atom-transfer radical copolymerization of furfuryl methacrylate (fma) and methyl methacrylate (mma):...

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Atom-Transfer Radical Copolymerization ofFurfuryl Methacrylate (FMA) and MethylMethacrylate (MMA): A Thermally-AmendableCopolymera

Amalin A. Kavitha, Nikhil K. Singha*

Polymers of furfurylmethacrylate (FMA) are interestingmaterials because of the presence of thefurfuryl group as the reactive diene functionality in the pendent group. Copolymers of FMA andMMA were prepared using atom-transfer radical polymerization (ATRP) catalyzed by CuCl, incombination with HMTETA as a ligand at 90 8C. It was very difficult to prepare by conventionalradical polymerization because of several side reactions involving the reactive diene group. Thecopolymer composition was calculated using 1H NMR studies. The reactivity ratios of FMA andMMA (r1 and r2) were determined using the Finemann-Ross and Kelen-Tudos linearizationmethods. The reactivity ratios obtained were r1¼ 1.56 and r2¼ 0.56. Diels-Alder chemistrywas carried out usingthe reactive diene ofthe copolymers and amaleimide as the dieno-phile. Interestingly, theresultant material wasobserved to be thermo-reversible as evidencedby FT-IR spectroscopyand DSC studies.

A. A. Kavitha, N. K. SinghaIndian Institute of Technology, Rubber Technology Centre,Kharagpur 721302, IndiaFax: þ91 3222 282700; E-mail: [email protected]

a : Supporting information for this article is available at the bottomof the article’s abstract page, which can be accessed from thejournal’s homepage at http://www.mcp-journal.de, or from theauthor.

Macromol. Chem. Phys. 2007, 208, 2569–2577

� 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Introduction

Copolymerization is a very versatile, synthetic tool for

controlling the functionality and tailoring the physical and

chemical properties of macromolecules. Conventional

radical copolymerization produces copolymers with un-

controlled molecular weight and broad polydispersity.[1,2]

In this case the composition drift is reflected in a variable

DOI: 10.1002/macp.200700239 2569

A. A. Kavitha, N. K. Singha

2570 �

number of macromolecular chains, which are created

or terminated during the copolymerization process. In

controlled radical polymerization,[3,4] initiation is very

fast: almost all of the chains grow at the same time and at

the same rate, with no or a negligible amount of chain

transfer and termination. In controlled radical copolymer-

ization, composition drift is distributed along the fixed

number of macromolecular chains formed at the start of

the copolymerization.

Furfuryl methacrylate (FMA) is an interesting monomer

because of the presence of its reactive furfuryl pendant

group. FMA is of particular interest in clinical applications,

as a biomaterial (bone cement), and in coating and adhesive

applications due to its low polymerization shrinkage.[5]

Perez et al.[6] reported that methyl methacrylate (MMA)

can be substituted with FMA as a traditional monomer

in the preparation of biomaterials, because it has a lower

volume shrinkage and a lower heat of polymerization than

MMA. The presence of the reactive furfuryl group also

makes the polymer interesting, as the polymer can be

cross-linked via UV radiation. Importantly, it can also be

made thermally amendable by suitable chemical reactions

like the Diels-Alder (DA) reaction using a suitable dieno-

phile.[7] Wudl et al.[8,9] and Laita et al.[10] reported thermo-

reversible materials based on the DA reaction between

organic materials containing a furan group and a male-

imide group.

Conventional radical polymerization of furfuryl metha-

crylate (FMA) leads to insoluble and gelled polymers even

at low conversion, due to excessive chain transfer

involving the reactive furfuryl group in the polymer and

in the monomer.[7,11–13] This restricts the use of this

polymer in adhesive and coating applications, as it is very

difficult to handle highly viscous materials. During last

decade, polymer scientists have developed different

methods of controlled radical polymerization in which

the different irreversible chain-breaking processes (like

transfer) are minimized or are absent. Of the controlled

radical polymerization (CRP) methods, atom-transfer radi-

cal polymerization (ATRP) has achieved increasing impor-

tance. By ATRP it is possible to prepare polymers with a

desired molecular weight, narrow polydispersity, well-

defined architecture and interesting topology.[3,4,14,15]

ATRP can be applied to a very broad range of monomers

(unlike living ionic polymerizations) with a wide range of

temperatures (�20 to 200 8C), and is tolerant to different

functional groups present in the monomers and initia-

tors.[4,16–18] Recently for the first time we reported the

successful ATRP of FMA using a copper catalyst.[17c,d]

The aim of this paper is to carry out atom-transfer

radical copolymerization (ATRcP) of FMA and MMA

to determine the reactivity ratios of the FMA/MMA

comonomer pair. Poly[(furfuryl methacrylate)-co-(methyl

methacrylate)] [P(FMA-co-MMA)] prepared by ATRP was


2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

gel free and had a controlled molecular weight. Interest-

ingly, thermally-amendable material was prepared by the

Diels-Alder reaction using the reactive furfuryl group in

the FMA/MMA copolymer.

