fullerene end-capped biodegradable poly(ε-caprolactone)

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104

Fullerene End-Capped BiodegradablePoly(e-caprolactone)

Weihua Kai, Lei Hua, Tungalag Dong, Pengju Pan, Bo Zhu, Yoshio Inoue*

Fullerene capped poly(e-caprolactone)s (PCLs), namely single- and double-fullerene end-capped PCLs with different fullerene content, were successfully synthesized. The effect ofthe fullerene end on the crystallization behavior and mechanical properties of the PCL wasstudied. The aggregation behavior of the fullerenemoieties at the end of the PCL chain was alsostudied. It was found that the aggregated full-erenes have two kinds of effect on the crystal-lization behavior of the PCL i.e., confinementeffect and nucleating effect. The fullerene con-tent shows certain balance between the confine-ment effect and the nucleating effect on thecrystallization rate of PCL. It was also found thatthe mechanical properties of the fullerene end-capped PCLs are strongly related to the content offullerene and the mode of end-capping style:either single or double end-capping.

Introduction

Fullerene and its derivatives have attracted much atten-

tion because of their promising applications in many

fields, such as solar-energy conversion and storage, fuel

cells, macromolecular materials, and biomedical and life

sciences.[1–11] However, its poor solubility and processa-

bility pose difficulties in utilizing it in practical applica-

tions.[12,13] Incorporation of fullerene into polymers is a

useful method to improve its solubility.[14–16] Fullerene-

containing polymers have been prepared by grafting the

oligomer with reactive end-groups, by polymerization of

fullerene-containing macromolecules, or by reaction of

W. Kai, L. Hua, T. Dong, P. Pan, B. Zhu, Y. InoueDepartment of Biomolecular Engineering, Tokyo Institute ofTechnology, Nagatsuta 4259, Midori-ku, Yokohama 226-8501,JapanFax: þ81-45-924-5827; E-mail: [email protected]

Macromol. Chem. Phys. 2008, 209, 104–111

� 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

fullerene with ‘‘living’’ polymers.[8] The attachment of the

fullerene moieties onto polymer chains bring attractive

properties.[11,17,18] For instance, Kojima et al.[19] found

that incorporation of fullerene into polystyrene greatly

improves the polystyrene’s optical limiting property.

Fullerene-functionalized, p-conjugated polyesters have

been used as photovoltaic cells and electroluminescent

devices.[20,21] Fullerene-containing poly(2,6-dimethyl-1,4-

phenylene oxide) (PPO) membranes have a much higher

gas permeability than those of the original PPO.[22]

Recently, fullerene end-capped polymers have aroused

much research interests.[23–27] Wang et al.[28] found that

single end-capped poly(tert-butyl acrylate) shows good

photoconductive properties. Due to the aggregation

behavior of the fullerene moiety at the end of the polymer

chain, double-fullerene end-capped polymers will form

a network-like structure, which will greatly increase

the physical properties of the polymer.[29] Goh et al.[30–34]

have successfully attached fullerene onto the end of a

DOI: 10.1002/macp.200700375

Fullerene End-Capped Biodegradable Poly(e-caprolactone)

poly(ethylene oxide) (PEO) chain and the resulting double-

fullerene end-capped PEO (FPEOF) showed excellent

mechanical properties. The aggregation of fullerenemoieties

in the double-capped polymer leads to the formation of

network-like structures, so that the combination of a

double-fullerene capped polymer and a linear polymer is

expected to give rise to a pseudo-semi-interpenetrating

polymer network (p-SIPN). Poly(methyl methacrylate)

(PMMA) blended with FPEOF shows a good reinforced

toughness, which is comparable to the effect of nanotubes

on PMMA.[35] The introduction of fullerene into these

commonly-used engineering plastics has achieved much

success, but there are few reports on the incorporation of

fullerene in to biodegradable polyesters.

