Random Block Copolymers via Segment Interchange Olefin ...

1438 

Random Block Copolymers via Segment 

Interchange Olefin Metathesis 

Nicole L. Wagner,* Francis J. Timmers, Daniel J. Arriola, Guenter Jueptner, 

Brian G. Landes 

Introduction 

Copolymers with discretely defined blocks which are 

chemically distinct can exhibit a well-known tendency for 

the blocks to separate into various self-assembled, ordered 

phases. [1] The nature of this order is largely controlled by 

composition of the block components and the degree of 

thermodynamic incompatibility of the discrete blocks. The 

N. Wagner, F. Timmers, D. Arriola, B. Landes 

The Dow Chemical Company, Core R&D, Midland, 

Michigan 48674, USA 

Fax: (þ1) 989 636 1705; E-mail: nlwagner@dow.com 

G. Jueptner 

Polycarbonate R&D, Dow Deutschland Anlagengesellschaft mbH, 

Werk Stade, 21677 Stade, Germany 

Communication 

Polycarbonate/polyethylene random block copolymers (RBCs) have been produced using 

olefin metathesis catalysis in a process termed segment interchange metathesis. An olefin 

metathesis catalyst tolerant of polar functionality was added to reagent polycarbonate and 

polyethylene polymers which contained internal unsaturated carbon–carbon bonds. Subsequent 

metathesis occurred, segmenting the 

reagent polymers, resulting in RBCs. The block 

copolymers self-assembled into microphase structures 

which persisted into the melt state as determined 

by small angle X-ray scattering (SAXS). 

order associated with olefin block copolymers (OBC) can 

lead to useful properties such as the elastomeric properties 

of a hard (crystalline or glassy), soft (amorphous), and hard 

block copolymer. To maintain the well defined blocks, 

these olefin block polymers have traditionally been 

prepared under living conditions in batch processes. 

Multi-block materials are desirable since the mechanical 

properties of block copolymers are known to improve as 

the number of blocks per molecule increases. [2] 

We have recently reported [3] on a catalytic system 

which produces OBC using two different catalysts and a 

chain shuttling agent which transfers growing chains 

between the two distinct catalysts. A single continuous 

reactor may be used to produce a copolymer having a 

random distribution of blocks and a random distribution 

of block lengths. When the catalysts employed in this 

Macromol. Rapid Commun. 2008, 29, 1438–1443 

ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/marc.200800344

Random Block Copolymers via Segment Interchange Olefin Metathesis 

process are electrophilic transition-metal species, the 

process is best suited for addition-polymerizable, hydrocarbon-based, 

and olefinic monomers. Our interest was in 

producing materials with similar block distributions as the 

OBC materials made by chain shuttling but containing 

blocks with more pronounced differences in compatibility 

as compared to OBC. 

We now report random block copolymers (RBCs) which 

display a similar distribution of blocks and block lengths 

as the OBC prepared via chain shuttling. a The new RBCs are 

prepared via olefin metathesis in a process we call 

segment interchange. With the advent of olefin metathesis 

catalysts tolerant to polar functional groups, [4] the block 

composition of these new materials can be extended to 

contain polar functionality. Thus, the thermodynamic 

incompatibility of the blocks can be substantially 

increased such that the appropriately designed materials 

spontaneously assemble into ordered structures which 

persist at temperatures well into the liquid phase of the 

bulk material. 

Segment interchange is related to the cross-metathesis 

(CM) of unsaturated polymers produced by acyclic diene 

metathesis (ADMET). ADMET is a metathetical stepgrowth 

polymerization reaction which produces polymers 

from low molecular weight a, v-terminated diene monomers 

resulting in polymer product with a regular 

distribution of unsaturated carbon–carbon bonds with 

the co-production of ethylene. [5] In the segment interchange 

olefin metathesis process however, the substrates 

are base polymers which contain low levels of olefinic 

unsaturation. Depending on the preparation methods 

used, the olefinic unsaturation can be randomly distributed 

along the polymer backbone. The polymer units 

between the backbone unsaturation are segments and can 

be much longer than products arising from CM of polymers 

formed via ADMET. When the two different types of 

polymers, both with backbone olefinic unsaturation are 

treated with a compatible olefin metathesis catalyst, the 

various segments will interchange and, at equilibrium, 

result in a material with a random distribution of 

segments coming from both base polymers. The molecular 

weight of the material is neither significantly less nor 

greater than the average molecular weight of the reactant 

polymers. Because the distribution of the backbone 

unsaturation in the base polymers is random, then the 

a The OBC and RBC polymers are expected to be comprised of a 

random assembly of like and unlike segments, each having a most 

probable weight distribution. The random assembly of segments 

in the RBC case results from a random distribution of the backbone 

unsaturation. 

distribution of blocks in the resulting block copolymer will 

also be random. 