Experimental Part

Materials

Furfuryl methacrylate (FMA) (Aldrich, USA), methyl methacrylate

(MMA) (Aldrich, USA), and toluene (S.D. Fine chemicals, Mumbai)

were purified according to standard procedures.[19] CuCl (Aldrich,

USA) was purified bywashingwith glacial acetic acid, followed by

diethyl ether, and then dried under vacuum. Ethyl 2-bromoiso-

butyrate (EBiB) (98%) (Aldrich, USA), 1,1,4,7,10,10-hexamethyl-

triethylenetetramine (HMTETA) (97%), and 1,1-(methylenedi-4,1-

phenylene) bismaleimide (BM), were obtained from Aldrich, USA

and were used as received.

Characterization

Size-exclusion chromatography (SEC) measurements were per-

formed at ambient temperature on a Waters model 510 HPLC

pump, aWaters series R-400 differential refractometer andWaters

Ultrastyragel columns with pore sizes of 10 000, 1 000, and 500 A,

which were preceded with a pre-filter. HPLC-grade tetrahydro-

furan (THF) (Spectrochem, India) was used as the solvent, at a flow

rate of 1 ml �min�1. The polymer solutions were filtered through

a pre-filter/filter combination system compatible with organic

solvents. Poly(methyl methacrylate) (PMMA) with a narrow

polydispersity index (PDI) was used as the calibration standard.

The molecular weight (MW) and PDI of the polymers were

calculated using a PMMA calibration curve. 1H NMR and 13C NMR

spectra of polymers were recorded using a 300 MHz Bruker NMR

spectrometer, using CDCl3 as the solvent, which contained a small

amount of tetramethylsilane (TMS) as an internal standard.

Fourier-transform infrared (FT-IR) spectra were recorded using a

Perkin-Elmer, Inc. version 5.0.1 spectrophotometer. In this case,

the polymer solution in CHCl3was film cast over KBr cells and then

the FT-IR spectra were recorded. IR spectra were recorded in the

range of 4 000 to 400 cm�1. Differential scanning calorimetry

(DSC) was carried out using a ‘‘Pyris Diamond DSC’’, Perkin Elmer,

(UK) under nitrogen atmosphere at a heating rate of 10 8C �min�1.

A sample weight of approximately 4 mg was used for the

measurements. The temperature against heat flow was recorded.

Reactivity Ratios and Statistical Methods

Statistical-method calculations were performed using SPSS (Statis-

tical Package for Social Sciences) version 10.00. The ‘‘sum-of-squares

space’’ (SS-space) approach was used to calculate joint confidence

intervals (JCIs), contour plotwas performed using Surfer version 8.0.

Copolymerization of FMA and MMA by ATRP

A typical polymerization was carried out in a 50 ml three-necked

round-bottom flask. Toluene (6 ml), FMA (2 g, 0.0120 mol), MMA

DOI: 10.1002/macp.200700239

Atom-Transfer Radical Copolymerization of Furfuryl Methacrylate (FMA) . . .

Scheme 1. Atom-transfer radical copolymerization (ATRcP) of furfuryl methacrylate and methylmethacrylate [P(FMA-co-MMA)].

(4.8 g, 0.048 mol), CuCl (0.0593 g,

0.0006 mol) were accurately

weighed and transferred to the flask.

The HMTETA ligand (0.1382 g,

0.0006mol) was then added. Oxygen

was removed from the reactionmix-

ture by passing nitrogen through the

round-bottom flask. The polymeriza-

tion was started by adding EBiB

(0.1170 g, 0.0006 mol) and was

carried out at 90 8C. Samples were

withdrawn at different time inter-

vals and some of them were used to

calculate the conversion, which was calculated gravimetrically.

The remaining samples was diluted with THF and purified by

passing through a column of aluminum oxide prior to SEC, NMR

spectroscopy and other analyses. The same procedures were

adopted for other feed ratios of ATRcP of FMA and MMA.

Yield: 1.4 g (70%).1H NMR (300 MHz, CDCl3) d¼7.4 (s, 1H, ––CH–O– of furan ring),

6.3 (m, 2H, ––CH–CH–– of furan ring), 4.9 (s, 2H, O–CH2– of PFMA),

3.5 (s, 3H, O–CH3 of PMMA), 0.9–1.9 (different aliphatic protons of

the methacrylate unit).13CNMR (300MHz, CDCl3) d¼177.65 (>CO), 149.33 (–C�of furan

ring), 110.33 (>CH– of furan ring), 143.60 (>CH– of furan ring),

125.90 (O–CH2 of PFMA unit), 52.12 (O–CH3 of PMMA unit), 58.68

(–CH2– of the methacrylate unit), 45.15 (>C< of the methacrylate

unit), 18.91 and 17.85 (atactic structure of a-CH3 side chain).