Aliphatic polyesters have attracted much research

interest due to their biodegradability and biocompatibil-

ity.[36–38] Poly(e-caprolactone) (PCL) is one of such typical

aliphatic polyesters.[39] It is fully biodegradable, biocom-

patible and nontoxic to living organisms.[39] Also, PCL has a

good resistant ability to water, oil, solvent, and chlorine.

The unique properties of PCL render it a high potential in

biomedical fields and it has been used in the development

of controlled drug-delivery systems as well as in surgical

sutures and other resorbable fixation devices.[39,40] PCL is a

linear aliphatic polyester, and there has no functional side

chains. This will greatly impede the application of PCL in

the medical area. The recent introduction of carbon

nanomaterials into PCL, to afford hybrids, is a good way

to improve its properties. Zeng et al.[41] have successfully

incorporated carbon nanotubes into PCL. According to

Goh’s and our previous work,[35,42–45] fullerene-capped

polymers are good additives for enforcing the mechanical

properties of other polymers.

In this study, a synthetic strategy for the synthesis of

fullerene-capped PCL, including single- and double-

fullerene end-capped PCL, is proposed. Due to the strong

aggregation nature of the fullerene moieties in the polymer

matrix,[31] the effect of the aggregation of fullerene at the

ends of single- and double-fullerene end-capped PCL on the

crystallization behavior and mechanical properties of PCL is

thoroughly investigated.

Table 1. Molecular characterizations of the PCL samples used for the

Sample code Initiator Mna) Polydisp

g �molS1

PCLL Lauryl alcohol 7 350

PCLH Lauryl alcohol 22 300

DPCLL 1,4-Butanediol 10 600

DPCLH 1,4-Butanediol 30 400

a)The number-average molecular weight (Mn) and polydispersity inde



Experimental Part

Materials

Fullerene (Lot: 4A0248-A)was purchased from the Frontier Carbon

Corporation (Tokyo, Japan). e-Caprolactone was purchased from

Kanto Chemical Co. Inc. (Tokyo, Japan) and distilled over CaH2

before use. Tin 2-ethylhexanoate [Sn(Oct)2], sodium azide,

chlorobutyryl chloride and tetra-n-butylammonium iodide were

purchased from Kanto Chemical Co. Inc. (Tokyo, Japan). PCL

samples with chains terminating in either 1 or 2 hydroxyl groups

were synthesized by ring-opening polymerization with lauryl

alcohol and 1,4-butanediol as the initiator with tin

2-ethylhexanoate as the catalyst at 120 8C. The molecular weight

and polydispersity index of the PCL samples are listed in Table 1.

PCLL and PCLH denote the single hydroxyl-ended PCL with the low

and highmolecularweight, respectively. DPCLL and DPCLH denote

the double-hydroxyl-ended PCL with low and high molecular

weight. After fullerene end-capping, an ‘‘F’’ was added to the end

of each sample name as PCLLF, PCLHF, DPCLLF and DPCLHF. PCL

with a molecular weight of Mn ¼1.15� 105 and polydispersity

index (PDI)¼1.47 was supplied by Daicel Chemical Ltd. (Japan)

and used after purification as the reference, PCLR.

Synthesis of Fullerene-Capped PCL

Themethod for synthesis of chloro-ended PCLL was similar to that

of Atthoff et al.[46] PCLL (10 g) samples were reacted with

chlorobutyryl chloride (1 g) in dry dichloromethane (DCM) (200 ml)

for 24 h at room temperature, in the presence of pyridine (1 ml) as

a catalyst. After that, the reaction mixture was poured into

ethanol to afford chloro-ended PCLL. The product was dried in a

vacuum oven at 40 8C for 48 h.

The chloro-ended PCLL (5 g) was reacted with sodium azide

(0.5 g) in anhydrous dimethylformamide (DMF) (100 ml) at 65 8Cfor 48 h with catalyst tetra-n-butylammonium iodide (0.2 g),

under nitrogen purging. The slurry was then ultra-centrifugated,

and the clear solution was poured into ethanol to afford azide-

ended PCLL. The product was dried in vacuum oven at 40 8C for

about 1 week.

