Preparation and characterization of graft terpolymers with controlled molecular structure

Preparation and Characterization of Graft Terpolymers withControlled Molecular Structure

JEAN-FRANCOIS LUTZ, NAZEEM JAHED, KRZYSZTOF MATYJASZEWSKI

Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue,Pittsburgh, Pennsylvania 15213

Received 29 December 2003; accepted 30 December 2003

ABSTRACT: Segmented terpolymers, poly(alkyl methacrylate)-g-poly(D-lactide)/poly-(dimethylsiloxane) (PLA/PDMS), were prepared with a combination of the “graftingthrough” technique (macromonomer method) and controlled/living radical polymeriza-tion (atom transfer radical polymerization or reversible addition–fragmentation trans-fer polymerization). Two synthetic pathways were used. The first was a single-stepapproach in which a low-molecular-weight methacrylate monomer (methyl methacry-late or butyl methacrylate) was copolymerized with a PLA macromonomer and a PDMSmacromonomer. The second strategy was a two-step approach in which a graft copol-ymer containing one macromonomer was chain-extended by a copolymerization of thesecond macromonomer and the low-molecular-weight methacrylate. The kinetics ofboth synthetic approaches were investigated, showing that the polymerizations exhib-ited a controlled/living behavior. Furthermore, the molecular structure of the terpoly-mers (composition, molecular weight distribution, and microstructure) was investi-gated by two-dimensional liquid chromatography. Well-defined terpolymers with con-trolled branch distribution, composition (Fw,PMMA/Fw,PLA/Fw,PDMS � 50/30/20)molecular weight (Mn � 50,000 g � mol�1), and a narrow molecular weight distribution(Mw/Mn � 1.3) were prepared via both pathways. © 2004 Wiley Periodicals, Inc. J Polym SciPart A: Polym Chem 42: 1939–1952, 2004Keywords: graft copolymers; two-dimensional (2D) chromatography; living polymer-ization; microstructure; atom transfer radical polymerization (ATRP); reversible addi-tion–fragmentation transfer (RAFT)

INTRODUCTION

Segmented copolymers such as block, graft, star–block, or miktoarm stars are particularly interest-ing materials because they combine the proper-ties of several different homopolymers in a singlemolecule.1 Moreover, because of the covalent bondbetween each segment, segmented copolymerslead to well-organized nanoscale morphologies ei-ther in bulk2 or in solution.3,4 In the last decades,several applications for segmented copolymers

have been reported including impact-resistantmaterials, thermoplastic elastomers, compatibi-lizers, emulsifiers, membranes, drug-delivery sys-tems, and biosensors.5,6 However, the synthesis ofsegmented copolymers such as block, star–block,or miktoarm stars is usually complex and re-quires multistep reactions.1,7 Another approach isthe preparation of graft copolymers via the “graft-ing through” method (or macromonomer method),which is probably one of the simplest ways tosynthesize segmented copolymers. Typically alow-molecular-weight monomer is copolymerizedwith a polymerizable macromonomer. This methodpermits the incorporation of various thermodynam-ically incompatible macromonomers such as poly-

Correspondence to: K. Matyjaszewski (E-mail: [email protected])Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 42, 1939–1952 (2004)© 2004 Wiley Periodicals, Inc.

1939

ethylene,8 poly(ethylene oxide),9,10 poly(methylmethacrylate) (PMMA),11 polysiloxanes,12–15

polylactide,16,17 and polycaprolactone18 into apolystyrene or poly(meth)acrylate backbone.Moreover, it is possible to design well-definedgraft copolymers by combining the “graftingthrough” method and a controlled/living radicalprocess.19–22 Controlled/living radical polymer-izations (CRPs) are based on a dynamic equilib-rium between a low concentration of active prop-agating chains and a large amount of dormantchains, which are unable to propagate or self-terminate. Thus, the probability of bimoleculartermination reactions decreases and the radicalpolymerization resembles a living system.23 Themost efficient and versatile CRP systems areatom transfer radical polymerization (ATRP),24–26

nitroxide-mediated polymerization,27 and revers-ible addition–fragmentation transfer polymeriza-tion (RAFT),28 which allow the synthesis of well-defined (co)polymers with controlled degree of poly-merization, molecular weight distribution (Mw/Mn),29 functionalities,30 microstructure,31–33 andarchitectures.34,35 Graft copolymers were preparedby CRPs, with various synthetic strategies such as“grafting through” or “grafting from”.36–38 The com-bination of CRP and “grafting through” led to graftcopolymers with precisely controlled Mw/Mn, func-tionality, copolymer composition, backbone length,branch length, and branch spacing.13,14,17,39 Thesuperior control over molecular structure signifi-cantly enhances the mechanical properties of thegraft copolymers.15

This article discusses the synthesis of graftterpolymers, which combine the properties ofthree different homopolymers in a single macro-molecule. The targeted structure is a well-definedterpolymer, poly(alkyl methacrylate)-g-poly(D-

lactide)/poly(dimethylsiloxane). This new class ofgraft terpolymers creates an interesting link be-tween different aspects of material science. Thecopolymers are organic–inorganic hybrids andmay possess the specific properties expected fromthis class of materials,40 but because of incorpo-ration of the poly(D-lactic acid) moiety, the copol-ymers exhibit the potential for biodegradability.41

The terpolymers were synthesized via the “graft-ing through” method, with low-molecular-weightmethacrylates, poly(D-lactide) (PLA) macromono-mers and poly(dimethylsiloxane) (PDMS) mac-romonomer (Scheme 1).

Two approaches for synthesizing graft terpoly-mers were investigated (Scheme 2). The first oneis a one-step approach in which the low-molecu-lar-weight methacrylate monomer, the methacry-late-functionalized PLA macromonomer, and themethacrylate-functionalized PDMS macromono-mer are copolymerized simultaneously [Scheme2(a)]. The second strategy is a two-step approachin which a graft copolymer containing one mac-romonomer is chain-extended by copolymeriza-tion of the second macromonomer and the low-molecular-weight monomer [Scheme 2(b)], form-ing a second block–graft copolymer. In bothapproaches, the control of the molecular structureof the terpolymer (i.e., composition, Mw/Mn, andmicrostructure) was evaluated by kinetic studiesand two-dimensional (2D) liquid chromatography.

EXPERIMENTAL

Chemicals

Monomers

Hexamethylcyclotrisiloxane (D3) (98%, Aldrich)was dissolved in benzene and refluxed overnight

Scheme 1. Structures of poly(lactide) and poly(dimethylsiloxane) macromonomersand macroinitiators.