FT-IR (KBr): 3 122, 2 957, 1 727, 1 501, 1 153, 1 012, 919, 816,

746 cm�1.

The Mn;GPC and PDI of the polymer were 10 063 g �mol�1 and

1.31 respectively.

Free-Radical Copolymerization of FMA and MMA

FMA (1 g, 0.0060mol), MMA (0.4 g, 0.004mol) and toluene (1.5 ml)

were taken in a 25 ml three-necked round-bottom flask. The

polymerization was carried out at 90 8C under a nitrogen

atmosphere by adding benzoyl peroxide (0.024 g, 0.0001 mol).

The viscous solution was precipitated into n-hexane.

Yield: 0.96 g (conversion 68%).

Table 1. Copolymerization of FMA and MMA: [EBiB]0:[M]0:[CuCl]0:[H

Monomer feed ratio:

FMA (M1):MMA (M2)

Total

monomer

conversion

Mn;Theo M

mol-% % g �molS1 g

60:40 70 10 118 1

50:50 65 8 900

20:80 60 7 027

80:20 45 7 052

a)Compositions were measured by NMR spectroscopy.



Preparation of Cross-Linked Polymer via the DA

Reaction of P(FMA-co-MMA) with Bismaleimide (BM)

Amixture of P(FMA-co-MMA) and BM (1:1 bymoles)was dissolved

in 6 ml of dichloromethane (CH2Cl2) (DCM) and stirred at room

temperature, followed by heating at 120 8C under a nitrogen

atmosphere. The reaction mixture was kept at room temperature

for 24 hours and the cross-linked polymer was obtained. The final

product was dried in a vacuum oven for 12 h.

Yield: 1.64 g (82%).

FT-IR (KBr): 3 132, 2 958, 1 710, 1 638, 1 395, 919, 826, 697 cm�1.

Results and Discussion

The atom-transfer radical copolymerization (ATRcP) of

FMA and MMA was carried out using ethyl 2-bromoiso-

butyrate (EBiB), CuCl and HMTETA, as initiator, catalyst

and ligand respectively (Scheme 1). The copolymerization

was carried out at different feed ratios of the FMA and

MMA as illustrated in Table 1.

The kinetic plot in Figure 1 shows that the dependence

of ln[1/(1�X)] (X¼ conversion of monomers) versus time

is linear. It is consistent with a controlled polymerization,

which is first order with respect to the monomer

concentration. The results of linear-regression analysis

(values of R2) are shown in Figure 1. The linear kinetic plot

indicates that the concentration of growing chain species

MTETA]¼ 1:100:1:1, T¼90 8C; polymerization time¼ 11 h.

n;GPC PDI FMA

compositiona),

m1

MMA

compositiona),

m2

�molS1 mol-% mol-%

0 063 1.31 65 35

9 020 1.42 53 47

6 820 1.43 23 77

7 200 1.48 83 17

www.mcp-journal.de 2571


Figure 1. The plot of ln[1/(1�X)], where X is conversion of mono-mers, versus time for copolymerization of FMA with MMA atdifferent feed ratios (FMA:MMA; mol-%): 60:40 (�), 50:50 (!),20:80 (~), and 80:20 ($). [EBiB]0:[M]0:[CuCl]0:[HMTETA]¼1:100:1:1, T¼90 8C.

2572 �

remains constant during the copolymerization process.

Figure 1 shows that as the concentration of FMA decreases,

the rate of copolymerization decreases. However, in the

case of the 80:20 FMA:MMA ratio, the rate of polymeriza-

tion is very slow. This may be due to the different

solubility of the copolymer in FMA.

Figure 2 shows that the molecular weight of the copoly-

mer increases linearly with conversion of the monomers.

This linear increase and the relatively low polydispersity

indicate the controlled character of the copolymerization

process. All of the copolymers were gel free and were

Figure 2. Dependence of molecular weight and polydispersity ontotal conversion of the monomers in the ATRcP of FMA and MMAat different monomer feed ratios, catalyzed by CuCl/HMTETA.The concentration of different ratios, as shown in Figure 1.



highly soluble in different organic solvents like THF,

toluene, CHCl3. However, the copolymers prepared by

conventional radical copolymerization were highly gelled.

