Effect of solvent, monomer structure, and pressure on reactivity in radical copolymerization : kinetic investigation within the monomer series ethylene - vinyl acetate - vinyl ester and methyl acrylate - butadiene

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Effect of solvent, monomer structure, and pressure on

reactivity in radical copolymerization : kinetic investigation

within the monomer series ethylene - vinyl acetate - vinyl ester

and methyl acrylate - butadiene

Citation for published version (APA):

Meer, van der, R. (1977). Effect of solvent, monomer structure, and pressure on reactivity in radical

copolymerization : kinetic investigation within the monomer series ethylene - vinyl acetate - vinyl ester and

methyl acrylate - butadiene. Technische Hogeschool Eindhoven. https://doi.org/10.6100/IR40642

DOI:

10.6100/IR40642

Document status and date:

Published: 01/01/1977

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EFFECT OF SOLVENT, MONOMER STRllCTURE,

AND PRESSURE ON REACTIVITY

IN RADICAL COPOLYMERIZATION

Kinetic Investigation WHhin the Monomer Series Ethylene -Vinyl Acetate - -Vinyl Ester and Melhyl Acrylate - Butadiene

PROEFSCHRIFT

TER VERKRIJGING VAN DB GRAAD VAN DOCTOR iN DE TECHNISCHE WETENSCHAPPEN AAN DE TBCHNISCHE

HOGESCI-IOOL TB EINDHOVEN,

or

GEZAG V AN DE RECTOR MAGNIFICUS, PROF. DR. p, V AN DER LEEDEN, VOOR EEN COMMISSIE AANGEWEZEN

DOOR HET COLLEGE VAN DEKANEN IN HET OPENBAAR TE VERDEDIGEN OP VRIJDAG

25 NOVEMBER 1977 TE 16,00 UUR

door

ROELOF VAN DER MEER

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DI'l' PROJo:FSCHRIF'l' IS CClED(;EKEURD DOOR DE PROMOTOREN

Dr- ir. h.L. German

en

Pr'of. dr. D. Ileikens

"' Et:(:luding thor..' pi.lmgwph~ ~lrcady puhli:-:..hr..:d hy JollJl Wlky &. SOI1!-:, Illc.

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han mijn ouders, Jellic,

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.s

5 llRIZlI.TION

S.l Introduction

Part ~: Mathematical lI.spects

5.2

Estlmatlon of monomor reactivity ratios in

Jnlricate schemes

S.3 Model [itling test

Porl S' Penultimate Unit Effects In Butadiene M~¢ro

radical Reactivity 1n The MBthyl Acrylule-Buladiene Copolymerization ~.~ Butadiene (eo)polymerizBtion 56 57 61 61 5.5 Penu1till\ilU, unit 5C\),:,mc 63 S. (, l:lutadj.en'~ copolYHIers 64 S.7 Experimental 66 5.7.1 Reagents 66 :'.7.2 COP01Y1M,(1zation 66 5.7,] Copolymer characterlcation 67

5.8 Results and discussion 70

S.B,1 Copolymeri.;:o.tion schemes 70

".8.2 Micro5t. n . .LC:t\.\r al f eutures of the copolymer 5 73

5.8.3 Overall rate of copolymerization 76

ClIlI.PT]cf{ 6. ON TUB CORREI,A',l'ION 13ETwr~EN VINYL ACETATB !{le:ACTI~ VI'rY liND VOLUME CHANG8S ON MIXING ViNYL ACETf"l'E WITII VlIll.IOUS SOLVP-NTS

6.1 Vo~ume chanqcs on (ni.xing vinylestcr5 wi.th

va.t:'i OilS solv~'nt.s

D.l.1 Intl~oducl.:i(Jn is. 1.2 Experiment'.ll

6 . .1.3 Result". and cl1.5cll".sion

79

5D

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6.1.3.1 EXCe$5-Volume~ of vinyl

ace-tate with various alcohols 81

6.1.3.2 Excess-volumes of vinyl acetate

with various solvents 82

6.1"3.3 Excess-volumes of variOllS vinyl

esters with tert-butyl alcohol 83

6.2 Effect of solvent on the ethylene-vinyl acetate

copolymcrizotion 85

6.2.1 Introduction 86

6.2.2 Experimentol 87

6.2.3 Results and discussion 89

6"2-3.1 Overall rate of oopolymerization 89

6.2"3.2 Monomer reactivity ratios 93

6.2.4 Conclusions 98

Rc'fe"" rioe ~

CHAPTER 7" COPOr..YMERJ;ZATION OJ" A HOMOLOGOUS SERJ.ES OF VINYTJ

ESTERS WITH DIPFERENT REFERENCE MONOMERS 101

7.), Ethylene as reference monomer

8Y'lOP$1:8

7.1.1 Introduction

7.1.2 Schemes for desc~1ption of mOnOmer

reacti-vity ratios

7.1_3 Taft equation 7.1.4 Experiment"l

7.1.5 Results and discussion

7.1.6 Conclusions

7"2 Vinyl acetate as reference monomer Synopsifl

7.2_1 Introduction

7.2.2 Ham relation

7.2"3 Experimental

7.2.4 Results and discussion

He .ri.~ T'e:' Ir(!~' 8

101 .1.02 103 103 104 107 113 114 114 115 116 118

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Cl1l\f."l'ICP. 8. En'GCT OF I'RGSS\lR8 ON FRm:::-R)'.DICAL COPOLY.M8IH ZA-TI0N lGNf:T1CS

8.1 Novel methods of measuring reactivl.ly .ratios

under hi.gh pressure conditionS

8 . .1.1 lntroduct.ion 8.1.2 :r;xpel:imer1tal

R . 1 . 2. J l\pp,'ln, .. Lus

8.1.2.2 introduotion of components 1nto

It.7 J 27 128 11.9 129 the rQactor 132 8.1.2.;3 Sampling 133

8.1.3 ~5timation ot monomer reactivity ratios 135

8. J .3. J "S"ndwicl1" met.hod 136

b.1..3.2 "Qn811(;hing" method 13"'1

8.1.4 I<.esu).ts ,l.nd c\iscu",sion 1>3

8.2 ~ concept of additivity of partinl mOlar volumo5

of actlvation 143 8.2.1. lflLt"r.odrlctje)t) 8.2.2 Pudical polymerlzation 8.2..] Cc)polymcri~,,'L10r\ 8.2.4 Concept of additivity B.2.5 EXDcrimentnl

8.2.6 l<.e5ults and discussion

13 • 2.7 Conclusio)"'"

e.)

Binary copol.ymer.·izations within t.he system

ethyl-ene-vinyl aoetate-vinyl nivaJnte

8.3.1 In Lrodt.lcU.c)r"l S.],) ~xperimAntal. ~-3.3 Rcs,Jl.ts 8.3.4 DiGc~8sion 144 1.44 140; ,146 J48 148 152 153 J 54 155 157 1&0

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APPENDIX l69

SUMMARY' 171

SAMENVA'l'TING 174

LEVENSBERICH'I' 177

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CHAPTER

1 Introduction

1_1 SHORT HISTORICAL 5URVEY

The polymeri"",-tion of organic comJ;l0\1nds has been known for almost 150 yearsl_ Nevertheless, the eOJ;lolymerization of

differ-ent monomers was not investigated2 until about. 1911_ The

proper-t.ies of copolymers were often found to be mOre useful than those of homopolymer,:; oonsisting of one single type of monc>mer. For ex-ample copolym,,"s of butadiene with styrene and acrylonitrile led

to valuable elastomers3. During the 1930's the emphasis of the

work was m"inl-y On the emJ;lirical preparation and develol?ment of useful products, and no systemat.ic attempts were made to

eluci-date the mechanism and kinetics of copolymerization itself4.

In 1941 wallS proposed an equation, which was shown to hold for only a few free-radical copolymerizations:

m = r"(.{

where q = M

1!M2, the ratio of the oonoentrations of the

respeo-tive monomers in the feed; m ~ the ratio of the monomer units in

the initial copolymer; and the constant. Y' t.he ratio Of the rate

constants in the addition of Ml and M2 to any growing chain. As

i t was soon reoognized that Wall's simple equation did not hold for mO$t feee-radical copolymer.1.zations, i t was amended by

sugges-ting th.,t the nature of the ultimate unit, ,-,0\11d also effect the

relative abilities of monomer 1"1 and M2 to add to a growing chaln.

