Olefin terpolymerizations. I. 1,4-hexadiene

Olefin Terpolymerizations. I. 1,4=Hexadiene

ZHENCTIAN YU, MARIA MARQUES, MARVIN D. RAUSCH, and JAMES C. W. CHIEN*

Departments of Chemistry and Polymer Science and Engineering, Materials Research Laboratory, University of Massachusetts, Amherst, Massachusetts 01 003

SYNOPSIS

Ethylene (E) , propylene ( P ) , and 1,4-hexadiene (HD) were terpolymerized with rac-1,2- ethylenebis ( 1-q5-indenyl) zirconium( IV) dichloride and methylaluminoxane (Et [ Ind12ZrC12/ MAO), and compared with the copolymerizations of E/ P, E/ HD, P/ HD, and terpolymerization using ethylidene norbornene (ENB) as the termonomer. HD lowers the polymerization activity, the effect is more pronounced for P / HD and E/ P/ HD using large amount of P, than for E/ HD and E/ P/ HD using feed low in P. The polymer molecular weight is most strongly affected by the temperature of polymerization ( T,) , whereas the E/ P ratio in the feed has virtually no effect. The reactivity ratios rE and rp are 3.0 and 0.3, respectively, at 20°C but rp becomes larger than rE at T, = 70°C. 'H-NMR spectra showed occurrence of cycloaddition in the homopolymerization of HD; on the other hand, HD is incorporated in the terpolymer only by linear 1,2-addition. 0 1995 John Wiley & Sons, Inc. Keywords: Ziegler-Natta polymerization EPDM metallocene catalysts

INTRODUCTION

The family of ethylene, propylene, and diene terpolymers, referred as EPDM, possess certain out- standing properties not shared by other types of elastomers. EPDM is currently produced by vana- dium catalysts, which are low in productivity and have toxicity concerns. Recently homogeneous metallocene catalyst systems have been developed which produce polyethylene, polypropylene, and ethylene/ a-olefin copolymer^^-^ with exceedingly high activities. Both zirconocene /methylaluminoxane (MAO) catalyst system and zirconocenium cation6 have been used for EPDM synthesis. A commercially useful zirconocene catalyst system should possess the following attributes: ( a ) high activity and efficient incorporation of diene; ( b ) random distribution of monomers; ( c ) good control of molecular weight and molecular weight distribution; ( d ) low tendency to side reactions (branching or cyclization of the diene) . The terpolymerization of ethylene / propylene / ethylidene norbornene by ( Cp)2ZrClz /MA03"pb exhibits long induction time. There is no induction period for the Et (Ind)zZrClz

* To whom all correspondence should be addressed. Journal of Polymer Science: Part A. Polymer Chemistry, Val. 33,979-987 (1995) 0 1995 John Wiley & Sons, Inc. CCC osS7-624X/95/oso979-09

( 1) /MA05 or the Et ( Ind)zZr+ R6 system both in solution and supported in silica. The nonbridged and the bridged zirconocene catalysts have similar in- trinsic activities but the latter reach full activity in a much shorter time and can incorporate a larger amount of diene than the former.

In this article, we have undertaken a systematic investigation of several dienes in EPDM synthesis catalyzed mainly by the Et ( Ind)2ZrC12/MA0 system. The results for 1,4-hexadiene (HD) are pre- sented herein. Subsequent articles will deal with vi- nylcyclohexene and cyclooctadiene.

EXPERIMENTAL

Materials Literature procedures were used to synthesize ( 1 ) , 2,2'-thiobis (6-t-butyl-4-methylphenoxy ( =TBP ) ti- tanium dichloride,8 triphenylcarbenium tetrakis- (pentafluorophenyl) borate [ Ph3CB (C$,),] ( 2) ,9910

and Et ( IndH4).+TiClZ/MA0.' MA0 and triethyl- aluminum (TEA) and tri-i-butylaluminum (TIBA) were purchased from Akzo Chemical Co. 1,4-hexadiene ( HD ) was purchased from DuPont. Its purity determined by GC are: trans-HD (92.4% ) and cis-HD (7.1%). It was dried over CaHz and distilled im- mediately before use.

