Pure & AppL Chem., Vol. 48, pp. 295—306. Pergamon Press, 1976. Printed in Great Britain.

A NEW CLASS OF POLYETHERS—POLY(1 ,4-DICHLORO-2,3-EP OXYBUTANE)S—

SYNTHESIS, MECHANISM AND PROPERTY ASPECTSt

E. J. VANDENBERGHercules Research Center, Hercules Incorporated, Wilmington, DE 19899, USA

Abstract—The cationic ring opening polymerization and copolymerization of the cis and trans isomers of 1,4-dichloro-2,3-epoxybutane (CD and TD) with an iBu3Al— 0.7 H20 catalyst at —78°C has led to an interesting new classof polyethers containing 50% chlorine. The crystalline, racemic diisotactic polymer, obtained from CD in quantitativeyield, has the most interesting combination of properties. It has a high melting point (235°C), a high glass transition(95°C), crystallizes readily from the melt, is unusually stable to heat and light, can be melt-processed up to 270°C, isflame resistant, has good barrier properties for air and water, and has good electrical properties. Its main deficiencyis poor impact strength which can be overcome by orientation and other methods. This polymer is derived from low-cost raw materials, i.e. Cl2, butadiene, and 02. The interesting combination of properties of the CD polymer combinedwith its potential moderate cost should learn to such uses as flame resistant plastics, fibers, films and coatings. The CDpolymer crystallizes with a helical chain conformation which appears to persist in the melt and in solutions and whichappears to influence the crystallization and glass transition behavior of CD polymef and copolymers.

The cationic polymerization of CD to highly stereoregular diisotactic polymer has unusual mechanistic aspects. Apossible polymerization mechanism is proposed.

INTRODUCTION

GeneralThis paper describes the preparation and properties of a

new family of polymers from the ring opening polymer-ization of the cis and trans isomers of 1 ,4-dichloro-2,3-epoxybutane (eqn 1)

These polymers were first described by the author in aU.S. patent.1 Subsequently a detailed presentation of thisnew family of polymers was given at a Symposium inhonor of Professor Carl S. Marvel's eightieth birthday.2

These new polymers may be thought of aspoly(ethylene oxide) with a chloromethyl group on eachcarbon or, alternatively, polyepichlorohydrin with anadded CH2C1 group on the unsubstituted CH2 carbon. Theadded chloromethyl group has an unexpected, largeinfluence on both the synthesis and the properties of thesepolyethers.

The preparation of these polymers has some unusualstereochemical and mechanistic aspects. In addition, thepolymers have an interesting combination of properties ofpossible value in the plastic, film and fiber areas; mostimportant is their flame resistance due to their 50%chlorine content and their high thermal stability comparedwith other commercial chlorine-containing polymers suchas poly(vinyl chloride). Also, these polymers are based oninherently low cost raw materials—chlorine, butadiene,and oxygen. This combination of circumstances will, Ibelieve, lead to their ultimate commercial development.

Early polyepoxide studiesLow molecular weight polymers of epoxides are readily

prepared with ordinary acid and base catalysts and have

been known for many years. However, it has only been inthe last 15—20 yr that it has been possible to make highpolymers of a wide variety of epoxides. This recentprogress has resulted from the discovery of new catalystsystems. My own participation in this area came aboutinitially from the discovery of some unique and widelyeffective organometallic catalysts.3'4 Some of these newcatalyst systems are the reaction products of aluminum,zinc, and magnesium organometallics with water (Table1). The ratio of components used generally gives a veryeffective catalyst. However, the ratio of these ingredientscan be varied over a wide range, and the best compositionwill depend on the conditions, the epoxide, and the type ofproducts desired; but, in general, the preformed catalystretains organometal bonds.

Although all of these new organometallic catalysts arequite effective, they do vary a great deal in their behaviorand nature. In our work we have found thealkylaluminum-based catalysts to be especially useful.The two types of alkylaluminum catalysts shown (Table 1)vary considerably in their performance. Both of thesealkylaluminum-water catalysts are stable and soluble inorganic media. These properties are to be contrasted withthose of the organozinc and organomagnesium catalystswhich usually are not storage stable and usually areheterogeneous. The fundamental reactions involved andbasic structures formed in making these alkylaluminumcatalysts are indicated in eqn (2).

C1CH2—CH—CH—CH2C1 —

0cis (CD) or trans (TD)

2R3A1 + H20 — R2A1-0-A1R2 + 2RH

+ CH3 CCH2C CH3/ II/ 00R R

A1-O-AlR" 0o\II C—CH3+RHC—C\

"HtHercules Research Center Contribution No. 1665.

(2)

295

296 E. J. VANDENBERG

Table 1. Organometallic catalyst systems

R3A1—O.5 H20R3A1—O.5 H20—O.5 acetylacetoneR2Zn—1.O H20R2Mg—1.O H20

With the alkylaluminum-H20 catalyst, water reacts atboth of its active hydrogens to form a bis(dial-kylaluminum) oxide species and liberates a hydrocarbon.Then, in the formation of the acetylacetone-modifiedcatalyst, to be called the chelate catalyst, acetylacetonereacts further with the underlined organoaluminumintermediate to liberate another mole of hydrocarbon andform what we believe to be the chelated type of speciesshown. The general nature of the initial alkylaluminum-water reaction has been determined by measuring theresidual organoaluminum groups in the final catalysts andalso by using tritiated water and showing that the finalcatalysts did not retain radioactivity. The exact nature ofthe catalytic species is unknown, because it is difficult todetermine during a polymerization. However, it isprobably built of the fundamental structural units by theirassociation with themselves, by their coordination withepoxide or other donor solvents, and by the reaction ofthe organoaluminum groups with the epoxide. Thepresence of the metal—oxygen—metal grouping in thecatalyst is particularly noteworthy. The zinc and mag-nesium catalysts also contain these groupings, as ourwork as well as the work of Furukawa5 and others hasshown. We early recognized the importance of having twoor more organometal groups joined together by anotheratom such as oxygen to obtain a good epoxide polymer-ization catalyst.

These new catalysts enabled us to synthesize many newhigh molecular weight polyepoxides, both homopolymersand copolymers (Table 2).- A few of the more interestingmonosubstituted epoxides that were polymerized to bothamorphous and crystalline homopolymers are illustrated.Some interesting amorphous copolymers are also shown.The epichlorohydrin amorphous homopolymer and itsamorphous copolymer with ethylene oxide are especially

tRegistered trademark of 13. F. Goodrich Chemical Co.

interesting as oil-resistant rubbers.6'7 These rubbers arebeing made in multi-million-pound quantities by HerculesIncorporated under the registered trademark, HERCLORand by the B. F. Goodrich Chemical Co. under thetrademark HYDRIN.t The properties and advantages ofthese rubbers make an interesting story.8'9 Briefly, thecopolymer is especially unusual-having a unique com-bination of properties. It has the oil resistance of the nitrilerubbers combined with good rubber properties andenvironmental resistance of neoprene.

