Living Cationic Polymerization

8/10/2019 Living Cationic Polymerization

1/9

HIGHLIGHT

Living Cationic Polymerization of Olefins. How Did the

Discovery Come About?

JOSEPH P. KENNEDYInstitute of Polymer Science, The University of Akron, Akron, Ohio 44325-3909

Received 19 January 1999; accepted 23 January 1999

ABSTRACT: The tortuous road toliving carbocationic polymerizationsis chronicled. The impetus for thisproject was my conviction that, justas living anionic polymerizationshave started with a critical insight, asimilar breakthrough will also bepossible with cations. Upon retro-spect, the facts show a three-stepprogression to the objective: Discov-ery of 1) controlled initiation, 2) re-

versible termination (quasiliving

systems), and 3) controlled chaintransfer. But what good is the dis-covery of a process without demon-strating its usefulness in terms of desirable products? Thus, a sectionconcerns unique microarchitecturesobtainable only by this technique:functional liquids, telechelics, ther-moplastic elastomers, etc. The mar-keting of some of these products hasalready started, and the fundamental

exploration of the promises of this

technique is in progress worldwide. 1999 John Wiley & Sons, Inc. J Polym

Sci A: Polym Chem 37: 22852293, 1999

Keywords: living carbocationicpolymerizations; cationic olenpolymerization; boron trichlo-ride; titanium tetrachloride; poly-isobutylene; polystyrene; tailor-made microarchitectures; telech-elics; thermoplastic elastomers

Joseph P. Kennedy started his university career in his native city, Budap-est. Just before graduating from the University he was removed by thecommunist administration because of his bourgeois origin. He escaped toVienna where he received his Ph.D. in biochemistry in 1954, and he was

postdocing in Paris and Montreal (19541957). He came to the US in1957 and became an industrial polymer researcher rst with Celanese andthen with Exxon. In 1961 he received an MBA at Rutgers. He resumedhis academic career at the University of Akron in 1960, where he is stillcarrying out research as a Distinguished Professor of Polymer Scienceand Chemistry. Kennedys main interest is in ionic (particularly cationic)polymerizations, and for the last 10 years in designed biomaterials. Hehas written three books, well over 600 publications, and has 75 issuedJOSEPH P.

KENNEDY

2285Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 37, 22852293 (1999) 1999 John Wiley & Sons, Inc. CCC 0887-624X/99/142285-09


2/9

PREAMBLE

The editors marching orders were quite explicit: Theygave me the title and wanted . . . a very personal viewof this topic, discuss the signicance of the art andfuture of this eld. It took me several months to seethe signicant events that led up to the breakthrough,and then to dare to chronicle my ndings. After all,this was to be scientic history cum analysis of keycontributions of some of my coworkers, not a reporton chemical phenomena, problems that I know how to

handle.I was pleased with the timing of this invitation be-

cause the rst tangible industrial consequences of ourdiscovery have just appeared in the market place: Epion,a premium architectural sealant of the Kaneko Co., andTS-Polymer, a soft barrier thermoplastic elastomer of Kuraray Ltd.

As usual, this discovery came by in two stages:conceiving the idea and then reducing it to practice (touse the lingo of patent people). The basic idea was, of course, a given. Living anionic polymerizations of styrene and dienes have been demonstrated in themid-1950s 1,2 and the spectacular synthetic power of this epochal discovery has immediately been recog-nized. Living anionic polymerizations have led to sty-renic thermoplastic elastomers (e.g., the Kratons of Shell Oil Co.), premium styrene butadiene rubbers,and many other successful industrial products. I hopedthat one day we in the cationic polymerization com-munity will also have living polymerizations of isobu-tylene and other olens, for example, styrene, and willalso have industrial processes with roots in livingcarbocationic polymerizations.

While recognizing the opportunity was easy, how toactually accomplish Living Carbocationic Polymeriza-tion was a difcult and long process. In hindsight (whichis always 20/20) the accomplishment came by in threesteps: (1) discovering controlled initiation, (2) recogniz-ing what we call today reversible termination, andnally, the toughest hurdle, (3) how to suppress chaintransfer. This Highlight recounts how these three stepswere accomplished, and briey analyzes the signicanceof these steps in terms of new products.

