity of its protons relative to the other protonson the ring. We have similarly lithiated and ally-lated (by quenching with allyl bromide) �-butryo,�-valero, and CL. As expected, the yields of thefunctionalized products increase with greaterring stability [Scheme 1(a)], as anionic initiated

FUNCTIONAL POLYESTERS 1985

ring-opening is a competing factor. We obtainedgood yields for allylation of BL and VL (�70%).CL in our hands was more problematic, and onlywith very careful monitoring of temperature andconcentration could the allylated product be ob-tained in yields of 50% or more. As VL representsa “middle ground” in terms of monomer function-alization and polymerizability, we further ex-plored the chemistry of �-allyl(valerolactone) 2,its homopolymerization to give highly functionalpoly(valerolactone)s, and its copolymerizationwith CL and VL [Scheme 1(b)] to give polyesterswith tunable degrees of functionality. To ourknowledge this is the first extensive use of a sub-stituted �-valerolactone in polymerization chem-istry, and we expect that these novel polymerswill substantially broaden the range of propertiesobtainable from conventional polyesters, and becomplimentary to the state-of-the-art examples ofpendant functionalized polyesters, such as thosereported by Hedrick and coworkers.22

Homopolymerization of 2

Early investigations of lactone polymerizationsrevealed difficulties in attempted polymerizationsof butyrolactones and substituted valerolac-tones23 due in part to the equilibrium between

ring opening and cyclization, where the more-stable monomers resist polymerization relative toless-stable rings (e.g., CL). These stable rings can,however, still be incorporated into polyesters, forexample, by copolymerization of BL with CLcomonomer that accelerates polymerization ki-netics and prevents depolymerization.18 We setout to similarly copolymerize compound 2 withCL to introduce the allyl functionality into thepolyester product. In the process, we were pleasedto observe that 2 can be homopolymerized to con-siderable molecular weights and with low PDIs,in a manner that resembles homopolymerizationof CL.

The polymerization of compound 2 to give ho-mopolymer 4 was carried out at room tempera-ture using Sn(OTf)2 catalysis, an effective cata-lyst for lactone polymerizations recently reportedby Moller et al.14 The kinetics of this polymeriza-tion, shown in Figure 1(a), reveal a linear in-crease of Mn with conversion, indicative of a well-controlled polymerization. Monomer conversionof 90% or greater could be achieved to give poly-mers with fairly low PDIs, typically in the rangeof 1.1–1.3 as analyzed by GPC (relative to poly-styrene standards) on samples taken from thepolymerization vessel. Attempts to achieve fullmonomer conversion resulted in broadening of

Scheme 1

1986 PARRISH, QUANSAH, AND EMRICK

the PDI, consistent with the increasing role oftransesterification events upon depletion ofmonomer. In addition, the calculated degree ofpolymerization was generally in reasonable ac-cord with the experimental values. The success ofthese polymerizations, and the rate at which theyproceed, is significantly affected by attention topurity. In addition to the need for water-free sys-tems, we found that the homopolymerization of 2was best run when the monomer had been puri-fied by column chromatography and vacuum dis-tillation. Attempted polymerization of insuffi-ciently pure samples of 2 proceeded very slowlyand only to the oligomer stage.

Although poly(�-caprolactone) (PCL) and poly-(�-valerolactone) (PVL) are semicrystalline poly-mers (mp’s ca. 55–65 °C), homopolymer 4, with itspendant allyl functionality, shows no such ten-dency to crystallize. The allyl groups disrupt crys-tallization to such a degree so as to afford a com-pletely amorphous polymer that is a liquid atroom temperature. We expect the liquid nature ofthese polymers to be very useful for some appli-cations. However, this also resulted in the needfor more tedious purification procedures becausethis allylated polyester could not be precipitated

in the conventional fashion as for PCL or PVL(see experimental for details).

GPC analysis of homopolymers of type 4 gavemonomodal molecular weight distributions [Fig-ure 1(b)], with polydispersities essentially un-changed from the crude reaction mixtures. TheNMR spectra of homopolymer 4 revealed featurescharacteristic of the polyester backbone and theallyl side chains. In the 1H NMR spectrum, theallyl CH2 integrated against the backboneCOOCH2 in the expected 1:1 ratio, and the ab-sence of signals for the COOCH2 of the lactone(� 4.26 ppm) confirmed the absence of any tracemonomer in the system. 13C NMR showed the oneexpected carbonyl resonance (� 175.2 ppm) as wellas signals for the five backbone and three pendantside-chain carbons.

