EUROPEAN

European Polymer Journal 43 (2007) 109–118

www.elsevier.com/locate/europolj

POLYMERJOURNAL

A novel route to the synthesis of PP-g-PMMA copolymervia ATRP reaction initiated by Si–Cl bond

Huayi Li, Haichuan Zhao, Xiaofan Zhang, Yingying Lu, Youliang Hu *

Joint Laboratory of Polymer Science and Materials, Key Laboratory of Engineering Plastics, Institute of Chemistry,

Chinese Academy of Sciences, Beijing 100080, PR China

Received 11 August 2006; received in revised form 10 October 2006; accepted 16 October 2006Available online 28 November 2006

Abstract

The copolymerization of propylene with allyldimethylsilane (ADMS) was carried out with conventional Ziegler–Nattacatalyst supported on MgCl2. The effects of the concentration of ADMS in the feed on the polymerization reaction andcopolymer properties were investigated. The resulting copolymer PP-co-ADMS was chlorinated to PP–Si–Cl by refluxingthe copolymer with SOCl2 in benzene. The chlorinated copolymer was used to initiate ATRP of MMA with CuCl/PMDETA as catalyst to produce graft copolymer PP-g-PMMA, which was characterized with 1H NMR, 13C NMR,GPC and DSC. Polymer blend of iPP/PP-g-PMMA/PMMA was prepared and the results shown that PP-g-PMMAwas an effective compatilizer.� 2006 Elsevier Ltd. All rights reserved.

Keywords: Polypropylene; Functionalization; Allyldimethylsilane; Copolymerization; Ziegler–Natta catalyst; Coordination polymeriza-tion; ATRP; Graft copolymer

1. Introduction

Polyolefins are relatively inert materials withpoor performance in adhesion, printability, painta-bility and compatibility. The functionalization ofpolyolefin has been a challenge in the academicand industrial fields. Direct copolymerization of a-olefin with polar comonomers is one facile way toprepare functional polyolefin. However, the hetero-atoms such as N, O and S with base nature in polar

0014-3057/$ - see front matter � 2006 Elsevier Ltd. All rights reserved

doi:10.1016/j.eurpolymj.2006.10.010

* Corresponding author. Tel.: +86 10 6256 2815; fax: +86 106255 4061.

E-mail address: huyl@iccas.ac.cn (Y. Hu).

comonomers usually poison the polymerization cat-alysts with Lewis acid nature. The functional reac-tions of polyolefin involving silane monomers haveseveral advantages. Silane is almost neutral andhas little negative effect on the coordination cata-lyst. The functional reactions of silane, whichinclude hydrolysis, alcoholysis, free radial reaction,halogenation and Si–H addition with C@C bond,are diversified and the reaction conditions are mild[1]. Longi and Rossi [2] and Asanuma and Matsuy-ama [3] synthesized propylene/allylsilane and pro-pylene/vinylsilane copolymers using the traditionalZiegler–Natta catalysts and studied the crosslink-ing reactions of the copolymers initiated by alkali/alcohol and c-ray, respectively. In recent years,

.

110 H. Li et al. / European Polymer Journal 43 (2007) 109–118

allyltrimethylsilane [4] and 7-octenyldimethylphe-nylsilane [5] were copolymerized with ethylene bymetallocene catalysts to modify polyethylene. Thereactive phenylsilane group was post treated toalcoxy- and halosilane groups [6]. Marks and Koo[7] synthesized silyl-capped and silyl-linked atacticpolypropylene using single-site cationic metallocenecatalysts and functionalized the prepared polymervia oxidative cleavage of C–Si bond to C–OH bond,obtaining OH-capped atactic polypropylene.