It is not enough to discover something new; one hasto demonstrate its signicance, a much more difcult

task. The discovery of living cationic olen polymer-izations is a case in point. The newness of the discov-ery is no longer in doubt; now the question shifts to:how signicant is it? The answer(s) may not be too farin the future. At the present I see the unfolding a fewavenues, and these will be outlined in the Conse-quences section. I will close with a glimpse into thefuture.

INTRODUCTION: THE IDEA HATCHESThe road to living cationic polymerizations started,sometime in the mid to late 1960s, during my halycondays when I was a budding polymer chemist at Esso(now Exxon) Research and Engineering Company inLinden, NJ. My boss, R. M. (Bob) Thomas, the coin-ventor of butyl rubber, was a truly Renaissance man,an ideal research leader, and partner full with insatia-ble curiosity not only for chemistry but for all thingshuman and otherwise. He was not afraid to follow hisinstincts and intuition wherever they led him, and waswilling to bet on people he trusted. Often he had toconfront corporate bean-counters to justify his exis-tence and deal with their revolting what did you dofor me lately ?

My ofcial job with Thomas was to investigate themechanism of low-temperature cationic polymeriza-tions, particularly that of isobutylene (IB). But moreimportant than my ofcial duties was my unofcialassignment. Thomas inspired me to go for technolog-ical quantum leaps; he was convinced that one day wewill have a breakthrough and will be paying for ourkeep. He had taken the chance trying to rejuvenatethe moribund eld of cationic polymerizations. Duringthe 1960s, after a period of exiting landmark develop-ments, research in cationic polymerization started tostagnate. Decreasing interest was mainly due to a shiftin emphasis in polymer synthesis to the emergingelds of Ziegler/Natta coordination polymerizationsand living anionic polymerizations, and because thepioneers of cationic polymerizations kept working onsecondary problems and got bogged down in kinetictrivia. I have written about these sorry times else-where. 3

U.S. Patents. He has received many awards, including the two premierpolymer awards of the American Chemical Society (Polymer Chemistry,and Applied Polymer Science). For obvious reasons, he derives hisgreatest satisfaction from the Honorary Doctorate awarded by the bestscience university in Hungary (Debrecen, 1989) and by his election as amember of the Hungarian Academy of Sciences (1993).

2286 J. POLYM. SCI. PART A: POLYM. CHEM.: VOL. 37 (1999)


3/9

My years with Thomas were extraordinarily fruitful;we have discovered, among other things, cationicisomerization polymerizations, 4 prepared the rst crys-talline polyolen by cationic means [poly(3methyl-1-butene)], 5 discovered crystalline polybenzyls, 6 discov-ered a new method of grafting and made a variety of

novel grafts, for example, butyl rubber- g-polystyrene7

(which much later matured into todays star-branchedbutyl 8 ), etc.

On one occasion Thomas invited Professor Ledwithof Liverpool for a seminar. After his lecture on vinylether polymerizations, during our private discussion,Ledwith mentioned that he heard about new rubbers,which behaved as truly crosslinked elastomers but didnot need vulcanization for crosslinking and could beremolded! Only later did I realize that he had the earlystyrenic thermoplastic elastomers in mind Shell scien-tists were rumored to have made. I was fascinated bythis news, and have decided to nd out the details. Mysearch soon led to Szwarcs work on living anionicpolymerizations, 9 and follow-up work by Milkovichand the Shell group 10 in Emeryville (for an account of the discovery and development of Kraton thermoplas-tic elastomer, see ref. 11). As I started to understandwhat was at the heart of this breakthrough (i.e., livingsequential anionic polymerizations leading to glassyrubbery polydieneglassy triblocks with unprece-dented morphologies and revolutionary properties) itdawned on me that this must also be the future of cationic polymerizations, particularly with polyisobu-tylene as the rubbery segment. After all, polyisobuty-lene is superior in many respects to the diene rubbersthat were described at that time. I conjectured(dreamed would perhaps be a better word) that theremust be a way to living carbocationic polymerizationsand from there to block copolymers, including glassyrubbery polyisobutylene glassy triblocks. BobThomas was immediately for the idea, but then-. . . fate interfered: I was transferred to another group,

and then to another, and still to another. I had tochange my priorities in a hurry: no more blue sky-ing, only strongly product oriented work (the realitiesof an industrial researcher!). While I was able to keep

my nose above water, I felt that my days as an indus-trial person were numbered (my freshly acquiredMBA and rapid promotions notwithstanding). I de-cided that I must do my own thing, sink or swim withmy own research. Although my times at Exxon weretruly enjoyable and memorable, the time to move onhas arrived. Among the academic opportunities Ichose was The University of Akron, a decision I havenever regretted.

