Makromol. Chem. 185,1177- I186(1984) 1177

The interaction of comonomers in the solution copolymerization of N’N-dimethyl-2-aminoethyl methacrylate with methacrylic acid

Jan Lokaj, Danica DoskoEilov&, Frantirek Hrab&k*

Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences, 162 06 Prague 6, Czechoslovakia

(Date of receipt: October 25, 1983)

SUMMARY The copolymerization parameters of N,N-dimethyl-2-aminoethyl methacrylate (DAMA) with

methacrylic acid (MAA) were determined at 50°C in benzene, dimethylformamide, and pyridine solutions. The Alfrey-Price constants e and Q of the two monomers were determined by copolymerization of DAMA grid MAA with styrene in the same solvents. Using these con- stants, the copolymerization diagrams of the pair DAMA-MAA were calculated and compared with the experimentally determined ones. The mutual interaction between the comonomers is discussed.

Introduction

The copolymerization parameters r,, r, can be regarded as coefficients in the rela- tion between the comonomer concentrations [M,], [M,] in the copolymerization mix- ture and the mole ratio of comonomers in the copolymer’) increment (m,/m,),

If the terminal copolymerization model were valid, r,, r, should be generally valid for the given pair of comonomers, provided the reactivity of the polymerization sites, i. e. double bonds and radicals, is not affected by the medium. In real systems, how- ever, reactivity of the polymerization sites may vary with the mole ratio and concen- tration of monomers, and also with the character and concentration of the other com- ponents of the system2-’). Molecular interaction of the components, including the forming polymer, also brings about a change in the steric hindrances to mutual approach of the reaction sites, in their mobility, local concentration and steric orien- tationa-12). The mole ratios of comonomers in the copolymer increment and in the monomer mixture, and consequently, the determined copolymerization parameters differ according to the extent to which these factors affect the copolymerization of the given pair of comonomers. An effort to determine the authentic characteristics of the copolymerization of two monomers unaffected by molecular interaction has led to a number of improved equations used in the calculation of the polymerization rate (R,) and copolymer composition l 3 -la).

0025-1 16X/84/$03.00

1178 J. Lokaj, D. DoskdilovB, F. HrabBk

The stronger the effect of the medium on the polymerization of the given pair of monomers, the less valid the assumptions under which the Alfrey-Price equations for the calculation of the copolymerization constants e, and Q, from the copolymeriza- tion parameters r,, r, were derived.

Hence, the difference between the determined e,, Q, and the hypothetical values of e,, Qz of the isolated molecule M, and its radical is the greater, the stronger the in- fluence of the medium and mutual molecular interaction of the reacting particles on the elementary copolymerization reactions of the pair M,, M,.

In this study, the Alfrey-Price e-Q scheme has been used to characterize the mutual molecular interactions of comonomers in the copolymerization of N,N-di- methyl-2-aminoethyl methacrylate (DAMA) with methacrylic acid (MAA). The e, Q values of the two comonomers were determined by their copolymerization with styrene (S), which does not specifically interact with either DAMA or MAA. From the e and Q values thus obtained, the copolymerization diagram of the pair DAMA- MAA was calculated, representing the hypothetical dependence of copolymer compo- sition on the initial monomer ratio DAMA/MAA with elimination of the effect of interaction between amine and carboxylic groups. The hypothetical copolymerization diagram was compared with the experimentally determined one of the same monomer pair. The differences between the calculated and determined copolymerization diagrams of the pair DAMA-MAA, found in various solvents, were compared with those obtained earlier lz, j7) between the determined and calculated copolymerization diagrams of the pair N-methyl-N-phenyl-2-aminoethyl methacrylate-MAA.

Mutual interaction between the DAMA-MAA comonomers was interpreted using new findings about the interaction of carboxylic acids with aliphatic and aromatic tertiary a m i n e ~ ~ ~ ~ ' ~ ) . The interaction is accompanied by the formation of hydrogen bonded acid-amine associates, which represent molecular and ionic complexes in equilibrium.

Experimental part

MateriaIs: N,N-Dimethyl-2-aminoethyl methacrylate (DAMA) (Schuchardt, Munich, Germany), and methacrylic acid (MAA) (Merck, Darmstadt, Germany) were redistilled twice under reduced pressure in a stream of nitrogen (DAMA. b.p. 72"C/1,60 kPa; MAA: b.p. 33 "C/0,013 kPa). Styrene (S), 2,2'-azodiisobutyronitrile (AIBN), benzene (B), and N,N-di- methylformamide (DMF) were purified by the usual proceduresm). Pyridine (Py) (Carlo Erba, Milan, Italy) was redistilled under normal pressure.

