Kinetics and mechanism of copolymerization of phenylglycidyl ether with ϵ-caprolactone by the action of aniline

Copolymerization of phenylglycidyl ether with 8-caprolactone

495

group in the partially dehydrated range near the chain by the formation of hydrogen bonds with chain units on the one hand and with the adsorbed small molecule, on the other, The authors are grateful to S. A. Ostrovskii for providing vinyl caprolactam. Tra~s/ated by E, SEM~RE REFERENCES 1. 2, 3. 4. 5. 6.

M. ZWICK, J. Appl. Polymer Sci. 9: 2393, 1965 Y. G. PRITCHARD and D. A. KINTOLA, Talanta 19: 877, 1972 G. OSTER and E. H. IMMERGUT, J. Amer. Chem, Soc. 76: 1393, 1954 Y. NEEL and B. SEBILLE, J. Chim. Phys. 58: 738, 1961" L MORIGUCHI, Y. ARAKI and N. KANENIWA, Chem. Pharm. Bull., 2088, 1969 Yu. E. K/RSH, T. A. SUS' and T. M. KARAPUTADZE, Vysokomol. soyed. AIg: 2774, 1977 (Translated in Polymer Sci. U.S.S.R. 19: 12, 3205, 1977) 7. S. HAYASHI, M, KOBAYASHI, H. SHIRAI and N. HOJO, J. Polymer Sci., Polymer Letters Ed. 17: 91, 1979 8. Kh. RAIKHART, Rastvoritieli v organicheskoi khimii (Solvents in Organic Che~nr~'i~ry)~ Khimiya, 1973 9. Yu. E. KIRSH, T.A. SUS', T. M. KARAPUTADZE, L. A. SINITISNA and S. A, OSTROV-~ SKIll, Vysokomol. soyed. A21: 2734, 1979 (Translated in Polymer Sci. U.S,S.R, 21: 12, 3014, 1979)

PolymerScienceU.S.S.R.Vol.28, No. 2, pp. 495-502,1981 Printed in Poland

0082-8950/811020495-08507.5010,

0 1982PergamonPrem Ltd.

KINETICS AND MECHANISM OF COPOLYMERIZATION OF PHENYLGLYCIDYL ETHER WITH ~.CAPROLACTONE BY T H E ACTION OF ANILINE* G. A. ESTRINA, S. P. DAVTYAN a n d B. A. ROZENBERG Branch of the Institute of Chemical Physics, U.S.S.R. Academy of Sciences

(Received 17 December 1979) A study was made of kinetic mechanisms of reactions taking place in a ternary mixture of phenylglycidyl ether-e-caprolactone-aniline. Rate constants of parallel reactions were determined. Constants of copolymerization, resembling alternating copolymerization, were evaluated. I t was shown that the rate constant of non-catalytic initiation of polymerization of 8-caprolactone depends on the ratio of phenylglycidyl ether : 8-caprolactone. It was found that phenylglycidyl ether additives an& * Vysokomol. soyed. ~ 8 : No. 2, 444-450, 1981.

496

G . A . Esz~n~A e~ a/.

other polar solvents have an accelerating effect on the initiation of polymerization of a.caprol~ctone. A hypothesis was put forward for explaining this effect, which is based on structural features of ~-caprolactone as a strongly associated liquid. ~-CAPROI~CTON~ (CL) is a n efficient modifier o f compositions based on e p o x y resins solidified b y diamines [1]. T h e m e c h a n i s m o f p o l y m e r i z a t i o n o f CL b y t h e action o f amines [2, 3] a n d t h e m e c h a n i s m o f i n t e r a c t i o n o f e p o x y groups w i t h amino groups [4] were pre* viously e x a m i n e d in detail. I n o r d e r to explain t h e m o d i f y i n g action o f CL in solidification o f e p o x y resins, studies were carried o u t o f t h e r e a c t i o n in a t e r n a r y s y s t e m containing CL, epoxide a n d amino groups. P h e n y l g ! y c i d y l e t h e r (PG) a n d aniline were used in this s t u d y as c o m p o u n d s simulating e p o x y resins a n d a m i n e hardeners. The purification of CL and aniline was described previosuly [3]. PGE was dried over calcium and repeatedly distilled at 90° and l0 -I torr. A fraction free from phenol was used. Purity was controlled chromatographically. I)iphenyloxide (DPO) was recrystallized from alcohol and dried in vacuo, m.p. 28°, d4 t° 1.07 g/cmS; phosphoric acid hexamethyl triamide (PHM) was distilled at 68° and 10-2 tort; malonie ester (ME) was distilled at 40° and 10-I torr. Reaction kinetics were studied di]atometrically [3] and by GLC [4]. Reaction products were ~n~lysed using an UV and IR spectrometer and chemically [3]. The dielectric constant D was determined using a "Universal dielectrometer" (ON-301) type. Polylactone adducts with carboxyl end groups were prepared by heating CL mixtures with a calculated amount of aniline in inert atmosphere at 180°. I n t h e C L - P G E - a n i l i n e system studied aniline, t h e initiating c o m p o n e n t , is used in t w o parallel reactions w i t h P G E a n d CL. T h e initial r a t e o f consumpt i o n voA is equal to t h e t o t a l o f initial rates o f c o n s u m p t i o n o f P G E , roE, a n d CL, vOM, a c c o r d i n g t o t h e e q u a t i o n ~,oA=~,OE+VO~,~