However, the graft polyolefin copolymer hasnot been synthesized via the functional reactionsmentioned above as a result of the absence ofan appropriate initial system. Recently we foundthat chlorotrimethylsilane/CuCl/N,N,N0,N00,N00pen-tamethyldiethyltriamine could act as a new initiatingsystem for the atom transfer radical polymerizations(ATRP) of methyl methacrylate (MMA) and styrene[8]. This ATRP reaction is expected to prepare graftand block polyolefin copolymers.

In this paper, we designed a new silane comono-mer, allyldimethylsilane (ADMS), to prepare poly-olefin copolymer. The copolymer of propylene withallyldimethylsilane was synthesized in the presenceof traditional MgCl2 supported Ziegler–Natta cata-lyst. The copolymer was chlorinated by SOCl2 toconvert the Si–H bond to Si–Cl bond. Then the chlo-rinated copolymer was used to initiate the ATRP ofMMA to prepare isotactic polypropylene (iPP) graftcopolymer.

2. Experimental section

2.1. Materials

All O2 and moisture-sensitive manipulationswere carried out inside an argon-filled drybox. Tol-uene and ethyl ether were refluxed with sodium/ben-zophenone under argon for over 24 h and distilledbefore use. Allyl chloride was dried over anhydrousCaCl2 and distilled before use. Dichlorodimethyl-silane and thionyl chloride (SOCl2) was distilledbefore use. Propylene (polymerization grade) wasprovided by YanShan Petrochemical Co. Ltd. andused as received. Conventional Ziegler–Natta cata-lyst (named CS-II catalyst, MgCl2/TiCl4/dibutylphthalate, Ti: 3.38 wt.%) was provided by YingkouXiangyang chemical plant. N,N,N 0,N00,N00-penta-methyldiethyltriamine (PMDETA, Aldrich, 99%)and triethylaluminum (TEA, Aldrich, diluted to1.8 mol/L in toluene) were used as received. MMAand benzene were dried over CaH2 and distilled

under reduced pressure before use. CH2Cl2 wasdried over P2O5 and distilled before use. CuCl waswashed by glacial acetic acid, absolute ethanol andethyl ether in turn and then dried under vacuum.The others reagents not mentioned were purchasedfrom Beijing Chemical Reagents Company and usedas received. Allylchlorodimethylsilane was synthe-sized by the reaction of allylmagnesium chloride anddichlorodimethylsilane [9]. PMMA (Mn = 2.26 ·105, Mw/Mn = 1.20) was synthesized according tothe literature [8].

2.2. Characterization

The 1H NMR and 13C NMR spectra wererecorded on a Bruker 300 MHz spectrometer withdeuterated orthodichlorobenzene without internalstandard (for polymer, at 100 �C) or CDCl3 as sol-vents. Molecular weight (Mw and Mn) and mole-cular weight distribution (Mw/Mn) were determinedby high temperature gel-permeation chromatogra-phy (GPC) at 140 �C on a PL-GPC220 instrumentusing 1,2,4-trichlorobenzene as solvent and mobilephase. Polystyrene standard was used for calibration.The melting temperatures (Tm) and glass transi-tion temperatures (Tg) of polymers were performedon differential scanning calorimetry (DSC) usingPerkin–Elmer DSC-7 at the heat rate of 10 �C/minand determined by the second scan. Field emissionscanning electron microscopy (FESEM) was per-formed on JEOL JSM 6700 F at 3.0 kV. FESEMsamples were prepared from cuboids cyrofracturedin liquid N2 and coated with a thin layer of gold priorto FESEM observation.