THE THREE STAGES ON THE ROAD TOLIVING CARBOCATIONICPOLYMERIZATION

In retrospect, living cationic polymerization of olenscame about in three landmark events: (1) accomplishingcontrolled initiation, (2) recognizing reversible termi-nation, and (3) nding conditions to suppress chain trans-fer. All three major events, particularly the rst, and of course the third one, spawned a host of desirable down-stream developments. Let me describe and analyzebriey the signicance of these three events:

Step 1. Controlled Initiation

Controlled initiation is initiation by the use of a well-dened moiety, which becomes the head group of thenew polymer. Controlled initiation is thus tantamount tohead group control:

R M 3 R M O nM

R O MMM O M

The initiating moiety R can be a small or large(polymeric) cation. In the former instance, controlledinitiation will lead to head group functionalized polymer,while in the latter case, block or graft polymers will arise.In this sense, there is no difference between head-func-tionalized polymers and block or graft polymers.

The road to the discovery of controlled cationic po-lymerization started when I realized that one of Nattaspatents to Montecatini, in which it was claimed that IBcould be polymerized by Et 2 AlCl,

12 was wrong. Let meoutline the facts and the logic that led me to this conclu-sion, and to the consequences of this insight.

During the late 1950s and early 1960s, stereoregu-lar ZieglerNatta polymerizations burst on the scene,and I was following these patents and publicationswith fascination. My friends at Esso, particularly EricTornqvist and Art Langer, have helped me to under-stand the intricacies of this emerging science. We hadmany exciting discussions on the mechanism of Z/Npolymerization, and we knew that IB was one of thefew common olens that could not be polymerized bythese systems operating by anionic coordinatingmechanisms. Thus, I knew that the Italian workers didsomething wrong when they claimed that they poly-merized IB by Et 2 AlCl. I was working with manykinds of Lewis acids, Et 2 AlCl included, and I havedecided to repeat the Italian work with Et 2 AlCl underthe conditions a cationic chemist would employ (i.e.,under reasonably dry conditions). It did not take uslong to determine that Et 2 AlCl alone did not initiate IB

HIGHLIGHT 2287


4/9

polymerization; however, it worked efciently in thepresence of added cationogens, i.e., Bronsted acidsl ike HCl or H 2 O. We became convinced that theItalian workers have used impure Et 2 AlCl, and that theimpurities (most likely moisture) mediated their reac-tions. We postulated that the Et 2 AlCl acted as a coini-tiator, helping the formation of the true initiatingmoiety, the proton, which then became the head groupof the new polymer:

We postulated that this initiation could be simpliedby short circuiting with tert -butyl chloride (tBuCl), acationogen, which will provide the initiating entity(CH 3 )3 C :

Indeed, we obtained consistently rapid, sometimes ex-plosive, polymerizations by adding tBuCl to quiescent IB/Et 2 AlCl mixtures. This seminal discovery of initiationwith tBuCl was, however, only of theoretical interestbecause the tBu headgroup is sterile, one cannot doanything with it. More importantly, this discovery was aspringboard for using a great many other cationogens forthe preparation of a large number of headgroup-function-alized polyisobutylenes. 13

Among the many derivative discoveries let memention only twoone that led to new grafting chem-istries, and another, which became important for livingpolymerizations. Thus, we discovered that halobutylrubbers are excellent cationogens because their halo-gens can be efciently mobilized by Et 2 AlCl, andthese rubbers can in fact be used as macroinitiators

for the cationic polymerization, of, for example, sty-rene:

These butyl rubber- g-PSt products are good TPEs.This discovery also led to a host of other grafts with allkinds of rubbery/glassy, rubbery/rubbery, glassy/glassycombinations prepared basically by the same controlledinitiation (grafting from) technique. 14,15

The discovery that cumyl chloride (C 6 H5 C(CH 3 )2 Cl)is an excellent initiating cationogen became of criticalimportance for living polymerizations, and with p-di-cumyl chloride Cl(CH 3 )2 C O C6 H4 O C(CH 3 )2 Cl for thedevelopment of telechelics.