(1)

w h i c h shows s~tisfactory a g r e e m e n t with e x p e r i m e n t a l results (Table 1). W e will e x a m i n e each r e a c t i o n separately. TABLE 1. INITIAL RA~ZS OF C O ~ S ~ O ~ OF co~o~r~Prs A~D ~ZAOZ~O~~A~Z CONSTANTS n~ ~m~ PGE-CL-AmLIz~ M~rrUR~ AT 180° [El0

5.49 4-68 5.24 4.20 3:90 3.47 3.84 3.97

J

,

[A]~ mole/1. 2.75 2.37 1.33 1 "05 1"95 1"79 0.83 0.39

~ozXlO s

0 1.42 1.60 2.10 1"95 3.48 3"84 3.96

19.00 7"60 3"20

1.60 5.00 3.90 0.75 0-16

I

v0A~10 s mole/l.-see

i9.00 8.70 4.00 2.40 5.40 4.50 1.00 0.28

~oK × 10~

bl × I0 s

l./mole, sec 0 1.05 0.80 0.74 0.39 0.54 0.21 0.12

0 0.31 0.31 0.18 0.18 0.08 0.08 0"08

Copolymerization of phenylglycidyl ether with e-eaprolaetone

497

Reaction of CL-aniline in the presence of PGE. Figure 1 shows t h a t there are no induction periods or S shape seen on kinetic curves of consumption of components in the system. At the same time it is known t h a t without PGE these curves are S-shaped depending on the auto-catalytic stage [3]. Elimination of

[E] motefl.

[M] , mole/t.

EA] mote/t C

2

Z 3 5

q

3

2

2 0

I

5 Time f~lO-a ~ee

3 0

I

Fie. 1. Kinetic curves of the consumption of PGE (a), CL (b) and aniline (o) in a ternary mixture at 180° with a stoichiometrie ratio oi epoxy and amino groups: 1--[E],-----5.40, [Al0=2.75 molefl.; 2--[E]o=4.68, [A]0=2.37; [M]0=1.42 molefl.; 3 -- [E]o-~ 3.47, [A]o= 1.79; IMp0----3-48 mole/1.

S-shape in the presence of PGE is the consequence of an increase in the rate of initial non-catalytic reaction, which is becoming commensurate with the m a x i m u m rate of the auto-catalytic stage in the binary system. At the same time, the mechanism of consumption of CL and aniline at the initial moment remains the same in the ternary system as in the binary system, in accordance with the equation %,-(

d~]),.0---- kl[MJo[A]0,

(2)

where kx is the non-catalytic rate constant of initiation, [M]0 and [A]0, the initial concentrations of CL and aniline (Fig. 2a). The kl value for the ternary mixture is higher by three orders of magnitude, compared with the binary system. Therefore, the first stage of addition of CL and aniline ceases to be the limiting stage, as shown previously [3]. This has the result t h a t the rate of aniline consumption is equal to the total rates of consumption of PGE and CL, according to equation (1). I n this ease kx becomes a variable value dependent on the ratio of [E]o : [1~o (Table 2). I t should be noted t h a t an increase in kx in the ternary system is not due to a change in the reaction mechanism, since identification of reactions by methods of spectroscopic analysis shows t h a t their structure corresponds to the structure of products of the model reaction of CL with 3-phenoxy-2-hydroxypropylaniline [5]. Assuming t h a t an increase in reaction rate involves a change in the dielectric constant of the medium D on varying the concentration of PGE in the system, D values were measured for components and their mixtures (Table 2) and the parameter (D--l)/(2D~l) was calculated from the Kirkwood equation [6] and

498

G.A. ESTRINA et (d.