Experimental Part 

Materials 

Cyclooctene (Aldrich) was distilled over calcium hydride under 

vacuum and passed through an activated alumina column. 

Toluene was passed through columns containing activated 

alumina and Q-5 1 catalyst. Compounds bis(tricyclohexylphosphine) 

benzylidine ruthenium(IV) chloride and 1,3-bis- 

(2,4,6-trimethylphenyl)-2-imidazolidinylidene dichloro(phenylmethylene) 

(tricyclohexylphosphine) ruthenium (Strem), tungsten 

hexachloride (WCl 6) (Aldrich), and tri-n-butylmethyltin [Sn(n- 

Bu)3Me] (Gelest, Inc.) were used as received. Butyl vinyl ether 

was purged with argon and brought into the glovebox. The 

polyethylene reagent polymer was prepared as previously 

described. [6] GPC: Mw ¼ 69 kg mol 1 , Mw=Mn ¼ 2.2. 1 H NMR 

showed there was 0.66 mol-% internal C–C doublebonds. 

Methods 

A Haake MiniLab Compounder, Rheomex CTW5 Type 557-2200, 

with co-rotating screws was used in the melt blend experiments. 

This unit uses 4–5 g of material and was used with the nitrogen 

purge to minimize detrimental effects of air on the polymer– 

polymer metathesis reaction. The chamber was warmed to the 

desired reaction temperature and calibrated at 100 rpm. 

Gel Permeation Chromatography (GPC) was performed on an 

Agilent 1100 Series LC System containing two PLgel 300 7.5 

Mixed C columns (5 mm, Polymer Laboratories) kept at 35 8C with 

tetrahydrofuran (THF) as the eluent. The columns were 

calibrated with narrow molecular weight polystyrene standards 

(Polymer Laboratories). Samples for GPC analysis were prepared 

in THF (1 mg mL 1 ) and run at 1.0 mL min 1 . An Agilent 1100 

Series Refractive Index detector was used. Data were analyzed 

using Agilent Technologies ChemStation GPC Data Analysis 

Software. 

Transmission electron microscopy (TEM) was performed with a 

JEOL JEM-1230 TEM running at an accelerating voltage of 120 kV. 

The polymer powders were pressed between two glass slides to 

form a film which was then clamped in a chuck for ultramicrotomy. 

The films were then polished with a diamond knife 

using a Leica UC6:FC6 cryo-ultramicrotome at 100 8C and stained 

with RuO4 vapors for 3 h at room temperature. After staining, thinsections 

of approximately 90 nm are collected at room temperature. 

Images are recorded digitally using a Gatan Multiscan CCD 

camera, Model 749 and postprocessed with Adobe Photoshop CS2 

to adjust the contrast and resize the image. 

The WAXS/SAXS simultaneous differential scanning calorimetry 

(DSC)/wide and small angle X-ray scattering (WAXS and SAXS) 

experiments were conducted at the Advanced Photon Source 

(APS), DND-CAT, 5-ID-D beamline. The standard APS Undulator A 

was used as the x-ray source, with the x-ray energy set at 15 keV 

(l ¼ 0.82656 A˚ ). Two-dimensional scattering patterns were 

collected on a MARUSA, Inc. CCD camera (SAXS), and a Roper 


ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.mrc-journal.de 1439

1440 

Scientific CCD camera (WAXS) with data acquisition time set at 1 s. 

The sample to detector distance was set at 531.9 cm for the SAXS 

experiments and at 23.01 cm for the WAXS experiments. Twodimensional 

scattering patterns were reduced to one-dimensional 

datasets of scattering intensity versus scattering angle by radial 

integration of the 2-D images, using a data visualization and 

analysis package developed by Dow on the PV-WAVE platform. 

Reduction and analysis of the one-dimensional patterns were 

performed using the commercial software package JADE 1 . 

Approximately 5–15 mg portions of samples were loaded into 

aluminum DSC pans. Sample pans were sealed with an aluminum 

lid. DSC experiments were performed using a Linkam DSC cell. 

Samples were heated from 20 to 300 8C at108C min 1 , and then 

cooled back to 20 8C at108C min 1 . WAXS and SAXS patterns 

were collected simultaneously, during the thermal cycle, at 2 8C 

intervals. 

Preparation of Polycyclooctene 

Reactions were performed in a dry nitrogen atmosphere using a 

glovebox. A lower molecular weight polymer was prepared by 

mixing cyclooctene (2.1 g, 0.019 mol) and 1,7-octadiene chaintransfer 

agent (0.12 g, 0.0011 mol) in 20 mL toluene in a jar 

equipped with a stir bar. A portion of bis(tricyclohexylphosphine) 

benzylidine ruthenium(IV) chloride catalyst (0.079 g, 0.096 mmols) 

was added. The capped jar was heated in a block heater with 

stirring at 55 8C for 2 h. An aliquot of butyl vinyl ether (1.3 mL) was 

added to terminate catalyst activity. The jar was removed from the 

glovebox, and the polymer was precipitated by adding methanol, 

filtered, and dried under vacuum at 60 8C overnight. GPC: Mw ¼ 

8.6 kg mol 1 , Mw=Mn ¼ 2.3. A higher molecular weight polymer 

was prepared by reducing the catalyst concentration to 0.10 wt.-%. 