Controlled initiation in various disguises is still ex-plored worldwide.

Step 2. Reversible Termination

I regard the conceptualization of reversible termination

C MtX n 1 CX MtX n

a critical milestone on the road to living carbocationicpolymerization. The key observation that later led to the



5/9

concept of reversible termination was made by StewFeinberg. We observed that termination of IB polymer-ization induced by the H 2 O/BCl 3 system invariably ledto CH 2 C(CH 3 )2 Cl end groups, irrespective of thequenching agent or method used 16 :

The end group remained the same even when activepolymerization charges were poured into methanol.These ndings were interpreted by postulating thatMeOH reacted with the excess BCl 3 pulling by massbalance the reaction to the right. Proof positive for thepresence of the tert -chlorine terminus was obtained bypreparing poly(isobutylene- b-styrene) blocks, i.e., add-ing styrene to PIB CH 2 C(CH 3 )2 Cl and starting theblocking with Et

2AlCl. 17 The rate of reversible termina-

tion was higher than that of chain transfer to monomer( Rt Rtr,M ) which signaled that BCl 3 -coinitiated IBpolymerizations could proceed in the absence of chaintransfer!

Reversible termination was rst spelled out as such in-methylstyrene polymerizations initiated by the

C6 H5 C(CH 3 )2 Cl/BCl 3 system18 :

In further studies we focused on various other olenpolymerizations and found the rst evidences for living-ness, i.e., molecular weight growth increase in tandemwith conversions. 18,19 We proceeded to develop the qua-si-living polymerization technique in which chain trans-fer was suppressed by adding monomer to active revers-ibly terminating systems. 18 Many BCl 3 -coinitiated olenpolymerizations have been investigated by this technique(besides IB and -methylstyrene, styrene, indene, etc.)and the results summarized and analyzed in a specialissue of J. Macromol. Sci. devoted to this subject. 20

Kelen (a mathematician) and Tudos (a kineticist) greatlycontributed organizing and describing quantitativelymechanistic aspects of quasiliving polymerizations.These investigations brought ideal and quasiliving poly-merizations sharply in focus:

Thus, in contrast to ideal (or truly) living polymeriza-tions in which both termination and chain transfer areabsent during the time frame of the experiment ( Rt

Rtr 0, for example in the living anionic polymer-

ization of styrene 2 ), in quasiliving polymerizations ter-mination and/or chain transfer are operational but theyare reversible , and the rates of these reversible reactionsare higher than that of propagation. In ideal living poly-merizations all the propagating species are active all thetime, and chain transfer and termination are absent ; Incontrast, in quasiliving polymerization, chain transferand termination are reversible and the rate of thesereversible processes are higher than propagation so thatthe only signicant monomer consuming process is prop-agation (monomer consumption by initiation is negligi-ble). While ideal living and quasiliving systems are ki-netically indistinguishable (quasiliving systems appear tothe uninitiated observer as ideal living systems), a num-ber of important observations exist that can be explainedonly by the quasiliving concept. 21

The following scheme helps to visualize the differ-ences between ideal living and quasi-living polymeriza-tions:

where A* active propagating species, D dor-mant species that arises by reversible termination and/orchain transfer, M olen monomer, and growth isindicated by the increasing number of signs. Thequasiliving equilibria between A* and D are rapid rela-tive to growth. The ultimate achievement of macromo-lecular engineering by addition polymerizations wouldbe to control these equilibria at every propagating step.This clear distinction between ideal and quasiliving po-lymerizations leads to the conclusion that all living car-bocationic olen and alkyl vinyl ether polymerizationsare, in fact, quasiliving systems. 22,23 These matters havebeen discussed in detail (see the rst two chapters in ref.20 and pages 3135 in ref. 21).