Copolymerization of 2 with CL: Copolymers ofType 5

We found that lactone 2 can be incorporated intocopolymers with CL in a controlled fashion, thusallowing for “fine-tuning” of the polyester compo-sition through the degree of incorporated func-tionality. The copolymers prepared from 2 andCL exhibited fairly low PDIs, with reasonablecontrol over the degree of polymerization. Thepresence of a second monomer does not signifi-cantly affect the rate of the polymerization as longas the monomers are sufficiently pure. Copolymer5 was prepared with a range of feed ratios, andthe actual degrees of incorporation of 2 in thepolyester products were calculated by 1H NMRintegration, using the ratio of the allyl CH2 signalat about � 5.1 ppm versus the backboneOCOOCH2O signal at about � 4.1 ppm. The ac-tual percent incorporation of 2 in the copolymersrelative to the feed ratios is shown in Table 1, and

Figure 1. Linear increase in GPC-derived molecularweight versus conversion in homopolymerization of 2(a) and GPC trace of isolated homopolymer 4 (b).

Table 1. Data for Copolymerization of 2 with CLIncluding Feed Ratios, Percent Incorporation of 2,Theoretical versus Experimental DP, and PDIs

PolymerNumber

FeedRatio2:CL

Incorporation2 DPtheor DPexp PDI

4 100:0 100 60 50 1.115a 75:25 74 60 48 1.155b 50:50 42 60 53 1.105c 25:75 21 60 48 1.086 0:100 0 60 62 1.18

FUNCTIONAL POLYESTERS 1987

an example of an 1H NMR spectrum of copolymer5b is depicted in Figure 2.

We were interested in determining the impactof pendant group incorporation on the thermalproperties of these copolymers. Melting point de-pression for copolymers of VL and CL with nopendant substitution has been reported by Storeyand Hoffman,24 where a minimum melting pointof about 10°C was observed at 40% incorporationof VL (i.e., both CL and VL homopolymers aresemicrystalline and have higher melting pointsthan all CL/VL copolymers). Although PCL in themolecular weight range used here exhibits a melt-ing transition around 55 °C, copolymer 5 contain-ing about 7% of monomer 2 exhibited a muchlower melting transition (by Ca. 20 °C) as a resultof substantial disruption of polymer crystallinity.Higher percent incorporation of 2 into copolymerswith CL caused marked reduction in the meltingpoint (e.g., mp � 8 °C at 25% 2-co-CL), and copol-ymers of type 5 with greater than 25% incorpora-tion exhibited no melting transition. These obser-vations represent a substantial departure fromthe properties of CL, VL, or copolymers thereof.

The 13C NMR chemical shifts of the carbonylsin polyesters of this type are known for theirsensitivity to the microstructure of the materialand can consequently be used to elucidate connec-tivity.25,26 The 13C NMR spectra of homopolymer4 and PCL revealed carbonyl resonances at �175.2 and 173.9 ppm, respectively (Fig. 3). Inspec-tion of the carbonyl region of copolymers of type 5,for example, copolymer 5a (74% incorporation of2) revealed several overlapping resonances sug-gestive of the expected random incorporation ofmonomers into the backbone, because one would

anticipate well-defined block copolymers of CLand 2 to largely exhibit carbonyl signals corre-sponding to homopolymer-like sequences.

Copolymerization of 2 with VL: Copolymers ofType 7

Compound 2 can also be incorporated into copol-ymers with VL in a well-controlled fashion, simi-lar to that described previously for CL. The extentof incorporation of 2 on the basis of the feed ratioand the PDIs of the resulting copolymers are sum-marized in Table 2. These polyesters also exhibitmelting point depression with incorporation ofcompound 2, up to 15% 2, after which the mate-rials no longer indicate a melting transition. Thecomplete spectroscopic features of these copoly-mers are not described in detail here but areconsistent with those expected for the depictedcopolymer.

Dihydroxylation of Allyl-Functionalized Polyesters

Our use of 2 in homo- and copolymerizations ofCL has afforded a new set of functional polyesters

Figure 2. 1H NMR spectrum of copolymer 5b pre-pared from 2 and CL.

Figure 3. Overlaid carbonyl regions of 13C NMRspectra of (a) copolymer 5a, (b) poly(�-caprolactone)homopolymer, and (c) poly(allyl-valerolactone) ho-mopolymer.

Table 2. Data for Copolymerization of 2 with VLIncluding Food Ratios, Percent Incorporation of 2,Theoretical versus Experimental DP, and PDIs

PolymerNumber

FeedRatio2:VL

Incorporation2 DPtheor DPexp PDI

4 100:0 100 60 50 1.117a 75:25 66 60 48 1.117b 50:50 41 60 63 1.167c 25:75 22 60 62 1.136 0:100 0 60 66 1.13

1988 PARRISH, QUANSAH, AND EMRICK

that can be prepared with controlled molecularweights and degree of pendant functionality aswell as exhibit thermal properties significantlydifferent from CL and VL homopolymers orCL-VL copolymers. It would be interesting andpossibly useful to modify this side-chain function-ality to afford, for example, hydrophilic polyes-ters. One potential route is by dihydroxylation ofthe pendant olefins to give diol chains pendant tothe polyester backbone. We were interested tostudy the feasibility of this functionalization,given the potential for transesterification/cycliza-tion to complicate this process.