2.3. Synthesis of Allyldimethylsilane (ADMS)

To a slurry of 5.6 g (0.15 mol) of lithium alumin-ium hydride in 20 mL of anhydrous ethyl ethercooled in an ice-water bath was added dropwise40.0 g (0.30 mol) of allylchlorodimethylsilane in40 mL of ethyl ether during 1 h. The mixture wasthen stirred overnight and filtrated through celite.After most of the ether was distilled out at 50 �Cfrom the filtrate, the residue was distilled underreduced pressure at 50 �C to give crude product,which was then subjected to a distillation througha short Vigreux. The fraction of 69–70 �C was pureallyldimethylsilane. The yield was 25.6 g (86%). 1HNMR (300 MHz, CDCl3): d = 5.77–5.84 (m, 1H,CH2@CH), 4.86–4.91 (m, 2H, CH2@CH), 3.85–

H. Li et al. / European Polymer Journal 43 (2007) 109–118 111

3.89 (m, 1H, Si–H), 1.59–1.62 (dd, 2H, Si–CH2),0.08–0.10 (d, 6H, Si–CH3).

2.4. Synthesis of copolymer of propylene with ADMS

(PP-co-ADMS)

In a typical experiment, a round 250 mL flaskequipped with a magnetic stirrer was dried in vacuo

at 80 �C for 1 h and then charged with propylene atatmospheric pressure. The flask was cooled down tothe temperature needed and 60 mL of toluene,ADMS and 2 mL of TEA were injected into thereactor. After the solution was saturated with pro-pylene, 50 mg of CS-II catalyst (Ti = 3.6 mmol,Al/Ti = 100) was added and the polymerizationstarted. During the polymerization, propylene wasfeed continuously and the pressure kept constantat atmospheric pressure. The polymerization wascarried out at 40 �C for 30 min and terminated bythe addition of 15 mL of ethanol. The producedpolymer was washed with ethanol three times anddried under vacuum at 60 �C for 12 h.

2.5. Chlorination of PP-co-ADMS

A mixture of 2.6 g of PP-co-ADMS (run 6),50 mL of benzene and 10 mL of SOCl2 was refluxedat 100 �C under argon for 36 h and cooled to ambi-ent temperature. The chlorinated PP-co-ADMS(PP–Si–Cl) was filtered and washed with CH2Cl2under argon and dried under vacuum at 60 �C for12 h.

2.6. Synthesis of PP-g-PMMA graft copolymer viaATRP reaction initiated by PP–Si–Cl

In a typical experiment, 0.30 g of PP–Si–Cl,0.10 g of CuCl, 10 g of MMA and 20 mL of toluenewere added to a 100 mL round flask equipped witha magnetic stirrer and a reflux condenser. The flaskwas degassed by three freeze-pump-thaw cycles andrecharged with argon. PMDETA (0.20 g) was addedand the mixture was stirred for 5 min at ambienttemperature. The flask was placed in a thermostatedoil bath at 100 �C. The reaction was stopped byaddition of a lager amount of ethanol and polymerpowders precipitated. The graft copolymer waswashed with ethanol to remove the Cu complexand subjected to a vigorous extraction process byrefluxing acetone in a Soxhlet extractor under argonfor 6 h to remove any PMMA homopolymer and

catalyst residue and then dried under vacuum at60 �C for 12 h.

2.7. Polymer blending

All the blends were performed in solution toobtain molecular level mixing. The mixture of poly-mers was dissolved in refluxing xylene under argonto prevent oxidation. After the polymer mixtureformed a clear, homogeneous solution, the solutionwas precipitated quickly into cold alcohol. Theblend was dried under vacuum and then mouldedto prepare the FESEM sample.

3. Results and discussion

3.1. Synthesis of copolymer of propylene with ADMS

(PP-co-ADMS)