In 1944 Mayo and Lewis6 and

Alf~ey

and GOldf1nger7 Bap.rately

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,;ltlmalc',-11niL ,].::pendC'nt. ch,'in-encl reac,ttviLy, Thj'5 scheme, u;;u,~lly

re[ct-recl tu ,',,-, the Alfl:")y-M'~lYo 5chemc, nowaday,:" was tOUlld teo hold

tor' moot frec'-L'adical copolymerizat"i_onsS. Up to thC1 pl-esent,

mon-Oll\<,r react.lvil-_j t."atio,,;, expl:c,;sing thO', preference of an ult'im,ltc!

cl1ai.n nntl radi_cal [or.- addlng a monomer of its own tYE'e over the

other monomer, were <.k:terminecl foe' a great r1umbe~: of bUi"I'j

com-blnat i.on",. c:ompilat.i.ol'l"; of report.ed I'-values Wf'l::Q cal-ri'.,d 0\1"1: by

Youn<,19, H<lm1, Llndeman,,10, and Ehrl'i_,)h and Mort __ i.mQr11. In

p1:'inci-ple,

th~_

,,;,:,mi-empirlcal (1-" scheme, propo,;c,<1 by Alfrey

~lnd

pr1ce12,

is carab1.H of predicting the ~-valuRs of ony p05~ible

combina-tion, provided tho ,Hid <' -values of both IDOr'lomers are known. In

a DtHTlbH r' (;f case 5 t.h<~ i"1(Jr'ccment. wt t 11. cxperipL~ntally det.8 ('min.ed ,'-\!.;.)llH".~s was found to be oat.j.-'SCc.lCLory.

However, it crradually be(::lme clear ·that exist ing metll0d" for t.he tletenn.i.r1dtion ot mO],Wnl"''-' reactivity ratios w"'t'G:: extremf>ly

Lnade-"luate (",'''co "hapler 4 of this thesi.s). Since 1961 many att.empts to

replace the uRually inaccurotR copolymer analysis hovG:: been

repor-ted, e.g .• by quantilalive ga~ chromatographic analy~ts ot the

13-18 1'1 19

monomer feed . In 1971 Ge(man and Hoikens ,- reportcd a

pr~n-iSing '~,'lmpling tec,bnj_quc permit.t.ing fre'juent analysis ()t the

cbang-lng ,\\o[)omcr feed cumposition tbroughout. the: COpolYlllerizaLion ",,~ac

L.i_OTl by means of ':J,,~-liC[uid cllX'omatograpllY (GLC). [lowf>vcr, i t

ap-. J7

pean"d t:llilL the corr<:,_sponding computational pt'ocedure - -For the

cev.'lluilt __ i_nn of the j"-V,_d_lles s t i l l no'oQded to I)Q refined, i.co.,

ex-~Hl-i.mGnL~l err0r~ ill 1)ot11 vari~!l)lcs have to k)c con~id~ccd. Tl1is

,,;ubSLantial i.mpr_'ovemcn t wi.11 be pre.sHntcd in Cll,'PtQ!~ .

.1..2 ::;COPE (w '.I'llIS TIlE::;')'"

1.2.1 PRACTICAL ASPECTS OF COPOLYMERIZATION

copolymer·.i ',{l.i:lon offe_C$ ;In excelJGnl ffi"thod of modifying t.h" rroperLieG of pOlymers. Fur this reason nowadays a great numher of copolymers nrc producotl on a 101:'ge industrial scale, and appJied in an Utunc:n.sc va."t:"'i~·~ty of COITIITI\.';!r·clr.ll product.s. Conse:qucntly, an

i.rl-t.cns.i.v(! (esearch i " the field of (,orolymeJ~i~£ltion w~,,; .stlL:r:leCl,

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copol-ymer analysis. Unfortunately, in many cases di[fe~.nt techniques did not lead to identical results for one and the same copolymer,

shedding doubt on their reliability21,22

Since quan~itative GLC-analysis of the monomer feed has been

introduced succe$$[ully17,19, Lhe troublesome analysis of Lhe co-polymer composition has become redundant fOr the determination of monomer reactivity r<:ttios. Nevertheless, research on accurate tech-niques for copolymer compositional analysis, necessary for investi-gating the structure of the copolymers obtained and for testing the kinetic model u5ed, s t i l l conLinues.

A new and reliable technique, based on thermogravimet~ic

ana-lysis of vinyl acetate-vinyl butyrate copolymers, and equally appli.-cable to other vinyl ester-vinyl ester copolymers, was developed recently in our laboratory23

1.:2.2 FUNDAMENTAl, ASPECTS OF COPOLYMERIZATION

As the comp08ition of a copolymer i8 determined by only one

type of reaction, viz., chain propagation, i t was ~oon recognized

that copolymerization studies offer special pos~ibilities for:

(a) the elucidation of (co)polymar1zation reaction mechanisms; (b) comparative studies of monomer reactivity.

However, unsatisfactory procedUtBS fOr the computation of monomer reactivity ratios and poor analytical taohniqu8s for copolymer com-posltional analysis hindered detailed quantitative inVestigations.

The present thesis will demonst~ate that both aspects mGntionBd

above can be studied in a very detailed way when both gn improved

analytical technique (chapte~ 3 and paragraph 8.1), and a more

justified and accurate procedure of evaluating mOnOmer reactivity ratios (chapter 4) will be available.

1.2.2. J. ELUCIDATION O}' (CO) POLYMERIZATION REACTION MECHl\NISM

MO~t

investigators implicitly assume21,24 that the simple

copolymer equation, where two monomers, as well as two chi\:Ln end

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radicals of different reactivity are considersd, does hold fet the

binary comb~nation W',c1er invastigation. llowev<n:, for (l number of

monomers there exists ev~dence that the reaction mechMnism in

free-n\<lical copolymerizati.on is mOte complex21,22/25. 'rhe most

impor-tanl case~, where th~ simple copolymer equation may be expected to

become inac1equate grD binary combinations where:

(l) onc of the monomers has a low cejl:cng temperaturO'!, and as

n consequence the depolymer!2ation reaction may play 8

26-29

parl ;

(J) the penultimate group influences the reactivity30; this

may occur if e.9., one of the monomet·s has il bulky (or

po.l.<l'") side group, whareas the comonolMn: has B. very smal J

sids group (e.g., ethylene);

(:3) a di ,~ne monomcr, s'lowing up In diffex:enl: configurations in

a c(.>polymer o;\lain, .1.S involved22,25.

1n ch"pLe;t:"_2 or. t,he pn,,:,~nL theo;is it w.i.l.l be sh()wn that the

5imple copolymer eq0DLion io; invaljd for the description of the

copolymerization )dne'Lics of .l,3-b'1t."diene (md methyl acryJ.<)te. It

will be demonstrated that a penultimate unit dependent effect in

th~. b\.JtClc1iene IM.(,,:oradic1l.l. rcactJ.vity has to be considered for thi.s binary combinat.ion.

) .2.2.2 COMT'AII.A'l"IVE S'1'lJDIES OF MONOMER RJ,;ACTIVITIES RAT lOS

1'"01' fre"'-r"ndical copolymeri·;.ation s(~veral mostly ;Jcmi -O'!mpirical. ;Jchemcs, relatLng the st.rUcLural parameter"R of monomers and

radi-cal", to cheir r(~activity, have been given. Out of. these, t.he lialn

relationJl, the Q_~l2, the' Q_H_o· 32 , the electrone'gativity33, and

the charge transfer schemeJ4 are the most

~mportant

approaches.

In fu,:L each investigator found those values in the abundant

lit-er(!tcure, that were in agree'ment with his particular scheme. It

will be obvious thal on thl.S basis it. is impossible t.o dcclde tile

Mxtenl to whi~h the separate schemes are valid or to find out wllich

one has the bAAt descrLptive character.

in lh'" first i.nHtance, t.his thesi.A dcscri.b~s reliilble met.hods

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detailed consideration of kinetic copolymerization data becomes

possible. This will be demonet~oted for a number of

copolymeriza-tion studies under systematically varied condicopolymeriza-tions, where the following phenomena will show up:

- a surprisingly large effect of the nature of the solvent

on the vinyl acetatc reactivity in ethylene-vinyl acetate free-radioal copolymerization (paragraph 6.2),

- a meaningful influence of the chemical conetitution of the

ester side group on monomer reactivity in a homologous

se-ries of vinyl esters with both ethylene and vinyl acetate as refe~eDce monomers (paragraph 7.1 and 7.2, reSpectively), and

- a significant effect of pressu"e on monomer and radical

re-activi'ty for all binary combinations wi thin the system

ethyl-ene- vinyl acetate -vinyl ?ivalate (paragrap,h",_8. 2 and 8 . .3).