TABLE 2. VARIATZONSOF THE DI~rLECTRI(] CONSTANT OF CL, ANILINE, PGE AND .r~u~rlg MIXTURES AT DIFFERENT TEMPERATURES

D at temperature, °C Medium

i

CL Aniline PGE t PGE : CL : aniline in a ratio ~. 1:1:0.1 1:1:0.2 1 : 0.5 : 0"5 1:0-3:0.5

22

40

60

180"

38.7 6.8 11.7

35.4 6.4 10.5

32.4 5.9 9.7

15-00 3.20 3.00

1 2DD- + - 1I at 180°

0-41 0.41 0.37 0.36

8"06 7"80 5.70 5"00

* Results obtainedby extrapolation,

t

Meamuredby P. P. Kushch. t Ratio in moles.

g i v e n in T a b l e 2. I t can be seen t h a t changes of D in t h e presence o f P G E a d ditives in t h e c o n c e n t r a t i o n r a n g e m e a s u r e d are such t h a t t h i s p a r a m e t e r v a r i e s slightly, changes o f D o f t h e m e d i u m m a y , therfore, be ignored. E x p e r i m e n t s o f i n v e s t i g a t i n g t h e r e a c t i o n o f C L - a n i l i n e in t h e m e d i u m o f solvents o f v a r i o u s k i n d s h a v e b e c o m e i m p o r t a n t for u n d e r s t a n d i n g t h e m e c h a n i s m of this process (Fig. 3). I t is o b v i o u s t h a t all t h e solvents t e s t e d , i n d e p e n d e n t o f t h e degree o f t h e i r p o l a r i t y , increase r e a c t i o n r a t e . A t t h e s a m e t i m e , s t r o n g e r e l e c t r o n donors, such as P G E y a n d P H M c a n r e m o v e t h e S-shape o f k i n e t i c curves, while t h e less s t r o n g ones (DPO, dichlorobenzene a n d P E ) do n o t r e m o v e S-shape c o m p l e t e l y a n d increase r e a c t i o n r a t e to a slighter e x t e n t .

Uohrn=lO~mo/e/L.svoexl ec Omde/L.aec ~ 0.5t~I/~2 I.0 a lOf~

[A]o [M]o Fio. 2

_•-

o~ I'0

q~ 2I

0"5 [E]o

0

J

200 Time,~00 rain 6O0 Fzo.3

FIG. 2. Experimental dependence in coordinates of equation (2) (a) and (3) (b~ for the reaction of PGE-aniline-CL at 180° and molar ratios of [El0 : [M]0= 1 : 1 (1}, 1 : 0.5 (2) and 1 : 0"3 (3). Flo. 3. Kinetic curves of polymerization of CL in a CL-aniline binary mix~uro with solvent additives at 200 °. 1--[M]o=8; [A]0=l.6 mole/l.; 2--[M]o=7.4; [A], ~1'48; VDPO=0'5 molefl.; 3--[M]o=7.52; [A]0=1.67; c~B=0.6 mole/].; g--[M], =4.26; [A]o=0.9; CpHH=3,8 mole]l.

4999

Copo]ymerization of phenylglycidyl ether with 8-caprolactene

I t m a y be assumed that reaction rate is determined b y the specific solvation of the monomer b y the solvent, however, it is doubtful whether solvation h a s such a strong effect on reaction rate. Nevertheless, to account for the quantitative e~ect of specific solvation on reaction kinetics, the correlation equation w a s used of the linear dependence of the logarithmic rate constant on the molecular fraction of the solvating additive [6]. Two sections m a y be clearly distinguished in the dependence shown in Fig. 4 (log kl as a function of the molar fraction o f

log k,

[/

_q -

, mo/e/l.