The conditions and results of the copolymeriza-tion of propylene with ADMS are listed in Table1. The effect of the concentration of ADMS in thefeed on the polymerization and copolymer proper-ties was investigated. The content of ADMS in thecopolymer increases linearly with the feed of ADMS(Fig. 1). The weight average molecular weight of thecopolymer decreases when a little amount of como-nomer ADMS is added, but keeps approximatelyconstant with the further increase of the feed ofADMS. The activity of the Ziegler–Natta cata-lyst decreases with the addition of ADMS (Fig. 2).This can be explained by two reasons. Firstly, theenchainment of ADMS with large size pendent(CH3)2SiH group on the central metal hinders steri-cally the incorporation of the next propylene mole-cule. Secondly, the agostic interaction [10,11]between the hydrogen atom in Si–H bond and theTi atom of Ziegler–Natta catalyst may hinder theincorporation of the propylene molecule becausethe electronegativity of H atom (2.1) is higher thanSi atom (1.8). The electron cloud density around theH atom is stronger than that around the Si atom inSi–H bond, which is on the contrary to the case ofC–H bond where the electronegativity of C atomis 2.5. The agostic interaction between the Ti atomand the H atom of Si–H bond can be establishedeasily and strongly (Scheme 1).

The molecular weight distributions of the copoly-mers are broad (9.3–10.5), which is the typical char-acter of the conventional Ziegler–Natta catalyst withmultiple active centers. The incorporation of ADMSunits destroys the crystallinity of polypropylene

Table 1The conditions and results of the copolymerization of propylene with ADMSa

Run ADMS in the feed(mol/L)

Yield(g)

Activity(kg/mol Ti Æh)

ADMS in copolymerb

(mol.%)Tm (�C) Mw

c

(103 g/mol)Mw/Mn

c

1 0 8.4 404 0 159.8 302.7 10.42 0.05 6.7 319 0.10 159.4 242.5 10.53 0.10 6.3 302 0.20 158.7 223.6 9.84 0.21 5.6 269 0.45 157.4 220.7 9.65 0.32 4.4 212 0.67 157.2 225.2 10.26 0.42 4.0 192 0.83 156.5 224.2 9.87 0.53 3.7 178 1.06 156.3 226.4 9.3

a Copolymerization conditions: toluene 60 mL; CS-II catalyst: 50 mg (Ti = 0.36 mmol); Al/Ti: 100; reaction time: 30 min; temperature:40 �C ; propylene: 1 atm.

b Calculated from 1H NMR.c Determined by PC.

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.2

0.4

0.6

0.8

1.0

1.2

Con

tent

of A

DM

S in

the

copo

lym

er (

mol

%)

Concentration of ADMS in the feed (mol/L)

Fig. 1. The dependence of the content of ADMS in copolymer onthe concentration of ADMS in the feed.

0.0 0.1 0.2 0.3 0.4 0.5 0.6150

200

250

300

350

400

Act

ivity

of t

he Z

iegl

er-N

atta

cat

alys

t (kg

/mol

. Ti.h

)

Concentration of ADMS in the feed (mol/L)

Fig. 2. The influence of the concentration of ADMS in the feedon the activity of catalyst.

LnTi+

H Si

CH3

CH3

P

δ+δ−

Scheme 1. The agostic interaction between the Ti atom and the Hatom of the Si–H bond.

112 H. Li et al. / European Polymer Journal 43 (2007) 109–118

chain and decreases the Tm of the copolymer. How-ever, the extent of the decreasing is low, whichresults in less negative influence on the performanceof the copolymer.

The reactivity ratios of propylene and ADMSwere estimated according to the Fineman–Rossextrapolation method [12]. The calculation is basedon Eq. (1):

a� a=b ¼ rPða2=bÞ � rC ð1Þ

wherein a is the mole ratio of propylene (P) andcomonomer (C) in the feed, b is the mole ratio ofpropylene and comonomer in the copolymer, rP isthe reactivity ratio of propylene and rC is the reac-tivity ratio of comonomer. The propylene concen-tration in toluene was calculated according to theliterature [13]. Fig. 3 shows the plot of a2/b versusa � a/b and the least squares best-fit line. The

results are: rP = 78.73 ± 0.80, rC = 0.096 ± 0.006,rP · rC = 7.56 and the correlation coefficient R =0.999. rP is much higher than rC, which indi-cates that it is hard to form the homopolymer ofADMS and the block copolymer of propylene andADMS.