1.3 STRUc'rURE OF THE PRBSENT Tf(ES IS

Although all subjeots desoribed in this thesis are related as indioated above, various chapters arc presented in the form of

separat~ (concept) publications. This implies that those chapters,

or paragraphS will start with a synopsis, and oontain the

rele-vant experimenta~ part as well.

HSFERSNC1,;8

1. M. Regnault, A'in. eldm, I'hY8., iQ, 157 (1838); E. Simon, A!lI1.,

12:.,

265 (1839).

2. J. ThJ.ele, Ann.,

ill,

220 (1910); S. V. Lebedev, J. [(U$$. PhiJ''!.

C;'em. Soc.,

B,

949 (1920); c. Harri~s, Ann.,

ill,

206 (1911).

3. H. Leoher, U.S.P., ,1" 780, 873 (1931).

4. G. E. Ham, Copo~ym,,,.>lF.("I;'ion, rntersciencc Publish",("s, New York,

1964 _

5. E'. T. Wall., J. A'M1'. Ch@lri. 500,,22, 1862 (J.941).

6. F. R. MayO and F. M. Lewis, J. Arne"'. Chr-)m. Soc.,

.if,

1594 (1944).

(17)

? t. I\)f.~cy, Jr'., and C. Gol(lfinger, d. Chom. [':'.11(:_,

_U'

205 (1944) 8.

'r.

Alfrey, ,I\~., ,To J. Loh\:'er, and IL Mark, ::>::polyr·,,-,pi,u,.I.io'1,

1n-Lerscience Publishel~e, New York, 19:;;:;.

~. L. ,T- ioung, ,I. !'o,:ym. :'/'0':" )4, 411 (1961).

lO. M- K. Lindemann, in Vinyl. l'o!yrrl<1Y'1::ic</':I:on, Volumf! 1, Part I,

G. F Uam,8d .• Dekker, New York, 1967, Chapter 4.

386 (1970).

1" '1'. 1\1 [roy, ,Jr., ar"l C. C. Price, J. i'olym. i;,:,! _,

1,

101 (1947). 13_ 1-1. J. H20rwood, 11. R<li1(owit~, and II. F. Trammer, Ai;;; 1'0 1 Y"'<:' l'

1',"-;-/Cu' I.: >1 !. i;:,

i,

13:l ( 1 96.3) .

14. E. L_ Mano apd R. R.iva dEO Almei.dfl, d. I'olym_ .'iei. ;1'-/, E" 2713 (1970) .

1). ll. F. John':lt:on aDd A. Rudin, .1- P,d,lI.: 'f'edvw! .. ,

!3.,

429 (1970).

lb. A. G\lyOt., C. LL-, rOo , J. C. Daniel, "rOd y:. 'l'ram\)ouze, i;ompl;. flo>].,!.,

253,179<; (1961); A. GUYO'L and J. Guillot, i.'ol'lpl;. Ne'd., 254_,

3(6) (1962) i J. GuLllot, ~ru!. Ch{',;.,

1,

44.1 (1968).

l'I. A. L_ Cet-man M)d D. Heiken_s, J. !'o!.ym. r;"i. ~-l,

2,

J22.5 (1971.) 18. if. l~ar.i.ta, V. Hoshi L, and ~L Macbida, ;l)'.'.U(·-~:.l? Mai-:.:r.lo,fnol.. ('hem' r

52, 117 (lnG).

l.~). A. I,. Cc:orman and D. Hoiken:';, 11''101 .. Ch'''rI.,

Q,

1940 (1910). 20. R. C. Schul:!.. and O. Aydin, in r!'l·r.;I::.~}~"I,ot-((,i'rI(~;': ::;ymr)()i~-1.r,-I.m 0)"1 MUI ..

-r·()·-20), J.-L. MLl<ln, E- T.. Madr-il~ja, C. G. Ov<£rber-9<£r, and ll- F.

Mark, ~ls., Tntersclenco, New Yor-k, 1915, p-497,

21. P. W. rpidwell ~'.lnd G. A. Mortimer, fl. ,~,1·1 .. :::/")()mol. ,1,:,',:'/. /i~~n.!~.

/L{(:r.-'.'!'i,i)')ii,')!. i.'lJe1J;., C4, 281 (lCJ70).

2') w, T. Kelen aDd 1,1, Tud(\~~r J, ~I1n:Up<),I'Il()Z. ,~'.;<~/.. "'(.?U:'rrI. f A9, 1, (1975).

2-'. R.

'27 (197(,) .

24_

n.

M. ,J(}.~hi, ,1_ M'li:l""'lOi: .. :)",':.-('!,(Om., 1\.7, 123J. (197:3). 25. 1".

,',1'::-/, !·\;/Jlm. ,';.,;,.'r:p. I .~_Q) I .J.-L. Milan, E. L. Mad:cu93, C. C. Over ...

b~rger, ~nd U. F_ Mark, ~ds_, Intereciencf!, New York, 1975,

p. 1 O~.

(18)

27. K. J. Ivin and R. H. Spensley, ,I. Maar·omo! .• :;(~·i.-r:h"m., Ai, 653 (1967).

28. Y. Yamashita, H. Kasahara, K. Suyama, and M. Okada, Mak'romol.

tI,..,m.,

.!l2,

242 (1968).

29. 8. K. Kang and K. 1·. a'Driscoll, J. i4acl'omol.

:,,-·-i..-C'wm.,

A7, 1197 (1973).

jO. F. E. Brown and G. E. Ham, /. I'o/'ym.

sd.

A I

1.,

3623 (1964).

31- G. E. Ham, J. PolUrri. nd. ~, ~, 2735 (1964); ibid.,

.£'

4169,

4181 (1964).

32. L. A. Wall, J. ['01-/1 111 • ,1")'(,:'i..

, l.,

.542 (1947) .

33. J. R. Hoyland, J. Pc)!..ym. .~' (.' "/., - ,1-1, _.§.' 885 (1970) •

34.

J.

R. Hoyland, J.

PoZym.

.)'(.' £ • ~-l , _.§.' 901 (1970) .

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CHAPTER 2 Some Aspects Of Free-Radical Polymerization Of

Vinyl Monomers

2.1 FREJc:-RADICl\I, COPOLYMERIzATION KINETICS

2 . .1.1 INTRODUCTION

Si.nce: only ()r)" lype o[ re:actJon step, viz., the: chai.n

prop8l-gatlofl, de:LerlT\i.n"'~ lhe copol.ymer Gomposi.t.:Lon r a'''£ither simple t.ype

of k i nC:lies aLi !;es wl1en the instantaneous copolymer composition is

.regaplc:d as a funelion of '-he monomer f:ee{l composition. In this

case quantitative considerat.ionsl-7 are relat.ively simple:,

2.1.2 COPOLYMERIZATION SCIIEMES AND THEIR DERIVATION

lndependently. Mayo Rnd Lewis8, and Alfrey end Goldfinger9

derived the simple copolymer eguetlon, The: following conditionw were assumed to he valid:

- consumption of both monomers only OGcure by chain

propaga-t i O ( l sleps I while: conS\lmption by ini tJ.alion "nd

rei.Tlitia-Lion, if any, .Is ilssumed to be nC~Jli':1ib.le; in general, this

condition is fulfilled j [ practlcnlly unhranched high

mole-cular weight copolymer is formed;

- t.he ~'cacti.vity of a GOpolY111er' cl1ai.Tl end radical is

indepen-dc:nl of t.h'" ehain lenglh (Flory pri.nciple), and determined only by the ulti)T1,lt.c unit of the mON'orad.i.G."ll;

- both monomers rencl wit.h chain end radicnls aCGording to

the 5f~mc, bi~nolQcular mechani5In~

- ,']1 propagation reactj,)r)S are .Ltt'eversible;).

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con-sidered under these conditions: "vl1

i

A'

'\Mi

+ _M1

J:2-",IVi

+ M2 I

JJ

o,M; 'UM

2

+ 112

Ij;

'oM;

"vM.i: + 111

k2;\

f\.JMT ₁

Assuming that the rate of change of the radical concentrations of

"vM~ and 'eM; is small as compared to the rate5 of radical production

and consumption, i t follows that:

or

["uM~J

The rab~S Of consumption of both monomers are given by,

The instantaneously formed copolymer composition is'

_ d[MJJ

at

_ d [11 2

J

dt (2.2) (2.3) (2.4)

By combining eqs. (2.2), (2.3), and (2.4) with eg. (2.1) the

radi-cal concentrations can be eliminated, yielding:

"J.