A soxhlet extraction showed that the copolymer (FMA:

MMA¼ 60:40) had 75% gelation. ATRP works in the

reversible equilibrium between the dormant species and

the active radicals. Thus the concentration of radicals is

lower and side reactions (like chain transfer) involving

the reactive furfuryl group are minimized. The copolymer

of FMA and MMA prepared by ATRcP was used as a

macroinitiator to monitor whether they have well-defined

halogen end-groups. In this case, fresh MMA was added

to the copolymer of FMA and MMA (60:40) (Mn ¼ 10 063

g � mol�1, PDI¼ 1.31) and the polymerization was carried

out at 90 8C using a CuBr/ pentamethyl diethylene

triamine (PMDETA) catalyst system. The resultant polymer

had Mn;GPC ¼ 18 205 g �mol�1 (Mn;Theo ¼ 18 573) and PDI¼1.37. Successful block copolymerization shows that the

poly(FMA-co-MMA) had well-defined halogen end-groups.

Recently Singha et al.[17a] reported successful ATRP of an

acrylate bearing reactive oxetane functionality, which

was very susceptible to undergoing gel formation during

conventional radical polymerization.

Structural Characterization andCopolymer Composition

The structural characterizations of FMA/MMA copolymers

were performed using NMR spectroscopy. Figure 3 shows

the 1HNMR spectra of the copolymer of P(FMA-co-MMA) at

a feed ratio of FMA:MMA¼ 60:40. The resonances of the

different types of protons have been assigned in Figure 3.

The peaks at 0.7 to 1.9 ppm are due to the different satu-

rated protons (–CH3 and –CH2–) of the PFMA and PMMA

units (designated as ‘‘6 and 7’’ in Figure 3). The peaks at

7.4 and 6.3 ppm correspond to the different aromatic

protons of PFMA (designated as ‘‘4’’ and ‘‘2 & 3’’ in

Figure 3). Interestingly, the ratio of these two types of

protons (designated as ‘4’ and ‘2 & 3’) was unaffected, and

was 2:1. Goiti et al.[7] reported that conventional radical

polymerization of FMA leads to gel formation due to the

excessive chain transfer involving the proton designed as

‘4’ in the FMA in Figure 3. In this case the ratio of protons

attached to C4 and C2 & 3 is 2:1. It indicates the C4 proton

was not affected during the ATRcP. All of the copolymers

were soluble in many of the organic solvents, such as THF,

CHCl3 and toluene, indicating the absence of any gel

formation during ATRP. The 13C NMR spectra of the

copolymer clearly indicated that the C4 carbon was not

affected during the polymerization (13C NMR and dis-

tortionless enhancement by polarization transfer (DEPT)

spectra are available in the Supporting Information). The

DEPT 135 spectrum was very useful in determining the

DOI: 10.1002/macp.200700239


Figure 3. Representative 1H NMR spectra of the FMA-MMA copolymer system with feed molar composition 60:40 (FMA:MMA): (a) initialcopolymer at 1 h (conversion¼ 7%); (b) final copolymer.

quaternary, methine (>CH–), methylene (–CH2–) and

methyl carbon. There were no undesirable resonances,

which indicated there were no side reactions during

ATRcP. The resonances at d¼ 3.5 ppm and 4.9 ppm are

due to –OCH3 and –OCH2– protons of the PMMA and

PFMA units and are designated as ‘‘8’’ and ‘‘5’’ respectively

(Figure 3). The average copolymer composition (mole

fraction of FMA and MMA) was calculated by using

Equation 1. The composition of the copolymers as

determined by 1H NMR spectroscopy, along with the feed

composition, is shown in Table 1.

Macrom

� 2007

FM ¼ 2A1

2A1 þ 3A2(1)

In Equation (1), A1 and A2 represent the total integrated

peak areas at d¼ 5.0 for –OCH2– protons in the PFMA unit

(‘5’ in Figure 3) and at d¼ 3.6 for the –OCH3 protons in the

PMMA unit (‘8’ in Figure 3) in the 1H NMR spectrum of the

copolymer.

Determination of Reactivity Ratios ofFMA and MMA in ATRcP

In the copolymerization of FMA (1) and MMA (2) the

reactivity ratio r1 is defined as k11/k12, where k11 is the rate

constant of the reaction between a growing polymer chain

with FMA as the terminal unit and FMA (homopropaga-

tion) and k12 is the rate constant of the reaction between

the same reactive chain-end and theMMAmonomer (cross

propagation). The corresponding reactivity ratio of MMA

ol. Chem. Phys. 2007, 208, 2569–2577

WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

(2) r2 is defined in the sameway as described for r1. A set of

ATRcP reactions of FMA and MMA, changing the initial

molar feed ratio, was carried out using the CuCl/HMTETA

catalyst system. The effect of FMA on the rate of the

polymerization was clearly observed. The polymerization

rate decreased and a lower monomer conversion was

obtained by increasing the amount of MMA in the initial

feed ratio (Figure 1 and Table 1).