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18

0

2

4

6

8

10

12

14

a-a/

b

a2/b

rP = 78.73 ± 0.80 rC = 0.096 ± 0.006 rP×rC = 7.56

Fig. 3. The reactivity ratios of propylene and ADMS estimatedaccording to the Fineman–Ross extrapolation method.

Fig. 4. (a) 1H NMR and (b) 13C N

H. Li et al. / European Polymer Journal 43 (2007) 109–118 113

The typical 1H NMR and 13C NMR spectra ofthe copolymer (run 7) are shown in Fig. 4. The res-onance signals centering at 0.91 ppm, 1.31 ppm and1.62 ppm correspond to CH3, CH2 and CH inpropylene units, respectively. The resonance signalsat 0.11 ppm and 4.05–4.15 ppm correspond toSi–CH3 and Si–H, respectively. The chemical shiftof Si–CH2 is immerged into the hydrogen chemicalshifts of propylene unit and cannot be detectedclearly. The content of ADMS in the copolymer iscalculated by the ratio of two integrated intensitiesbetween Si–H and protons in propylene unit. Tworesonance signals centered at 4.66 ppm and4.72 ppm arise from the vinylidene end-group ofcopolymer [14], which indicates that b-H trans-fer chain-termination mechanism exists. The 13CNMR spectrum of PP-co-ADMS is similar to that

MR spectra of PP-co-ADMS.

Fig. 5. 1H NMR spectrum of chlorinated PP-co-ADMS.

114 H. Li et al. / European Polymer Journal 43 (2007) 109–118

of typical isotactic polypropylene [14] except the chem-ical shift at �3.27 ppm corresponding to Si–CH3.

3.2. Chlorination of PP-co-ADMS

SOCl2 is usually used as chlorination agent tochange Si–H to Si–Cl [15]. This chlorination reac-tion is highly selective to the Si–H bond. The chlo-rination of PP-co-ADMS was carried out byrefluxing PP-co-ADMS with SOCl2 in benzene.The polymer was swelled during the reaction. Afterthe chlorination reaction, SOCl2 was separatedeasily by filtration. The 1H NMR spectrum ofthe chlorinated copolymer (PP–Si–Cl) is shown inFig. 5. Compared with the 1H NMR spectrum ofPP-co-ADMS, the intensities of doublet resonancesignal at 0.11 ppm and signal between 4.05 and4.15 ppm reduce and a new singlet signal at

SiCH3 CH3

H

CH2 CH

CH3

CH2 CH

CH2

SiCH3 CH3

Cl

x y

+Ziegler-Natta c

SOCl2

benzene

MM

CuCl/PM

Scheme 2. The synthesi

0.43 ppm corresponding to Si(CH3)–Cl arises. Theconversion of Si–H to Si–Cl can be calculated bythe ratio of integrated intensities of these two sig-nals. After reaction for 36 h, the conversion is upto 55%. The chlorination reaction was also carriedout with CCl4 as solvent without the change of theother conditions. The 1H NMR spectrum shownthat the conversion of Si–H to Si–Cl was about15%. The lower conversion is possibly caused bythe worse swelling of PP-co-ADMS by CCl4 thanthat by benzene.

3.3. Synthesis of PP-g-PMMA graft copolymer

The graft polymerization of MMA initiated byPP–Si–Cl/CuCl/PMDETA was carried out in tolu-ene at 100 �C (Scheme 2). The effect of polymeriza-tion time on the conversion of MMA and Mn of

CH2 CH

CH3

CH2 CH

CH2

SiCH3 CH3

H

n m

CH2 CH

CH3

CH2 CH

CH2

SiCH3 CH3

x y

PMMA

atalyst

A

DETA

s of PP-g-PMMA.