~

+ I 0.[11 1

1

(11 2J d[M 2J [M₂J (2.5) 1"2 _(MIJ + 1

9

(21)

wiler", ".1 = k11/:']2 and {'2 = 1(22/"'11 are the monomer reaotivity

ra-tios ur rl-values expressi.ng the ~)re[ercnce of a given radical cl1aj,rl

end for it~ own monomer over tile other monomer (= comonom8~).

Re-ClcLivity rile.i.0!,; eIre dimensionless quanLi.t.ies, as they are quoticnt::;

of two y'Qt:c constant~ havillg the ~ame dimensi.on.

Dcriv1ltlon of more Hxtcnded sohemcs, sucll Cl5 those considering

penu!timple unit dep",ndcnl effeot!';, is basically onalogous LO the

aboVM-mcnlloned d~rlvalion of thc simple oopolymer equation leg.

(2.5).1, as will be:· sl"lowrl in chapter 5.

'2.1.:3 SCllEMES HP:I.A'l'ING MONOMER k\CACTIVITi RATIOS TO MONOMER S'l'll.UC~

TUPF: PARAMETERS

1n section 1.7.2.2 iL has al~eady be8n mentioned that a

num-ber of empirical 5ch8[)\8S h,·,ve been formulated [or the descr:iption

of the c{: 1 a tion bE'twe",n t.he monomer 1:eact i vi ty 1~n Lios aTH] tile

structu.re of the monomers (lnc1 the ra,li.cals invol.ved. TwO ('lasses or mntlclG call b~.: .... d 1 ~tlngLli~hed~

(1) lx,t.h monomer anel l:,,,.lical strUGt.ure of either monomer Clre

cnn~iJered; in 8_~lD, Q_e_~·ll, electronRgaLivityl2 (EN)

and

Gh~l\"'ge

Lransfer·13 (CT) 5chc·;mes £9th r£activit.y ratio,,",

can b~ Jescribed by unc1 derived [rom the model

paramA-(2) !:'cClcme5 originating from organic chenl:i.5t.ry in which, for

c'x<~mpl (0, UK' monomer rei(c:-r.l.vity O[ " homologolls series of monomers tow,Jr',]s a rcferen("" radical is cOll::;idereO;

typ-i c,ll

1:epl·e5ent~tiv,~"

arc the H.1mmet equiltionl4, th(! Ya·

mamoto-OU;U equat.j.onl:;, an(l th(,

'.l'.~f l relation

16.

Jrl the SUCcco("dl.nq l;eclion t.h.:, mOSl wid",Jy used 5ch,"me, i . e . , t.he

1;-(' scheme wi]l be tleCll.t wJ.th <.:omprehen~:i.vcly. Next a I1l1IT1J-J,,"' of

schemes basicully relaLed to the

Q-~

5chRma10 will be outltn£d.

l"urthermon" the tOl1l1clat.ions of new pl.·omising 5chf!meS 11ke the

EN1J anJ the CT-Gchem",13 will be m",ntioned. The

charact~ri9lic5

of t.ht; T,.,lL 16 and lIarn 17 , 18

,'e.ialion~

will be

tr~lat.ed

summarily

(22)

2.1.3.1 Q-Q SCHEME

The Q-e scheme, proposed by Alfrey and Price10 can be

consid-ered as a semi-quantitative <'tttempt2 to ch<>racterize the observed

kinetics o£ a copolymerization system in terms of resonance sta-bilization <'tnd polarity of the participating monomeric units. The propagation constanL k12 is expressed as:

(2.6)

where i'l and Q

2 arc constants oonnected with the general

re<'tctivi-ty of the radical ~Mi and the monomer 11

2, successively, in terms

of stabilization by resonance; u

1 and Q2 are quantities

propOr-tional to the "charge" on the end group of radical ~Mi and the

"double bond cha,ge" of monomer M

2, respectively.

AS5umipg that the charge on the double bond of a monomer equals that on the end group of the radical, the propagation constant

kll can be expr~s5~d as'

"1.1

1'1 (J 1 exp (~(' 1 ) 2

Hence, the expressions for the r-values become'

and p 1 r' • 'y~ 1 . 2 (J/Q2 li₂

lri

₁ TI exp exp (2.7) (2.8) (2.9)

The Q-8 scheme has been found to be very successful in predicting

p-value>i o[ unknown binary combinlltions3-6, .in cases, where:

q

and

co -valu"'$ of both \I\onomer $ are ava!.lable. on the ot.her hand, "

number of shortcomings have been recognized for this relationship.

(l) The zero point of the Q-e scale has been (:~\O$en r<lther

arbilrarjly. Alfrey and PricelO took styrene as reference

(23)

monomer, nRRlgning i t d Q-value of unlty and an ~-value

of -1, HUW8v~r, the best value for ~ WQS supposed to be

slightly le~M ncgaLive and for that reo Ron Price19

propo-sed to shift the ~-scale of styrene by 0.2. This new

ref-erence poinL for styrene is most.).y lised nowold"ys; 11=1

and ,'=-0.8. Nevertheless, it SBems to be more obvious

tu toke ethylenH DR reference monomer, a6 suggested by

hlf.t:""y et aJ.:<, an,} illust.rot.ed by

Burkr'~'ll:'L

and zutty20,21.

(;';) Ac:corClin'J to t.ll" Lheory or the

q-e

sch,~me, the product

of the monom,,)"' rcac ti vi t.y t'ntios, II, of any binary

combi-naLion can never exceed unity, as can be derived I)"'om eq. (2.9). A grE:fJI. number Of experim",ntal data, howover,

is in conflict with this constrnint3,22. Wall.l l suggested

th<lt t.his problem m:i.ght be met by assigning i'l different

electronegaLivity to monomer (al' Dnd radiC~l (9

1' ) . This lead;; t.O;

(2. 10)

In thi5 event., II can exc:~ed unity if the difference

be-Lween .t.h" ,.:),ain end electronegativ'i ti.es is opposite in

8i91"1 to"> t.llc difference between thO'! monomer eJ ectl'one'Ja-t1vjticA. Such a sit.untion may only be expect.cd, when

th" monomel'5 j1aV(~ <lpproximat.ely equal

elO'!cLrone.gat-.ivi-Lie~.

According to a'Driscoll ct al.22 thiH condition

is far [,'om being ADLisfied, for combinot,ions wit.hlPl,

and t.hey Guggest. that tho;;e b i ["l,,-(y comb.! nnLi.ons should

be discarded, rather than to ossume that the product

equals unity, QA is often done.

(3) C18boralion of the Q-n relationship fOr all three binary combinilLions within a tGrIHlry systel\1 le;Hls to a T"<llaLion

J.Clp.TlI'.i(;nl LO the diRputed Ham-relation17

,le

(2.11)

whcce " .. ~ I, ,/1:,. and ," .. = /, .. Ii<,. Q.('~ Lhe monomer

1 j I I 1J .11 JJ J).

(24)

monomer M, and M .•

1 J

Unfor Lunately, eq. (2.11) cannot be deJ:'l ved from a

calcu-lus of probabilities, as altempted by Haml' , without

mo-king assumptions conflicting with reality4,23. MOl;eover,

the above rela~ion often shows deviations considerably

larger than mighl be expected on account of the

reliabi-lity of the

~-values23.

In the present thesis this will

be demonstrated fOr some ethylene~vinyl acetate-vinyl

ester systems (paragraph 7.2).

From the above considerations i t becomes apparent that the

R-e

relationship has no strong theoretical basis. Surprtsingly, a number of quantum chemical studies carried out by various investigators24-30 led to unexpected correlations between certain physical quantities

and experimental Q and e-values. Among these probably the mOat

con-vincing treatment has been given by Fleischer et al.28-30. These

in~

vestigators found by MO-calculation29,30 (CNDO) that the original

meaning of Q in terms of resonance stabilization of the monomer, could be confirmed. The physical meaning of e was thought to be an electrostatic interaction between monomer and radical in tl1e transition state, caused by tl1e dipol", moments of mOnomer and radical

Finally, a recent study of Greenley3l on the determination of Q and

~-values

has to be mentioned. The author31 claims the

calculation of more precise values of Q and ,~ by the application

of a roundabout linear least-square5 technique applied to prac-tically all the r-values, relevant to a selection of vinyl monolllers

-~~:;):3:::. oS i~ 0 n

The Q-e sch~llle still. is a convenient <lnd rather useful framc~

work for predicting ,,-value!;; of un investigated binary combinations. Although !;;Ome interesting correlations have been found between structural parameters Dnd reactiVity, i t seems justified to

con-clude that the Q-a scheme pOssesses only a limited theoretical

foundation.