1940 LUTZ, JAHED, AND MATYJASZEWSKI

over calcium hydride under nitrogen atmosphere.After removing the solvent under reduced pres-sure, D3 was sublimed into a Schlenk flask andstored in a drybox at room temperature. High-purity D-lactide (�99.9%) was provided by MitsuiChemicals and was purified by recrystallizationfrom toluene and dried in a vacuum (�3 Torr)overnight at room temperature. Methyl methac-rylate (MMA; 99%, Acros) and butyl methacrylate(BMA; 99%, Acros) were distilled from calciumhydride and were stored over molecular sieves.

Catalysts

2-Methyl-1,4-naphthoquinone (98%, Aldrich),bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum(0) complex in xylene (Karstedt’s cata-lyst, 9.6 � 10�2 mol � L�1, Gelest), and tin(II)2-ethylhexanoate (Aldrich) were used as received.Copper(I) chloride (95%, Acros) was washed withglacial acetic acid to remove any soluble oxidizedspecies, filtered, washed with ethanol, and dried.CuBr/4,4�-dimethyl-2,2�-bipyridine (dMbpy) cata-lysts immobilized on crosslinked polystyrene(CuBr/PS8-dMbpy, 8 �m size, 1.028 � 10�3 mol-Cu/g-cat),42 tris[2-(dimethylamino)ethyl]amine(Me6TREN),43 4,4�-di-(5-nonyl)-2,2�-bipyridine,44

and cumyl dithiobenzoate45 were synthesized ac-cording to published procedures.

Initiators

n-Butyllithium (2.5 mol � L�1 solution in hexanes,Aldrich), ethyl 2-bromoisobutyrate (98%, Acros),and benzoyl peroxide (BPO; 75%, Fischer) were

used as received. 2-Hydroxyethyl methacrylate(97%, Aldrich) and 2-hydroxyethyl acrylate (97%,Aldrich) were both dried over molecular sieves.

Functional Reagents

3-Methacryloxypropyldimethylchlorosilane (98%,Gelest) was used as received. Dimethylchlorosi-lane (98%, Aldrich) was distilled from calciumhydride and was stored in a drybox. Allyl 2-bro-moisobutyrate was synthesized according to apublished procedure.46

Solvents

Toluene (Fisher Scientific, 99.9%) and tetrahydro-furan (THF) (Fisher Scientific International,99.9%) were distilled over sodium and were storedon molecular sieves. p-Xylene (99%, Aldrich) wasdistilled over calcium hydride and was stored onmolecular sieves. Diphenyl ether (99%, Acros Or-ganics) was dried over molecular sieves.

Synthesis of PDMS Macromonomer PDMS-M

In a drybox, D3 (10 g, 45 mmol) was added into adry flask and was dissolved in a mixture of dryTHF (3.2 mL) and dry toluene (3.2 mL). The mix-ture was stirred for 1 h until a clear, colorlesssolution was obtained. Then, 1.8 mL (4.5 mmol) ofn-butyllithium solution in hexane (2.5 mol � L�1)were added. The mixture was stirred at roomtemperature. After 2 h of polymerization,3-methacryloxypropyldimethylchlorosilane (1.19mg, 5.4 mmol) was added in the flask. The mix-

Scheme 2. Different synthetic approaches for the ATRP synthesis of graft terpoly-mers: (a) one-step copolymerization and (b) two-step sequential approach.

GRAFT TERPOLYMERS 1941

ture was stirred at room temperature for an ad-ditional 3 h. Then, the flask was removed from thedrybox. The lithium chloride salt was precipitatedby the addition of 20 mL of hexanes. The mixturewas filtered to remove the precipitated salt, andsolvents were removed by rotary evaporation. Theresidual monomer was removed by drying thereaction mixture under high vacuum (10�7 Torr,4 h). About 8.7 g of yellow oil [number-averagemolecular weight (Mn) � 3000 g � mol�1, Mw/Mn� 1.21] were obtained (yield: 87%).

1H NMR (CDCl3) � (ppm): 6.1 ppm (s, 1H � f,CHHA), 5.55 ppm (s, 1H � f; CHHA), 4.1 ppm (t,2H � f, OOCH2), 2 ppm (s, 3H � f; ACOCH3),1.75 ppm (q, 2H � f, OOCH2O CH2O), 1.35 ppm(m, 4H, CH3O(CH2)2), 0.9 ppm (t, 3H,CH3O(CH2)2), 0.6 ppm (m, 4H, OCH2OSi), 0.1ppm (m, 6H � degree of polymerization (DPn),(CH3)2OSiO). The vinyl functionality (f) of themacromonomer was around 99%.

Synthesis of PDMS Macroinitiator PDMS-Br

Synthesis of PDMS with Terminal HydrosilylFunctionality (PDMS-SiH)

In a drybox, D3 (10 g, 45 mmol), dry THF (5 mL),and dry toluene (4 mL) were added to a dry flask.The mixture was stirred until a clear, colorlesssolution was obtained. Then, n-butyllithium (2.5mol � L�1 in hexane) (0.36 mL, 0.9 mmol) wasadded, followed by stirring at room temperaturefor 6 h. The polymerization mixture was addeddropwise to a solution of dimethylchlorosilane(0.85 g, 9 mmol) in 2 mL of dry THF. The heter-ogeneous white mixture was stirred in the dryboxovernight at room temperature. All volatiles, in-cluding unreacted D3, were separated from thepolymer by vacuum transfer at 1 Torr at roomtemperature. Finally, the lithium chloride saltwas removed from the polymer by filtrationthrough a Gelman Acrodisc PTFE filter (0.2 �m[ca. 8.7 g (87%) yielding a clear, colorless polymer(Mn � 8400 g � mol�1, Mw/Mn � 1.19].

1H NMR (CDCl3) � (ppm): 4.73 (s, 1H, SiOH),1.33 (m, 4H, CH3O(CH2), 0.92 (t, 3H,CH3O(CH2)2O, 0.58 (m, 2H, CH2OSi), 0.11 (s,6H � DPn, SiOCH3). Integration of the methylgroup from the n-butyl chain end (0.92 ppm) andthe hydrosilyl proton (4.73 ppm) indicated thatfunctionality was 97%.