Table 2The conditions and results of the graft copolymerization of MMA initiated by PP–Si–Cl/CuCl/PMDETAa

Run Time (h) Yield(g)

Conversion(%)

PMMA in copolymerwt.%

MMA/Pmol/mol

Tgb (�C) Mn

c

(g/mol)Mw/Mn

c

8 0 0.30 – – 0 – 22,870 9.89 2 0.56 2.6 46.4 27/73 n.d. 29,740 8.3

10 4 0.72 4.2 58.3 37/63 n.d. 35,460 7.111 8 1.05 7.5 71.4 51/49 n.d. 52,700 6.212 12 1.47 11.7 79.6 62/38 92.1 67,700 5.3

a Polymerization conditions: PP–Si–Cl: 0.30 g (Si–Cl content: 3.26 · 10�5 mol); toluene: 20 mL; temperature: 100 �C ; CuCl: 0.10 g;MMA: 10 g; PMDETA: 0.20 g.

b Determined by DSC; n.d: not determined.c Determined by GPC.

H. Li et al. / European Polymer Journal 43 (2007) 109–118 115

graft copolymer has been investigated (Table 2).The dependence of ln([M0]/[M]) of MMA on thepolymerization time is linear (Fig. 6a), which is sim-ilar to the ATRP of MMA initiated by Me3SiCl/CuCl/PMDETA [8]. The crude graft copolymerwas extracted with acetone to remove the PMMAhomopolymer. The result shows that the PMMA

0 2 4 6 8 10 1220000

30000

40000

50000

60000

70000

Mn o

f PP

-g-P

MM

A

Conversion of MMA %

0 2 4 6 8 10 120.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

ln([

M0]/[

M])

Time (h)

Fig. 6. (a): Dependence of ln ([M0]/[M]) on polymerization timeof MMA, and (b) dependence of Mn of PP-g-PMMA on theconversion of MMA.

homopolymer is less than 5 wt.% of the crudecopolymer. The Mn of the graft copolymerdetermined by GPC increases linearly with theconversion of MMA (Fig. 6b). The GPC curves ofPP-co-ADMS (run 6) and PP-g-PMMA (run 11and run 12) are shown in Fig. 7. The GPC tracesof the grafted polypropylene shift toward highmolecular weight region.

According to the definition of molecular weightdistribution, the molecular weight distributionof block and graft copolymer with two compo-nents (Mw co/Mn co) can be expressed as followingequation:

Mwco

Mnco

¼ aMw1 þ bMw2

aMn1 þ bMn2

ð2Þ

where a and b are molecular fractions of two com-ponents respectively. Calculated according to Eq.(2), Mw co/Mn co is between Mw1/Mn1 and Mw2/Mn2. Polypropylene (component 1) prepared byZiegler–Natta catalyst is characterized with broad

2 3 4 5 6 7

log M

PP-co-ADMS run 4 PP-g-PMMA run 11 PP-g-PMMA run 12

Fig. 7. GPC curves of PP-co-ADMS (run 4) and PP-g-PMMA(run 11 and 12).

116 H. Li et al. / European Polymer Journal 43 (2007) 109–118

molecular weight distribution, but PMMA (compo-nent 2) prepared by ATRP is characterized withnarrow molecular weight distribution. For the graftcopolymer of polypropylene and PMMA preparedin this study, a, b, Mw1 and Mn1 are constant butMw2 and Mn2 increase with the content of PMMA.Therefore, Mw/Mn of PP-g-PMMA should decreasewith the increase of the content of PMMA. As ex-pected, Mw/Mn of PP-g-PMMA determined byGPC decreases from 9.8 (run 8) to 5.3 (run 12) withthe increase of the PMMA content (Table 2).

Tg of the PMMA side chain is detected by DSC,which is 92.1 �C (run 12) (Fig. 8). The typical 1HNMR spectrum of PP-g-PMMA (run 12) is shownin Fig. 9. In addition to the major signals corre-

50 100 150

Temperature (ºC)

Tg = 92.1 oC

a

b

Fig. 8. DSC curves of (a) PP-co-ADMS (run 4) and (b) PP-g-PMMA (run 12).