The amorphous copolymers of propylene oxide withsmall amounts of an unsaturated epoxide, such as ally!glycidyl ether, are sulfur vulcanizable rubbers withexcellent low temperature properties, excellent dynamicproperties similar to natural rubber, good ozone resis-tance, and good heat aging resistance. This polyetherelastomer is available commercially from HerculesIncorporated under the registered trademark PAREL andhas been found to be especially useful as a specialtyelastomer in applications such as automotive enginemounts. The development and properties of this interest-ing elastomer has been described recently.'°"

Butadiene monoxide is interesting because it can bepolymerized to both an amorphous rubber and a lowmelting crystalline polymer without affecting its vinylgroup. Styrene oxide has given both amorphous andcrystaffine, isotactic high polymers which have physicalproperties and behavior very much like amorphous andcrystalline, isotactic polystyrene (Table 2).

2,3-Epoxybutane studiesMy studies of the polymerization of symmetrical

disubstituted epoxides as exemplified by the cis- andtrans -2,3-epoxybutanes proved to be particularly instruc-tive (Table 3),4 and, of course, are especially pertinent tothis paper.

Catalyst behavior (Table 3). The alkylaluminum-water catalyst polymerized both isomers essentiallyinstantaneously at dry ice temperature. This rapidpolymerization is to be contrasted with the fairlyslow polymerization of propylene oxide withthis catalyst, even at room temperature. With thiscatalyst, the cis-oxide gives only an amorphous high

Table 2. High polymers from monosubstituted epoxides

AmorphousCrystalline(m.p., °C)

—CH2—CH—O— 120

CH2CI

CH2CHCH2CH2O

CH2C1

Solvent-resistantrubbers

—CH2---CH—O—CH2—-CH--O--

CH3 CII,

S-Vulcanizablerubber

O—CH2---CH=CH2

—CH2--CH—O—

dH=CH2—CH2--CH—O--

C6H5

Rubber

Like polystyrene

74

149

A new class of polyethers 297

Table 3. High polymers from cis and trans-2,3 epoxybutane

CH3CH—CHCH3\ /0 CatalystTemp.(C)

Polymerizationrate Polymer

cis R3AI—H20 —78 Instantaneous Amorphous rubbertrans R3A1—H20 —78 Instantaneous Crystalline polymer

m.p., 100°Ccis R3A1—H20—Acetylacetone 65 Slow Crystalline polymer

m.p., 162°Ctrans R3AI—H20—Acetylacetone 65 Very little

molecular weight rubber; the trans -oxide gives only arystalline high molecular weight plastic with a meltingpoint of 100°C. On the other hand, the alkaluminum-water-acetylacetone catalyst polymerizes the cis -oxideslowly at 65°C, and, under these conditions, the product islargely a crysstalline polymer with a melting point of162°C. This crystalline polymer from the cis-oxide istotally different from the crystalline polymer obtainedfrom the trans-oxide with the alkylaluminum-watercatalyst, having a completely different X-ray pattern,different solubiity properties, and a higher melting point.This chelate-modified catalyst, however, caused very littlepolymerization of the trans-oxide at 65°C. In general,these results indicate that the polymerization site in theacetylacetone-modified catalyst is much more hinderedthan that of the unmodified catalyst, since the modifiedcatalyst facilitates the formation of crystalline polymerfrom the less hindered cis -oxide and does not polymerizethe more hindered trans -oxide very well. Based on thiswork, we classified the chelate catalyst, thealkylaluminum-H20-acetylacetone catalyst, as a coordi-nation catalyst.

The chelate catalyst also polymerizes oxetanes such astrimethylene oxide by a coordination route. This resultwas first reported by the author in the patent literature12and further details were presented in 1974.10 Incopolymerizations of trimethylene oxide with epoxideswith the chelate catalyst, evidence was given that thiscatalyst contains sites varying in copolymerization abilityand, thus, presumably varying in steric hindrance.10

The unmodified alkylaluminum-H20 catalyst, on theother hand, is apparently behaving as a cationic catalystwith the cis - and trans-oxide, based on the very facile,low temperature polymerization observed. With epoxideswhich do not readily polymerize with cationic catalystsbut do polymerize readily with coordination catalysts, thiscatalyst can also behave as a coordination catalyst.

However, with the 2,3-epoxybutanes and the 1,4-dichloro-2,3-epoxybutanes, this catalyst appears to behave solelyin a cationic manner.

Mechanism aspects. Our ability to polymerize the2,3-epoxybutanes with different catalysts to differentproducts offered us a unique opportunity to learn moreabout the mechanism of epoxide polymerization. Sinceboth the main chain carbon atoms in the monomer unit ofthe polymer are asymmetric, the stereochemistry of themonomer unit would tell us whether the ring-openingcarbon atom retained or inverted configuration duringpolymerization. Of course, the crystalline polymersinitially appeared most attractive since we would expectthese to have regular steric sequences.

Table 4 shows the possible stereochemical configura-tion of dimer units from these crystalline polymers andindicates the polymerization mechanisms by which eachcould be produced. Fortunately, there are only fourregular stereochemical structures possible, two diisotacticand two disyndiotactic. The 2,3-epoxybutane polymersare ideal for studying stereochemistry since all thecarbon atoms in the chain are chemically equivalent,thereby restricting the number of isomers to the fourindicated. Of the four possible stereo sequences, onlyone, the racemic diisotactic sequence, can exist in anoptically active form. The other three structures are allmeso. Any particular structure could theoretically beobtained from either the cis- or trans-oxide by using anappropriate mechanism. There are two features as-sociated with each oxide that influence the final stericstructure of the crystalline polymer. First: each isomer,cis or trans, can polymerize with either inversion orretention of configuration of the ring-opening carbonatom. Secondly: the cis-oxide is a meso-isomer and canpolymerize either head-to-tail or head-to-head. On theother hand, the trans -oxide is a racemic mixture and canpolymerize by either an isomer selection process or by an

Table 4. Stereochemistry and polymerization mechanism of the 2,3-epoxy butane polymers

Carbon atomconfigurations

Polymerization mechanism

cis -oxide trans -oxide

C\/CH H C\/H H\/CH C CMeso-diisotactic —RS—RS-- Retention, head to tail Inversion, selectionRacemic diisotactic —RR—RR—

—SS—SS—

Inversion, head to tail Retention, selection

Meso1-disyndiotactic —RS--SR— Retention, head to head Inversion, alternationMeso2-disyndiotactic —RR—SS— Inversion, head to head Retention, alternation

298 E. J. VANDENBERG

isomer alteration process, but there is no possibility ofhead-to-tail or head-to-head polymerization, since eachenantiomorph has an identical head and tail. Whether onehas retention or inversion of the configuration of thering-opening carbon atom is readily detrmined byexamining the stereochemistry of a monomer unit in thepolymer chain. On the other hand, whether a head-to-tailor head-to-head polymerization is involved with thecis -oxide, or an isomer selection process or alternationprocess is involved with the trans-oxide, can only bedetermined by examining the stereochemistry of a dimerunit.