(25)

/." I .3.:2 SCHEMES BlISICALLY REI,ATED TO THE (:-c SCHEME

In a(lcl i Lion to .l.mprove!TIer"l ts proposed mor", 01~ Ie 55 wi t.hin th<'>

baRic con~<,>pL of the 4-~ schem~, as djscussed .in the pre~eJin9

5'·'Ct!'.>,., 2.1.3.1, ,:\ number of apPf.\renlly different. IlPP1·oacbe5 have

also b~-:C'n fOl:"lnu1.0.LCd t.o r)VI::.!::t'come th~ dofj c.lenccs of the ~i'-{.' scl1A:mc.

MorHover, othc~ existing schemes, originally used in org~nic

cltemi5t-r·y have been tlpplied an(] were Of Len found Lo 9i ve

8uffi-C,iCllL correl,al~on betw(~Qn subst.i.tucnt paromcters and TI10nomCr

re-act-iv) I.y. lin ex"mplc of

th(~

latter j.g the I1aww-,t.t "'QUi'lLion14,

log (!:II" ) o

whcre oriq.i.n,:clly 1'"0 ,1n(l i, are t.l,e rate OJ"' cqui.l.ibl":ium cOfls"l:ants COl": the rencLion of unAubstituted benzene, and maLa or pora-sub-stituted benzone, r·E,sDcctiv"ly; () is " pal·ameh'r reflecting the

abil:i t.y of th~, !;ub,;Liluent. to (lonate e,l' Lo w.i t.hdraw e1.<'o(;\.ron8 [t"om

th€:' r'cQclion .".i.te:; and ,I, <'>xpl'csse5 t.hc effe"t of (-.b" clcctrorl

HvailaJ)i 1 i t.y [or any p!l1.' Licular type of .reaction. 'l'he HanUllC L L

(:quation14 [,,'q. (;:.J.2)

I

has ,-,,,on reported to provide a

s.lgnif.i.-cAnt corrRl~Lion among the monomer r"'Q~LivitjcA within a number

of homologous scrie!; t.c,warCl a -""fcrence'

polymerj.~

radiGi11.32-34•

On tJ1C

ot}l~r

11andl ImoLo et D1.

35

found that

(2.13 )

whcrE' ~ Ls ~ para!TIet.nr conne~tecl witb t.hc re80nsncc stabilization

1 n the tr·oITl:;<.lLlon ~t"t.c, descr Lbcd copolymertzat:lons of

p-subst.i-t".llt:(~c...l styrerl'7~!-\.

Yamamot.O and Otsul.

c

, propo!;ed LO exp'·<-:5A i: 1n (,C), (2.J.3) in

t.(:r'Ins of t.hoo r'csonance subAlitup.nt eonst.i"\t I·.

n

awl Lhe eff",cL of

.:;1,,·;h rC50nafl(:~' ilvailabi liLy y fot a part. i(:Lllar typ,~ of reij(~Lion.

log y 1.

1\ ( J . H )

Damfc..n~(1

ct.

~"J.l.

Jf;

d(~vcloI~ed. ~~

comparC1.1)le

schetnE~ -qT:';.~t.t~rnsll-,

(26)

and a number of substrates, including monomers are given by:

log k. log ~T

+

lW + B (2.15 )

where It and i3 are constants characteristic of a given monomer; (J

is the B¥rtmett constant for t.he 5ubsti,tuent in the terminal unit

of the polymeric radical; and Ie'l' i,; the rat" cOnstant far chain

transfer to toluene.

Equat.ions (2.13), (2.14), and (2.6) can be written in the

following form37,38, successively,

log k log k

0

+

¢o + R (2.16 )

log k log k

0

+

¢(J

+

Y!'R (2.17)

log k12 log J~>

₊

(! e + log Q

2 (2,18)

, 1 _{l' 2}

Comparison of ega. (2.15) - (2.18) indicates that in each case

the first term on the right-hand side st.ands for the general

reac-t,~vity of the attacking radical. The second Lerm relatas to the

polar effects of radicals and reactants. while the third term

re-lates to the resonance factor of the reactants38. As a consequence,

these four correlational methods appear to be formally eQuivalent37

Co)") ,', ~1-wi on

--_.,""'_ ... _--...

-In fact all above-mentioned schemes for correlating monomer reactj,vity ratios with structural parameter,:-; comprise terms

simi-lar to thoee ~ertaining to the Q-8 scheme. Therefore, in the

pres-ent thesis only the most widely used sohemA, viz., the 8-~ scheme

will be applied to correlat~ the monomer reactivity ratios of

a homologous series of vinyl esters toward both ethylene and

vi-nyl acetete

ss

reference monomers (chapter 7).

2.1.3.3 NEW PROMISING MODEr,S

Recently, UOYland12,13 derived two Dew models for the

de-soription of f("aa-radical mOnOmer reacUvity raLios related Lo mon-omer an(l )"i:lJical structure. These interesting model!;, viz., the

(27)

el~ULrOnegatLvity12

(EN) and charge transfer (eT) schemel3, are more sophisticated and seem to have a better theoretical

founda-tLon39, Lhan the

~uhemes

previously mentioned.

'l'\'e EN

)1~11'"",e12

is based on t.he concept of electronegiJt.ivity

as introduced by paulin940. Three parameters are as8igned to each

monomG.I:'; the elect)~')rl"g,:ttivity of t.he monomer and of the .racli,~al,

X[J[ and X

R, respe"tively, and a qtHtntity !., presumably related to

the reO(,)rL':HL(:C ~:;·ta.bilizatiQn.

log )" 1 log )' ~ (2) -/, (1) ·1

I

X T1 (l) (1) -I (2)1·1 X 1'\ (2)

'M(l)I-i

Xn(l)

~

_XM

(2)1

X[J[(2)I-1

Xr«2) - X M(

1)1

(2.19 ) (2.20)

The CT s<:;herne_l1 j,; also a three parame Lcr model. Monomer

pa-ral1\"LC,rs would be l~elaLed to the highest. occupied orbLtal level,

\ 0 ' and the lowesL unoccupied energy Jevel, Uu' and to Lhe

ener-gy level of Lhe singly occupied radical level. An' The expression

tor Pi is proposed U8;

log " _J. (2.2))

where

A/'CT (i. j) = min ( (2.22 )

39

Accord i 1'1<'1 t,.> 1·IOy L:md Lhese mode 1 s le ad to "t be t ter COI"re la t i on

r.han Lhe (1-'" and (/-';-1'" scheme fo)"' the majori.t.y of a seri.es of

,'-val UfOS invol Vi nq 17 monomers. IlowQver, .l t remains deb1\ table

whether the i.mpr0ved description is cause" by a more meaningful

physical foundation or by the l",rgc;)r number of paramE'-ters

used~"9.

'rhe EN 1<nd C'1' scheme have never been ."pplied I except by

lIoy-land12.13.39 himself. pcobably because:

- tIle number of .,tl~uctural pa.l:ameLcrs fo.l~ ,my mOnOmeI" i8

three, and a~ a consequence 0 relatively large number of

{~quation5 (= ,'-values) i'5 r\eeded; a po,:;sibility for

6lppli-cat.·iQn, howeve(, may a1·ise wh~n for set.s of three monomers

(28)

Conoluf';{on.

Application of the EN and CT schemes seems to be promising from a theoretical point of view. Unfortunately, the schemes are rather complex and cumbersome to apply, while, fvrthermore, a rath-er larg~ number of ~-values appeor$ to be necessary for each monomer in order to evaluate the structural parameters. Mainly for these reasOns the schemes will nOt be applied to the copoly-mexization systems descrihed in this thesis.

2.2 EFFECT OF PRESSURE ON REACTION KINETICS

2.2.1 INTRODUCTION

The study of the alteration of the physical and chemical prop-erties of substances under high pressure is of much scientific and tecl,nological impor tance. Research on the pre ssure inf 1 uence on chem.i.cal r",act.Lvi ty comprises two main areas of interest'

(1) the induction of new chemical reactions and the enhance-ment of prOduct yield and quality;

(2) the elucidation of reaotion mechanisms; studies on the

effec~ of pressure on reao~ion rates provide a powerful

tool for gaining knowledge on the structure and proper-ties of the transition state.

The most striking affects of high pressure on free-radical (co)polymerization kinetics are;

(1) an increase of the rate of (co)polymerization;

(2) the enhancement of the polymerizability, as a polymer-monomer equilibrium may undergo a significant shift t.o-wards polymer (increase of the ceiling temperature).