The idea of reversible termination has recently beenused to explain the mechanism of controlled/livingfree radical polymerizations. 24

A historical footnote: M. Sawamoto was a visitingscientist in Akron during the times when living cationic

HIGHLIGHT 2289


6/9

polymerization was formulated. Because of his priorexperience with alkyl vinyl ethers, he was motivated tostudy the quasiliving polymerization of methyl- andisobutyl vinyl ethers. 25 He must have gotten infectedwith the living cationic polymerization virus, because notmuch after his return to Kyoto, in 1984, he startled theworld by coauthoring the rst-ever publication of livingalkyl vinyl ether polymerizations and thus opened a mostfruitful chapter in polymer synthesis. 26

Step 3. Suppressing Chain Transfer

The nal phase of this saga was the search for counter-anions that promote initiation and propagation, are suf-ciently stable not to cause termination, but will notcause or assist proton elimination (i.e., chain transfer).The critical experiments toward these objectives weredesigned, performed, and interpreted by Rudi Faust. Heused various tert -acetate/BCl 3 combinations in his initialinvestigations. 27 Initiation, for example, with the cumylacetate/BCl 3 system was postulated to occur by

The rst indication for the absence of chain transferwas by 1H-NMR analysis, which showed the absence of terminal unsaturation in the PIBs obtained; had chaintransfer taken place, we would have seen terminal un-saturations! Livingness was demonstrated by linearlyascending M n vs. g PIB plots starting at the origin (nointercept!) together with horizontal number-of-PIBchains vs. g PIB plots with (horizontal) intercepts at [ I o ],the molar concentration of the initiating cumyl acetateemployed. Another unmistakable sign of livingness wasthat the molecular weight distributions narrowed in tan-dem with increasing molecular weights (conversion).Figure 1 is a representative plot from the original publi-

cation showing these critical facts.In addition to presenting irrefutable chemical and

kinetic evidence for living IB polymerization, the criti-cality of the rst-order (counteranion mediated) chaintransfer in determining molecular weights, relative to themuch less important second-order chain transfer, waspointed out for the rst time. And last but not least, livingpolymerizations could be carried out under conventionallaboratory conditions, and high-vacuum drying was un-necessary. 27

The discovery was complete in 1984, and the rstlinear telechelics were in our hands (see the last sentencein our rst full article, ref. 27), however, due to strategicreasons we delayed publication until patents have beenled. 28 The history of some of these events has beenrecounted. 22 The rst full article describing the livingpolymerization of IB was published in the Journal of Polymer Science in 1987 27 and some 10 years later it wasreprinted together with commentaries in the 50th anni-versary issue of this journal among the 50 most inuen-tial articles that have appeared during the 50 years his-tory of this journal.

The scope of the basic discovery was immediatelyextended by the use of bifunctional acetate initiators forthe preparation of tert -chlorine ditelechelic polyisobuty-lenes. 29 Almost simultaneously with these developmentsM. Mishra showed that cumyl methyl ethers (specical-ly, the mono-, di-, and trifunctional homologuesC6 H5 C(CH 3 )2 OCH 3 , pCH 3 O(CH 3 )2 C O C6 H4 O C(CH 3 )2OCH 3 , and 1,3,5-C 6 H3 O (C(CH 3 )2 OCH 3 ))3 , in conjunc-tion with BCl 3 , are also excellent living initiators andyield mono-, di-, and tri- tert -chlorine telechelic PIBs,respectively. 3032

Another signicant development was when Kaszasand Puskas demonstrated that the relatively inexpensive

Figure 1. M n and N , the number of PIB chains (in-sert), vs. the weight of PIB formed W PIB In the CuOAc/ BCl 3 /IB/CH 2 Cl 2 polymerization system using the IMA technique at 30C: [ I o ] 5 .6 10