[M], ol /l.

x , . , . J ''~"

fJ I

I

0.5

f

!~ 2 ~

- 6 xf

0 I

=

I

J

0.1

I

I

0.5 m Fzo. 4

20

20 r i m e ~, lO'8,~ec

~/0

°" 40

6O

FIe. 5

FIG. 4. Logarithmic dependence of the rate constant of the non-catalytic reaction of CL -- aniline on the molar ratio of PGE (m) at 180°. Fie. 5. Kinetic curves of consumption of components of the PGE (1), CL (2) (a) and aniline (b) ternary system with non-stoichiometric ratio of epoxy groups to amino groups: [E]0 3-84; [Ale 0.83; [M], 3.84 mole/1.; 180°. PGE): a non-linear (in the range of low concentrations of P G E additives) and a linear section. It is obvious that the second section reflects the effect o f specific solvation on the initial reaction rate. The reactivity of P G E - C L complexes in the reaction with aniline is higher than that of unsolvated CL, since extrapolation of the straight line on the ordinate gives the rate constant o f initiation of solvated CL (5 × 10 -s 1.~mole.sec). Therefore, specific solvation b y P G E only influences the increase of the rate constant of initiation b y one order of magnitude, while an increase of the rate constant b y two orders of m a g n i t u d e (kl for an unsolvated double bond being 0.43M 10 -e 1./mole.see) is evidently due to a factor which is responsible for a non-linear change of rate in the range of very low additions of PGE. I t m a y be assumed that this effect is due to specific structural features and physical properties of CL [7-10], as shown in Table 3. A comparison is made of physical properties o f lactones with properties of linear analogues--acyclic esters. I t m a y be concluded from a comparison of these properties that lactones have much higher Then values and densities, compared with linear analogues. This is, apparently, the consequence of the formation of strong associates o f lactone molecules, as a consequence of the cyclic structure and strong polariz~

G: A. ESTRINA ~ aZ.

~00

tion o f molecules. This is aided b y high dipole moments and corresponding D values. The associated form of CL molecules is, apparently, much less reactive than the monomer form, which exists as solvates with solvents. From the point o f view of this hypothesis polar solvent additives increase the concentration .of the more reactive solvated form of the monomer, which results in a sudden increase in rate. TAB~ 3. PHYSICO-CHE~ICALCO~ST~'rS OF CYcle XWD AOYCLICF~S~2S [8--11] rumber of carbon atoms 3 4 6

41o

Compound

Methyl acetate p-propiolactone Ethyl acetate ?-butyrolactone Butyl acetate CL

T~oil

at 20°, g/cm~

56.5 155 77 204 126 232

0.93 1.15 0.90 1.14 0.88 1.07

D at

9.0 °

6.6 44.0 6.0 42.0 5.0 39.0

Debye 1.76 4"18 1.81 3,82 1.84 --

It should be noted that all these effects only take place at the stage of noncatalytic initiation. After all the aniline has reacted the rate of consumption ~)f CL is of an order, which is usual for the rate of chain growth ( ~ 10 -~ mole/1. •sec), previously determined for a binary system. Reaction of PGE with aniline in the Fresence of CL. It was previously shown for a PGE-aniline system that the initial reaction rate of second order for aniline a n d conforms to the relationship [4] r e . - ( - - ~ t ]),.o=k.[A]~[E]o,

(3)

where [El0 is the initial concentration of PGE, ks--non-catalytic rate constant o f the reaction of P G E with aniline. Formula (3) shows satisfactory agreement with experiment (Fig. 2b) and t h e value of ks-----0.3 × 10 -31.2/moleS'sec at 180 ° with value of 0.1 X 10 -s 1.Smole~"sec derived previously [5] b y extrapolation with a temperature interval of 20-60 °. As shown b y Fig. 2b, the constancy of the reaction rate constant in the entire interval of CL added is evidence of the fact that it is an inert solvent. Comparison of rates of reactions (2) and (3) shows that at 180 ° they are of the same order. After aniline has been fully used up the rate of consumption ,of P G E slows down and is of the same order as the current rate of consumption o f CL. Copolymerization in a PGE-CL--aniline ternary system. A reduction in the r a t e of consumption of P G E and CL after aniline has been used up is duo to the f a c t that copolymerization with the new functional groups appearing becomes

Copolymerization of phenylglycidyl ether with 8-caprolactone

501

limiting stage. B y the reaction of CL-aniline amino acids are formed, which have two carboxyl end groups [2]; these m a y combine a P G E molecule, as well as CL molecules (chain growth) [11]. The hydroxyl group obtained b y epoxy ring opening can combine a CL molecule to form ether acids with a carboxyl end group, as indicated in [5]. As the CL molecule m a y be added at two active centres and the P G E molecule a t one centre, the current rate of CL consumption at 80 ° becomes higher than the current rate of P G E consumption. This is particularly marked with a nonstoiehiometric ratio of epoxy- and amino groups in the initial mixture (Fig. 5). All reactions at the stage of chain growth m a y therefore be presented b y the scheme CL~- ~ RjCOOH - ~