Synthesis of PDMS-Br

PDMS-SiH (5.4 g, 0.64 mmol), allyl 2-bromoisobu-tyrate (798 mg, 3.85 mmol), and 15 mL of de-

gassed toluene were added to a 50-mL round-bottom flask sealed with a septum. The solutionwas purged with nitrogen for 15 min. In another5-mL flask, a solution of 2-methyl-1,4-naphtho-quinone (0.22 mg, 1.28 � 10�3 mmol) in 1 mL ofdry toluene was prepared. This solution was alsopurged with nitrogen for 15 min, and thenKarstedt’s catalyst (6.7 �L, 6.4 � 10�4 mmol) wasadded. The mixture contained in the 5-mL flaskwas transferred to a 50-mL round-bottom flaskvia cannula. The reaction mixture was placed inan oil bath set at 70 °C and was stirred overnight.After reaction, the polymer was precipitated fromthe yellowish homogeneous mixture by additionto 50 mL of methanol. The slurry was stirredvigorously for 20 min. The stirring was stopped,allowing the PDMS to settle down to the bottom ofthe glassware. The bottom PDMS layer was thendissolved in 5 mL of hexanes and was dried byrotary evaporation and then in vacuo (1 Torr)providing 4 g (yield: 74%) of a colorless oil (Mn� 8400 g � mol�1, Mw/Mn � 1.19).

1H NMR (CDCl3) � (ppm): 4.06 (t, 2H, OOCH2),1.86 (s, 6H, C(Br)O(CH3)2), 1.61 (m, 2H,CH2OCH2OO), 1.23 (m, 4H, CH3O(CH2)2O),0.89 (t, 3H, CH3O(CH2)2O) 0.55 (m, 4H,SiOCH2), 0.08 (6H, s, SiOCH3). The functionalitywas determined to be around 80% by the integra-tions of the terminal methyl group from n-butyl(0.89 ppm) and the methyl group of the 2-bro-moisobutyrate (1.86 ppm).

Synthesis of PLA Macromonomer PLA-M

Five grams of D-lactide (34.7 mmol) were added toa dry Schlenk flask and were placed in vacuo (1Torr) overnight. Then, a solution of tin 2-ethyl-hexanoate (5 mg, 0.012 mmol) in xylene (100 �L)was added via a degassed syringe. Finally, theinitiator (2-hydroxyethyl methacrylate or 2-hy-droxyethyl acrylate) (1.73 mmol) and p-xylene (5mL) were added via degassed syringes. The re-sulting mixture was stirred for 20 h at 90 °C.After the reaction was complete, the mixture wascooled down, and 5 mL of chloroform were addedfollowed by 200 mL of isopropyl alcohol to precip-itate the macromonomer. The macromonomerwas filtered, washed two times with isopropylalcohol, washed one time with methanol, anddried in vacuo for 1 h (1 Torr). About 4.1 g of awhite powder (Mn � 3000 g � mol�1, Mw/Mn� 1.26) were obtained (yield: 82%).

1H NMR (CDCl3) � (ppm): 6.1 (s, 1H, CHHA),5.6 (s, 1H, CHHA), 5.15 (q, 1H � DPn,


OCH(CH3)OOO), 4.35 (m, 4H, OOCH2, 1.95 (s,3H, ACOCH3), 1,6 (d, 3H � DPn,OCH(CH3)OOO).

One-Step ATRP Synthesis of Terpolymer PMMA-g-PLA/PDMS

PLA-M (Mn � 3000 g � mol�1) (1 g, 0.33 mmol),PDMS-M (Mn � 3000 g � mol�1) (1 g, 0.33 mmol),p-xylene (2 mL), and diphenyl ether (2 mL) wereadded to a dry Schlenk flask. The mixture wasthoroughly purged by flushing with nitrogen andwas heated to obtain complete solubilization ofthe crystalline PLA-M. Then, a solution of copperchloride (13.2 mg, 0.133 mmol) and 4,4�-di-(5-nonyl)-2,2�-bipyridine (dNbpy) (109 mg, 0.266mmol) in MMA (1.5 g, 15 mmol) was added to theSchlenk flask. Finally, a solution of ethyl 2-bro-moisobutyrate (EBI) (13 mg, 0.066 mmol) inMMA (0.5 g, 5 mmol) was added. The mixture washeated in a thermostated oil bath at 90 °C, andsamples were withdrawn through a degassed sy-ringe at timed intervals.

One-Step RAFT Synthesis of Terpolymer PMMA-g-PLA/PDMS

PLA-M (Mn � 3000 g � mol�1) (0.6 g, 0.2 mmol),PDMS-M (Mn � 3000 g � mol�1) (0.6 g, 0.2 mmol),p-xylene (1.2 mL), and diphenyl ether (1.2 mL)were added to a dry Schlenk flask. The mixturewas thoroughly purged by flushing with nitrogenand was heated to obtain complete solubilizationof the crystalline PLA-M. Then, a solution ofcumyl dithiobenzoate (10.9 mg, 0.04 mmol) andbenzoyl peroxide (2.6 mg, 0.01 mmol) in MMA (1.2g, 12 mmol) was added to the Schlenk flask. Themixture was heated in a thermostated oil bath at75 °C, and samples were withdrawn through adegassed syringe at timed intervals.

Example of a Two-Step Synthesis of a Terpolymer,(PMMA-g-PLA)-b-(PMMA-g-PDMS)

The same conditions as previously mentionedwere used for the synthesis of block copolymers.First, block (PMMA-g-PLA) was initiated withEBI (1 equiv) and was polymerized in the pres-ence of a CuCl(dNbpy)2 complex (1 equiv). Poly-merization of the second block (PMMA-g-PDMS)was initiated by the PMMA-g-PLA macroinitiator(1 equiv), and the polymerization was also con-trolled with a CuCl(dNbpy)2 catalyst complex (2equiv).

Measurements and Analysis

1H NMR

1H NMR measurements were conducted with ei-ther a 600-MHz (Bruker Avance DRX 600) spec-trometer or a 300-MHz (Bruker WM300) spec-trometer.

Gel Permeation Chromatography (GPC)

GPC was conducted with Polymer Standards Ser-vice SDV columns (Styragel 105, 103, and 102 A)with either THF or toluene as an eluent (flowrate: 1 mL � min�1). The GPC system wasequipped with Waters 515 pump and Waters 410differential refractometer. The average molecularweights and Mw/Mn’s of the graft copolymers weredetermined by GPC using THF as an eluent. Lin-ear poly(methyl methacrylate) (PMMA) stan-dards were used for calibration. Because of thelow difference in refractive index between PDMSand THF, PDMS-M was not detected with GPCwith THF as eluent. Therefore, PLA-M conver-sion was calculated with GPC using THF as aneluent by following the decrease of the mac-romonomer peak area (Fig. 1). GPC chromato-grams were normalized to the peak intensity ofdiphenyl ether used as a reference solvent. Be-cause of the low difference in refractive indexbetween PLA and toluene, PLA-M was not de-tected in GPC using toluene as an eluent. Thus,PDMS-M conversion was calculated with GPCusing toluene as an eluent by following the de-crease of the macromonomer peak area (Fig. 1).