GPC: Mw ¼ 197 kg mol 1 , Mw=Mn ¼ 1.74. 

Preparation of Polycarbonate 

The polycarbonate reagent polymer was prepared as previously 

described. [8] A jacketed reactor was temperature controlled by a 

water bath at 35 8C. Aqueous alkaline bisphenol-A solution 

[bisphenol-A (6.2 g, 27 mmol) dissolved in 50 mL of a 1.5 M 

sodium hydroxide solution] was added to a nitrogen-flushed 

reactor and stirred at 300 rpm. After 20 mL of dichloromethane 

was added, the pH was adjusted to 13 ( 0.1) by the addition of 

32% aqueous HCl. Within 2 min, 27 mL of the triphosgene solution 

[4.5 g bis(trichloromethyl)carbonate] in 45 mL dichloromethane 

was added and the mixture stirred for 30 min. The pH was again 

adjusted to a value of 9 by the addition of 15% aqueous HCl 

followed by the addition of 0.46 g fumaryl chloride using a special 

syringe. After 10 min, the pH was increased to a value of 12.5 by 

the addition of 20 wt.-% NaOH solution followed immediately by 

the addition of 10 mL of the terminator solution [para tertiary 

butylphenol (PTBP) (0.281 g, 1.87 mmol) dissolved in 50 mL dichloromethane]. 

Within 2 min, 11 mL of the triphosgene solution was 

added and the mixture stirred for 30 min. Subsequently, 30 mL of 

triethyl amine solution (2.0 g in 150 mL dichloromethane) and 3 mL 

of 30% NaOH solution were added and stirred an additional 10 min, 

during which time the pH-value was kept at 12.5 by the addition of 

further 20 wt.-% NaOH solution. The lighter aqueous phase was 

decanted and the mixture was added to a 250 mL separating 

N. L. Wagner, F. J. Timmers, D. J. Arriola, G. Jueptner, B. G. Landes 

funnel and mixed vigorously two times with 100 mL of 2 M 

aqueous hydrochloric acid. The polymer was then washed four 

times with 100 mL deionized water. The resulting pure polymer 

solution was added to an aluminum pan and warmed on an 

electrical heating disk to completely remove the dichloromethane 

by evaporation. The resulting solid polymer disk was dried at 

100 8C at 10 mbar for 12 h. GPC: Mw ¼ 31 kg mol 1 , Mw=Mn ¼ 1.7. 

1 H NMR showed there was 10.5 mol-% C–C double bonds. 

Solution Metathesis Reactions 

Inside a glovebox, a 50:50 w/w mixture of the low and high 

molecular weight polycyclooctene polymers was added to a 12 oz 

jar and dissolved in toluene at 35 8C to make a 5% (g polymer/mL 

toluene) solution. Bis(tricyclohexylphosphine) benzylidine ruthenium(IV) 

chloride catalyst (1 mol-% with respect to polymer 

double bonds) was added. The viscosity of the polymer mixture 

noticeably decreased within 1 min. The catalyst mixture was 

stirred for 2 h, taken out of the glovebox, precipitated in methanol, 

filtered, and dried under vacuum at 45 8C. GPC: Mw ¼ 18 kg mol 1 , 

Mw=Mn ¼ 2.5. Similarly, either 50:50 or 80:20 w/w of polycarbonate 

and polyethylene polymers were heated to 105 8C followed 

by the addition of [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene] 

dichloro (phenylmethylene) (tricyclohexylphosphine) 

ruthenium) (2.8 mL of 4 10 3 M stock solution) and the capped 

reaction mixture stirred at 105 8C for 1 h. The polymer was isolated 

as described above. TEM and SAXS analysis were performed on the 

product. 

Melt Metathesis Reaction 

A mini twin-screw extruder was heated to 80 8C at which time 

2.5 g each of the low and high molecular weight polycyclooctene 

polymers were added to the feed chamber. The temperature was 

increased to 125 8C and the polymers blended at 100 rpm for 

10 min under a nitrogen purge. Bis(tricyclohexylphosphine) 

benzylidine ruthenium(IV) chloride catalyst was added (1 mol-% 

with respect to polymer double bonds) through the feed chamber. 

The nitrogen purge was momentarily turned off during catalyst 

addition. Within 1 min, the viscosity readings on the instrument 

panel dropped to zero presumably indicating the polymer– 

polymer metathesis reaction was complete. The melt mixture 

was blended for 10 min at 125 8C and cooled to room temperature. 