The stereochemistry of the cis - and trans -2,3-epoxybutane polymers was elucidated by devising afacile, unique, general method of cleaving polyethers (eqn3)413

—0—c—c

H / —p BuHBu—LiC

This method involves cleaving the polyethers with aGroup IA organometallic, such as butyl lithium, in anorganic solvent, such as benzene, at room temperature orat elevated temperature. In this reaction, a f3 -eliminationoccurs by attack of the butyl anion of butyl lithium on ahydrogen beta to the ether atom to yield a lithium alkoxidechain end and a double-bond chain end. The lithiumalkoxide chain end is, of course, readily converted withacid to the hydroxyl group. Further random reaction willultimately yield some fraction of the product withhydroxyl groups on each end of the cleaved fragment. Inthis way we were able to obtain diols containingmonomer, dimer, tnmer and higher polymer units. Fromthe monomer and dimer diols we unequivocally estab-lished the stereochemistry of the cis- and trans-2,3-epoxybutane polymers (Table 5)4

Thus the cis-oxide crystalline polymer prepared with

the chelate coordination catalyst was the racemicdiisotactic polymer, the trans-oxide crystalline polymerprepared with the alkylaluminum-H20 cationic catalystwas meso-diisotactic, and, surprisingly, the amorphouscis-oxide polymer, also prepared with the alkylaluminum-H20 cationic catalyst, or indeed any cationic catalyst, waslargely (about 80%) meso-disyndiotactic.

A number of important mechanistic conclusions comefrom these results. First, the observed products, whetherprepared by a coordination or cationic mechanism, wereall formed by inversion of configuration of the ring-opening carbon atom. My subsequent work as well as thatof Price14 indicated that all polymerizations of mono- aswell as di-substituted epoxides with all known anionic,cationic, or coordination catalysts occur with completeinversion of configuration of the ring-opening carbon

O—CC + Li C

O,-c

H20

+ HO

atom. This result appears to be a very important firstprinciple of epoxide polymerization.

Let us consider now, briefly, our proposed mechanismfor these stereoregular polymerizations. First, as shown ineqn 4, the coordination polymerization of a monosubsti-tuted epoxide must involve two metal atoms in order tomake possible a rearward attack on the epoxide. A similarcoordination mechanism also applies for a disubstitutedepoxide such as the cis -oxide.

It is now clear why we obtain active epoxide catalystsby reacting organometallics with difunctional reagentssuch as H20. Two metal atoms are required in thepropagation step. Thus, the epoxide coordinates with onealuminum atom prior to its attack by the growing chain onthe other aluminum atom. In this mechanism thecoordination bonds in the catalyst structure are needed tomove the growing polymer chain from one metal to an

Table 5. Stereochemistry of 2,3-epoxybutane polymers

Polymer Stereochemistry of dimer unit

CH (S) (S) H3\\(R) (R)/c—c

H" 'CH3

.Cationic >

coordination

Cryst.

Trace, cryst.

RS—RS1Meso-diisotactic

RS—RS

trans

CationicAmorph. RR—SS disyndiotactic

CH3\(R) (S)/C13

H"coordination > Cryst.

RR—RR)j racemic diisotactic

cis

+

OH +0

(3)

A new class of polyethers 299

(4)

adjacent one without altering the valence of the metal.The formation of the racemic diisotactic polymer from thecis isomer required that this isomer be presented to aparticular type of chain end in the same way in eachsuccessive propagation step, i.e. in a head—tail propaga-tibn, where a chain end with an RR monomer unit attacksonly the S carbon of the monomer. There is no chemicaldifference in whether the R or S carbon is attacked butjust purely stereo differences. Thus, the propagation sitemust have the precise stereochemistry to make this occur.There are, of course, enantiomorphic sites which willgrow either all R or all S chains. The steric requirementsof these sites must be quite severe, so that it is notunreasonable that the more sterically hindered trans -oxide would not polymerize well by this coordinationroute.

The cationic polymerization of the cis - and trans -oxides involves a very different mechanism. Usually, wethink of carbenium ions in cationic polymerization.However, with the very basic oxygen atom of theepoxide, one would expect the oxonium ion to be thepredominant, if not indeed the sole, reactive species (Fig.1). Thus, the cationic mechanism proposed involvesgrowth of the oxonium ion as shown. This cationicmechanism is similar to that first suggested by Meerweinfor the polymerization of tetrahydrofuran with Friedel—Crafts catalysts.'5 This mechanism involves a rearward,nucleophilic attack of an epoxide molecule, B, on eitherequivalent carbon atom of the epoxide molecule, A,involved in the propagating oxonium ion.

With racemic monomer, A and B must be the sameoptical isomer to obtain the stereoregular diisotacticpolymer. Molecular models of the transition state, basedon the likely assumption that the plane of epoxide ring Bis perpendicular to the plane of the epoxide ring A,indicate that steric hindrance inherent in the monomer canbring about this selection process. Thus, the stereoregu-larity of this polymerization appeears to be controlled bythe monomer rather than by the catalyst structure whichoften controls the stereoregularity of many otherpolymerizations, particularly of epoxides, 1-olefins andvinyl ethers. This conclusion is supported by the fact thatone can obtain only stereoregular polymer with a widevariety of cationic catalysts, including the Friedel—Craftstype such as BF3-etherate. An occasional failure of this

/C)H OH3

(A) (B)

Fig. 1. Mechanism of polymerization of trans-2,3-epoxybutane.

isomer selection process would lead to a stereo-blockstructure with —RS—RS—RS sequences followed by —SR—SR—SR—sequences of carbon atoms. Such a stereo-blockstructure appears tO occur in the crystalline polymerprepared from the racemic monomer since the polymerobtained from a pure enantiomorph has sOmewhatdifferent solubiity properties.'6 Also our examination ofdimer and trimer cleavage fractions from the racemicpolymer confirms that it is a stereoblock polymer withrather short block lengths.4

A proposed propagation mechanism by which thecis -oxide gives disyndiotactic polymer is shown in Fig. 2.The mechanism is essentially the same as proposed forthe cationic polymerization of the trans-oxide with arearward attack by monomer on a growing oxonium ion,but differing greatly in the stereochemical details. Now, inthis case, the carbon atoms in the oxonium ion aresterically different although still chemically equivalent.Since we have only one monomer, the meso cis -oxide, thestereochemistry of the chain unit formed is determinedsolely by whether it attacks the R or S carbon on theoxonium ion. If the S carbon of the oxonium ion, i.e. thecarbon with the same configuration as the last unit in thepolymer chain, is attacked, as shown, that carbon isinverted and the ring opened to form an RR unit, thusgiving the required unit to propagate a disyndiotacticchain. In the process, the oxonium ion is regenerated. Inthe next propagation step the R carbon is attacked. Thus,as the chain propagates, the R and S carbons of theoxonium ion are alternately attacked.