979

980 YU ET AL

Polymerizations

The polymerization apparatus was described pre- viously." Ethylene and propylene were mixed in the desired proportion in an intermediate cylinder to a total pressure of 30 psi, which was left overnight at 50°C to ensure homogeniety of the mixture. A pressure bottle containing about 50 mL of toluene and the desired amount of diene was saturated with the mixture of E and P, and was heated or cooled to the reaction temperature. MA0 was first added and then the catalyst 1 was injected to start the polymerization. The reaction bottle was continuously stirred and fed by the gaseous mixture of constant monomer composition." The polymerization mixture was quenched with acidic methanol (1% HC1) and the formed polymer worked up by two methods. When the product can be precipitated by acidic methanol, it was filtered, washed with methanol, and dried in vacuum at 60°C overnight. If the products could not be precipitated by acidic methanol, then water was added to the mixture after quenching. The organic phase was separated and was washed with water, MgSO, added, filtered, solvent removed by the vacuum, then the polymer was dried in vacuum at 60°C overnight. Et ( Ind),ZrC12 was also activated by a cation forming agent 2, in which case the order of addition of catalyst components is TIBA, 1 and then 2.

Characterization

The ethylene and propylene composition in polymers and rE - rb3 were determined by 13C-NMR spectra recorded at room temperature using CDC13 as a solvent with a Brucker AMX 500 spectrometer. The amount of diene incorporated was determined by proton NMR recorded with Brucker AC 200 spectrometer.

Molecular weight was measured by Ubbelhode viscometer on - 0.04% (w/ v) polymer solution in decaline at 135OC. The following equations l6 were used to estimate the molecular weights:

Copolymer

77 = 3.8 X 10-4M0.74 (E = 50-70%) ( 1 )

17 = 4.6 X 10-4M0.73 ( E 80-90%) ( 2 )

Terpolymer

77 = 2.47 X 10-4M0.759 ( 3 )

Melting temperature ( T,) and enthalpy ( AHf ) were determined with a Perkin-Elmer DSC-4 system at 20"C/min heating rate. The sample was first

heated to above T,,, , returned to room temperature, then a second DSC scan was recorded.

RESULTS

Table I show the polymerization results using Et ( Ind),ZrCl,/MAO with ethylene feed composition of 40-8076 and temperature (T,) from 20-50°C. The activities for terpolymerization with HD are comparable to the previous results for ENB as the t e r m ~ n o m e r . ~ ~ These activities are higher by one order of magnitude than the ENB terpolymerization catalyzed by CpzZrClz/MA0.3a Figure 1 compared the well-known I3C-NMR spectra of an E / P copolymer sample with that of an EPDM. The com- plexity of the latter is consistent with several ways HD can be incorporated in an EPDM chain.

A concentration about 0.167M of HD ( [ HD]/ [ Zr] - 6000) lowers the polymerization activity by one order of magnitude (from l o7 to lo6 in g/mol Zr h ) ; further increase of diene concentration leads to additional but more gradual loss of activity. The amount of diene incorporated in terpolymer is almost directly proportional to the amount of diene in the feed, up to 40 wt %. A change of T, from 20 to 50°C almost double the diene content in the EPDM (runs 117,146; 152,112; 149,143). The ratio of ethylene/propylene in the feed range of 1 : 1 to 4 : 1 seems not to affect the diene incorporation (runs 117,149; 146,143). A slight decrease of diene incorporation (40% ) was observed at lower ethylene/propylene ratio (runs 117, 152; 112, 146).

The results in Table I1 shows that the addition of diene lowers the molecular weight of the polymers, this effect is more pronounced at high T, (runs 121, 120; 111, 115; 106, 110). Variation of the feed composition of either HD (runs 121, 117; 118, 120; 148, 149), or of ethylene (runs 117,149,152), seems not to have much effect on the molecular weigh of terpolymers. The molecular weight of terpolymer obtained with this catalyst system is in the range from 3000 to 37,000. These values are smaller than the MW of EPDM obtained with ( Cp)2ZrClz/MA0.2a In the case of high E / P feed ratio and T, = 2O"C, the polymerization rate of propylene is decreased more by HD (runs 121,117, and 118) than at lower E / P ratio (runs 150-152). This trend was already seen in the lower copolymerization activities of P / HD than E / HD (Table I11 ) . The E / HD copolymerization activity is comparable to the terpolymerization activity at low diene concentration, but the amount of diene incorporated (HD - 3%) is much less when compared to terpolymerization of the same diene feed concentration.