The azide terminated PCLL (2 g) was reacted with fullerene

(0.21 g) in chlorobenzene (100 ml) at 135 8C with nitrogen purging

for 24 h. The solution was ultra-centrifugated and then filtered.

The clear filtrate was cast in the dishes to afford a wine-red

synthesis of the fullerene-capped PCLs.

ersity index, PDIa) Code of fullerene capped sample

1.2 PCLLF

1.4 PCLHF

1.2 DPCLLF

1.4 DPCLHF

x (PDI) were estimated from the GPC experiments.

www.mcp-journal.de 105

W. Kai, L. Hua, T. Dong, P. Pan, B. Zhu, Y. Inoue

Scheme 1. Reaction 1: chlorobutyryl chloride, pyridine, dichloromethane, room tempera-ture; reaction 2: sodium azide, tetra-n-butylammonium iodide, DMF.

106

product. The other fullerene-capped PCL sampleswere synthesized

following the same procedure as mentioned above and shown in

Scheme 1. The sample codes are listed in Table 1.

Characterizations

In order to confirm the synthesis of the fullerene end-capped PCL,1H NMR spectra of PCLL, chloro-PCLL, azide-PCLL and PCLLF were

measured at room temperature in CDCl3 solution on a Bruker

Avance 600 MHz spectrometer with a 30 8 pulse, 3.7 s-pulse-

repetition time, 32 000 data points and 256 free-induction-decay

(FID) accumulations.

The UV/Vis spectra of the PCLL and PCLLF were recorded on a

JASCO V-550 UV/VIS Spectrophotometer at room temperature.

The molecular weights of the PCLs were determined using a

Toso HLC-8020 gel-permeation chromatography (GPC) system

(Toso Co., Tokyo, Japan)with an SC-8010 controller and a refractive

detector with TSK gel G2000HXL columns, at 40 8C. Chloroformwas used as the eluent at a flow rate of 1 ml �min�1, and the

sample concentration was 1 mg �ml�1. Polystyrene standards of

low polydispersity were used to construct a calibration curve. The

GPC data were processed on an SC-8010 data processor in order to

calculate the number-average molecular weight (Mn) and weight-

average molecular weight (Mw).

Thermogravimetric (TG) analyses of fullerene-capped PCLs

were carried out using a Seiko (Tokyo, Japan) TG/DTA 220U with

the Exstar 6000 Station. The sample (10mg)was heated from 25 8Cto 600 8C at a heating rate 5 8C �min�1.

The melt-crystallization temperature (Tmc) of the PCLs and

fullerene-capped PCLs was measured through the crystallization

from the melting state on a PYRIS DIAMOND DSC (Perkin-Elmer).

The sample was firstly directly heated to 100 8C in the DSC cell and

held for 3 min at this temperature, followed by cooling at a rate of

10 8C �min�1 until the completion of non-isothermal crystallization.

The peak temperature of the non-isothermal crystallization curve

in the DSC experiment was recorded as the Tmc. The crystallization

enthalpy (DH) was determined from the peak of the crystallization.

Dynamic mechanical thermal analysis (DMTA) was performed

on a SEIKO-DMS210 instrument (Seiko Instrument Inc., Tokyo,

Japan) in the tensile mode at 5 Hz and a thermal-scanning rate of



2 8C �min�1. The samples were cut into

dimensions of 30 mm�10 mm� 0.2 mm

for the test.

Tensile mechanical tests were performed

at room temperature with an EZ test

machine (Shimadzu Corp., Tokyo, Japan)

at a crosshead speed of 3 mm �min�1. The

sample was cut into a ‘‘dog-bone’’-shape,

with width¼ 4.76 mm, length¼22.25 mm,

and thickness¼ 0.2 mm. For each sample,

more than 3 specimens were tested.