GPC: Mw ¼ 17 kg mol 1 , Mw=Mn ¼ 2.0. 

Results and Discussion 

To demonstrate the viability of this approach, two 

compositionally identical unsaturated polymers, polycyclooctene, 

which differ only in molecular weight, were 

prepared via ROMP. When these two polymers are 

combined, either in solution with benzylidene-bis(tricyclohexylphosphine)dichlororuthenium 

or with a tungsten 

catalyst system, WCl6-(n-C4H9)3SnMe, [7] or in the 

melt with benzylidene-bis(tricyclohexylphosphine)dichlororuthenium, 

the bimodal distribution of molecular 

weights collapses into a single narrow peak that is the 

weighted average of the starting base polymer molecular 




Figure 1. GPC traces for polycyclooctene samples before and after 

segment interchange metathesis using benzylidene-bis(tricyclohexylphosphine)dichlororuthenium. 

Green ¼ higher molecular 

weight base material; magenta ¼ lower molecular weight base 

material; blue ¼ solution segment interchange; red ¼ melt phase 

segment interchange. 

weights. Figure 1 shows the GPC traces for the base 

polymers and the products resulting from segment 

interchange. 

In the preceding example the coalescence of molecular 

weight and polydispersity is the only overt manifestation 

of segment interchange due to the chemically similar 

nature of the precursor polymers. In contrast, when 

chemically distinct base polymers are employed 

(Scheme 1), self-assembly or spontaneous ordering is 

observed subsequent to segment interchange. 

Figure 2 shows TEM micrographs of an isolated material 

resulting from solution blending of an unsaturated 

polyethylene with an unsaturated polycarbonate. For 

the samples shown in Figure 2b, an olefin metathesis 

catalyst was added during the solution blending step 

whereas no metathesis catalyst was added for the material 

in Figure 2a. It is clear from the domain size and domain 

distribution that the metathesized sample displays micro- 

Scheme 1. Segment interchange between a polycarbonate base polymer with a polyethylene both with random backbone unsaturation (i.e., 

x 6¼ y 6¼ z and p 6¼ q 6¼ r 6¼ s) between the segments (i.e., x, y, and z for PC and p, q, r, and s for PE). After segment interchange, the product has a 

random distribution of segments in the polymer chain to give RBCs. Triblocks are depicted only due to space limitations. 



1442 

Figure 2. TEM images of polyethylene/polycarbonate (50:50 wPE/ 

wPC) material isolated from solution blends. Figure 2a: no 

metathesis catalyst added; Figure 2b: benzylidene[1,3-bis(2,4,6trimethylphenyl)-2-imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium 

metathesis catalyst added. 

phase ordering indicative of a block copolymer. The microphase 

separation of these materials is observed for other 

base polymer ratios as demonstrated by the TEM 

micrograph for a 20:80 w/w, polyethylene/polycarbonate 

RBC (Figure 3). 

To further establish this micro-phase ordering, the 

samples from Figure 2 were analyzed via SAXS a technique 

diagnostic for this ordering. Figure 4 shows successive 

SAXS traces as a function of temperature. The presence of a 

discrete scattering peak throughout the temperature range 

is indicative of micro-phase separation. The peak position 

at 0.1 2u is indicative of an ordered micro-phase separated 

block copolymer structure. It is highly unusual for block 

copolymer materials to exhibit micro-phase ordering 

which persists well into the liquid phase such as displayed 

by these RBC materials. The SAXS and TEM data for the 

sample without the metathesis catalyst added are 

representative of a simple PE/PC blend. 

Conclusion 

N. L. Wagner, F. J. Timmers, D. J. Arriola, G. Jueptner, B. G. Landes 

Figure 3. TEM image of a self-assembled RBC prepared from 

segment interchange, 20% polyethylene—80% polycarbonate 

(stained dark). 

Segment interchange via olefin metathesis is a new 

method for the preparation of RBCs from base polymers 

with randomly distributed backbone unsaturation. The 

extent of segment interchange (i.e., block lengths and 

block distribution) is governed by the degree and 

distribution of backbone unsaturation in the base polymers 

as well as the extent to which metathesis is allowed 

to proceed. When chemically dissimilar base polymers are 

used, RBCs form which can display micro-phase ordering 

that persist at temperatures well into the melt phase of the 

material. 




Figure 4. SAXS traces as a function of temperature (heated from 20 to 300 8C and cooled back to 20 8C) for the PE/PC materials in Figure 2. 

Left: segment interchange metathesis sample. Right: sample with no metathesis catalyst added. 

Received: June 3, 2008; Accepted: June 12, 2008; DOI: 10.1002/ 

marc.200800344 

Keywords: block copolymers; olefin metathesis; SAXS; segment 

interchange; self-assembly 

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