3 M, [BCl 3 ] 2.810 1 M. Numbers indicate M w / M n values.



7/9

TiCl 4 is also an excellent living polymerization coinitia-tor, both with cumyl esters 33 and ethers. 34 Then the samehusband and wife team went on to discover that electronpair donors (EDs), such as dimethylsulfoxide, dimethy-lacetamide, that is compounds which until this time wereconsidered grave poisons (!), in fact mediate living car-bocationic polymerizations. 35 They showed that by theuse of select EDs various undesirable side-reactions(e.g., chain transfer) that plague conventional cationicpolymerization can be eliminated and well-dened nar-row dispersity products can be prepared. A new mecha-nism to explain the observations was developed 36 and thenature of EDs was rened. 37,38

Although living cationic polymerization of olens is areality, its exact mechanism is still not entirely settled.Sufce to state that available information may be treated interms of three species connected by two equilibria 3941 :

The nature of the living cationic species is still anissue. 24 The nding that the inifer technique developedfor the synthesis of telechelic PIBs in the late 1970s 42

also operates by the living mechanism was of greattheoretical and practical signicance. Bela Ivan investi-gated the mechanism of IB polymerizations induced bydicumyl chloride (DiCumCl)/BCl 3 systems and recog-nized that the polymerizations exhibit an initial phase

with relatively slow DiCumCl consumption and lowinitiation efciency ( I eff 1.0), followed by a livingphase characterized by controlled initiation and chaintransfer by the DiCumCl and I eff 1.0.

43 Thus, telech-elics can be prepared by the inifer and/or living tech-niques:

Consequences of Living Carbocationic

PolymerizationThe discovery of living cationic olen and alkyl vinylether polymerizations in the mid-1980s brought carbo-cationic polymerizations back to center stage of syntheticpolymer science. As explained above, living polymeriza-tion of IB yields well-dened polyisobutylenes with tert -chlorine end groups, predictable molecular weights, andnarrow dispersities ( M w / M n 1.031.3). These in-termediates became the fountainhead of many designed

downstream products which, after all, were the justica-tion and ultimate aim of this long quest.

We started by demonstrating the synthesis by livingpolymerization of mono-, di-, and tri- tert -chlorinetelechelic PIBs and their quantitative conversion to ole-n. Miklos Zsuga prepared even four-arm star PIBs ttedwith tert -chlorine and isopropylidene end groups. 45

These intermediates, in turn, became the source of stillfurther telechelics, for example, O OH, CHO, epoxy, O CH 2 SO 3 X , O CH 2 Si(CH 3 )2 Cl, O C6 H4 OH, etc.,terminated products. Schematically 46 :

The synthesis of allyl-terminated PIBs by the directquenching of active polymerization charges with allyl-

trimethylsilane was accomplished by Lech Wilcheck,47

and became the prototype of a successful recently com-mercialized sealant (Epion by Kaneka). The OH-telech-elic intermediates were used for the preparation of unique hydrophobic polyurethanes of biomaterial inter-est. 48

Rudi Faust also prepared the rst polystyrene 49

poly( p-styrene) 50 and poly(2,4,6-trimethylstyrene) 51 byliving cationic polymerization, and these investigationsnally led to the triblock thermoplastic elastomers Ienvisioned some 25 years ago (see Introduction)! Thecritical experiments were carried out by Gabor Kaszasand Bill Hager, who worked out the conditions for thesequential living polymerization of IB followed by sty-rene. 52,53 These breakthroughs spawned industrial devel-opments world wide and the test marketing of the rstcationically prepared styrenic (I would prefer the ad- jective isobutylenic) TPE has just begun (TS-Polymerby Kuraray Ltd).

A Glimpse into the Future

I have looked at where we came from, and what we (sortof) know; so what lies ahead? Parts of the answer(s) arealready apparent: witness the steady stream of publica-tions and patents, mainly by American, European, andJapanese investigations, focusing on the exploration of living carbocationic polymerizations; witness also therecent commercial introduction of Epion and TS-Poly-mer (see above). And after costly market introduction of a new product by the pioneer, industrial research/devel-opment by timid second-comers will surely follow. Arecent publication by Sawamoto et al. hints at the pos-sibility of living cationic polymerization in water, 54 apromise with potentially revolutionary consequences.

HIGHLIGHT 2291


8/9

This technique should make its mark in tailor-de-signed new microarchitectures. TPEs are most likely inthe picture, and I am expecting developments in highmolecular weight low viscosity multiarm star-block TPEs readily obtainable by the living carbocationic tech-nique. The superior mechanical properties and process-ing characteristics of these materials, which also offerrecyclability and potential cost advantages (tolerance toimpurities), have been recognized.