The monomer reactivity ratios were obtained by the

Finemann-Ross method,[20,21] the Jaacks method[22] and

the Kelen-Tudos[23] method, with varying monomer feed

compositions. According to the Kelen-Tudos[23] method, h

was plotted versus j, as shown in Figure 4 (the results and

the notation of different variables have been explained

in the Supporting Information). The monomer reactivity

ratios of FMA andMMAwere determined to be rFMA¼ 1.54

and rMMA¼ 0.57 from the slope (h¼ r1) and intercept (j¼ r2,

calculated by Equation 2) of the best linear fitting. The

values of the monomer reactivity ratios seem to indicate

that growing radicals with an FMA end were added to

the FMAmonomerwith a higher preference, while radicals

with an MMA end also preferred to be added to the FMA

monomer.

j ¼ �r2a

ð1� jÞ (2)

The reactivity ratios were also calculated using the

Finemann-Ross method.[20,21] In this case M� (M/P) was

plotted againstM2/P (whereM¼molar feed ratio (M1/M2),

P¼ copolymer composition (m1/m2)) and the reactivity

ratios r1 and r2were calculated from the slope and from the



Figure 4. Kelen-Tudos plot for copolymerization of FMA withMMA. F¼M1/M2 (monomer feed ratio); f¼m1/m2 (copolymercomposition). (PFMA¼M1, PMMA¼M2). Figure 5. 95% joint confidence region of r1 and r2 values for the

copolymerization of FMA and MMA.

2574 �

intercept respectively[21] The Jaacks method[22,24,25] has

also been applied to determine the reactivity ratio of FMA,

whichwas used in excess of the othermonomerMMA. The

reactivity ratio of FMA (r1) was calculated from the slope of

the linear logarithmic plot of the comonomer conversions.

(The Finemann-Ross plot and the Jaacks plots and equations

are available in the Supporting Information). Table 2

shows the reactivity ratios determined by different

methods. The r1 and r2 values obtained by each method

are in good agreement.

The reactivity ratios (r value) of the monomers were

determined by the non-linear least-squares fit calculation

(error-in-variables (EVM) method).[26,27] The 95% confi-

dence limit gives an idea of the experimental error and the

accuracy of the experimental conditions used to generate

the composition data.[28] Figure 5 shows the elliptical

graph of the 95% joint confidence limit, generated using a

non-linear least-squares-fit calculation method. The deter-

mined values of r1 and r2 are found to be 1.55 and 0.56,

Table 2. Reactivity ratio of FMA and MMA determined by differ-ent methods.

Methoda) r1(FMA)

r2(MMA)

r1/r2 1/r1 1/r2

Kelen-Tudos 1.54 0.57 0.8778 0.65 1.75

Finemann-Ross 1.56 0.56 0.8736 0.64 1.79

Jaacks plot 1.55W 0.05 – – – –

a)The value for r1 in the Jaacks plot was calculated using FMA in

excess.



respectively, which indicates the presence of a greater

amount of FMA units in the copolymer than in the feed.

Diels Alder Reaction between the Furfuryl Group ofthe Copolymer and a Bismaleimide

Diels-Alder (DA) cycloaddition reactions are used in the

polymer synthesis, modification and cross-linking in poly-

meric materials.[13] These copolymers have reactive furan

rings which act as a dienic reagent to undergo cycloaddi-

tion DA reactions with different bisdienophiles.[29,30] The

DA reaction was carried out between P(FMA-co-MMA) and

a maleimide monomer: (1,1-(methylenedi-4,1-phenylene)

bismaleimide (BM). The furan rings in the PFMA part of the

copolymer and themaleimide group in the BM acted as the

diene and dienophile respectively. Equimolar quantities

of P(FMA-co-MMA) (60:40) and BM (1:1, by moles) were

dissolved in dichloromethane and stirred at room tem-

perature, followed by heating at 120 8C under a nitrogen

atmosphere. The reaction mixture was then kept at room

temperature for 24 h and the cross-linked polymer was

obtained. An increase in the viscosity of the solution was

observed during the DA reaction. The thermo-reversible

properties of the furfuryl-maleimide system have been

studied by FT-IR analysis by many researchers.[17d,31,32]