The interpretation of these and other phenomena, like I:.he increas£: of molecular weight and the change of thc structure of the

(00)-polymer 5 formed, requires knowledge of Lhe cffccl: of pres sure on

th", separate reaction steps which compose the overall

(29)

rizat10n raDction, In practice, i t app~ars to be quite complicated

tu nbLain direct. ,i.nfOl'maLion un th£o ~eparate react.ions, In some

ca~Gs, 1nvBstigat.ion~ of Lhe offect of pressure on similar

roac-Lions in nonpolymarl~ing systems can be helpful to a considerable

extont41, Some of the chief feat.ure8 of 11igl1 p1'e8.'O\.11-e rc,acLion

k1-netic~ will be outl1ned brJefly in the next. section,

VIHW~

ore given by uamann12, Wealo41,43, LeNoble44,

KOhnsLam46, Dnd

Eck~~l47,

ACTIVA'l'ION VOLUMES

General

n;'-<l~ Wha11"'y'

2,2,2, 1 P!l.E55URE DI,PlC:NDENCE OF REACTION PATE CONS'['ANTS

The basic expression in t.hA pseudo-thermodynamic transit.ion SLate tl1eory i.s the general eLjU(ition for the re,lC:tion rate con-st.ant".

where .'\"0 j.:-:i Boltzmann' 5 con-5t~.u)t; h is P1EU1(;r. I ~ constant.; i:=:::

t.he lemp'ocatllu, ()K); ;'.' is th.! g,'S constant.; c,nd /lC '! is the C;ibbs

Cree energy of (lCL1vat1on at constant pressure fo~ the formation

of the transiti,Hl .~t(ltc, along the ensiest path Cram the initJ,(ll

to the final stat.e45,

Different.tat.io" of ,"quat.ion (2,2:3) with res[)eGt to pressure

i;-!t c:onsLo.nt temt)erdt.ur'~ l~:::;lds to:

(? 24)

wh(~I:e 11/ .is tl1<:' dif[""'encc between t.1t.-, volume of th':! ","cLivated ,,,'llnplex" and the react.lilll:s, indicated in brief a", vol ume of act. i-vrlLinnL

Jc:q, (2.~4) J.S c(lr"(.:CL I.,,:!.)/ if th'~ r(JLe con5tant (k) is

c!e-[ined as in (-:"(1- (2.23', and is express.::d in recipr.'o(:all:ime unit.s.

This 18 the ca~e whan illl concentcations are expr"cSAed in unitA

th,)L do not c,)nt·.i\in l.he volume u( the system, J.·iJ.;", mole fract.ion

(30)

con-centration units, a term -(n-llX_{T 1n which}~ is the order of the

reactlon and

X

_T

the isothermal compress1b11ity of the reaction

mixture must be added to the right-hand side of eq. (2.24). In the investigation on the effect of pressure on copolymeri-zation kinetics (chapter 8), only effects of pressure on r-values have to be considered- Since the r-values are the ratios of chatn

propagation constants, the Qompressibility terms in (a In p!~p)r

cancel out.

2.2.2.2 EVALUATION OF VOLUMES OF ACTIVATION

In principle, OVH can be determined simply by measuring the

reaction rate constants as a function of pressure. A complicating tactor, however, may arise from the pressure-dependence of volumes of activation, as the compressibility of the transition state al-most invariably differs from that of the reactants. The pressure

dependence of In kIp) is typically illustrated in Figure 2-1.

De-pending on the sign of

ov

H the roaction rate may be either

in-creaSed or decreased by pressure, whereas both effects tend to

I

Fig. 2-1 Illu~tl~tion of the effect af pressure on chemic~l r~~cti0n$

(31)

lev~l of[ at higher prAssures, Unfortunately, no exact relations

have been dc:velopecl IJrtLil now t.o ,,<':scribe th.;,so curv"lR. 'rhe

va.(-ious met.bocl.q developec.l [or the eV£lluatio[l Of AVII, ,'\re bElsed on

different aRRumption~ concerning tho funct.~Qn.lity. The ~esults

appHUr to be highly sunsitlve to the method apPlied

47 ,

GeI1er~11y, l,t is a~~11m8d that voluffi8s of activation are

pres-sure-i.nclopondent up to pressure5 of 1000-1::'00 kg-/cm2, onlY. This

pre ",,,,"0'0-inclependel'lcH has a1.5o

b,,~"'n

observed by Ogo et 01. 48,49

[or th8 ,~"livation volumes of t.he homopropagiAt.ion steps of

var-2

1-()\.1S vi.r)yl monomers, Up Lo 1000 kg!r;m . 'I'herefore, it. ::;ccms to

be jU5t l.[i.c~d La expect. " similar Pr'ARsul-e-indepencel for t.he

ac-t.ivation volumes in the oopolymeri~ation reactlons (up to 1200

kg/cm2" as de:,;cl"l.bcd in c!1,q:ltcr 8 of the present theS1S.

2.2.2. J IN'rCRP!l.E'l'A'1'ION OF VOLUMES m' ACTIVI\.TJ:ON

In practice. volumes of ~ctivation appelar to vary from abOUl

+20 Lo -:10

(:m')/mOl~41.44.

Activation volumes have Of Len been of

cr'\.lcial jl'npOI·'t:.anc~ in a5!:ie$~.1ng reaction. mechani.sTlis, as for

in-st~nce for Diels-Alder reactlon~47_

Although it is beyond th8 scope of this lhesis to give a

u

compleLe revi.ew o[ ~ll aspects of AV i.t. will be uSe[l.ll to point

I'

O~\t_ some of t.he mORt general [e,"ltures of {\'/.

II

(al) A positive Av 1$ observed for reactions with bond cleavage,

such as Lhe dls50oiation reaction of radical inilators (~e

cr'CQSC of reaction rate with increasing pr8Ssurc, cf_ c\lrVC

II in Figure 2-1).

(a2) A rela~i.vHly sLrongly negative value of AI" for reactioM8

whelre steric hlndraMoe plays a parL;

(aJ) A negative

A~n

for t.ho formation of covaJent bonds;

:1

(.14) I\. positivA AV for diffusion cOntrolled regctions. I~ this

(b)

oase. the volumes of activation erA only formally defined as

in e'1 - (2. 24 ). 1/

,', 'I o[t.en can IJe r.ii.vidcd into two part,5, v i.~., one ten1\

]:'c-preaanLing the etrlJotural contribution. being an intrinsic ditferencc in molecul.ilt' size betcween react.,;mts and

(32)

t.r.'(lnsi-ticn s~ate, and a second term representing the volume changes

of the solvent shell surrounding the reactants4l,44,47;

(c) Somet.~mes, for relatively simple reactions such as initiator

decompOsition reactions, i t is possible46 LO calculate the

cleaving bond length in the transition state from the known

hV' . The reVerse oan also be done46, as was demonstrated by

Luft50 fOr the chain propagation of ethylene where

infOrma-tion about the length of the newly formed bond in the transi-tion state was available;

(d) In reaction dynamics bV# i5 often compared to the volume change

on reaction (tv), in order to ascertain the relative

po-sition of the tranpo-sition state along the reaction

coording-te41,47. Recently, r,eNoble and

As,~no51

pointed out that

their findings for bV' and 6V of some Menshutkin reactions

cou,ld be interpreted ir! terms of the well-Known Hammond pos-tulate, i.e., an early transition state -more comparable to the reactants- occurs in strongly exothermic reactions, and

a

late transition state -more comparable to tho final

pro-duct- is observed for les! exothermic reactions.

2.3 EFFECT OF PRESSURE ON COPOLYMERIZATION

In copolymerization the effect of pressure shows up in a

changing relation between monomer feed and copolymer

composi-t:i.on41,43. This offers an interesting advantage in comparisOn

w.~th

hornopolyrnerization, as the effect of pressure on only one type of

constant, viz., chain propagation constants, is involved. The pres-sure-dependence of reactivity ratios is given by:

In 2'1 ~ ln k 11

In

_k12

..

I\VU II + IIY 12 #

ap '" -d-P-~- ;lp RT (2.29)

In _1'2 _{In k:U} In _/(21

-

t.V

_n

II

+

6 V 2,], Ii

op 3p ;)p /1'[' (2.30)

(33)

ThlS mean8 thal in copolymerization the effect of pre55U~e on

co-polymer Gomposition i", governed by differences between the

volu-mes of: ,1,]tivatiol1 p'H·taining to r.adical-nlonomer add.i.tion reactions. for abouL 50 di.f["r.ent free-"dical copolymerizations, r-values h<>ve

been measured a s " [unction of. prcssure41,52. In most. eases the

observed di[[erence5 of the volumes o[ activation as defined in ,".qs. (2.",)) <\nd (2.30) are raLher small43. Tl"lis indicat.",;,; ll"lat.

the 8ffects of pres!'lure on r"any chain p1"opagations are

a!,proxima-Le1y

Dr

i·.he same order of magnitude.