OLEFIN TERPOLYMERIZATIONS 981

Table I. Ethylene-Propylene-1,4 Hexadiene Terpolymerization Catalyzed by Et(Ind)zZrClz/MAO System'

121 117 118 120 144 145 146 147 148 149 141 142 143 150 151 152 111 112 113 115

20 20 20 20 50 50 50 20 20 20 50 50 50 20 20 20 50 50 50 50

4 4 4 4 4 4 4 1 1 1 1 1 1 2/3 2/3 2/3 2/3 2/3 2/3 2/3

0 0.166 0.830 1.66 0 0.083 0.166 0 0.083 0.166 0 0.083 0.166 0 0.083 0.166 0 0.166 0.830 1.66

19.7 2.4 1.0 0.5 32.0 4.9 3.3 19.2 3.0 1.1 17.6 3.3 2.2 17.6 1.2 0.8 16.1 0.96 0.81 0.81

79.3 85.8 81.0 75.0 76.6 75.0 78.0 70.7 65.5 78.5 71.2 45.4 47.1 74.5 70.0 73.6 46.6 58.0 55.8 51.6

3.0 12.0 21.0

3.0 5.5

1.4 2.6

5.6 8.7

0.3 1.4

3.0 13.0 22.4

4.0 6.0 13.0 18.0 3.0 3.0 4.7 2.0 2.0 4.0 2.5 1.0 1.0 3.3 2.3 3.0 0.9 1.5 1.7 2.0

a [ 11 = 25 pM, [Al]/[Zr] = 1240, 50 mL toluene.

5 m a L 5. A 1 _-

.b. TERPOLYMER

7--------- -7--- c L 5

a. COPOLYMER

Figure 1. (a ) 13C-NMR spectra of ethylene and propylene copolymers (sample 131). ( b ) 13C-NMR spectra of ethylene, propylene, and 1,4-hexadiene terpolymers (sample 110).

The copolymerization reactivity ratios l3 for Et ( Ind)2ZrC12/MA0 have values of about 3.0 and 0.3 for r E and r p , respectively, at Tp = 20°C. The copolymerization reactivity ratios for E / HD have values of r E - 90 and r D - 0 at Tp = 20°C. Similar

Table 11. Et(Ind)z ZrClJMAO System"

Molecular Weights of EPDM Produced by

Run Tp E/P [HD] v No. ("C) (Ratio) (M) (g/dL) Mu X

121 20 4 0.0 1.99 10.6 117 20 4 0.166 0.5 2.5 118 20 4 0.830 0.5 2.3 120 20 4 1.66 0.48 2.1 145 50 4 0.083 0.4 1.7 146 50 4 0.166 0.46 2.0 106 70 4 0.0 1.6 8.1 110 70 4 1.66 0.11 0.31 148 20 1 0.083 0.64 3.2 149 20 1 0.166 0.72 3.7 143 50 1 0.166 0.22 0.77 152 20 2/3 0.166 0.59 2.8 111 50 2/3 0.0 1.48 7.1 115 50 2/3 1.66 0.13 0.39

a See Table I for experimental conditions.

982 YU ET AL.

Table 111. P/D (g/mol Zr h)"

Activities of Copolymerization of E/D and

Copolymerization Activity Diene ( M ) Ethylene Propylene

0.0 41 X lo6 4.6 X lo6 0.83 3.3 x 106b 1.2 x 104

a [Zr] = 75 p M , Tp = 20"C, time = 2.5 h, 5 psi of E or P. HD in copolymer - 3%.

results of r E and rp were obtained earlier for this catalyst6 and for Et (Ind)zZrClz activated by 2 and TEA.' They are also in agreement with the reactivity ratios obtained at Tp = 0°C by Zambelli et a1.I8 for Et (Ind )zZrClz/MAO. An unexpected observation was the inversion of reactivity ratios at elevated Tp of 70°C. The values of rE ( - 0.5) became smaller than rp ( - 1.4) both in the absence and in the presence of HD.

The 'H-NMR spectra of HD terpolymer contain peaks for aliphatic proton between 0.8-1.55 ppm, two resonances at 1.65 and 1.92 ppm for the CH3 and CH2 proton of HD, and the olefinic protons at ca. 5.4 ppm. There are two kind of insertion pro- cesses for a diene molecule: cyclopolymerization in- volving both double bonds and linear addition of the terminal double bond leaving the other double bond intact. In the latter addition of HD, there are dif- ferent regiochemical pathways leading to 1,2-, 2,1-, 4,5-, and 5,4-adducts. The extent of cyclopolymerization may be estimated from the ratio of the integrated intensities of the olefinic protons to the aliphatic protons of the diene ( 1.65 and 1.92 ppm). If there is only linear polymerization, then this sp2/ sp ratio should be 2 / 5 = 0.4. A smaller ratio would indicate cyclopolymerization. When there was spec- tral baseline drift, the spectra integration was per- formed manually. The results in Table V showed

that the products contains little (< 6%) or no cyclopolymerization structures.