The thermo-reversible properties of the copolymer-BM

system were characterized by FT-IR spectroscopy and DSC

analysis during its heating/cooling cycle. The thermal

reversibility of the reaction was proven by the cleavage of

the poly-adducts at high temperature (heating) and the

ambient temperature (cooling), as shown in the FT-IR

spectra in Figure 6. Figure 6(a–c) represent the FT-IR spectra

DOI: 10.1002/macp.200700239


Figure 6. FT-IR spectra of (a) P(FMA-co-MMA); (b) non-cross-linked polymer (heating at 120 8C); and (c) cross-linked polymer (roomtemperature).

of the P(FMA-co-MMA) (60:40) copolymer, the copoly-

mer-BM mixture at 120 8C (non cross-linked polymer) and

the copolymer-BM adduct under the cooling condition

(cross-linked polymer), respectively. Figure 6a shows

intense peaks at 1 153 cm�1 and 1 012 cm�1, which are

attributed due to the ether linkage and ring breathing in

the furan ring respectively. It clearly indicates that the

furfuryl group was unaffected during the ATRcP. Earlier

NMR studies have also confirmed that the furfuryl group

was not affected during copolymerization. In Figure 6(a–b)

there is no peak at 1 636 cm�1, indicating the absence of

>C––C<. In the heating condition (Figure 6b) the char-

acteristic peaks are well distinguished, compared to the

cross-linked polymer at ambient conditions (Figure 6c).

Figure 6b shows an intense peak at 1 012 cm�1, which

indicates that the furan ring of the copolymer is not

affected. On cooling the sample at ambient temperature,

the peak at 1 012 cm�1 completely disappears (Figure 6c). A

new peak appeared at 1 636 cm�1, which indicates the

formation of >C––C< due to the cross-link formation

between the P(FMA-co-MMA) and BM. It confirms the

(4þ 2) cycloaddition chemistry in the DA reaction between

the furfuryl diene in the copolymer and maleimide

dienophile in the BM. The strong absorption of the >C––O

stretching shifted from 1727 cm�1 to 1 710 cm�1 due to

the interaction between the copolymer of PFMA and BM.



Tarducci et al.[31] also reported the shifting of the >C––O

stretching during a DA reaction involving maleimide

derivatives.[10,32] The weak shoulder at 1 713 cm�1 can be

attributed to the different carbonyl environment, formed

after the DA reaction. When this cross-linked polymer

was heated again at 120 8C, FT-IR spectroscopy again

showed the spectrum in Figure 6b, thus the inter-

monomer linkages opened, indicating the system is

thermo-reversible. Several cycles of heating and cooling

were carried out to confirm the thermally-amendable

character of the copolymer in the presence of BM.

Usually, the thermo-reversible properties of thermally-

amendable materials are characterized by DSC analy-

sis.[8,9,13,17d] Those reports mainly involve the DA reaction

between maleimide and the organic material with the

furfuryl functionality or the FMA homopolymer. This work

involves the thermoreversible DA reaction between BM

and the furfuryl functionality present in a tailor-made

copolymer of FMA and MMA. Figure 7 shows the different

heating and cooling curves of the DSC analysis of the

cross-linked P(FMA-co-MMA) and maleimide materials.

Figure 7a shows the heating curve of the cross-linked

polymer when heated from 25 8C to 250 8C. It has an

endothermic peak at 147 8C, which indicates that the

cross-linked material is cleaved into furan and maleimide

moieties. The DSC analysis of the cross-linked material



Figure 7. DSC curve for the cross-linked polymer (P(FMA-co-MMA)-BM): (a) first heating curve; (b) cooling curve; (c) secondheating curve.

2576 �

based on the furfuryl functionality and the maleimide

groups showed an endothermic transition at 120 8C.[8,9,17d]

In our case we observed this at 147 8C, because of the

presence of PMMA in the copolymer. The cooling curve

(Figure 7b) shows an exothermic peak at 122 8C to 158 8C.This indicates that the disconnected furan and maleimide

moieties on the heated samples come closer together on

cooling and then finally reconnect very efficiently,. The

second heating curve (Figure 7c) shows a transition at

118 8C, which is due to the Tg of the cross-linked polymer.

Thus the DSC analysis shows an endothermic as well as an

exothermic peak, which are due to the disconnection of the

inter-monomer (a ‘diene’ based on the furfuryl function-

ality in the tailor made P(FMA-co-MMA) and a ‘dienophile’

based on a maleimide) linkages on heating and due to the

reconnection of these inter-monomer linkages, respec-

tively. This indicates that the copolymer-BM materials are

thermo-reversible.

Conclusion

The copolymerization of FMA with MMA was successfully

carried out by ATRP using EBiB as the initiator, CuCl as the

catalyst, in combination with HMTETA as the ligand.