Efforts have been made to commercialize OH-telech-elic polyisobutylenes for use in polyurethanes by theAkron Polymer Development Co. Methacrylate telechel-ics, especially multiarm star methacrylate telechelics,offer obvious advantages for UV-curable coatings. Poly-isobutylene-based linear and multiarm star telechelics,particularly those tted with hydroxyl and methacryloylend groups, and telechelic sulfonated ionomers deserve along look for a variety of potential end uses.

The scope of living cationic olen polymerization

should be expanded over heretofore unexplored olensand diolens, particularly to those giving rise to isomer-ization polymerization, such as 3-methyl-1-butene,4-methyl-1-pentene. Living isomerization polymeriza-tions would extend microarchitectural control possibili-ties beyond simple addition polymerizations.

Among the most promising uses of precisely designedmolecules will conceivably be in biomaterials, wherecost is less of an issue than function. According to recentanimal studies, unique implantable/retrievable immu-noisolatory membranes assembled partly by the use of living cationic polymerization, hold promise to correctType I diabetes. 55

In the future we have to strive for increasing ourunderstanding of the fundamentals of living cationicprocesses; this will lead to better, cheaper, and easierprocess control, which in turn, will yield products withenhanced combinations of useful properties.

Although support has been received from many sources duringthese extended investigations, this discovery and follow-upresearches could not have been accomplished without contin-uous and signicant help by the National Science Foundation(Grants DMR-84-18617, INT-86-07993, DMR-89-20826, andINT-89-05410).

REFERENCES AND NOTES

1. Szwarc, M. Nature 1956, 178, 1168.2. Szwarc, M.; Levy, M.; Milkovitch, R. J Am Chem Soc

1956, 78, 2656.3. Kennedy, J. P. In Cationic Polymerizations of Olens: A

Critical Inventory; WileyInterscience: New York, 1975;p. 93, 113.

4. Kennedy, J. P. In Encyc Polym Sci Tech; WileyInter-science: New York, 1967, p. 754, vol. 7.

5. Kennedy, J. P.; Thomas, R. M. Makromol Chem 1962, 53,28.

6. Kennedy, J. P.; Isaacson, R. B. J Macromol Sci 1966, 1,541.

7. Kennedy, J. P.; Baldwin, F. P. U.S. Pat. 3,94,708 (1975).8. Ban, L. L.; Duvadevani, I.; Wang, H. C. In Presentation at

the 137th Technical Meeting of the ACS Rubber Division,

Las Vegas, May 29June 1, 1990 (Paper No 63, May 31,1990); and previous papers in this series.9. Szwarc, M. In Carboanions, Living Polymers and Elec-

tron-Transfer Process; John Wiley & Sons, Inc, 1968.10. Holden, G.; Milkovich, R. U.S. Pat. 3,231,635 (1960).11. Holden, G.; Legge, N. R. In Thermoplastic Elastomers;

Hanser Pub: Munich, 1987; p. 47.12. Belgian Pat. 605,351, to Montecatini (June 1960).13. Kennedy, J. P.; Marechal, E. In Cationic Polymerization;

John Wiley & Sons: New York, 1982, p. 104.14. Kennedy, J. P. In Cationic Graft Copolymerization; Inter-

science Publishers; New York, 1977.15. Kennedy, J. P.; Baldwin, F. P. U.S. Pat. 3,560,458 (1971).16. Kennedy, J. P.; Feinberg, S. C.; Huang, S. Y. J Polym Sci

Chem Ed 1977, 15, 2869.17. Kennedy, J. P.; Huang, S. Y.; Feinberg, S. C. J Polym Sci

Chem Ed 1978, 16, 243.18. Faust, R.; Fehervari, A.; Kennedy, J. P. J Macromol Sci

Chem 198283, A18, 1209.19. Puskas, J.; Kaszas, G.; Kennedy, J. P.; Kelen, T. J Mac-

romol Sci Chem 198283, A18, 1229.20. Kennedy, J. P. J Macromol Sci Chem 198283, A18.21. Kennedy, J. P.; Ivan, B. In Designed Polymers by Carbo-

cationic Macromolecular Engineering. Theory and Prac-tice; Hanser Publisher: Munich, 1992, p. 33.