The 'H-NMR spectra of the terpolymer sample 115 ( M u = 3900,22.4 mol % HD) was recorded with the 500 MHz instrument (Fig. 2) . The resonance intensities for the diene was precisely by electronic integration. The ratios of sp2/sp3 carbon is 0.71/ 1.853 indicating there may be 3% of cyclic structures.

Additional small resonances can be discerned in the olefinic regime: 6 = 4.86-5.02 and 6 = 5.67-5.88 ppm. This indicates the presence of vinyl double bonds probably due to the end groups.

Homopolymerizations of HD using the Et- ( Ind)2ZrClz/MA0 catalyst were very slow. The activities were 4 X lo3 and 1.6 X 10' g polymer/ (mol Zr h ) at Tp of 50 and 20"C, respectively. Figure 3 is the 'H NMR spectrum of the poly ( 1,4-hexadiene). There is no significant difference between the above system and Et ( IndH4)2TiCIz/MAO; the latter has an HD polymerization activity of 1.4 X 10' g/ (mol Zr h ) at 20°C. The activity is only 70 g/ (mol Zr h ) at 20°C using a CpTiC13/MA0 catalyst.

The results of copolymerization and terpolymerization catalyzed by 1 +/ 2 (Table VI) show that the amount of diene incorporated is lower at low content of diene in the feed. At high diene concentration of 0.83M, the amount of diene incorporated by this catalyst system is the same as that obtained with the MA0 system. However, the reactivity decreased about 10 times despite the higher activity of copolymerization for the "bare" cation. A t temperatures lower than 20°C no polymer could be obtained at 0.83 M concentration (runs 278, 281 ) . The amount of HD incorporated in EPDM at 0°C is lower than the one at 20°C using the same experimental conditions (run 344,284). The MW of the EPDM produced by the catalyst 1 +/ TIBA/ 2 are quite similar to those produced by 1 /MAO.

The effect of temperature on copolymerization activities, corrected for the negative dependence of

Table IV. Reactivity Ratios of Co- and Terpolymer Obtained from I3C-NMR Spectra

Feed EPDM

Run TP [HDI E No. ("C) E/P ( M ) (mol %) E/P r E rP r E * r p

271 70 4 0.0 63 1.7 0.40 2.0 0.80 106 70 4 0.0 68 2.1 0.47 1.60 0.70 110 70 4 1.66 52.6 2.7 0.64 1.26 0.81

0.0 63 1.66 2.81 0.25 0.70 1.01 138 20 1/4 0.0 46 0.85 2.90 0.35

131 20 2/3


Table V. Terpolymers

'H-NMR (200 MHz) Results of HD

HD Run Content sp2/sp3 Cyclopolymerization No. (mol %) (Ratio) (%)

148 1.4 0.42 - 0 151 1.4 0.42 - 0 117 3.0 0.40 0 118 12.0 0.40 0 113 13.0 0.37 5.6 119 12.7 0.39 - 0

monomers solubilities on Tp is shown in Figure 4. Homopolymerization results of ethylene and propylene polymerization by the same catalyst systems are shown in Figure 5 and Table VII. The activation energies a t elevated Tp are comparable to the copolymerization catalyzed by 1 +/ TIBA/ 2. But at low Tp the polymerization by 1 /MA0 have higher activation energies of 11 kcal/mol for ethylene, 12.9 kcal/mol for propylene, and 16.8 kcal/mol for copolymer.

The results of copolymerization and terpolymerization catalyzed by ( TBP)TiC12/MA0 are sum-

marized in Table VIII. The main difference between the (TBP) TiC12 and the zirconocene system is the low incorporation of propylene monomer and slightly higher molecular weight. Some heterogeneity of the polymer has been observed with this particular catalyst system (runs 169 and 160).