Scanning electron microscopy (SEM)

observations of the morphology of the gel

sample was performed on a scanning

electronmicroscope (JEOL JSM-5200, Japan).

Results and Discussion

The synthesis of fullerene-capped PCL follows three steps.

The PCL samples with the hydroxyl end were reacted with

chlorobutyryl chloride to afford the chloro-ended PCL

sample. The chloro-ended PCL was then reacted with

sodium azide to afford the azide-terminated PCL. The

production of the intermediate products of the PCLL

derivatives was monitored by 1H NMR spectroscopy

(Figure 1). For hydroxyl-group-ended PCL, the methylene

group at the chain end (t, 2H, –CH2–OH, chain end)

corresponds to the 1H resonance at a chemical shift of

3.64 ppm,[39] while for chloro-terminated PCL, themethylene

group of the chain end (t, 2H, –CH2–Cl, chain end) to the

resonance at 3.59 ppm. For the azide-terminated PCL,

the methylene group of the chain end (t, 2H, –CH2–N3,

chain end) corresponds to the resonance at 3.35 ppm. The

almost disappearance of the peak at 3.35 ppm indicates

that the almost all of the azide-terminated PCL is reacted

with the fullerene. That is, the 1H NMR spectroscopy

data indicate that the yield of fullerene-capped PCL is

about 100%.

The covalent attachment of fullerene to the PCL chain

end was also confirmed by the UV/Vis spectra. Fullerene

itself is insoluble in THF, so the THF solution of full-

erene-capped PCL contains only the fullerene covalently

attached to the end of a PCL chain. The UV/Vis spectra of

fullerene and fullerene-capped PCLL are shown in Figure 2.

The characteristic peak at 326 nm in the spectrum of

fullerene is also found in the fullerene-capped PCL samples.

The disappearance of the absorption peak at 400–600 nm

is due to the color change of the derivatives.[30] Here, the

attachment of fullerene onto the end of PCL greatly

increases the fullerene’s solubility in organic solvents.

Figure 3 shows the GPC traces of PCLL and PCLLF

samples. The GPC samples were prepared by dissolving the

solid in chloroform. The GPC trace of PCLLF shifts to a lower

elution-volume region and the peak becomes broader than

DOI: 10.1002/macp.200700375


Figure 1. 600 MHz 1H NMR spectra of PCLL, chloro-PCL, azide-PCLand PCLLF in chloroform.

Figure 3. GPC traces of PCLL and PCLLF.

that of the original PCLL. This may be due to hydrophobic

interactions or absorption phenomena rather than the size

exclusion.[47] The UV/Vis spectra and the GPC traces

confirm the production of fullerene-capped PCL.

The TG curves of the fullerene-capped PCLs are shown in

Figure 4. PCL was almost completely degraded above

500 8C, while the fullerene is stable up to a temperature of

600 8C. Thus, the weight content of the fullerene incorpo-

rated into the polymer ends, can be estimated from the

Figure 2. UV/Vis spectra of fullerene in hexane and PCLLF in THF.



remaining weight when the temperature is about

600 8C.[30] The fullerene weight content in fullerene-

capped PCL was estimated and the results were listed in

Table 2. They agree well with the theoretical values.[30]

The DSC curves observed during the melt crystallization

of DPCLL and its fullerene-capped derivative are shown in

Figure 5. In Figure 5, the Tmc value of DPCLL is higher than

that of DPCLLF, indicating the relatively higher crystal-

lization rate of DPCLL than DPCLLF. Thus, the introduction

of the fullerene moiety to the end of DPCLL has a negative

effect on the crystallization rate (confinement effect) of

DPCLL. The Tmc values for all of the PCL samples are listed in

Table 2. The Tmc values of the fullerene-capped PCL

samples are not always lower than the corresponding

mother PCL samples. The fullerene shows a certain balance

between the confinement effect and the nucleating effect

on the crystallization rate of PCL. For example, the Tmc

value of PCLH is almost the same as that of its fullerene

derivative, while the Tmc value of DPCLHF is higher than

that of its mother DPCLH sample.