Fig. 9. 1H NMR spectrum o

sponding to PP and PMMA, the signals corre-sponding to Si–H (0.11 ppm) and Si–CH3 (4.05–4.15 ppm) are also observed.

It was known that Si–H bond could react withcarbon free radical to generate Si free radical andC–H bond [1]. However, the reaction between theSi–H bond in PP–Si–Cl and the free radical in theATRP reaction of MMA can be ignored. Becausethe concentrations of the carbon radical of ATRPreaction [16] and the Si–H bond in PP–Si–Cl areboth very low and the Si–H bond located in theswell polypropylene chain is less mobile. Therefore,the probability of the reaction between Si–H andcarbon free radical in the ATRP reaction is verysmall. Moreover, 1H NMR spectrum (Fig. 9) provesthat the Si–H bond is preserved after the ATRPreaction. It indicates that the Si–H bond do hardlyparticipate in the ATRP reaction and the propaga-tion carbon free radical is seldom disturbed bySi–H bond.

3.4. PP-g-PMMA used as compatilizer

The graft copolymer was first proven by Molautest [17]. iPP (run 1), PP-g-PMMA (run 12) andPMMA were dispersed in acetone and milky colloi-dal suspension solution was produced, which indi-cated not only that the graft structure existedbut also that the graft copolymer could be a poten-tial good compatilizer in polymer blend. In orderto investigate the compatibility of PP-g-PMMAcopolymer in iPP and PMMA blends, two polymerblends have been performed. One is a simple mix-ture of 80/20 weight ratio of iPP and PMMA and

f PP-g-PMMA (run 9).

Fig. 10. FESEM images of the cross-sections of two polymer blends: (a) two homopolymers with PP/PMMA = 80/20 (2000·); (b)(10000·); (c) two homopolymers and PP-g-PMMA with PP/PP-g-PMMA/PMMA = 75/10/15 (2000·) and (d) (10,000·).

H. Li et al. / European Polymer Journal 43 (2007) 109–118 117

the other is comprised of 75/15/10 weight ratio ofiPP, PMMA and PP-g-PMMA (run 12).

Fig. 10 shows the FESEM micrographs of thecross-sections of the two polymer blend samplescyrofractured in liquid N2. In the homopolymerblend (Fig. 10a and b), the polymer shows grosslyphase-separated as can be seen by the PMMA phasewhich exhibits nonuniform and the size of PMMAphase is big. The PMMA domains are pulled outof the PP matrix. The polymer blend containingthe graft copolymer shows a totally different mor-phology in Fig. 10c and d. The cross-section exhibitsalmost flat mesa-like regions similar to that of pureiPP and size of PMMA phase domains is smaller,which proves that PP-g-PMMA is an effective com-patilizer in iPP/PMMA blends.

4. Conclusion

The copolymerization of propylene with allyldi-methylsilane (ADMS) was carried out in the pres-

ence of the conventional Ziegler–Natta catalyst.With the increase of the concentration of ADMSin the feed, the content of ADMS unit in the copoly-mer increased linearly, but the catalyst activitydecreased. PP-co-ADMS was chlorinated to PP–Si–Cl by refluxing with SOCl2. PP–Si–Cl was usedto initiate ATRP of MMA with CuCl/PMDETAas catalyst. The graft polymerization reactionoccurred efficiently. This is a new route to preparegraft polyolefin copolymer via silane. The PP-g-PMMA copolymer was proved to be an effectivecompatilizer in iPP/PMMA blends by FESEM.

Acknowledgement

The authors express thanks for the supportsof the National Science Foundation of China(No. 20334030, No. 50403024 and No. 50573081)and China Petroleum & Chemical Corporation(SINOPEC).

118 H. Li et al. / European Polymer Journal 43 (2007) 109–118

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