DISCUSSION

Kinetics of Polymerization

The commonly accepted mechanism for Ziegler- Natta catalysis invokes the ?r-complexation of monomer followed by migratiory insertion. This can be written as

ki k2

k-i A -* C+-@ + M M + C+-@ +A- A+ C+-P+, (4)

C* C*M C'

where A represents a MA0 molecule, P is the propagation chain, M is the monomer, and C *, C *M are the dormant and active metallocene species.

The rate of polymerization is given byzo

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 'PPR 5 4 3 2 1

Figure 2. 'H-NMR spectra of ethylene/propylene copolymer (sample 115).

984 YU ET AL.

8 6.5 6 . 0 5 . 5 5 . 0 4 . 5 4.0 3.5 3 . 0 2 . 5 2 0 1 . 5 1 0 5

PPH

Figure 3. diene ) .

'H-NMR spectra of homopoly (1,4-hexa-

At low Tp (< 20°C in Fig. 51, k2 + k-l + kl[ MIo

At high Tp (> 30°C in Fig. 5 ) , the rr-complex is unstable, kl + k2 + kl[ MIo,

where K, = kl/ Ll. At Tp = 20°C the homopolymerization activities

catalyzed by Et(Ind)2ZrC12/MA0 are 4.1 X lo', 1.9 X l o7 , and 1.65 X lo2 g/ (mol Zr h ) for E, P, and HD, respectively. The two-fold greater activity for E polymerization than P polymerization suggests k2,EKI,~ - 2k2,pK1,p. This difference changes with Tp. For instance, we have compared the two polymerization catalyzed by rue- ( 1,4-butane- diyl ) silylene-bis ( 1-q5-indenyl) dichlorozirconium ( 3)/MA0.20 The ethylene activities (AE) are 303, 154, 18.9, 6.92 X lo6 PE/ (mol Zr [ E l h ) a t Tp = 70,50,25, and O"C, respectively. The correspond- ing propylene polymerization activity ( A p ) are 173, 52.3, 1.4, and 0.32 X lo6 g PP/ (mol Zr [ PI h ) . At 70°C AP = 0.6 AE but it decreases AP = 0.05 AE at 0°C. In the presence of MAO, the higher activation energy observed in low temperature range in poly-

Table VI. Et(Ind)2ZrClz/TIBA/Ph3CB(C6F6)4 System"

Ethylene-propylene-1,4 Hexadiene Terpolymerization Catalyzed by

Feed EPDM (mol %)

Run T P [HDI A X No. ("C) WP ( M ) [g/(mol Zr h)l HD E E/P M , x 10-~

280 281 341 344 278 297 284 119 271 272

-30 -30

0 0 0

20 20 20 70 70

4 4 4 4 4 4 4 4 4 4

0.0 0.83 0.0 0.0 0.83 0.0 0.166 0.83 0.0 0.166

14.5 81.8 4.5 0.0

17.6 0.48 0.9 0.0

34.6 72.5 2.7 8.3 1.48 1.7 83.8 5.9 3.8 0.11 12.7 85.0 3.7 3.7 9.8 62.6 1.0 7.1 1.04 0.8 56.0 1.3

a [Zr] = 25 p M , [Ph,CB(C,F,),] = 25 p M .


24 1

lrr

Figure 4. l /MAO, SD = 0.50; ( 0 ) l / T I B A / 2 , SD = 0.51.

In A vs. 1/ T for copolymerization E/ P: (0 )

merization of either ethylene and propylene (Fig. 5) may be attributed to the complexation of MA0 to the zirconocenium cation. In this case, the kinetic region at low temperature will be better expressed by eq. (8) instead of eq. (6)" and the slope of Arrhenius plot will correspond to El + AH3,

where K3 is constant of dissociation of MA0 complex and AH3 is the enthalpy of this dissociation.

In the polymerization catalyzed by the "bare" cations formed by the reaction of either 3 with TEA and 2," or 1 with TIBA and 2 (Table VII), the values of A E are comparable to those of AP within a factor of two to three at the same Tp. The results

00028 0.0032 0.00% O.OD(0 0 . W

I/?

Figure 5. In A vs. 1 / T for propylene and ethylene polymerization ( l / M A O ) ( 0 ) ethylene, SD = 0.14 for left line and SD = 0.14 for right line; (A) pr~pylene,'~ SD = 0.15 for left line and SD = 0.15 for right line).