H OH\/3 /H3 OH3 0(S) -——O

(R)(R) I I \RO—CH—OH—O—OH—OH--o C(R)

(S)(S) \ /\OH3 OH3 X/CR)

H OH3

H OH3

Fig. 2. Propagation mechanism for disyndiotactic poly (cis-2,3-epoxybutane).

How is this rather unusual result explained? If you lookat the right side of the oxonium ion, particularly if you usemodels, it is quite clear that there is no steric factorinvolved at either site of attack that would cause it toattack one or the other carbon preferentially, andcertainly nothing that would say it ought to alternate.Therefore, you have to look to the other side of thepropagation step, that is, the chain end side. At first sightone might conclude that the counterion, X, was playing arole. However, this possibility was excluded since weexamined a wide variety of cationic catalysts and foundthat the stereochemistry of the chain was independent ofthe nature of the counter-ion. Therefore, we were forcedto conclude that the chain end dictates which carbon in

R C—R R—C CC±0CC)I /\

C_C-R>

OH H

/(R)

cboxApiurucE! 'I bLGbL!0U 01 CZ- uq J4-qcpJoLo-3-

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300 E 1 AVMDEJ4BEKO

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J 0111 4flqC2 MC bLCbsLCq (JC q' - suqsuA OIJC I2OUJCL•8

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(CD) (ID)%

/O\Cf CHSCHCHCH1Cf + CH2COOH

OOH

OVI O

C CHS_CH=CHCI.1SCf

Cf + CH =CH—CH=CH5 Cf

CH=CH—cH—CHC I

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cbOX1tpcum7c2 1U 5)20 GC5I12C JJCA SIC CJJJOIOWCJJAJ!UCLC2!U LC2flJ2 114W JJC - q --WOUOWGL2 MCLC 21X1JG 111 G5)J UOj 0UJA GCSfl2C 010111JOLO 2flP2)WC 5U9J0811C2 01 JJC 53-CbOXApn5uC2 JJJC2CJ-qICpJoLo-3-cboxApnsuc2 1G jJJC 2A1JJUJC14C5J qJcp-

112 COU2JqCL UOM 0111 MOLJC M)jJJ WC J' - -

KE2IThL2 V74D D12C1221014

A new class of polyethers 301

Table 6. Coordination copolymerization of CD with ethyleneoxide

Polymerization

CD,g 9EO,g 1

Toluene, ml 48Chelate catalyst, mmol Al 4

4hr, 65°C

Product

3.4% cony., flh 3.52.6% CD (Based on % Cl)

Based on ideal copolymerization, EO enters copolymer Ca.400X as readily as CD.

difference. First, the much larger CD molecule may not beable to fit into coordination sites which are large enoughf or EO and mono-substituted epoxides as ECH. As notedearlier, small steric differences in epoxides affect theircoordination polymerization. Also, the oxygen agom ofCD must be much less basic because of the twoelectron-withdrawing chloromethyl groups attached to theoxirane ring. Therefore, CD should be less stronglycoordinated with a coordination site on a metal than EOand ECH and thus less likely to participate in acoordination copolymerization. Probably, both factorsapply.

The cationic polymerization of both CD and TD wasthen studied in the best system found previously for thecis- and trans-2,3-epoxybutanes, i.e. CH2CI2 diluent withiBu3Al—0.7 H20 catalyst at —78°C (Table 7). Bothmonomers polymerized quite readily in this system—bothgiving high conversions and nearly quantitative yields ofhigh molecular weight, CH2C12-insoluble, crystallinepolymer. X-ray clearly showed that two different crystal-line polymers, I, and II, with different X-ray patterns,were obtained. The CD polymer was much moreinteresting since it was higher melting (235°C) comparedwith the TD polymer (145°C), was of higher molecularweight, and was less soluble, being insoluble in allcommon solvents at room temperature, whereas the TDpolymer was soluble in THF at room temperature. Bothcrystalline polymers were soluble in dimethyl formamideat 50°C and these conditions were used for measuringinherent viscosity (heating to a higher temperature todissolve, if required). The CD polymer is about 35%

crystalline, based on heat of fusion (HF) data (Table 7)and the estimation that 100% crystalline CD polymer has aIHF of 31 cal/g, based on Ke's extrapolation method.21

Both CD and TD also polymerized with an ordinaryLewis acid type cationic catalyst, BF3, to similar but muchlower molecular weight polymers. Also the polymers fromCD with BF3 catalyst were clearly less stereoregular,based on the decreased melting points, the increasedamount of CH2CI2-soluble polymer, and the lower heats offusion.

Since CD gives the most interesting and the highestmolecular weight polymer, and polymerizes more readilythan TD, the effect of the important variables in CDpolymerization was studied. Some of the requirements ofthis polymerization result from the fact that CD is acrystalline solid at lower temperatures (melting point—11°C) and is insoluble in aliphatic hydrocarbons such asn-heptane. In our experience, CD does not polymerizewhen it is completely in the solid state. Thus, one mustuse a diluent which not only has a low freezing point, butalso one which is fairly good solvent for CD, e.g. CH2C12and CH3CHC12. Mixtures of these good solvents withnonsolvents such as aliphatic hydrocarbons can be used.

Monomer concentration is critical in CD polymeriza-tion and must, in general, be at least 5%, or preferablyhigher, e.g. in the 1O—20% range. Higher monomerconcentrations generally give higher rates, conversions,and catalyst efficiencies but can also lead to monomercrystallization from solution, depending on the tempera-ture and solvent. Very low monomer concentrations, 2%or less, give very poor polymerization.

Ether is a potent inhibitor and/or retarder of CDpolymerization. Ether is no doubt too strong a basecompared with CD, so that it complexes with the Lewisacid sites in the catalyst and prevents them fromfunctioning. This result is also in accord with theineffectiveness of BF3-etherate as a catalyst.