In Ghepler B of the present thesls relatively large

diffe-1"011005 of activation volumes arc repo,ted for the binary copolyme-t'izations wit.hin Ll"le 5y.st.em ,,,thylene-vinyl acet(l.te-vinyl pJ.valate. Furthermore, a pYQViOUSly53 formulated concept of addltivity of volumes of actLvnlion in free radical (co)polymerization is

eva-luaLed in pa~agraph 8.2.

1. F. R. Mayo (l.nd C. Walling, ('111'''1. (I(;:{).'!.,

2£,

J.91 (1950). 2. T. P.1.frey, .1,'., J . • "J. [Johr"'~, and H. Mark, (:opo/.ymeY":;la!;/[Jrt,

Interscience Publishers, New York, 1951.

3. L. J. 'ioung, ,I, i'0/.1Im. :::0:' 54, 4J.1 (196J.)

4. F. R. Mayo, liel'. :,'I/I·"·,erli/o,,,. Ph.yD. ('hem.,

]..9.,

233 (196(j).

5- C;. E. Ham, COr10rt:(ml:~rll~:~(~[;'r:()I'l~ Lnt.crSc'1.encc Publishers, New

York, 1964.

fi. G. F:. Ham, I.n V'l:)'!Yr~ .!,J(Jr.,ym~!rl'i:;::al .. 1on., VolumQ: 1, l~rlLl I f (~. E.

ilanl, Ed .• Dekker, New York, J. 967 I Chapte\~ 1.

7. PT w~ '.l'iClwell. {lnd G. A. Mortimer, .J. Mt."f..or'(;/IIO!., /i<.''1:. /;'c:0:',;" ,

/1((.-"1 "

"'''''''.11 ..

C·hom., C4, 281 (1970).

8, P. R. Mayo a(Iel P. M. T.,G:!WlS, ,I. ~mer'. e'I"""!, So,:,., .66, 1594 (). 944) ,

9. T. Alfrey, Jr" and G, Goldfinger, ,./. ·h".!!'I. 1'11.'1::.,

J..l.r

205 (lH4) ,

.10. T, Alfrey, Jr., and C. C. Price, .}. f'(J~!!rIi' C';",:.,

d,

101 (1',47).

(34)

12. J. R. HoyUmd, ,I. ('orym. Se--{ . A-I, _§.' 885 (1970) .

13. J. R. Hoyland, ,I. Poiym. S.:..~l . Ii - i ,

_1,

901 (1970) .

14. L. )1. Hammett, d. Ii m(\" 1'. Chem. Sa r..~.

,

~~, 96 (1937) .

15. T. Yamamoto and '1'. Otsu, Or'g. Syn.. Chern. d')PM1,

ll,

643 (1965).

16. R. W. Taft, Jr- I in Sl.~~i~ Kff~~t~ in Uvgania C'hCntl:CtPYr M. S.

17.

18. 19.

Newman, Ed., Wiley, New york, 1956, p.556.

G. E. lIam, ,/

.

Po/.ym. Sen: . il, _{- '}~ 2735 (1964) .

G. E. Ham, J. Pc) lym. B07: • ~

,

1,

4169 (1964) .

c.

C. Price, ,1. 1"0 /,yrn. So 'I.: •

,

1,

772 (1948) .

20. R. D. Bu~khart and N. L. Zutty, J. PoZym. Sai. Ii,

!,

1137 (1963)

21. R. D. BUl;'kh$rt and N. L. Zutty, J. Polym . . ';a£.,

22,

793 (1962).

22. K. F. O'Dr~scoll, T. Higashimura, and S. Okctmura, MaK1'Ornoi .. Cbm'" ~, 178 (1965).

23. F. R. Mayo, d. PoZym. 3rli .. . ~, ~, 4207 (1964).

24. T. Yonezawa, K. Hayashi, C. Nagoto, S. Okamura, and K. Fukui,

,I. i'olym. 8ai.,

.!:..i,

312 (1954).

25. K. Hayashi, T. Yon~zawa, C. Nagatha, S. Okamura, and K. Fukui,

J. Po1.ym. Sd., 20, 537 (1956).

26. G. S. Levinson, J. l'olym. SoC, iQ, 4;3, (19 62 ).

27. G. G. Camoeron and D. A. Russell, d. M(l a 1'(.l1n() 1 .. ;;,?i.-Ch"'n., AS,

1229 (197l).

28. G. Fleischer and F. Keller, ['last" KauL, ,!2, 721 (1972).

29. G. Fleischer, Ptasts Kw"t.,

lQ,

10 (197.3).

30. IL-K. Roth and G. Fleischer, in 1>!ter'lat'l:cmal Syrnpr)ldum 0,'

,11.-,-eromoi.ern.l.l{'Ii, H(!L.~";rl!d, 19?2) (J. Poly"l. Sc.''':. "'ol.ym. Symp.,

il),

O. Harva and C. G. Overberger, Eds., Inter~cience, New York,

1973, p.369.

31. R. Z. Greenley, d. Mao"('omol·. s"i.-Chem., A9, 50:' (1975).

32. C. Walling, E. R. Briggs, K. B. Wolfstirn, and F. R. MayO,

J.

Amer. Chern. Soc., lQ, 1537 (1948).

33. K. Tsuda, S. Kobayashi, and T. Otsu, j . Po/ym. Sci. A-l,

f,

41;

,I. MacI'omoL 8Gi.-Ch.8m., AI, 1025 (1967).

34. M. Kinoshita, 'l'. Irie, and M. Imoto, Mak1'omoL Ch(,'m., l.!Q, 47

(1967) .

35. M Imoto, M. Kinoshita, and M. Nj.shigO>.ki, M(,krrolliol. CIiem., 94,

238 (1966).

(35)

36. C. H. Ba[Tlfo.nl, A. lJ. Jenkins, and R . • Johnston, ',"'I'(U·:.IJ. fo'u'·',.,day

, .},?.' 418 (1959); C. H. Bamford and 1\. D. Jenkins, ibid.,

21,

530 (1963).

37. A. CaflllTlon·"t<J anJ S. J. Yall, J. polym. Sc.i .. 1\-.1., .§.' 1303 (1970) 38. I1~ SaWi.J.d~l, J, /V;(i.(~p:.)m()!.. /I'OT~ _ hle'uti. M(,:t,(?1'O'nl)/,- (:hum., Q.ll, 257

(197~) .

39 . • J. R. Hoyland, .J. /'i.ili/I'I. ,'ki. il-.I, ~, J,863 (1,)70). 40. L. P,wling, .f. illller. vh'.!I1[ . .

"0('.,

54, 3570 (19J2).

41. K. E. Weale, chem/(."a!. !?e({,·!t:·I~orlil 01 .. !;,.:~,!h jlp(U~~:I./.r·(:'1 SpOlll London, 1967.

42. S. D. Hamann, i);:?I~:·icr:.I-(:h<"IIJ"I.~I,·I.~1.. r,'rr/30t:n of j~r'i';\;j{"j/"/.t't21 Butt8Y'worLhs

L()ndon, 1957; in !.'/~Ih l'.r.!ng~~.7"e r'>hy~-~/(.~)'~ (if"l,d (.'luo'l'lr.';-:r.·y'u, R. S.

B~adley, Ed., Academic Pre~~, New York, 1963, ChopLcr 8.

43. K. E. ~VC"ale, in n(!(iC~~;/li''i:f;y, ;11,,~( .. ha'''!·I·~Jrn and .'"!'f.:?'·;'.~(·f .. I..!.(·O, 1\.. D. ~1"en""

kins and II. T.ec.Jw.i.t.h, Eds., Wiley, ),c)rl()l)n, 1974, Cl"laf'te.l~ 6. 44. W. J . I...f.!:Noblc, in JJrl(.i:).l"'t:'O~l ·;1·7 ;·'hy:;/,.·ul. ()i"l(7t~n.·r:("!" Che, .. r·;,'il .. PJj, Vol ..

5, A. StreitW).e5f'r and R.

w.

'rafl, Ed"., Interscionce PubliAhcrs

Now York, 1967, p.207.

45-

F..:.

Whc)l.lt~y, in jl(/I'():h('\-;":.~ I:n ehUi-1{(:or. OY'gCU·I{'~·· ('i··U.·I·l"I"i.~t:i .. r)j, vol. 2, V. Gold. Ed., Acadomic Pre55, New York, 1964, p.93; Iler'. jl'.P·(D,·!/·/-:1'""" P Ii !I D. Ci, >.:"n., 7 0, 958 ( 1 966) .