Gas Chromatography (GC)

GC was conducted on a GC 17A Shimadzu gaschromatograph. MMA and BMA conversion wascalculated by comparing the monomer peak areato the peak area of diphenyl ether.

2D Chromatography—First Dimension [Liquid-Adsorption Chromatography under CriticalConditions (LACCC)]

LACCC was performed at 32 °C on a Macherey &Nagel, Nucleosil Si-300-5 A column (particle size:5�m and column dimensions: 250 � 4 mm i.d.),with a Waters 600 Controller and pump. The mo-bile phase was a mixture of methyl ethyl ketoneand cyclohexane 73/27 v/v (critical point ofPMMA). The flow rate was 0.4 mL � min�1.


2D Chromatography—Second Dimension (GPC)

Sample fractions from the first dimension weretransferred to the second dimension via an eight-port valve system (VICI Valco EHC8W), whichconsisted of two 200-�L loops. GPC was per-formed on a Polymer Standards Service SDV lin-ear M, high-speed column (pore size: 5�m, dimen-sions: 50 � 20 mm i.d.) at a flow rate of 5 mL �min�1, with a Waters 515 pump. The results weremonitored with an evaporative light scatteringdetector (Polymer Laboratories, PL-ELS 1000).Linear PMMA standards were used for calibra-tion. Data acquisition and processing were per-formed with Polymer Standards Service software:WINGPC 7 and PSS-2D-GPC Software.

Theoretical Molecular Weight

In controlled/living radical homopolymerizations,experimental molecular weights are expected toincrease linearly with monomer conversion.22

However, in controlled/living radical copolymer-izations, experimental molecular weights cannotbe directly expressed as a function of comonomerconversions because they also depend on the mo-lecular weight of each comonomer and on theinitial molar fraction of each comonomer. Thispoint is particularly important in the case of graftcopolymerizations because these reactions in-volve low-molecular-weight monomers and mac-romonomers. In such copolymerization systems,

experimental molecular weights are expected toincrease linearly with polymer yield (Fw, eq 1)

Fw � �convMMAwMMA � convPLA-MwPLA-M

� convPDMS-MwPDMS-M/�wMMA � wPLA-M

� wPDMS-M (1)

where conv is the monomer conversion and w isthe initial weight of monomer. Therefore, the the-oretical molecular weight (Mn,th) can be expressedas a function of polymer yield. Equations 2 and 3show the expression of Mn,th, respectively, forATRP and RAFT reactions where M is the molec-ular weight of each monomer.

Mn,th � Fw�MMA�0MMMA � PLA-M�0MPLA-M

� PDMS-M�0MPDMS-M/�EBI�0 (2)

Mn,th � Fw�MMA�0MMMA � PLA-M�0MPLA-M

� PDMS-M�0MPDMS-M/�CDB�0 � 2BPO�0 (3)

RESULTS AND DISCUSSION

Synthesis of Terpolymers Poly(alkyl methacrylate)-g-PLA/PDMS with a Single-Step Approach

A simple, one-step copolymerization approachwas used for the synthesis of graft terpolymersPMMA-g-PLA/PDMS. Several experiments are

Figure 1. Evolution of THF and toluene GPC traces for the ATRP synthesis ofgradient terpolymer PMMA-g-PLA/PDMS. For toluene GPC, the negative chromato-grams were inverted.


compared in Table 1. A homogeneous ATRP sys-tem with a CuCl/dNbipy catalyst complex wasexamined first (Table 1, entry 1). Figure 2 illus-trates the kinetic plots for this ATRP terpolymer-ization of MMA, PLA-M, and PDMS-M. The copo-lymerization exhibited a controlled/living behav-ior. The Mw/Mn values were close to 1.2 and themolecular weight increased, as expected, withpolymer yield (because of the differences in hy-drodynamics volumes between the terpolymerand the PMMA standards used for GPC calibra-tion); the experimental values of Mn determinedby GPC were higher than the theoretical values.

The overall reactivity ratios were calculated forthis terpolymerization system (Table 1, entry 1)with the Jaacks method.47 Figure 3 shows theJaacks plots for the ATRP copolymerization ofMMA, PLA-M, and PDMS-M. The slopes of theJaacks plots showed that PLA-M possesses ahigher reactivity with MMA (rMMA/PLA � 0.8)than PDMS-M (rMMA/PDMS � 1.4). These reactiv-ity ratios are apparent values, which considerseveral experimental parameters such as the in-herent reactivity of the macromonomers vinylfunctionality, the diffusion of the macromonomerin the reaction medium, and the thermodynamiccompatibility between the growing polymer chainend and the macromonomer.13,14,17 The latter wasprobably the governing parameter in this terpo-lymerization because both PLA-M and PDMS-Mpossess similar methacrylate end groups (Scheme1) and similar molecular weights. PLA is misciblewith PMMA,48,49 and PLA macromonomers canbe easily incorporated into a growing PMMAbackbone.17 However, the PDMS macromonomeris thermodynamically incompatible with organic

PMMA. Because of the expected thermodynamicrepulsive interactions, copolymerization of MMAand PDMS-M usually leads to graft copolymerswith a heterogeneous distribution of PDMS seg-ments13,50 (i.e., a gradient distribution of the seg-ments in the case of CRP).51 It seems that forPDMS, initially the apparent reactivity ratio iseven larger than the average value (Fig. 3) andthen progressively decreases with conversion be-cause of a compatibilizing effect of the already-incorporated PDMS. The apparent reactivity ra-tios (rMMA/PLA � 0.8, rMMA/PDMS � 1.4) indicatethat the synthesized terpolymer had a gradientdistribution of segments, with a higher content ofPLA branches on one side of the backbone and anenriched content of PDMS branches on the otherside [Scheme 2(a)].