Polymerization temperature is a very important vari-able in CD polymerization (Table 8). As with manycationic polymerizations, molecular weight is inverselyproportional to temperature. However, more important,polymer stereoregularity is dependent on temperature anddecreases rapidly with increasing temperature. Thepolymer made at —20°C is so low in crystallinity that itdoes not crystallize from the melt and is completelysoluble in CH2CL2 instead of being completely insolubleas is usual for the highly crystalline polymer; incidentallya lower temperature than —78°C does not increase M.P.s

Table 7. Polymerization of CD and TD with cationic catalysts at —78°C

CH2C12, 10% (W/V)monomerCH2CI2-insol. CH2C12-sol.

X-ray m.p. LHFtMonomer Hr % Cony ,,,,,t Cryst °C .(cal/g) % Cony

CD 3iBu3Al-0.7 H20 catalyst (4 mmol Al/lOg monomer)

88 1.8 I 235 10.8 2TD 21 66 0.58 II 145

BF3(2 mmol/10 g monomer)

8.9 3

CD 20 50 0.22 I 229 8.1 32TD 20 49 0.12 II 149 12.5 6

at 0.1%, dimethyl formamide, 50°C.tLIHF = heat of fusion from DSC. The estimated AHF of 100% crystalline CD polymer is 31.0 cal/g,

based on Ke's extrapolation method.2'§flinh = 0.05, Form I by X-ray, m.p. = 192°C, /HF = 2.4cal/g.

302 E. J. VANDENBERG

Table 8. Effect of temperature on CD polymerization

°C(CH3CHC12, i-Bu3

M, x 104tAl-0.7 H20 catal

m.p. 9'yst)o Crystallinity

—78 1.4 56 235 30—50 0.6 13.5 210 15—20 0.23 2.7 180 9

0 0.17 1.6 — 0

tBased on [] = 5.44 x 10 M°5 from Forsman and Poddar.23

or stereoregularity. Actually, we believe that the polymermade at —78°C is highly stereoregular, based on theresults of the LiA1H4 reduction to be discussed later.

TD polymerizes in much the same way as CD but, ingeneral, less readily. Rates, molecular weights, andcatalyst efficiencies are lower at equal monomer concent-ration. TD melts at 20°C, i.e. 31°C higher than CD, and isless soluble than CD at —78°C, so that the highest usablemonomer concentration of TD is lower than CD under thesame conditions. Similar diluent requirements and asimilar dependence of molecular weight on temperatureare also experienced with TD. However, stereoregularityof the polymer is independent of temperature from —78 to—30°C as we previously observed for trans -2,3-epoxybutane. Higher temperatures do affect thestereoregularity of the trans polymer.

Copolymerization. The copolymerization of CD withTD is surprisingly good, being very close to ideal (Table 9)in solution copolymerizations in CH2C12 over a wide rangeof temperatures (—78 to —20°C) and monomer composi-tion. This result was very unexpected in view of thegreater rate of polymerization of CD compared to TD.Also, our prior studies on the copolymerization of the CISand trans -2,3-epoxybutanes indicated that the cis isomerentered the copolymer at twice the rate of the transisomer.

In order to introduce a factor which may play a role inthis anomalous behavior, we will digress somewhat andtell you about some aspects of the solid state and solutionproperties of the crystalline CD and TD homopolymers.Dr. R. J. Samuels of our laboratory and Dr. G. Wildman,formerly of our laboratory, have determined by X-raystructure analysis that TD homopolymer crystallizes witha planar trans zig-zag chain conformation, similar to thatobserved with most crystalline polyethers.22 However,CD homopolymer crystallizes with a helical chainconformation containing four monomer units per turn ofthe helix. Also solution studies'on these polymers by Dr.W. Forsman and Dr. S. Poddar of the University ofPennsylvania suggest that the helical conformation of thecis homopolymer chain can persist in solution under some

Table 9. Copolymerization of CD with TD compared to cis- andtrans -2,3-epoxybutanes

(iBu3Al-0.7 H20 Catalyst, —78°C)Monomer charge Diluent

% cis

CD and TD

20 CH2C1255 CH2C1280 CH2C12

1.3tlitlOt

2,3-Epoxybutanest50 n-Heptane 2.0

tSimilar data at temperatures up to —20°C.UBu3A1—0.5 H20 catalyst.4

conditions—particularly at low temperatures.23 Thus, thetendency of sequences of cis isomer in the polymer chainto assume a helical conformation may, in some undefinedmanner, such as blocking the chain end, impede theaddition of cis isomer to the growing oxonium ion andthereby give the more favorable copolymerization ob-served. Such a factor could also play a role in thestereochemistry of the polymer formed; an alternativemode of chain end control to be compared with the morespecific one which will be suggested later.

Another possibility is that a diluent such as CH2C12 maysolvate the CD and TD monomers via hydrogen bondingbetween the somewhat acidic hydrogens on the CH2C12and the somewhat basic oxirane oxygen. Such a complexshould be stronger in the case of the less hindered cisisomer and thus impede the cis copolymerization.However, the apparent faster homopolymerization of CDcompared with TD is evidence against this hypothesis.Also, recent preliminary work on the copolymerization ofthe 2,3-epoxybutanes in CH2C12 confirms the much morefavbrable copolymerization behavior of the cis isomerfound in n-heptane. Further work is needed to elucidatethe excellent copolymerization behavior of CD and TD.

Stereochemistry of polymersThe stereochemistry of the crystalline CD and

TD homopolymers was determined by reducingthe polymers with LiA1H4 to the corresponding 2,3-epoxybutane polymers (Table 10). This generalmethod was previously used by Steller24 to reducepolyepichlorohydrin to poly(propylene oxide) and therebyobtain reliable information on the stereochemistry and thehead-to-tail nature of polyepichlorohydrin. The reducedCD polymer was obtained in two highly crystallinefractions, melting at 132°C, and 138°C, which had thesame X-ray pattern as the racemic diisotactic 2,3-epoxybutane polymer. The reduced TD polymer melted at74°C and had the same X-ray pattern as our meso-diisotactic 2,3-epoxybutane polymer. The reduced CDand TD polymers had inherent viscosities of 1.8 and 1.1respectively, indicating that little or no degradationoccurred during the reduction.