46 .. (~. Kolil1SLam, in. r·!)·":~OP(:~"i;l lrr. neu.2~,lo;·1 X!··I··~(fi.:,'.:(.·~~, :l?ergafr'1.0r"1 LJ.(.'I2:=:=,

Oxf01:'d, 1970, p.33').

4"1. C. A. l::c:kOl'l, ,liPI. He v. /'h·U ,<.~ • (;·hIHn. J3, 239 (1972)

48. Y. Ogo, M. Yokawa, and T. 1molo, !4!~i:: "r"'omli X _ (: {-J (:~ /"!! •

,

17l, J.23 ( 1973 M. Yoi<awa, y. _Ogo, OInd '1'. Imolo, ibid.

,

175, 179, 2903, 2913

(1974); M. y"kilWil and Y. Ogo, tbl(l., }.J.J..' 4~,:) (197(;); M. Yokawa, .J. YOAhida, Clnd Y. Ogo, ,'·Ia/p'omo/.

(.'1,'''11.,

ill.

443 (1977).

4,). Y. 090 Dna M. Yoi<awa, Y":) 1>10 I. (·/"".'m.,

ill,

~.1.3 (1977). 50. G. Luft, ph. D. Thesis, Darm5tadt University of Technolosy,

Darmst,3.clt, .1.%7.

S1..

'oJ.

J. LeNoble ",nd '1'. Asano, d. MII,:r'. 1.'1,:1'.':':. ,::" •. ,.,

2.:7..,

1778 (l'n5)

52. W. F. Dellep@r9Br, Ph. D. The5is, Imperial College of Science and Tcchnolugy, London, 1973.

53. ~. Do Kok, ph. n. Thesis, Eindhoven University of Technology,

(36)

CHAPTER 3 Determination Of Copolymerization I(inetics By Means Of

Gas-Liquid Chromatography

3.l INTRODUCTION

The introduction of gas-liguid chromatographic (GLC) analysis

of the monom~r feed was an important step forward in

copolyrneriza-tion1,2, as

~t

replaced the more troublesome and inaccurate

copo-lymer composition('tl analysis. The "sequential s('tmpling" method

re-ported by German and Heikens2,3 has several advantages over other

existing GLC-techniquesl. In the fOrmer method a specially

con-structed device4 affords £ampling up to pres5ure5 of about 50

kg/cm2, and moreover, i t enables continual, on line measurement of the numbers of moles of both monomers throughout the

copolymeri-zation reaction up to relatively high conversions (20 - 40%). This

technique also haS been applied to all "low" pressure (35 kg/om2)

experiments reported in the present thesis.

For the determination of high pressure kinetics De Kok5

ro-sort~d to the "sandwich" method, which is balO~d on the application

of the "sequential sampling" method to the low prGssure stag~s pr~

oeding and succeeding the relevant high pressure stage. This method has some drawbacks, and therefOl;'E: '" new method based also on

quan-titative GLC has

b~en developed during this investigation

6. In

par-agraph 8.1 this method, referred to as the "quenohing" m~thod,

will be treated oomp:rehensively, and compared with the pr~viOu$

"sandwich" method.

3.2 APPARATUS

The apparatus consists of two main parts'

(37)

- th~ r~D~tor Wilh its accessories for temperature Dnd pressure

cO r'l t. (()1. , cLe., and

- t.l,,-:, vrlrious components neCe",!;,'l:'Y for a rapJ.d i)ncl accurate qU(ln-tit.ative CLC-analysts of the reaction mjxtu1'.'c.

Two different types of reactors liove beon used in the present st.l),ly, namely a react.or for "low" presc;u.,e oopolymerizatj.ons and

Or",: fOr' high pressure, "

3~,

kg/(:m2, react.iorl$.

Copolymerizations at low p~assure can be carricd out with a

relal1vely simple typ~ or apparaLus, A block cl1agram of such a

compleLe apparatu5 t.ogether with the GLC-equipment i5 presented

.i n Pigu1-e 3-J. 'I'f,chnical dotails of the reactor, «ndLr.e

tempera-ture and pressure conlrol systeMS have been described elsewhere7.

The high pressure copolymerLzotions require the use of heavi~r

reactors. During the investig~tion described in this thesi~ 0 new,

A .: reQctor

D. = comprlrtmi..:'l:'It;-. f"o,~ pl""essure

control C s~ITlling dcvi~e D ..:. g.as-c[l/:'omalograpb E - electr()niC integrator F G H diyit..:.d. J;-'(,inl:er

pi.'e.~$ll"!:'e and flow

cont:".(Oll.ers

(38)

improved high pr~$$ure vessel has been put into use. The main ame-loriations of this reactor in comparison with the previous reactor, are its improved mixing characteristic$8. The new high pressure re-actOr will be discussed in more detail in paragraph 8.3, while the

"old" reactor, which has only been used in a comparativ~ study of

the "sandwich" and "quenching" methods will be described in para-graph 8.1.

(; /,(:-appar'Q t 1<8:

Besides the low pressure equipment, Figure 3-1 shows schemat-iccally the basic component$ Of the GLC-apparatus. One of the most important elements for applying the method of "sequential sampling"

is the sampling diSK valve4 developed earlier, permitting repeated

injection of s!;lmpleS Of egual volume ( 5ul in all studies, unless reported otherwise). The temperature of the disk-valve was

maintained at 62°C during all experilMnts. The cOmponents of the react10n mixture are separated On the gas chromatograph. In the relevant chppters details on the various gas Chromatographic con-ditions will be given. The peak areas were registered by a

record-er, determined by means of an electronic integrator, and printed

out by a digital printer.

3.3 QUA~TITATIVE GLC-ANALYSIS OF THE REACTION MIXTURE

After introducing the reaction components - i.e., both

mono-mers, the solvent, and the initiator - into the reactor, and

ad-justing the desired temperature and pressure levels, samples of

the reaction mixture were taken and injected into the IIe~carrier

gas stream of the GLC. Any copolymer present in the samples

precip-itated just behind the metering oompartment of the samplin<] valve.

After each kinetic experiment the sampling valve was rinsed with toluene in order to remove the precipitated copolymer.

(39)

j _ 3 _ 1 ClILCULJ\TJON Or MONOMER FEEf) J1-ATIO I\ND DE(;REE OF CONVERSION

In chapLer 4 iL will become clear that the integrated fo\;m

of the simple Alfrey-Mayo scheme leq. (2.5)

I

is needed for the

calculation of monomer reactivity ratios from high conversion

ex-periments_ This integrated equation requires the determination of

lhe molar feed ratto, 0, and the degree of conversion bilsed on

mon-S 7

om",~ l ' r~· J::lsr"wh'.'l-e' it has been shown th<~t ({ c<)n I)Q Qxprcssed in Lerms of Lhe peak areas of Lhe monomers and a constant.

rll III

'I I'~

.,

il-~ K ref

w})crc)~ and ~2 arc t}lO respective numbers of moles of monomer Ml

and M2 in the reactor; Al and ~2 are the corresponding peak Dreas

of t.h •. , IIIOnomel-s; and 1(reY: is the response rat.io, whic;h hilS to be

det.ermined by means of reference injections of the pure monomers.

Experimental details on the measurement of K

re[ will be given in

seeLion ].3.2.

'rhQ ~egrQA of conversion,

f

2, is Qxprcssod on a percentage

scalQ anJ Ls given by:

(

"2)

(AZ'/'sO)

./' ~ 100 . 1 - -, - = 100 . 1 - '!.,

? I, 2 0 !! ",' II :lO

where A is Lhe peak area of Lhe solvent; and the subscyjpt zero

s

denotes initial condiLions.

J. _).2 LJE'l'j,;l{MINA'rION 0]7 'TilE RESPONSE RATIO

In order to measure Lhe response ratio , the pure monomers were injected int.o th'1 qas chromatograph by me,"ns of the

above-men t i.onecl saJTlpl:i ng d i. sk -v;:ll.ve, unc:lcr condi Lions equivalent to the

rcact_.i.on C:,,)nditions. 1n prine'ipIe, the procedure a5 descr'.i.ber.l by

De KOt;5 waS followed. Sampling volumes smaller than 2111 were used during the reference injections.

Effect of solvent, monomer structure, and pressure on reactivity in radical copolymerization : kinetic investigation within the monomer series ethylene - vinyl acetate - vinyl ester and methyl acrylate - butadiene