We found that treatment of copolymers oftype 5 with NMO/OsO4 resulted in complete con-version of the allyl olefins to hydroxyalkyl groupsto give polymer 8, as shown in Scheme 2. GPC of8 gave molecular weight and PDI values veryclose to those of the starting copolymer 5 (e.g., Mw

6600 g/mol, PDI 1.16 before dihydroxylation: Mw

6800 g/mol, PDI 1.13 after dihydroxylation). Veryslight decreases in the observed PDI are probablydue to the precipitation step used to purify 8.Daily GPC analysis of this material revealed aslow degradation process, whereby molecularweight gradually decreased, the PDI increased,and small molecules “grew in” to the chromato-graph. For example, in polymer 8 described pre-viously, after 7 days we observed a decrease in Mw

to 5900 and an increase in PDI to 1.25 over aperiod of 7 days.27 Not surprisingly, this degrada-tion process was much more rapid in the case ofdihydroxylation of homopolymer 4. In fact, initialattempts to isolate the dihydroxylated version of4 were unsuccessful because only low molecularweight material was recovered. Future studieswill examine different routes toward effectivefunctionalization as well as trapping the function-alized polymer before degradation occurs. Never-theless, tunable degrees of functional group incor-poration, hydrophilicity, and degradation rates incopolymers of this type may be interesting forsome specific applications, both medical and oth-erwise.

The authors acknowledge financial support from theUniversity of Massachusetts, the Healey Foundation,and the NSF-supported MRSEC. J. K. Quansah (MountHolyoke College, South Hadley, MA) gratefully ac-knowledges a summer research fellowship as a partic-ipant in the MRSEC-REU program.

REFERENCES AND NOTES

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3. Langer, R. Acc Chem Res 2000, 33, 94.4. Peppas, N. A.; Langer, R. Science 1994, 263, 1715.5. Han, D. K.; Hubbell, J. A. Macromolecules 1996,

29, 5233.6. Jacoby, M. Chem Eng News 2001, Feb. 5th, 30.7. Mecerreyes, D.; Miller. R. D.; Hedrick, J. L.; De-

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13. Kros, A.; Gerritsen, M.; Murk, J.; Jansen, J.; Som-merdijk, N.; Nolte, R. J Polym Sci Part A: PolymChem 2001, 39, 468.

14. Moller, M.; Kånge, R.; Hedrick, J. L. J Polym SciPart A: Polym Chem 2000, 38, 2067.

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17. Vanhoorne, P.; Dubois, P.; Jerome, R.; Teyssie, P.Macromolecules 1992, 25, 37.

18. Duda, A.; Penczek, S.; Dubois, P.; Mecerreyes, D.;Jerome, R. Macromol Chem Phys 1996, 197, 1273.

19. Molander, G. A.; Harris, C. R. J Am Chem Soc1995, 117, 3705.

Scheme 2

FUNCTIONAL POLYESTERS 1989

20. Johns, D. B.; Lenz, R. W.; Luecke, A. In Ring-Opening Polymerization; Elsevier Applied Science.New York, 1984: Chapter 7, Vol. 1.

21. Swada, H. Thermodynamics of Polymerization;Marcel Dekker. New York, 1976; p 150.

22. See reference 7 for a report on the polymerizationof 6-allyl(caprolactone), a monomer obtained byBaeyer–Villager oxidation of 2-allylcyclohexanoneand subsequent separation from the epoxidized by-product.

23. Hall, H. K., Jr.; Schneider, A. K. J Am Chem Soc1958, 80, 6428.

24. Storey, R.; Hoffman, D. Makromol Chem MacromolSymp 1991, 42, 185.

25. Duda, A.; Biela, T.; Libiszowski, J.; Penczek, S.;Dubois, P.; Mecerreyes, D.; Jerome, R. Poly DegradStab 1998, 59, 215.

26. Nakayama, A.; Kawasaki, N.; Aiba, S.; Maeda, Y.;Avanitoyannis, I.; Yamamoto, N. Polymer 1998, 39,1213.

27. This PDI was taken from the polymer signal anddid not integrate the signal for small molecules(baseline separated from polymer) into thecalculation.

1990 PARRISH, QUANSAH, AND EMRICK