The molecular structure of the graft terpoly-mer PMMA-g-PLA/PDMS was also investigatedwith 2D liquid chromatography.52 This technique,which combines LACCC and GPC, was previouslyreported to be a useful tool for characterization ofgraft copolymers.39 First-dimensional LACCCwas run in a methyl ethyl ketone/cyclohexanemixture (73/27 v/v), the critical point of adsorp-tion of PMMA.53 Figure 4 displays the LACCCchromatograms measured with these solvent con-ditions for various PMMA, PLA, and PDMS setsof standards. At the critical point of adsorption forPMMA, all PMMA standards eluted at the sameretention volume. However, PLA and PDMS stan-dards were size-excluded. Therefore, the ordinateof the 2D contour plots (Fig. 5) shows the PLA/PDMS composition of the terpolymers. When thecontour plot is spread more in the y direction,then the chain-to-chain distribution of the

Table 1. Experimental Conditions and Properties of Terpolymers PMMA-g-PLA/PDMSPrepared with a Single-Step Approach

Control Reagent Initiator t (h) ConvMMA ConvPLA ConvPDMS Mn Mn,th Mw/Mn

rMMA/

PLAd

rMMA/

PDMSd

1 ATRPa MMA CuCl/dNbpy EBI 21 0.85 0.95 0.69 52,200 50,100 1.20 0.8 � 0.1 1.4 � 0.12 ATRPa,b MMA (CuBr/PS8-dMbpy) EBI 21 0.83 0.86 0.70 52,800 48,300 1.35 1.1 � 0.1 1.4 � 0.13 ATRPa MMA CuCl/dNbpy PDMS-Br 23 0.88 0.87 0.68 68,400 58,050 1.30 0.9 � 0.1 1.7 � 0.14 RAFTc MMA CDB BPO 80 0.60 0.49 0.37 56,000 22,400 1.24 — —5 ATRPa BMA CuCl/dNbpy EBI 22 0.78 0.98 0.92 60,000 61,500 1.24 0.5 � 0.1 0.5 � 0.1

a ATRP at 90°C in p-xylene/diphenyl ether 1/1 v/v: [methacrylate] � 3.25 mol � L�1; [PLA-M]0 � 5.4 � 10�2 mol � L�1; [PDMS-M]0� 5.4 � 10�2mol � L�1; [control reagent]0 � 2.16 � 10�2 mol � L�1; [initiator]0 � 1.08 � 10�2 mol � L�1.

b [CuBr2/Me6TREN]0 � 2.16 � 10�4 mol � L�1.c RAFT at 75°C in p-xylene/diphenyl ether 1/1 v/v: [methacrylate] � 3.25 mol � L�1; [PLA-M]0 � 5.4 � 10�2 mol � L�1; [PDMS-M]0

� 5.4 � 10�2 mol � L�1; [control reagent] 0 � 1.08 � 10�2 mol � L�1; [initiator]0 � 0.27 � 10�2 mol � L�1.d Measured by the Jaacks method.


branches in the sample is broader. Additionally,the abscissa of the 2D plots (Fig. 5) shows theMw/Mn of the terpolymer. A narrow contour plotcan be observed [Fig. 5(a)] for the terpolymerprepared under homogeneous ATRP conditions(Table 1, entry 1), indicating homogeneous chaincomposition and a low Mw/Mn.

The copolymerization of MMA, PLA-M, andPDMS-M was also investigated in the presence ofa hybrid ATRP catalyst system (CuBr/PS8-dMbpy)/(CuBr2/Me6TREN) (Table 1, entry 2).42

As previously reported, the hybrid catalyst sys-tem affords good control over the copolymeriza-

tion, comparable to the homogeneous catalyst sys-tem CuCl/dNbpy.54 Nevertheless, the contour plotmeasured for the terpolymer synthesized with thehybrid system [Fig. 5(b)] was broader than thatmeasured for the terpolymer prepared with CuCl/dNbpy [Fig. 5(a)]. These results indicated thatboth chain composition and polydispersity arecontrolled to a lesser degree in the presence of thehybrid catalyst.

It has been reported that the apparent reactiv-ity of MMA versus PDMS-M may be decreasedwith a PDMS macroinitiator (PDMS-Br), whichacts as a compatibilizer and decreases the ther-modynamic repulsive effect between the growingorganic backbone and PDMS-M.13 The effect ofsuch a macroinitiator (Mn � 8400 g � mol�1,Mw/Mn � 1.19) was also studied in the copolymer-ization of MMA, PLA-M, and PDMS-M (Table 1,entry 3). No significant effect of the PDMS-Brmacroinitiator was observed. The measured reac-tivity ratios were nearly the same as those mea-sured in the presence of a low-molecular-weightinitiator (Table 1, entry 1). This behavior may beexplained by the presence of PLA-M, which ispreferentially incorporated into the backbone andprobably decreases the compatibilizing effect ofthe PDMS macroinitiator. However, the contourplot [Fig. 5(c)] revealed a well-defined terpolymerstructure. A one-step RAFT terpolymerization ofMMA, PLA-M, and PDMS-M was also investi-gated, with cumyl dithiobenzoate as the transferagent (Table 1, entry 4). This CRP technique hasbeen found to be less efficient for controlling the

Figure 2. (a) Plots of ln([M]0/[M]) versus time for theATRP copolymerization of MMA (■), PLA-M (Œ), andPDMS-M (F) at 90 °C. (b) Mn (■) and Mw/Mn (F) versuspolymer yield Fw for the copolymerization of MMA,PLA-M, and PDMS-M at 90 °C. Fw � (conv.MMAwMMA

conv.PLA-MwPLA-M conv.PDMS-MwPDMS-M)/(wMMA

wPLA-M wPDMS-M), where conv. is the monomerconversion and w is the initial weight of monomer.Theoretical Mn � Fw ([MMA]0MMMA ([PLA-M]0MPLA-M ([PDMS-M]0MPDMS-M)/([EBI]0), where Mis the molecular weight of each monomer.

Figure 3. Jaacks plots of ln([MMA]0/[MMA]) versusln([macromonomer]0/[macromonomer]) for the ATRPcopolymerization of MMA, PLA-M (F), and PDMS-M(Œ) at 90 °C.


macromonomer copolymerization than ATRP.The experimental molecular weight was signifi-cantly higher than the theoretical molecularweight. Furthermore, after 80 h at 75 °C, only lowconversions of both PLA-M and PDMS-M mac-romonomer were observed. This behavior wasconfirmed by the contour plot recorded for thisRAFT sample [Fig. 5(d)]. The LACCC elution vol-ume of the maximum intensity of the 2D chro-matogram (white zone in the contour plot) wasaround 2.3 mL, whereas in the case of ATRP [Fig.5(a–c)] this value was 2.0 mL. These differencesindicated that the terpolymer prepared by RAFThad a lower incorporation of PLA/PDMS into thebackbone than for copolymers prepared by ATRP.