Thus, the stereochemistry of the TD polymer is asexpected, but the CD polymer stereochemistry is exactlyopposite; the meso-disyndiotactic polymer was expectedsince it was obtained under these polymerization condi-tions with cis-2,3-epoxybutane. Also the good meltcrystallizability of the reduced CD polymers indicates theCD polymer is highly stereoregular since our priorpreparation of racemic diisotactic poly(cis-2,3-epoxybutane) often crystallized poorly from the melt.4

Mechanism of polymerizationThe unusual, racemic diisotactic stereochemistry

of the CD crystalline polymer requires a modificationof the propagation mechanism proposed for thecationic polymerization of cis-2,3-epoxybutane (Fig.2). CD monomer must attack the carbon in theoxonium ion with an opposite configuration to thatof the chain end; for example, in Fig. 2, the R carbonmust be attacked to form an SS unit which has thesame configuration as the chain end. Then the propagationis continued by attack on the R carbon of each newlyformed oxonium ion, Of course, you will have both R andS chains growing. How do we esplain this? Actually, thissame phenomenon ws previously reported in our studiesof the polymerization of cis-2-butene episulfide.25 With acationic catalyst this cis -episulfide gave the same result aswe obtained with CD, i.e. formation of the racemic

A new class of polyethers 303

Table 10. Stereochemistry of crystalline polymers from CD and TDt

diisotactic polymer. Our previous explanation for thisfinding (Fig. 5) postulated that the sulfur atom in the lastchain unit coordinates with the counterion and brings thechain away from the carbon of the oxonium ion of thesame configuration as the chain end, thus eliminating thesteric facilitation. Presumably this causes a stericinteraction with the carbon of opposite configuration inthe oxonium ion, and thus a steric facilitation at that sitewould cause ring opening there. We might ask whyoxygen doesn't do the same thing and even better?Oxygen normally coordinates better with aluminum thandoes sulfur. However, in this case the oxygen is in apolymer chain and is flanked by a methyl-substitutedcarbon on each side and also the carbon—oxygen bonddistance is shorter than carbon—sulfur. Therefore, wehave concluded that sulfur would operate better in thismechanism than oxygen. Sulfur also forms bonds atgreater distance, which is another favorable factor forsulfur.

Actually, on further reflection, coordination of the lastsulfur atom in the chain with the negative counterion maynot be the most favorable possibility to explain our cisepisulfide results. Instead, I now suggest that the lastsulfur atom in the chain would more reasonablycoordinate with the positive sulfonium ion as shown inFig. 5. This suggestion does involve a four membered ringbut this does not appear to be an unreasonable possibilitybecause of the large size of the sulfur atom and theavailability of d orbitals for bonding in sulfur. Also,coordination of the electronegative sulfur with a positive

(R)' Ct /HCH C(R) CH(R)7 N®/' /H

CH3 CH (b) S I C(R)—

SX(S) — — — — V Ir'(a) 7R CH3 H

C'NH(a) Prior postulate(b) Current proposal

Fig. 5. Mechanism of cationic polymerization of cis-episulfide todiisotactic polymer.

ion is more reasonable than coordination with a negativeion which is probably already coordinatively saturated.The counterion effect previously observed can still beincorporated in this mechanism by postulating a variationin the tightness and closeness of binding of the negativecounterion, X, to the positive sulfonium ion, dependingon the nature of the X. Oxygen would probably be evenless likely to work via this mechanism because of thesmall size of the oxygen atom and its lack of d orbitals.

In accord with the cis-episuffide proposal (Fig. Sb), Inow propose that the cationic polymerization of CDmonomer involves a similar type of mechanism except, inthis case, the chlorine on the f3 chloromethyl groupsinteracts with the positive oxonium ion in a five-membered ring (Fig. 6). This postulate is reasonable sincethe electronegative chlorine is known to associate withelectrophilic centers.26

CHCI H CHC\2 NV2(R)'bH C(R) H CHCI7 NV NV 2R CH,°NI

2 /NH CH2Ct

Fig. 6. Mechanism of cationic polymerization of cis-1,4-dichloro-2,3-eposybutanetodiisotactic polymer.

Polymer propertiesThermal stability. The thermal stability of CD- and

TD-based polymers is of considerable interest as well asof possible practical importance. The commercialchlorine-containing polymers such as poly(vinyl chloride)and poly(vinylidene chloride) are very deficient in heatresistance so that it is difficult to melt-fabricate them. TheTGA curve for CD homopolymer (Fig. 7) is typical of thisentire family of CD and TD homopolymers and copoly-mers. It shows that appreciable decomposition does notoccur until 300°C. This TGA curve is very similar to whatone would obtain with other related polyethers such aspolyepichlorohydrin, poly(propylene oxide), and the

CH2C1 CH2CI CH3 CH3

—O—H—CH—CH—CH— LH4 ) —O—H—Ck—O—CH—CH—

CH2C1 CH2C1 CH3 CH3Reduced Reduced

CD polymer TD polymer

% yield 48 48 9271h(0.1, CHCI3, 25°C) 1.8 1.1% CD (or TD) leftt 2.8 3.8 6.5m.p., °C 1321 l38l 74LHF, cal./g 11.4 19.2 7.9X-ray pattern Racemic-diisotactic Meso-diisotacticStereochemistry —RR—RR—

—SS—SS—

—RS—RS—

tUsing the general method of Steller,24 1.00 g polymer (flih: CD, 0.76 and TD, 0.58) mixedunder nitrogen with 25 ml of dry tetrahydrofuran (THF) and 35.5 ml of 1M LiA1H4 in THF(2.6 moles LiAIH4 per Cl). Agitated 8 hr at 50°C and then 70 hr at 65°C. Isolated product by slowlyadding 70 ml of THF containing 5% H2O, filtering, washing twice with THF and then drying thecombined THF extracts.

tA second fraction was obtained in (a) by treating the THF-insol with 200 mol of 3% (aq) HClfor3 days, collecting the insol, washing neutral with H2O and drying.

§Based on % Cl analysis.¶Crystallized readily from melt.

304 E. J. VANDENBERG

100 IbO OO u iouTemp. 'C

Fig. 7. TGAdataon CDhomopolymer.

2,3-epoxybutane polymers. The appreciable (18%), stableresidue at 400°C is unusual. Typically, the non-halogenpolyethers leave little or no residue, whereas polyepich-lorohydrin leaves much less (ca. 10%). The stable residuehas not been studied, but presumably results fromcrosslinking and/or aromatization reactions after HC1liberation leads to double bonds.

As a result of the good heat stability, these polymerscan be melt-processed at temperatures up to 270°Cwithout any problems. Thus, the thermal stability is about100°C higher than that of poly(vinyl chloride) orpoly(vinylidene chloride). This result also means that thehigh melting CD homopolymer can be melt processed andfull advantage taken of its high melting point. Why arethese polymers more heat stable than poly(vinyl chloride)since they both can split out HC1? Presumably this is duein part to the chlorine in our polymers being primaryrather than the less stable secondary type as withpoly(vinyl chloride).27 Also, some of the weak links whichare reported to facilitate the decomposition of poly(vinylchloride) such as tertiary chlorine, and especially allylicchlorine, should not occur in our polymers.