The polymerization was controlled, with a linear increase

of the molecular weight and a relatively narrow molecular-

weight distribution. The copolymers prepared by ATRP

were completely soluble in organic solvents, whereas the

polymers prepared by conventional free-radical copoly-

merization were gelled. The FT-IR and NMR spectra of

P(FMA-co-MMA) showed that the reactive furfuryl func-



tionality was not affected during the ATRcP. The copoly-

mer compositionwas calculated using the 1HNMR spectra.

The reactivity ratios for the copolymerization of FMA

and MMA were determined using the Kelen-Tudos and

Finemann-Ross methods and were found to be r1,FMA¼1.56 and r2(MMA)¼ 0.56. These values were compared with

the 95% joint confidence limit. Interestingly, the reactive

furfuryl functionality in the copolymer was used to make

thermally-remendable cross-linked polymer in combina-

tion with BM. The reversible nature of the cross-linked

polymer was confirmed by FT-IR spectroscopy and DSC

analysis. In the DSC experiments the copolymer-BM

systems show a clear endotherm during heating, indicat-

ing the cleavage of the inter-monomer linkages; they

also show an exotherm during cooling, indicating recon-

nection of the dienes and dienophiles. This hypothesis was

corroborated by FT-IR analysis during the heating/cooling

cycle.

Acknowledgements: The authors gratefully acknowledge theDepartment of Science & Technology (DST), New Delhi and IIT,Kharagpur (for the sanction of ISIRD project) for the financialsupport. Thanks are due to Prof. B. M.Mandal andMr.D. Chatterjeeat IACS, Calcutta, for their help in GPC analysis of the polymersamples.

Received: May 2, 2007; Revised: August 30, 2007; Accepted:September 3, 2007; DOI: 10.1002/macp.200700239

Keywords: atom-transfer radical polymerization (ATRP); copoly-mers; Diels-Alder reaction; thermo-reversible

[1] G. Moad, D. H. Solomon, ‘‘The Chemistry of Free RadicalPolymerization’’, 1st edition, Elsevier Science Ltd, Oxford 1995.

[2] [2a] T. Fukuda, Y. D. Ma, H. Inagaki,Makromol. Chem., Rapid.Commun. 1987, 8, 495; [2b] T. Fukuda, Y. D. Ma, H. Inagaki,Macromolecules 1985, 18, 17; [2c] K. Kostakis, S. Mour-mouris, K. Kotakis, N. Nikogeorgos, M. Pitsikalis, N. Hadji-christidis, J. Polym. Sci., Part A: Polym. Chem. 2005, 43,3305; [2d] H. A. S. Schoonbrood, R. C. P. M. van Eijnatten,B. van den Reijen, A. M. van Herk, A. L. German, J. Polm. Sci.,Part A: Polym. Chem. 1996, 34, 935; [2e] A. M. Aertds, A. L.German, G. M. P. van der Velden, Magn. Reson. Chem. 1994,32, 704; [2f] A. M. Aerdts, J. W. deHaan, A. L. German,Macromolecules 1993, 26, 1965.

[3] [3a] K. Matyjaszewski, Controlled Radical Polym., ACS Symp.Ser. 1997, 685, 2; [3b] ‘‘Controlled Radical Polymerization:Progress in ATRP, NMP and RAFT’’, K. Matyjaszewski, Ed.,American Chemical Society, Washington DC 2000.

[4] [4a] K.Matyjaszewski, J. Xia, Chem. Rev. 2001, 101, 2921; [4b]M. Kamigaito, T. Ando, M. Sawamoto, Chem. Rev. 2001, 101,3689.

[5] N. Davidenko, D. Zaldivar, C. Peniche, R. Sastre, R. J. J. San,J. Polym. Sci., Part A: Polym. Chem. 1996, 34, 2759.

[6] E. Perez, Degree Thesis, Havana University, Havana 1990.[7] E. Goiti, M. B. Huglin, M. R. Jose, Polymer 2001, 42, 10187.

DOI: 10.1002/macp.200700239


[8] X. Chen, M. A. Dam, K. Ono, A. Mal, H. Shen, S. R. Nutt, K.Sheran, F. Wudl, Science 2002, 295, 1698.

[9] X. Chen, F. Wudl, K. A. Mal, H. Shen, R. Steven, Macro-molecules 2003, 36, 1802.

[10] H. Laita, S. Boufi, A. Gandini, Eur. Polym. J. 1997, 33, 1203.[11] J. Lange, J. Rieumont, N. Davidenko, R. Sastrec, Polymer

1998, 39, 2537.[12] C. Peniche, D. Zaldivar, A. Bulay, S. R. Roman, J. Appl. Polym.

Sci. 1993, 50, 2121.[13] [13a] C. Gousse, A. Gandini, Polym. Int. 1999, 48, 723; [13b] A.

Gandini, M. N. Belgacem, Prog. Polym. Sci. 1997, 22, 1203[13c] E. Goiti, M. B. Huglin, J. M. Rego, Eur. Polym. J. 2004, 40,219.