The synthesis of graft terpolymers was alsoinvestigated by examining copolymerization withanother low-molecular-weight monomer—BMA.The motivation behind this study was to evaluatethe influence of the backbone on the terpolymers’properties, and BMA was selected because of thelow glass-transition temperature of the ho-mopolymer (�30 °C for PBMA instead of �110 °Cfor PMMA). The terpolymerization of BMA, PLA-M, and PDMS-M was examined in the presence ofa homogeneous ATRP system, CuCl/dNbipy (Ta-ble 1, entry 5). The copolymerization exhibited acontrolled/living behavior with a final Mw/Mn forthe terpolymer equal to 1.25 and experimentalmolecular weight close to the theoretical value.However, both PDMS-M and PLA-M macromono-mers showed higher reactivities with BMA thanwith MMA (rBMA/PLA � 0.5, rBMA/PDMS � 0.5). The

synthesized terpolymer possessed a random dis-tribution of both PLA and PDMS branches.

Synthesis of Terpolymers (PMMA-g-PLA)-b-(PMMA-g-PDMS) with a Sequential Approach

The synthesis of a graft block terpolymer (PMMA-g-PLA)-b-(PMMA-g-PDMS) was investigated

Figure 4. LACCC chromatograms of PMMA, PLA,and PDMS homopolymers (eluent: methyl ethyl ketone/cyclohexane 73/27; critical conditions for PMMA).

Scheme 3. Proposed molecular structure for terpolymers (PMMA-g-PLA)-b-(PMMA-g-PDMS) prepared with a sequential approach.


with a two-step sequential approach [Scheme2(b)]. Under these sequential copolymerizationconditions, both macromonomers PLA-M andPDMS-M were grafted into different regions ofthe backbone; however, the branch spacing of thegrafts along the terpolymer backbone differed de-pending on the synthesis conditions.

A PMMA-g-PLA graft copolymer was initiallyprepared and was then chain-extended by copoly-merizing MMA and PDMS-M (Table 2, entries 1aand 1b). At the end of the first step, a well-definedmacroinitiator (PMMA-g-PLA) was obtained (Ta-ble 2, entry 1a). The kinetics of this copolymer-ization (rMMA/PLA � 0.6) agreed with the reportedstudies.17 However, in the second step (Table 2,entry 1b), PDMS-M exhibited a very low reactiv-ity with MMA (rMMA/PDMS � 2.7), suggesting anirregular branch distribution. This behavior may

Figure 5. 2D chromatograms recorded for gradient terpolymer PMMA-g-PLA/PDMSprepared with (a) ATRP homogeneous catalyst CuCl/dNbipy, (b) ATRP immobilizedcatalyst, (c) ATRP with PDMS-Br macroinitiator, and (d) RAFT.

Figure 6. 2D chromatograms recorded for terpolymerPMMA-g-PLA/PDMS prepared via a sequential ap-proach: (a) first step: ATRP copolymerization of MMAand PLA-A and (b) second step: extension of PMMA-g-PLA by the ATRP copolymerization of MMA andPDMS-M.


be explained by a strong incompatibility betweenthe organic grafted macroinitiator and the inor-ganic macromonomer. It seems that the presenceof a high PLA content in the backbone increasesthe thermodynamic repulsion interactions be-tween the backbone and the PDMS-M mac-romonomer. The final terpolymer therefore exhib-ited an unsymmetrical structure, with a gradientdistribution of PLA segments at one extremity ofthe backbone and a “palm tree” distribution ofPDMS at the other extremity (Scheme 3).

To prepare a terpolymer with a more regularbranch spacing along the backbone, the reversesynthetic strategy was investigated (Table 2, en-tries 2a and 2b). The PMMA-g-PDMS block wassynthesized first (Table 2, entry 2a), leading to ahigher reactivity of PDMS-M with MMA (rMMA/PDMS � 1.3), which suggested a more regularbranch spacing (Scheme 3) and a more homoge-neous distribution of macromonomers along thebackbone. For the second step, where the PMMA-g-PDMS copolymer was used as a macroinitiator(Table 2, entry 2b), the reactivity of PLA-M withMMA was the same as in a copolymerization con-ducted in the presence of a low-molecular-weightinitiator (rMMA/PLA � 0.6). Control over branchspacing was also investigated with a PLA mac-romonomer with a different functionality: PLA-A(Scheme 1). Acrylate-terminated PLA mac-romonomers are less reactive than PLA-M andtherefore should be incorporated into the back-bone at a later stage of copolymerization withMMA.17 This behavior was confirmed by the co-polymerization kinetics measured in the first stepof the terpolymer synthesis (Table 2, entry 3a).The calculated apparent reactivity ratio (rMMA/PLA � 1.4) suggested slow incorporation of PLA-Ainto the backbone throughout the reaction. In thesecond step, as previously mentioned, PDMS-Mexhibited lower reactivity with MMA (rMMA/PDMS� 1.7). Therefore, the microstructure of the finalterpolymer comprised a copolymer with two suc-cessive gradient copolymers, each with differingbranch compositions (Scheme 3).

The molecular structure of the graft terpoly-mer (PMMA-g-PLA)-b-(PMMA-g-PDMS) was alsoinvestigated by 2D liquid chromatography. Fig-ure 6 shows the contour plots obtained after eachsynthetic step in the synthesis of the block ter-polymer with PLA-A and PDMS-M comonomers(Table 2, entries 3a and 3b). At the end of theinitial copolymerization of MMA and PLA-A, anarrow contour plot was observed. This indicatedthat the first PMMA-g-PLA block has a well-de-T

able

2.E

xper

imen

tal

Con

diti

ons

and

Pro

pert

ies

ofT

erpo

lym

ers

PM

MA

-g-P

LA

/PD

MS

Pre

pare

dw

ith

aS

equ

enti

alA

ppro

ach

Mac

rom

onom

erB

lock

t(h

)C

onv M

MA

Con

v macr

om

on

om

er

Mn

Mn

,th

Mw

/Mn

ra

1aP

LA

-MP

MM

A-g

-PL

A10

0.71

0.95

35,4

0025

,000

1.14

r MM

A/P

LA

�0.

6�

0.1

1bP

DM

S-M

(PM

MA

-g-P

LA

)-b-

(PM

MA

-g-P

DM

S)

320.

900.

7061

,900

60,8

001.

35r M

MA

/PD

MS

�2.

7�

0.1

2aP

DM

S-M

PM

MA

-g-P

DM

S8

0.80

0.65

29,6

0021

,700

1.26

r MM

A/P

DM

S�

1.3

�0.

12b

PL

A-M

(PM

MA

-g-P

DM

S)-

b-(P

MM

A-g

-PL

A)

7.5

0.60

0.88

66,2

0059

,200

1.25

r MM

A/P

LA

�0.