Glass transition (Fig. 8). The glass transition tempera-ture, Tg, of CD homopolymer is 95°C and is much higherthan the Tg of TD homopolymer (55°C). This result is nodoubt due to the previously noted helical conformation ofCD homopolymer in the solid state. The helical chainconformation should be more rigid and give a higher Tgthan the trans zig-zag conformation of the TDhomopolymer.

The effect of copolymer composition on Tg isinstructive (Fig. 8). Since the comonomer units are nearlyidentical, one would expect the linear, dotted theoretical

relationship of Tg vs % CD.29 Actually Tg, as determinedby DTA, does not change until 50% CD is reached, atwhich point Tg increases rapidly with % CD. These datawere all obtained at high molecular weight so thatmolecular weight is not a factor. The unusual dependenceof Tg on copolymer composition is probably related to thetendency of successive CD units with the samestereochemistry to form a helical conformation. Since onedoes not have appreciable successive CD chain units in arandom copolymer until the CD content of the copolymerexceeds 50%, the shape of curve may be very reasonable.This result suggests that as soon as you have twosuccessive CD chain units with the same stereochemistry,there is a strong tendency to form a helical chainconformation, even in the amorphous state.

General. The specific gravity of these polymers is high(Table 11) in keeping with their 50% chlorine content. Therate of crystallization of the CD homopolymer from themelt is very rapid; the half-time of crystallization at 130°Cis 30 sec. Indeed under some fabrication conditions, suchas orientation, the high rate of crystallization can be aproblem. This result is further evidence that our CDpolymer is highly stereoregular and also that the helicalconformation persists in the melt. On the other hand, thevery low rate of crystallization of the TD homopolymerindicates poor stereoregularity and/or random conforma-tions in the melt. The rate of crystallization of the TDhomopolymer is so low that melt fabricated specimens areusually in the amorphous state. Thus, the properties givenfor the TD homopolymer are for the amorphous state andare very similar to what we find for generally amorphousCD—TD copolymers except for Tg-dependent propertiesin copolymers with over 50% CD.

Water absorption of these polymers is low. Mostsignificant is the high Limiting Oxygen Index, 28%, ofthese polymers. This result is in the range generallyaccepted as good for flame resistance. Oxygen permeabil-ity of these polymers is low and in the extrudable Saranrange. Water vapor transmission is also low. Films andmoldings of these polymers, including the crystalline CDpolymer, are clear. Electrical properties are good andmuch like oriented polyester (such as Mylar).

The melt rheology of these polymers is also interesting.Limited studies have indicated that the crystalline CDpolymer has an unusually high melt viscosity comparedwith TD homopolymer. This no doubt results from thestiffer chain of the CD homopolymer, due to its helicalconformation persisting in the molten state as well as insolutions, as noted earlier. Even so, the CD polymer

Specific gravity 1.45 1.50

Crystalline m.p., °C 235 150Rate of crystallization from melt Very High Very LowWater absorption (24 hr) % 0.06 —

Flammability Self-extinguishingLimiting Oxygen Index (% Oxygen) 28.1 27.2U.L. 646 rating SE-i

Permeability (1 ml, biaxially oriented)02, cc/100 in2/24 hr/atm 6 2.6WVT, g/100 in2/24 hr 2.2 0.15Clarity TransparentMolding qualities GoodElectrical properties Like mylar

10'C/min, N2 atmosphere

0—0 —

20 -30 -40 -50-

70 -80-90 -

100 -

0 50 350 400 450 5 J

0

00

80

60

40

Table ii. General properties

reticaI

I I I

HomopolymersCD TD

0 20 40 60 80 00

%, CDFig. 8. EffectofCD—TDcopolymercompositionon T0.

A new class of polyethers 305

appears to be readily fabricated if the molecular weight isnot excessive (preferably ii1of 0.6—0.7).

Mechanical and related propertiesUnoriented tensile properties (Table 12) are good for

both homopolymers except for the low elongation whichleads to the low impact strength noted. The higherstrength properties of the CD homopolymer on injectionmolding are probably due to orientation effects. Moldshrinkage is low. Hardness of these polymers is high.

Uniaxial orientation of these polymers (Table 13)greatly enhances tensile properties and improves tough-ness as indicated by the higher elongations. Biaxialorientation also increases strength and toughness and stillgives clear products.

The heat distortion temperature of CD homopolymer(Table 14) is high, but not as high in the 264 psi test as onemight expect based on the melting point of this polymer.This result is no doubt due to the somewhat lowcrystallinity levels, about 30—35%, that are attained withthis polymer. Thus, the high load properties are deter-mined by the glass transition temperature. The low load(66 psi) heat distortion temperature is much higher anddoes reflect the high crystalline melting point of the CDpolymer.

The oxidation resistance and light stability of CDpolymer are excellent and greatly exceed those of mostsimple polyepoxides (Table 14). TD polymer andcopolymer also have similar properties.

Presumably, this enhanced oxidation- and light-stability

Table 12. Mechanicalproperties unoriened

HomopolymersCompression molded CD TD

Tensile strength, psi 7500 5100Tensile modulus, psi 320,000 320,000Elongation at break, % 2.7 2.2Injection molded

Tensile strength, psi 9300Tensile modulus, psi 550,000Elongation at break, % 2.0Impact,t in lb 1.9Mold shrinkage, in/in 0.006Hardness

Rockwell, R 126M 100

tMiniaturized test. In a comparable test general purposepolystyrene gives 3.7 in lb.

Table 13. Mechanical properties oriented

HomopolymersUniaxial CD TD

Draw 6.7x 3.6xTensile strength, psi 30,000t 13,000—23,000Tensile modulus, psi 660,000 260,000-600,000Elongation at break, % 12 40Biaxial

Draw 2.5x 3.25xTensile strength, psi 10,500 12,700Tensile modulus, psi 330,000 450,000Elongation at break, % 27 75

tl.5 g/Denier.

Table 14. Environmental resistance of CD homopolymer

Heat

Distortion temp., °F264 psi 205

66psi 316Stability in air 1 week or more at 175°Ct

. Light

hr in fade-0-meter ca. 200tDependent on stabilizer formulation and use conditions.

is due to having an electron withdrawing group on everymain chain atom. It is, however, desirable to add both anantioxidant and an acid acceptor to our polymers in orderto achieve maximum oxidation- and heat-resistance.Indeed, the data cited here are based on polymersstabilized with 0.5% Irganox 1010 and 2% of the diglycidylether of bisphenol A.