~ Rj+ICOOH

(I)

kit

P G E Jr ~ RjCOOH - - - ~ ~ RjCOOCH~CHCH~OPh

(II)

I

OH CL-t- ~ R j O H PGE+~R~OH

~°' -~~RjO(CH=)sCOOH

(HI)

~:', ~RjOCH2CHCH,OPh

(IV)

I

OH Rate constants of chain growth of polycaprolactone were determined previously:/¢11 and/c21 in studies [4] and [5], respectively. The reaction rate of the CL-amino alcohol model system at 180 ° is ~ 3 times lower than the rate of chain growth of CL on carbanions. Reaction kinetics of P G E with carboxyl groups (II) were studied at 180 ° using polycaprolactone oligomers previously obtained. Kinetic curves of the reaction indicated are described b y a second order mechanism (Fig. 6), while rate constant/~---- 0.18 × 10-3 1./mole. sec.

:/CEJ,

[E]~mole/l. 3

III

Cl

5

IO

I0 5 T/me ~x lO-rm/n

10

Fig. 6. Kinetic curves of consumption of POE in the reaction between polylactone and PGE at 180° (a) and transformation of a second order reaction (b): 1--[El. 2.93; [COOH],~ 2.9 mole/1.; 2--[E]o-~ 1.78; [COOH],~ 1.8 mole/l.

502

G . A . EsI~J.~A e~ a/.

Reaction (IV) does not take place in practice under the conditions examined b y us, i.e. k ~ = 0 . Th e constant of copolymerization rx=0-18 for CL and r2-----0 for PGE. I t can hence be seen t h a t the distribution of units in the chain in the copolymer examined is close to the alternating mechanism. A s t u d y of kinetics and the mechanism of processes taking place in the P G E CL-aniline system t h e r e f o r e indicates t h a t reactions of PG E -ani l i ne and CL-aniline are the f as t e s t reactions, while copolymerization taking place w i t h low aniline concentrations in the mixture take place at a much lower rate. CL polymerized on two active centres and added only to earboxyl groups i s used up a t a higher rate t h a n P G E after the complete consumption of amino groups. Translated by E. SE/~ERE

REFERENCES 1. Belgian Pat. 617540; Chem. Abstrs. 58, 8102f, 1963 2. G. A. E8TRINA, 8. P. DAVTYAN and B. A. ROZENBERG, Vysokomol. soyed. AI8: 2438, 1976 (Translated in Polymer Sei. U.S,S.R. 18: 11, 2782, 1976) 3. G. A. ESTRINA, S. P. DAVTYAN and B. A. ROZENBERG, Vysokomol. soyed. A21: 782, 1979 (Translated in Polymer Sci. U.S.S.R. 21: 4, 855, 1979) 4. Kh. A. ARUTYUNYAN, A. O. TONOYAN, S. P. DAVTYAN, B. A. ROZENBERG and N. 8. YENIKOLOPYAN, Dokl. AN SSSR 214: 832, 1974 5. O. A. ESRTINA, 8. P. DAVTYAN and B. A. ROZENIIERG, Vysokomol. soyed. A22: 2322, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 10, 2549, 1980) 6. V. A. PAL'M, Osnovy kolichestvennoi teorii organicheskikh reaktsii (Principles of the Quantitative Theory of Organic Reactions). Khimiya, 1967 7. O. A. OSIPOV and V. L MINIClN, Spravochnik 13o dipornym momentam (Handbook o n Dipole Momenta). Vysshaya shkola, 1965 8. Kratkaya khimicheskaya entsitdopediya (Brief Chemical Encyclopedia). Sovetskaya entsiklopediya, vol. 2, 1963 9. A. VAISBERGER, E. PROSKAUER, D. RIDDIKH and E. TUPS, Organicheskiy0 rastvoriteli (Organic Solvents). Izd. inostr, lit., 1958 10. A. P. TOMILOV, M. Ira. FIOSHIN and V. A. SMIRN0V, Elektrokhimieheskii sintez organicheskikh veshehestv, Khimiya, 1976 11. M. F. SOROKIN and E. L. I~HINCHINA, Lakokrasochnyye materialy i ikh primeneniye (Paints and Varnishes and their Application). 1go. 5, 1964