Table VII. Ethylene and Propylene Homopolymerizations Catalyzed by Et( Ind)2ZrC12/ TIBA/Ph&B( C6F5)4 System

A" X

Ethyleneb Propylene

- 30 -20

0 20

100 139 312

75

87.7 90.0

a In g polymer/(mol 21 [mon] h). Reference 22.

of homopolymerization of either ethylene or propylene in Table VII showed that the "bare" cation 1 have activities, which are nearly independent of Tp, i.e., low activation energy. When the catalyst system used is 1 / TIBA/ 2, the activation energy in both homopolymerization and copolymerization reactions is lower than that of 1 /MA0 system.

Figure 5 indicates that higher activity of propylene polymerization can be obtained at 70°C as compared to that of ethylene. Thus, a higher value for rp was observed as compared to r E at this temperature. This may be attributed to the smaller enthalpy of formation of ethylene zirconocenium complex than that of propylene zirconocenium if one consid- ers that the activation energies for the migratory of ethylene and propylene are very similar a t high Tp.

The polymerization activity of HD is only 5 X that of P. This ex- tremely low activity is most reasonably attributable to competition between the following structures:

that of E and 4 X

/ i-c=-T

986 YU ET AL.

Table VIII. Ethylene-Propylene-1,4 Hexadiene Terpolymerization Produced by (TBP)TiCI,/MAO

Feed EPDM

Run Tp [HDI E% D% T m AH/ [sl No. ("C) E/P ( M ) A"X (wt %) (mol %) ("C) (cal/g) (g/dL) Mu X

169 20 4 0.0 21.0 95.6 0 130.2 26.8

160 50 4 0.0 36.0 80.0 0 129.0 37.0

b 165 20 4 0.83 1.3 93.0 115.0 14.1 1.3 7.9

161 50 4 0.166 3.4 76.0 9.0 121.3 19.6 0.81 4.3 178 50 2/3 0.83 0.4 66.6 9.0 108.6 5.4 0.44 1.9

a g/(mol Zr h). Not detectable.

Only a has some activity for migratory insertion, species c is inactive because an internal double bond is coordinated to Zr' . Among the remaining structures either the monomer (b) or the propagating chain (d and e) is chelated Insertion can not occur in these structures. The rate expressions 6 and 7 need to be multiplied by the factor [ a] { [ a] + [ b] + [ c ] + [dl + [ e l } - ' .

In the usual copolymerization kinetic treatment of two monomers Mi and MJ, the addition of one to the propagation species Ri and R, generates the cor- responding intermediate and Ri + Rj = Rtotal. The same assumptions were applied to Ziegler-Natta copolymerizatios. The copolymerization of E and P is very sensitive to the structure of the catalyst precursor. Simple metallocenes have rE values orders of magnitude greater than rp. The r E and rp values are comparable for the ansa-metallocene (Table IV) . The product rE * rp are usually close to but less than unity for all the metallocene catalysts. This is also true for higher a-olefins, i.e., 1-hexene, 1-octene, etc. This characteristic ensures that the copolymerization is random.

Matters are more complicated when diene is in- volved. For simplicity but without loss of generality, let us consider the copolymerization of E and D. The copolymerization steps are:

CE + E E-+ CE + CE (9)

(10)

(11)

CE + D

Co + D

D -+ CE + b-C + Co + b-c

D -+ CD, + E + Co. -+ CE + E -+ Car,

( 1 2 ) Co + D = a + b-e -. CD + b-e

In the above equations the asterisk for C has been omitted, CE and CD are the active species having the last inserted monomer being ethylene and diene, respectively, CD., CD has the pendant group 7r-corn-

plexed and not r-complexed to the transition metal, a is the active and b-e are the inactive structures for D + CD (uide supre). Therefore, in the rate expressions

and

dMj dt - kjj[ CJ] [ Mj] + kij[ Ci ] [ Mj] (14)

the Ci and C, should be corrected for the inactive structures as discussed above. It is exceedingly dif- ficult if not impossible to determine these structures quantitatively, the best we can do is to describe the copolymerizations with apparent rate constants

kaPP = [ cacti ki,, etc. ( 15) 2, [ Cact + C cpt] n

where n is the number of the inactive and dormant species, and

k ipp k y ' ri = - etc.