Chemical resistance has not been extensively studied,but is good to weak acids and bases and aliphatic solvents.CD polymer should have at least moderate resistance toaromatics, ketones, and chlorinated aliphatics.

UsesCertainly, CD homopolymer is by far the most

interesting material in this new family of polyethers. It hasa useful combination of properties. I believe that there arenumerous market areas where it would find application,depending, of course, on price. Some of the mostpromising areas are high performance plastic, fiber, ifim,bottles, pipe and coatings. The high performance plasticand fiber areas appear particularly interesting since thereis an important market need for flame resistance in bothareas.

The properties of CD homopolymer are compared inTable 15 with two large volume, high performanceplastics, acetal and polycarbonate. Tensile properties aresimilar except for our low elongation and thus poorimpact properties. Mold shrinkage is equal to polycarbo-nate and better than acetal. Heat distortion temperature isinferior in the 264 psi test, but in the same range as acetaland polycarbonate for the 66 psi test. The LimitingOxygen Index is as good or better and no doubt can beeasily improved with appropriate additives such asantimony oxide, based on the high chlorine content of ourpolymer. Hardness is somewhat higher and water absorp-tion markedly lower than for either acetal or polycar-bonate. CD polymer should have large advantages inchemical resistance over acetal and polycarbonates. Ourgreatest deficiency is, of course, impact strength whichcan be greatly improved by orientation In general, theproperties of CD polymer are sufficiently attractive toacquire volume usage in the high performance plasticarea, assuming that the impact problem is eliminated andthat the cost is reasonable.

In the fiber area, we have done limited work onpreparing melt spun fibers (Table 16) from crystalline CDpolymer, actually a 99-1 CD-TD copolymer. Properties,although not optimized, are in a useful fiber range withtensile strength at about the level of some importantcommercial fibers such as wool and rayon. The fibers haveexcellent resilience and are dyeable with disperse dyes.

In the coatings area, limited studies have shown thatthese polymers have attractive properties for protectingsteel from corrosion. This conclusion applies to amor-phous copolymers in solution coatings. This ability to

306 E. J. VANDENBERG

Table 16. Fiber properties of crystalline CD polymer

Tensile, gpd 1.8—2.4

Modulus, gpd 32-42Elongation, % 19—12

Zero strength temp., °C 200

Elastic recovery, %at2% 100

3% 98-10010% 98Dyeability Disperse dyes

protect steel from corrosion is surprising in view of theknown steel corrosion problem which has been ex-perienced with epichiorohydrin elastomers.3°

CONCLUSIONS

A new class of polyethers containing 50% chlorine havebeen described. These new polymers are prepared by thecationic homo and copolymerization of the cis and transisomers of 1,4-dichloro-2,3-epoxy-butane.

The crystalline, racemic diisotactic polymer from thecis monomer is especially significant. It crystallizes with ahelical chain conformation which appears to persist,under some conditions, in solution and in the melt andalso influences the crystallization and glass transitionbehavior of the CD polymer and copolymers.

The crystalline CD polymer has an interesting combina-tion of properties. It has a high melting point (235°C),crystallizes readily from the melt, is unusually stable toheat and light, can be melt-processed up to 270°C, is flameresistant, has good mechanical properties, and has goodbarrier properties for air and water. Its main deficiency ispoor impact strength which can be overcome byorientation and other methods. This polymer is derivedfrom low cost raw materials, i.e. Cl2, butadiene, and 02,and should ultimately be of moderate cost. The combina-tion of properties of the CD polymer should lead to suchuses as flame-resistant plastic, fiber, ifim, and coatings.

The cationic polymerization of CD to highly stereoregu-lar racemic, diisotactic polymer has unusual mechanismaspects. Possible polymerization mechanisms are prop-osed. Further work is needed to elucidate the detailedmechanism aspects, particularly to explain the excellentcopolymerization of CD with TD.

Acknowledgement—The author is indebted to numerous HerculesResearch Center personnel for contributions to this work,particularly Dr. K. F. Foley, W. F. Marchlewski and D. L. Winmillfor monomer synthesis studies, W. E. Powell and Mary W. Morrisfor polymerization studies, B. H. Mahiman and Dr. W. S. Ropp formechanical property and application studies, L. J. Logan for thefiber spinning work, and J. D. McCarty for DSC studies.

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6E. J. Vandenberg (to Hercules Incorporated), U.S. Patent3,158,580 (1964).7E. J. Vandenberg (to Hercules Incorporated), U.S. Patent3,158,581 (1964).

'E. J. Vandenberg, Hercules Chemist 51(1) (1965).9W. D. Willis, L. 0. Amberg, A. E. Robinson and E. J.Vandenberg, Rubber World 153, 88 (1965).

10E. J. Vandenberg, Coordination polymerization of trimethyleneoxide, in: Polyethers (Edited by E. J. Vandenberg), AmericanChemical Society, Washington, D.C. (1975).

11C. R. Boss. Vulcanization and stabilization studies on propyleneoxide rubber, in: Polyethers (Edited by E. J. Vandenberg),

American Chemical Society, Washington, D.C. (1975).'2E. J. Vandenberg (to Hercules Incorporated), U.S. Patent

3,205,183 (1965).'3E. J. Vandenberg, J. Polymer Sci., Polym. Chem. Ed. 10, 2887

(1972).

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(1960).'°E. J. Vandenberg, .1. Am. Chem. Soc. 83, 538 (1961).'7L. F. Hatch, Hydrocarbon Process. 42(4), 157 (1963)."F. J. Bellringer and C. E. Hollis, Hydrocarbon Process. 47(11),

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Carbide Corp.), U.S. Patent 2,804,473 (1957).21B. Ke, .1. Polymer Sci. 50, 79 (1961).22R. J. Samuels and G. Wildman, Hercules Incorporated,

unpublished work.23W. C. Forsman and S. K. Poddar, Chain dimension and dilute

solution behavior of poly(1,4-dichloro-2,3-epoxybutane)s, Dis-sertation in Chemical Engineering of S. K. Poddar, U. ofPennsylvania (1974).

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Table 15. Properties compared to high performance plastics.

CD polymer Acetal Polycarbonate

Tensile, psi 7—9000 11,000 8700Modulus, psi x 10 320—560 40 350

Elongation, % 2.5 15 80

Mold shrinkage, in/in 0.006 0.020 0.006

Heat distortion temp., °F264 psi 205 255 270

66 psi 316 338 280

Limiting Oxygen Index (% oxygen) 28.1 15.0 26—28

Hardness, Rockwell R 126 120 120Water absorption, % 0.06 0.25 0.18