Figure 4. TG curves of fullerene-capped PCLs.



Table 2. Thermal properties of the PCLs and their fullerene-capped derivatives.

Sample Code DHa) Tmca) Fullerene

contentb)Fullerene

contentc)

J � gS1 -C % %

PCLL S77.4 31.6 – –

PCLH S71.1 32.7 – –

DPCLL S72.2 27.3 – –

DPCLH S64.0 28.7 – –

PCLLF S65.7 25.9 10.5 8.8

PCLHF S59.4 32.5 3.7 3.2

DPCLLF S51.6 22.7 12.7 12.0

DPCLHF S50.1 30.5 4.9 4.5

a)The crystallization enthalpy (DH) and melt crystallization

temperature (Tmc) were determined from DSC and normalized

by PCL content; b)The fullerene weight content was determined

from the TG at the temperature of about 600 -C; c)The fullerene

weight content was determined from the theoretical calculation

based on 100% conversion.

Figure 6. Dynamic study of the fullerene-capped PCLs.

108

The values of crystallization enthalpy are also listed in

Table 2. The crystallization enthalpies generally decreased

with the introduction of fullerene. The decrease of the

crystallization enthalpy is related to the molecular weight

of PCL for double-fullerene end-capped PCL, and the higher

the PCLmolecular weight is, the smaller the decrease of the

crystallization enthalpies is.

The dynamic-mechanical behavior of PCLR and fullerene-

capped PCL was investigated by measurements of the

temperature dependence of the storage modulus and

tangent (tand). As shown in Figure 6a, the storage modulus

Figure 5. DSC curves of the melt crystallization of DPCLL andDPCLLF.



of PCLR is higher than that of fullerene-capped PCL at a

temperature below the glass transition (as seen from

Figure 6b). At a temperature higher than glass-transition

temperature, the order of the storagemodulus is as follows:

PCLHF>DPCLLF� PCLR>DPCLHF.

The tand curve is shown in Figure 6b: for a clear view,

only PCLR and DPCLHF are shown. Generally, the glass-

transition temperature Tg was determined as the peak

temperature of tand. For PCLR, the Tg is estimated to be

�51 8C, while for PCLHF, DPCLLF and DPCLHF, it is

estimated to be �43 8C, �37 8C and �39 8C. respectively.Thus, the introduction of fullerene onto the end of the PCL

chain greatly increases the Tg value of PCL.

The tensile properties of PCLR and fullerene-capped PCL

are shown in Figure 7 and Table 3. As the PCLLF samplewas

too brittle to study, its tensile parameters are not available.

The Young’s modulus was determined from the linear part

of the stress-strain curves with strain less than 2%. The

PCLHF has the highest Young’s modulus, about 290 MPa.

The DPCLLF has almost the same Young’s modulus as the

PCLR, and DPCLHF shows the lowest Young’s modulus,

DOI: 10.1002/macp.200700375


Figure 8. SEM photograph of hydrolyzed DPCLHF surface.Figure 7. Strain-stress curves of fullerene-capped PCLs.

about 170MPa. The fracture strain for the fullerene-capped

PCL is also listed in Table 3. The PCLHF achieved the highest

fracture strain, which is almost the same as that of PCLR.

That of DPCLHF is about 70% andDPCLLF is only about 10%.

Also, in Figure 7, the PCLR and PCLHF show a yield process,

while DPCLHF shows a strain-hardening process.

The reason for the particular mechanical properties of

fullerene-capped PCLs is strongly related to the state of

fullerene in the PCL matrix.