5�

0.1

3aP

LA

-AP

MM

A-g

-PL

A9

0.75

0.60

26,3

0020

,250

1.12

r MM

A/P

LA

�1.

4�

0.1

3bP

DM

S-M

(PM

MA

-g-P

LA

)-b-

(PM

MA

-g-P

DM

S)

310.

810.

6852

,200

51,3

001.

40r M

MA

/PD

MS

�1.

7�

0.1

aM

easu

red

byth

eJa

acks

met

hod

.


fined structure with a homogeneous chain compo-sition and a narrow Mw/Mn. After the second step(chain extension of PMMA-g-PLA with MMA andPDMS-M), the y axis of the 2D chromatogramclearly showed incorporation of PDMS into thefinal terpolymer structure. At the critical point ofadsorption of PMMA, LACCC was more sensitiveto PDMS than PLA. This behavior is illustratedin Figure 4, which shows that a 2000 g � mol�1

PDMS standard eluted at a lower elution volumethan a 2700 g � mol�1 PLA standard. in Figure6(a), the LACCC elution volume of the maximumintensity of the 2D chromatogram (white zone inthe contour plot) was equal to 2.7 mL. After thesecond step [Fig. 6(b)], this maximum shifted to2.0 mL. This shift of the LACCC maximumclearly indicated that the composition of the ter-polymer changed during the second step (i.e.,PDMS was incorporated). However, Figure 6(b)shows that the final terpolymer was not quite aswell defined as the macroinitiator PMMA-g-PLA.The contour plot is not symmetrical, indicatingthat some macroinitiator did not initiate theMMA/PDMS-M copolymerization. This led tobroader chain composition and broader Mw/Mn’s.Similar contour plots were also observed for thetwo other terpolymers (Table 2, entries 1b and2b).

Comparison of the Different Synthetic Approaches

Two synthetic pathways were investigated for thesynthesis of graft terpolymers containing PMMA,PLA, and PDMS segments: single-step copoly-merization and two-step sequential polymeriza-tion.

Control of Composition

Both pathways led to a comparable incorporationof PLA and PDMS into the backbone. This behav-ior was revealed by 2D liquid chromatographicanalysis. In both cases, the LACCC elution vol-ume of the maximum intensity of the 2D chro-matograms was at 2.0 mL [Figs. 5(a–c) and 6(b)],which shows that the terpolymers roughly pos-sessed the same overall PLA/PDMS composition(average compositions were Fw,PMMA/Fw,PLA/Fw,P-

DMS � 50/30/20, based on monomer consump-tions). However, terpolymers obtained via the sin-gle-step approach exhibited narrower composi-tion distributions (y dimension of the 2D plotswas 0.8 mL) than the terpolymers prepared via a

two-step approach (y dimension of the 2D plotswas 1.35 mL).

Control of Mw/Mn

The kinetics of both synthetic pathways exhibitedthe criteria required for a controlled/living radicalcopolymerization. However, because of the lowerefficiency of initiation by macroinitiators used inthe sequential copolymerization approach, thetwo-step pathway led to terpolymers with abroader molecular weight distribution (Mw/Mn� 1.35) than obtained for terpolymers preparedvia a single-step copolymerization (Mw/Mn � 1.2).

Control of Microstructure

Both pathways allowed control over the branchdistribution. The sequential approach allowed theadditional adjustment of the distribution of themacromonomers along the backbone because atevery step the reaction parameters can be modi-fied. However, we demonstrated that the single-step approach does allow synthesis of a terpoly-mer with a gradient distribution of each graftsegment along the backbone (i.e., a rich content ofPLA branches on one side of the backbone and arich content of PDMS branches on the other side).Such a gradient terpolymer had a tailored micro-structure comparable to the structure of terpoly-mers prepared via a sequential approach (e.g.,Scheme 3, entry 1b).

CONCLUSIONS

Segmented terpolymers poly(alkyl methacrylate)-g-PLA/PDMS were prepared via a combination ofthe “grafting through” method and CRP (ATRPand RAFT). Two synthetic pathways were com-pared: a single-step approach in which a low-molecular-weight methacrylate monomer was di-rectly copolymerized with both a PLA mac-romonomer and a PDMS macromonomer and atwo-step approach in which a graft copolymercontaining one macromonomer was chain-ex-tended by a copolymerization of the second mac-romonomer with a low-molecular-weight methac-rylate. Both approaches exhibited controlled/liv-ing copolymerization behavior and allowedcontrol over the molecular structure of the ter-polymer in terms of composition, Mw/Mn, and mi-crostructure (i.e., branch spacing and branch dis-tribution). These results confirmed that the com-bination of the “grafting through” method and


CRP process provide a simple and practical syn-thetic approach for the preparation of complexsegmented macromolecules. With the comono-mers examined in this study, terpolymers pre-pared with the single-step approach possessed amore homogeneous molecular structure thanthose synthesized via a sequential copolymeriza-tion process. Moreover, the single-step approachallowed the synthesis of terpolymers with a gra-dient distribution of each macromonomer alongthe terpolymer backbone (i.e., a rich content ofPLA branches on one side of the backbone and arich content of PDMS branches on the other side).The properties of such tailored macromoleculesare now under investigation.

The authors thank the National Science Foundation(DMR 00-09409), Environmental Protection Agency,and the members of the CRP Consortium at CarnegieMellon University for their financial support. J.-F. Lutzthanks Dr. Hosei Shinoda (Mitsui Chemicals) for thefruitful discussions and synthesis of PLA macromono-mers.

REFERENCES AND NOTES

1. Hadjichristidis, N.; Pitsikalis, M.; Pispas, S.; Iat-rou, H. Chem Rev 2001, 101, 3747.

2. Bates, F. S. Science 1991, 251, 898.3. Discher, D. E.; Eisenberg, A. Science 2002, 297,

967.4. Riess, G. Prog Polym Sci 2003, 28, 1107.5. Russell, K. E. Prog Polym Sci 2002, 27, 1007.6. Kato, K.; Uchida, E.; Kang, E.-T.; Uyama, Y.;

Ikada, Y. Prog Polym Sci 2002, 28, 209.7. Ishizu, K.; Tsubaki, K.; Mori, A.; Uchida, S. Prog

Polym Sci 2002, 28, 27.8. Hong, S. C.; Jia, S.; Teodorescu, M.; Kowalewski,

T.; Matyjaszewski, K.; Gottfried, A. C.; Brookhart,M. J Polym Sci Part A: Polym Chem 2002, 40, 2736.