Polymer Structure

In principle either double bond in a diene can insert into the Zr+ -P species. However, in the case of 1,4- hexadiene 1,2 addition is the only likely process. Both 2,l insertion and 4 3 or 5,4 type are far less possible. There is also the cyclo-addition pathway.20 In the case of 1,5-hexadiene, the optically active catalyst precursor, ethylene-1,2-bis ( v5-4,5,6,7-te- trahydro- 1 -indeny1 ) zirconium( IV ) l,l'-bi-2-naph-


tholate, initiated enantion-selective cyclopolymerization to trans-isotactic poly ( methylene-1,3-cyclo- pentane) with main chain chirality.'* We have considered the possibility of cyclopolymerization of HD.

The ratio of sp'/ sp3 protons in HD terpolymers (Table V and Figure 2) are close to 0.4 indicating very little if any cyclic structures. This is under- standable because of the unreactive internal double bond and the unstable cyclo-addition products. The 1,2 iniertion product (structure f ) possesses a 4,5 trans-vinylene bond which is not active in Ziegler- Natta catalysis. If this internal double bond does insert the product would be the unstable cyclobutane ( g ) . Therefore, there is very little if any cyclo-addition of HD in EPDM synthesis.

The ratio of sp2/sp3 protons of HD is much smaller in Figure 3 than they are in the EPDM of Figure 1 and Table IV. The ratio is 0.15 and 0.16 by electronic and manual integration, respectively, for estimates of 40 and 33% of cyclo-addition. It seems that during the long intervals between slow insertion of HD in the absence of an olefin, insertion of the second double bond can occur.

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8. T. Miyatake, K. Mizunuma, S. Yoshinori, and M. Kakugo, Makromol. Chem. Rapid. Commun., 1 0 , 3 4 9 (1989).

9. ( a ) J. A. Ewen and M. J. Elder, Eur. Pat. Appl. 0426637 (1991); ( b ) J. A. Ewen and M. J. Elder, Makromol. Chem. Macromol. Symp., 6 6 , 179 (1993).

10. J. C. W. Chien, W-M Tsai, M. D. Raush, J. Am. Chem. SOC., 113,8570 ( 1991).

11. J. C. W. Chien and B. P. Wang, J. Polym. Sci. Part A: Polym. Chem., 2 0 , 3 0 8 9 ( 1988).

12. The polymerization time for those copolymerization are < 5 min, and about 1 h for terpolymerizations. The dissolved monomer concentrations are controlled by the pressure reading. There are almost no pressure drop for copolymerization because it runs so quickly, and about 10 psi drop for terpolymerization during 1 h, i.e., about 20% change of monomer composition in dissolved monomers. For example, E / P = 4 may change to E / P = 3.2 after 1 h. The formed polymer was dissolved in toluene solution while it grows (homogeneous). The polymer was precipitated only when it was quenched by CHBOH. The well stirring remains during this homogeneous polymerization process in order to avoid the gradient of polymer compositions.

13. The reactivity ratios were determined from 13C-NMR spectra using the equations reported by Soga14 and Kakugo15 and the 13C-NMR chemical shift assignment are the same as those reported by Carman."

14. K. Soga, T. Schiono, and Y. Doi, Polym. Bull., 1 0 , 168 (1983).

15. M. Kakugo, Y. Naito, K. Mizunuma, andT. Miyatabo, Macromolecules, 1 5 , 1150 (1982) .

16. C. J. Carman, R. A. Harriugton, and C. E. Wilkes, Macromolecules, 10 ( 3 ) , 536 ( 1977).

17. E. P. Baldwin and G. V. Strate, Rubber Chem. Tech- nol., 4 5 , 7 0 9 (1972).

18. A. Zambelli and A. Grassi, Makromol. Chem. Rapid Commun., 1 2 , 5 2 3 (1991).

19. J. C. W. Chien and R. Sugimoto, J. Polym. Sci. Part A: Polym. Chem., 2 9 , 4 5 9 ( 1991 ).

20. W.-M. Tsai and J. C. W. Chien, J. Polym. Sci. Part A: Polym. Chem., 32, 149 (1994).

21. (a) G. W. CoatesandR. M. Waymouth, J. Am. Chem. SOC., 113,6270 ( 1991 ) ; ( b ) L. Resoni, G. W. Coates, A. Mogstad, and R. M. Waymouth, J. Macromol. Sci. Chem. Ed., A28, 1225 (1991); (c ) G. W. Coates, R. M. Waymouth, J. Am. Chem. SOC., 115,91(1993) .

22. W. Song and J. C. W. Chien, unpublished work.

Received August 16, 1994 Accepted October 24, 1994

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Olefin terpolymerizations. I. 1,4-hexadiene