In order to study the state of fullerene in the PCL matrix,

an SEM photograph of the DPCLHF surface after degrada-

tion is shown in Figure 8. The DPCLHF degraded sample

was prepared by dipping the DPCLHF film into 1 N KOH

solution for 3 d, then washed with a large quantity of

water, and dried in the vacuumoven. From the SEMpicture

shown in Figure 8, the size of fullerene aggregates was

estimated to be from 200 to 500 nm, which is similar to

that of the fullerene aggregates observed for fullerene-

capped PEO.[34] The fullerene aggregates were formed by

aggregation of fullerene moieties at the end of PCL chains.

Considering the formation of fullerene aggregates in the

PCLmatrix due to the aggregation of the fullerenemoieties

at the ends of the PCL chains, it is easy to interpret why the

capped PCLs show the peculiar crystallization behavior and

Table 3. Tensile properties of PCLR and fullerene-capped PCLs.

Sample code Young’s Modulus Fracture strain

MPa %

PCLR 240W 20 620W 40

PCLLF – –

PCLHF 290W 10 600W 40

DPCLLF 250W 10 10W 2

DPCLHF 170W 4 70W 17



mechanical properties. In the crystallization process,

the fullerene aggregates have two possible effects on

the crystallization of PCL: the confinement effect and the

nucleating effect. According to Hoffman’s theory of

polymer melt-crystallization, the lower chain mobility

results in a lower crystallization rate.[48] The aggregation

of the fullerene moieties confines the motion of the PCL

chain, so that the crystallization rate of the PCL decreases.

Also, the fullerene aggregates at the ends of the PCL chains

can act as the nuclei, and promotes the crystallization of

the PCL chain. These two contradictory effects compete

with each other. If the confinement effect is larger than the

nucleating effect, the crystallization rate of the fullerene-

capped samples decreases, as found in PCLLF and DPCLLF. If

the nucleating effect is balanced with the confinement

effect, the crystallization rate of the fullerene-capped

samples will not change much from that of its mother PCL,

as found in PCLHF. If the nucleating effect is larger than

that of confinement effect, the crystallization rate of the

fullerene-capped samples increases, as in DPCLHF. The

values of crystallization enthalpy of all of the fullerene

capped PCLs are smaller than those of the original PCL.

Because the segments of PCL chain connected with the

fullerene particles are very hard to crystallize, the

crystallization enthalpy decreases.

The mechanical properties of fullerene capped PCLs are

much different from those of the original PCL samples. The

original PCL, PCLL, PCLH, DPCLL, and DPCLH samples are

very brittle, while after capping with fullerene, they

become very tough materials, except for PCLLF. For the

single-end fullerene-capped PCL, the fracture strain of

PCLHF is almost the same as that of PCLR and its Young’s

modulus is higher than that of PCLR. The aggregation of the

fullerene ends at the end of the PCLHF has a similar effect

to increasing the molecular weight of PCLH, so that the

fracture strain of PCLHF is almost the same as the value of



110

PCLR. The aggregation of the fullerene ends at the end of

the fullerene-capped PCL, leading to an increase in the

apparent molecular weight, has been verified by the GPC

measurements (Figure 3). A similar phenomenon has been

found in fullerene single end-capped PEO.[30] Also, due to

the reinforcement effect of the fullerene particles in PCLHF,

the Young’s modulus is higher than that of PCLR. For the

double-fullerene end-capped PCL, its mechanical proper-

ties are very different from those of the single-end

fullerene-capped PCL and PCLR. DPCLHF showed no yield

process in its strain-stress curve as PCLHF and PCLR, while it

did show a strain-hardening process. The fracture strain

andmodulus are also much lower than those of PCLHF and

PCLR (Figure 7 and Table 3). The aggregation of the

fullerene ends in DPCLHF leads to the formation of

pseudo-networks (p-N) with the fullerene aggregates as

the physical cross-linker.[35,42] The relatively lower fracture

strain of DPCLHF, to those of PCLR and PCLHF, is just due to

the formation of the p-N, which makes the PCL chains of

DPCLHF less ductile, as verified by a much increased

glass-transition temperature (Figure 6b). The much-

decreased Young’s modulus of DPCLHF, compared to that

of PCLR and PCLHF, is probably due to the large decrease in

crystallinity, which has been verified by DSC studies.