[14] [14a] S. V. Arehart, K. Matyjaszewski, Macromolecules 1999,32, 2221; [14b] J. Huang, R. Gil, K. Matyjaszewski, Polymer2005, 46, 1168; [14c] G. Moineau, M. Minet, P. Dubois, P.Teyssie, T. Senninger, R. Jerome, Macromolecules 1999, 32,27; [14d] V. Percec, T. Guliashvili, J. S. Ladislaw, A. Wistrand,A. Stjerndah, M. J. Sienkowska, M. J. Monteiro, S. Sahoo,J. Am. Chem. Soc. 2006, 128, 14156.

[15] [15a] D. P. Chatterjee, B. M. Mandal, Polymer 2006, 47, 1812;[15b] D. M. Haddleton, C. B. Jasieczek, M. J. Hannon, A. J.Shooter, Macromolecules 1997, 30, 2190; [15c] D. M. Had-dleton, M. C. Crossman, B. H. Dana, D. J. Duncalf, A. M.Heming, D. Kukulj, A. J. Shooter, Macromolecules 1997, 32,2110.

[16] [16a] V. Raghunadh, D. Baskaran, S. Sivaram, Polymer 2004,45, 3149; [16b] A. Mittal, S. Sivaram, D. Baskaran, Macro-molecules 2006, 39, 5555.

[17] [17a] N. K. Singha, B. D. Ruiter, U. S. Schubert, Macromol-ecules 2005, 38, 3596;[17b] H. Dutta, A. K. Bhowmick, N. K.Singha, J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 1661;[17c]A. A. Kavitha, A. Choudhury, N. K. Singha,Macromol. Symp.2006, 240, 232;[17d] A. A. Kavitha, N. K. Singha, J. Polym. Sci.,Part A, Polym. Chem. 2007, 45, 4441.



[18] H. Schlaad, B. Schmitt, A. H. E. Muller, Angew. Chem. 1998,110, 1497;Angew. Chem. Int. Ed. 1998, 37, 1389.

[19] D. D. Perrin, W. L. F. Armarego, D. R. Perrin, ‘‘Purificationof Laboratory Chemicals’’, 2nd edition, Pergamon, Oxford1980.

[20] M. Fineman, S. D. Ross, J. Polym. Sci. 1950, 5, 259.[21] J. M. G. Cowie, ‘‘Polymers: Chemistry and Physics of Modern

Materials’’, 2nd edition, CRC Press, Boca Raton, FL 1991, p. 106.[22] V. Jaacks, Makromol. Chem. 1972, 161, 161.[23] T. Kelen, F. Tudos, J. Macromol. Sci., Chem. A. 1975, 9, 1.[24] I. Ydens, P. Degee, D. M. Haddleton, P. Dubois, Eur. Polym. J.

2005, 41, 2255.[25] ‘‘Polymer Handbook’’, J. Brandrup, E. H. Immergut, E. A.

Grulke, Eds., John Wiley & Sons, New York 1999, p. 112.[26] [26a] S. G. Roos, A. H. E. Muller, K. Matyjaszewski, Macro-

molecules 1999, 32, 8331; [26b] M. J. Ziegler, K. Matyjas-zewski, Macromolecules 2001, 34, 415.

[27] M. Dube, A. M. Samayei, A. Penlidis, K. F. O. Driscoll,P. M. Reilly, J. Polym. Sci., Part A: Polym. Chem. 1991, 29,703.

[28] P. W. Tidwell, G. A. Mortimer, J. Polym. Sci., Part A: Gen. Pap.1965, 3, 369.

[29] [29a] B. Gacal, H. Durmaz,M. A. Tasdelen, G. Hizal, U. Tunca,Y. Yagci, A. L. Demirel,Macromolecules 2006, 39, 5330; [29b]R. Gheneim, C. P. Berumen, A. Gandini,Macromolecules 2002,35, 7246.

[30] [30a] X. Chen, F. Wudl, A. K. Mal, H. Shen, S. R. Nutt,Macromolecules 2003, 36, 1802 [30b] X. Chen, M. A. Dam, K.Ono, A. Mal, H. Shen, S. R. Nutt, K. Sheran, F. Wudl, Science2002, 295, 1698 [30c] Y. L. Liu, C. Y. Hsieh, Y.W. Chen, Polymer2006, 47, 2581.

[31] C. Tarducci, J. Pal, S. Badyal, A. Stuart, S. Brewerb, C. Willis,Chem. Commun. 2005, 406, 406.

[32] Y. Imai, H. Itoh, K. Naka, Y. Chujo,Macromolecules 2000, 33,4343.


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