22. Kennedy, J. P.; Ivan, B. In Designed Polymers by Carbo-cationic Macromolecular Engineering. Theory and Prac-tice; Hanser Publisher: Munich, 1992, p. 32.

23. Ivan, B. Macromol Symp 1998, 132, 65.24. Matyjaszewski, K. ACS Symp Series 1997, 665, 12.25. See the three papers by M. Sawamoto in ref. 20, pp. 1275,

1293, and 1301.26. Miyamoto, M.; Sawamoto, M.; Higashimura, T. Macro-

molecules 1984, 17, 265.27. Faust, R.; Kennedy, J. P. J Polym Sci Part A Polym Chem

1987, 25, 1847.28. Kennedy, J. P.; Faust, R. U.S. Pat. 4,910,321, 1990.29. Faust, R.; Nagy, A.; Kennedy, J. P. J Macromol Sci Chem

1987, A24, 595.30. Mishra, M. K.; Kennedy, J. P. J Macromol Sci Chem 1987,

A24, 933.31. Mishra, M. K.; Kennedy, J. P. Polym Bull 1987, 17, 7.32. Mishra, M. K.; Wang, B.; Kennedy, J. P. Polym Bull 1987,

17, 307.33. Kaszas, G.; Puskas, J.; Kennedy, J. P. Organic Appl Sci

Proc 1987, 57, 77.34. Kaszas, G.; Puskas, J.; Kennedy, J. P. Polym Bull 1987,

18, 123.35. Kaszas, G.; Puskas, J. E.; Chen, C. C.; Kennedy, J. P.

Polym Bull 1988, 20, 253.36. Kaszas, G.; Puskas, J. E.; Kennedy, J. P.; Chen, C. C.

Macromolecules 1990, 23, 3909.



9/9

37. Kaszas, G.; Puskas, J. E.; Kennedy, J. P.; Chen, C. C. JMacromol Sci Chem 1989, 26, 1099.

38. Kennedy, J. P.; Hayashi, A. J Macromol Sci Chem 1991,A28, 197.


40. Kennedy, J. P. Polym Prepr 1992, 33, 903.41. Majoros, I.; Nagy, A.; Kennedy, J. P. Adv Polym Sci 1994,112, 1.

42. Kennedy, J. P.; Smith, R. A. J Polym Sci Polym Chem Ed1980, 18, 1523.

43. Ivan, B.; Kennedy, J. P. Macromolecules 1990, 23, 2880.44. Kennedy, J. P.; Ivan, B. In Designed Polymers by Carbo-

cationic Macromolecular Engineering. Theory and Prac-tice; Hanser Publisher: Munich, 1992, p. 168.

45. Huang, K. J.; Zsuga, M.; Kennedy, J. P. Polym Bull 1988,19, 43.


47. Wilczek, L.; Kennedy, J. P. J Polym Sci Part A PolymChem 1987, 25, 3255.

48. Ivan, B.; Kennedy, J. P.; Chang, V. S.-C. J Polym SciPolym Chem Ed 1980, 18, 3177.

49. Faust, R.; Kennedy, J. P. Polym Bull 1988, 18, 21.50. Faust, R.; Kennedy, J. P. Polym Bull 1988, 18, 29.51. Faust, R.; Kennedy, J. P. Polym Bull 1988, 18, 35.52. Kaszas, G.; Puskas, J. E.; Kennedy, J. P.; Hager, W. G. J

Polym Sci Part A Polym Chem 1991, 29, 427.53. Hager, W. G. Ph.D. Thesis, The University of Akron (1993).54. Satoh, K.; Katayama, H.; Kamigaito, M.; Sawamoto, M.

ACS Symp Series 1997, 665, 106.55. Kennedy, J. P.; Fenyvesi, G.; Levy, R. P.; Rosenthal, K. S.

Lecture at Bioarticial Organs, Camore, AL, Canada;1998.

HIGHLIGHT 2293

Documents

Living Cationic Polymerization