DPCLLF has a relatively higher modulus than DPCLHF, due

to the higher content of inorganic particles in DPCLLF than

in DPCLHF.

Conclusion

Fullerene-capped PCLs were successfully synthesized and

characterized by NMR spectroscopy, UV spectroscopy, and

GPC. It was found that the fullerene moieties at the PCL

chain ends can aggregate into small particles. Due to

aggregation, the mobility of the PCL chain greatly

decreased, resulting in an increase of the glass-transition

temperature and a change of crystallizability. The full-

erene aggregates were found to have both confinement

effect and nucleating effect on the crystallization of PCL.

The crystallization behavior, that is, retardation or

acceleration of crystallization, of fullerene-capped PCL

depends on a balance between these two kinds of effects.

Also, the mechanical properties of the fullerene-capped

PCL greatly rely on the capping styles and the fullerene

weight content. Considering the biodegradable and bio-

compatible properties of PCL, the fullerene-capped PCLs

will be expected to have applicability in biomedical engi-

neering.

Received: July 11, 2007; Revised: September 5, 2007; Accepted:September 10, 2007; DOI: 10.1002/macp.200700375



Keywords: crystallization; double-fullerene end-capped poly(e-caprolactone); networks; poly(e-caprolactone); single-fullereneend-capped poly(e-caprolactone)

[1] M. E. Rincon, H. Hu, J. Campos, J. Ruiz-Garcia, J. Phys. Chem. B2003, 107, 4111.

[2] K. Hinokuma, M. Ata, Chem. Phys. Lett. 2001, 341, 442.[3] S. Delpeux, F. Beguin, R. Benoit, R. Erre, N. Manolova,

I. Rashkov, Eur. Polym. J. 1998, 34, 905.[4] L. Y. Chiang, R. B. Upasani, J. W. Swirczewski, J. Am. Chem. Soc.

1992, 114, 10154.[5] Z. Slanina, S. L. Lee, L. Adamowicz, L. Y. Chiang, ‘‘The Chemistry

and Physics of Fullerenes and RelatedMaterials’’, K. M. Kadish,R. S. Ruoff, Eds., Vol. 3, Electrochemical Society, Pennington,NJ 1996, p. 987.

[6] L. Dai, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1999, C39,273.

[7] J. F. Nierengarten, New J. Chem. 2004, 28, 1177.[8] H. Imahori, S. Fukuzumi, Adv. Funct. Mater. 2004, 14, 525.[9] N. Martın, Chem. Commun. 2006, 2093.[10] T. M. Figueira-Duarte, A. Gegout, J. F. Nierengarten, Chem.

Commun. 2007, 109.[11] U. Hahn, F. Cardinali, J. F. Nierengarten,New J. Chem. 2007, 31,

1128.[12] H. W. Kroto, A. W. Allaf, S. P. Balm, Chem. Rev. 1991, 91, 1213.[13] R. S. Ruoff, D. S. Tse, R. Malhotra, D. C. Lorents, J. Phys. Chem.

1993, 97, 3379.[14] M. Prato, J. Mater. Chem. 1997, 7, 1097.[15] Y. Chen, Z. E. Huang, R. F. Cai, B. C. Yu, Eur. Polym. J. 1998, 34,

137.[16] Y. Ederle, C. Mathis, Macromolecules 1997, 30, 2546.[17] L. Kuang, Q. Chen, E. H. Sargent, Z. Y. Wang, J. Am. Chem. Soc.