9. Wang, Y.; Huang, J. Macromolecules 1998, 31,4057.

10. Yilmaz, F.; Cianga, I.; Ito, K.; Senyo, T.; Yagci, Y.Macromol Rapid Commun 2003, 24, 316.

11. Roos, S. G.; Muller, A. H. E.; Matyjaszewski, K.Macromolecules 1999, 32, 8331.

12. Smith, S. D.; DeSimone, J. M.; Huang, H.; York, G.;Dwight, D. W.; Wilkes, G. L.; McGrath, J. E. Mac-romolecules 1992, 25, 2575.

13. Shinoda, H.; Miller, P. J.; Matyjaszewski, K. Mac-romolecules 2001, 34, 3186.

14. Shinoda, H.; Matyjaszewski, K. Macromol RapidCommun 2001, 22, 1176.

15. Shinoda, H.; Matyjaszewski, K.; Okrasa, L.; Mier-zwa, M.; Pakula, T. Macromolecules 2003, 36,4772.

16. Eguiburu, J. L.; Fernandez-Berridi, M. J.; San Ro-man, J. Polymer 1996, 37, 3615.

17. Shinoda, H.; Matyjaszewski, K. Macromolecules2001, 34, 6243.

18. Liu, Y.; Schulze, M.; Albertsson, A.-C. J MacromolSci Pure Appl Chem 1998, 35, 207.

19. Controlled Radical Polymerization; Matyjasze-wski, K., Ed.; ACS Symposium Series 685; Ameri-can Chemical Society: Washington, DC, 1998.

20. Controlled/Living Radical Polymerization. InProgress in ATRP, NMP, and RAFT; Matyjasze-wski, K., Ed.; ACS Symposium Series 768; Ameri-can Chemical Society: Washington, DC, 2000.

21. Advances in Controlled/Living Radical Polymeriza-tion. Matyjaszewski, K., Ed.; ACS Symposium Se-ries 854; American Chemical Society: Washington,DC, 2003.

22. Handbook of Radical Polymerization; Matyjasze-wski, K.; Davis, T. P., Eds.; Wiley InterScience:Hoboken, NJ, 2002.

23. Greszta, D.; Mardare, D.; Matyjaszewski, K. Mac-romolecules 1994, 27, 638.

24. Wang, J.-S.; Matyjaszewski, K. J Am Chem Soc1995, 117, 5614.

25. Matyjaszewski, K.; Xia, J. Chem Rev 2001, 101,2921.

26. Kamigaito, M.; Ando, T.; Sawamoto, M. Chem Rev2001, 101, 3689.

27. Hawker, C. J.; Bosman, A. W.; Harth, E. Chem Rev2001, 101, 3661.

28. Chiefari, J.; Rizzardo, E. In Handbook of RadicalPolymerization; Matyjaszewski, K.; Davis, T. P.,Eds.; Wiley InterScience: Hoboken, NJ, 2002, p 621.

29. Patten, T. E.; Xia, J.; Abernathy, T.; Matyjasze-wski, K. Science 1996, 272, 866.

30. Coessens, V.; Pintauer, T.; Matyjaszewski, K. ProgPolym Sci 2001, 26, 337.

31. Lutz, J. F.; Pakula, T.; Matyjaszewski, K. In Ad-vances in Controlled/Living Radical Polymeriza-tion; ACS Symposium Series 854; American Chem-ical Society: Washington, DC, 2003; p 268.

32. Lutz, J.-F.; Kirci, B.; Matyjaszewski, K. Macromol-ecules 2003, 36, 3136.

33. Lutz, J.-F.; Neugebauer, D.; Matyjaszewski, K.J Am Chem Soc 2003, 125, 6986.

34. Patten, T. E.; Matyjaszewski, K. Adv Mater 1998,10, 901.

35. Davis, K.; Matyjaszewski, K. Adv Polym Sci 2002,159, 1.

36. Beers, K. L.; Gaynor, S. G.; Matyjaszewski, K.;Sheiko, S. S.; Moeller, M. Macromolecules 1998, 31,9413.

37. Borner, H. G.; Beers, K.; Matyjaszewski, K.;Sheiko, S. S.; Moeller, M. Macromolecules 2001, 34,4375.

38. Borner, H. G.; Matyjaszewski, K. Macromol Symp2002, 177, 1.


39. Roos, S. G.; Muller, A. H. E.; Matyjaszewski, K. InControlled/Living Radical Polymerization; Matyjas-zewski, K., Ed.; ACS Symposium Series 768; Ameri-can Chemical Society: Washington, DC, 2000; p 361.

40. Pyun, J.; Matyjaszewski, K. Chem Mater 2001, 13,3436.

41. Ikada, Y.; Tsuji, H. Macromol Rapid Commun2000, 21, 117.

42. Hong, S. C.; Paik, H.-J.; Matyjaszewski, K. Macro-molecules 2001, 34, 5099.

43. Xia, J.; Gaynor, S. G.; Matyjaszewski, K. Macro-molecules 1998, 31, 5958.

44. Matyjaszewski, K.; Patten, T. E.; Xia, J. J AmChem Soc 1997, 119, 674.

45. Le, T. P.; Moad, G.; Rizzardo, E.; Thang, S. H., PCTInt Appl, WO 9801478, 1998.

46. Miller, P. J.; Matyjaszewski, K. Macromolecules1999, 32, 8760.

47. Jaacks, V. Makromol Chem 1972, 161, 161.48. Eguiburu, J. L.; Iruin, J. J.; Fernandez-Berridi,

M. J.; San Roman, J. Polymer 1998, 39, 6891.49. Zhang, G.; Zhang, J.; Wang, S.; Shen, D. J Polym

Sci Part B: Polym Phys 2002, 41, 23.50. Tsukahara, Y.; Hayashi, N.; Jiang, X. L.; Ya-

mashita, Y. Polym J 1989, 21, 377.51. Matyjaszewski, K.; Ziegler, M. J.; Arehart, S. V.;

Greszta, D.; Pakula, T. J Phys Org Chem 2000, 13,775.

52. Kilz, P.; Pasch, H. In Encyclopedia of AnalyticalChemistry; Meyers, R. A., Ed.; Wiley: Chichester,England, 2000; p 7495.

53. Pasch, H.; Brinkmann, C.; Gallot, Y. Polymer 1993,34, 4100.

54. Hong, S. C.; Neugebauer, D.; Inoue, Y.; Lutz,J.-F.; Matyjaszewski, K. Macromolecules 2003,36, 27.


Documents

Preparation and characterization of graft terpolymers with controlled molecular structure