2003, 125, 13648.[18] J. Venturini, E. Koudoumas, S. Couris, J. M. Janot, P. Seta,

C. Mathis, S. Leach, J. Mater. Chem. 2002, 12, 2071.[19] Y. Kojima, T. Matsuoka, H. Takahashi, T. Kurauchi, Macro-

molecules 1995, 28, 8868.[20] M.G. Nava, S. Setayesh, A. Rameau, P.Masson, J. Nierengarten,

New J. Chem. 2002, 26, 1584.[21] T. Lee, O. Park, J. Kim, Y. C. Kim, Chem. Mater. 2002, 14, 4281.[22] D. M. Sterescu, L. Bolhuis-Versteeg, N. F. A. Vegt,

D. F. Stamatialis, M. Wessling, Macromol. Rapid Commun.2004, 25, 1674.

[23] H. Yu, L. H. Gan, X. Hu, S. S. Venkatraman, K. C. Tam, Y. Y. Gan,Macromolecules 2005, 38, 9889.

[24] A. W. Jensen, B. S. Maru, X. Zhang, D. K. Mohanty,B. D. Fahlman, D. R. Swanson, D. A. Tomalia, Nano Lett.2005, 5, 1171.

[25] P. Ravi, S. Dai, C. H. Tan, K. C. Tam, Macromolecules 2005, 38,933.

[26] T. Kawauchi, J. Kumaki, E. Yashima, J. Am. Chem. Soc. 2005,127, 9950.

[27] H. Okamura, K. Miyazono, M. Minoda, K. Komatsu, T. Fukuda,T. Miyamoto, J. Polym. Sci., Part A: Polym. Chem. 2000, 38,3578.

[28] J. Yang, L. Li, C. Wang, Macromolecules 2003, 36, 6060.[29] T. Song, S. Dai, K. C. Tam, S. Y. Lee, S. H. Goh, Polymer 2003, 44,

2529.[30] X. D. Huang, S. H. Goh, S. Y. Lee, Macromol. Chem. Phys. 2000,

201, 2660.[31] T. Song, S. H. Goh, S. Y. Lee, Polymer 2003, 44, 2563.

DOI: 10.1002/macp.200700375


[32] X. D. Huang, S. H. Goh, Macromolecules 2000, 33, 8894.[33] X. D. Huang, S. H. Goh, Macromolecules 2001, 34, 3302.[34] T. Song, S. Dai, K. C. Tam, S. Y. Lee, S. H. Goh, Langmuir 2003,

19, 4798.[35] M. Wang, K. P. Pramoda, S. H. Goh, Chem. Mater. 2004, 16,

3452.[36] P. A. Holmes, Phys. Technol. 1985, 16, 32.[37] ‘‘Biodegradable Polymers as Drug Delivery Systems: Drugs and

the Pharmaceutical Science’’, Vol. 45,M. Chasin, R. Langer, Eds.,Marcel Dekker Inc., New York 1990.

[38] Y. Inoue, N. Yoshie, Prog. Polym. Sci. 1992, 17, 571.[39] G. A. Sung, G. C. Chang, Macromol. Rapid Commun. 2004, 25,

618.[40] F. Buffa, H. Hu, D. E. Resasco, Macromolecules 2005, 38, 8258.



[41] H. Zeng, C. Gao, D. Yan, Adv. Funct. Mater. 2006, 16, 812.[42] W. Kai, L. Zhao, B. Zhu, Y. Inoue, Macromol. Rapid Commun.

2006, 27, 109.[43] M. Wang, K. P. Pramoda, S. H. Goh, Macromolecules 2006, 39,

4932.[44] W. Kai, L. Zhao, B. Zhu, Y. Inoue,Macromol. Chem. Phys. 2006,

207, 746.[45] W. Kai, L. Zhao, B. Zhu, Y. Inoue, Macromol. Rapid Commun.

2006, 27, 1702.[46] B. Atthoff, F. Nederberg, L. Soderberg, J. Hilborn, T. Bowden,

Macromolecules 2006, 7, 2401.[47] N.Manolova, I. Rashko, H. VanDamme, F. Beguin, Polym. Bull.

1994, 33, 175.[48] J. D. Hoffman, Polymer 1983, 24, 3.


fullerene end-capped biodegradable poly(ε-caprolactone)

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