Methods: Purity of the monomers and solvents was checked with a gas chromatograph CHROM 3 (Laboratory Instruments, Prague, Czechoslovakia). H NMR spectra of copolymers DAMA-MA4 were recorded at 95 "C with a PS-100 JEOL spectrometer at 100 MHz using hexamethyldisiloxane as the internal standard and 10 wt.-% polymer solutions in Py.

The pairs S-MAA in B and Py, S-DAMA in DMF and DAMA-MAA in B, DMF, and Py were copolymerized at 50 "C in glass dilatometers ca. 8 cm3 in volume in an inert atmosphere. With

The interaction of comonomers in the solution copolymerization. . . 1179

each pair, nine copolymerizations were performed at various initial copolymer ratios expressed through the mole fraction (F) of the first comonomer (Tab. 1, Fig. 1). The starting overall concentration of the two comonomers was 2 mol/l each time. The copolymerizations DAMA- MAA were initiated with 0,Ol mol/l AIBN, those of S-MAA and S-DAMA with 0,02 mol/l AIBN; all were interrupted at ca. 10% conversion of the monomers to copolymer, and their course was linear. In the copolymerizations S-MAA and DAMA-MAA in B, copolymers separated out from the solutions; only in mixtures with the starting mole fraction of S or DAMA above 0,7 the copolymerization proceeded in homogeneous phase, similarly to all copolymerizations in DMF and Py.

Copolymers S-MAA and DAMA-MAA prepared in B and Py were precipitated from the polymerization mixtures with hexane or cyclohexane, and from solutions in DMF with ether cooled to - 60 "C. From the mixture S-DAMA in DMF, unreacted monomers and solvents were removed by distillation in vacuo (13 Pa), and polymers were precipitated with water from the distillation residue. All copolymers were dried at 60 OC/13,5 Pa. The copolymer composition was determined by elemental analysis and for DAMA-MAA copolymers also from 'H NMR spectra. 'H N M R analysis was based on the integrated intensities of the band of a-methyl protons at ca. 1,5 ppm which is common for both components of the copolymer, and of the

0 II

band of protons of the group -C-O-CH2- at 4,2 ppm, characteristic of DAMA. For N M R and elemental analysis, the copolymers S-MAA were reprecipitated with cyclohexane from ethanol-tetrahydrofuran solutions, the copolymers DAMA-MAA in B and DMF having F > 0,5 were reprecipitated with cyclohexane from methanol-benzene solutions; copolymers from the reaction mixtures having F < 0,5 were extracted with acetone. The copolymers S-DAMA obtained in DMF were precipitated with water from acetone solutions. The polymerization rates (R,) in B were determined gravimetrically, while in DMF and Py they were determined volumetrically in view of considerable losses during isolation. Using the copolymer composition thus determined and specific contraction of DAMA (0,116 cm3 . g-l), MAA (0,178 cm3 * g-'), and S (0,206 cm3 * ggl) at 50°C, specific contractions of the respective copolymers were calculated and subsequently used in the calculation of R,.

The copolymerization parameters were calculated from data on the copolymer composition by the Joshi-Joshi methodz1). Using the copolymerization parameters of the pair S-MAA in B and Py, and of S-DAMA in DMF, the copolymerization constants e,, Q2 for MAA in B and Py and for DAMA in DMF were calculated by means of Eqs. (2) and (3) (el = -0,8 and Q, = 1,O). The e, Q constants of DAMA and MAA were used in the calculation of the copolymeriza- tion parameters r; , r; of the pair DAMA-MAA in B, DMF, and Py by means of Eqs. (2) and (3); in the case of Py, the e and Q constants determined in DMF (0,81 and 0,74, respectively) were used for DAMA. The e and Q constants were calculated for MAA from the experimentally determined copolymerization parameters of the pair DAMA-MAA using the e and Q constants for DAMA determined in the copolymerization S-DAMA.

Results

Data on the copolymerization S-MAA in benzene (B), DMF and pyridine (Py), S-DAMA in B and DMF, and DAMA-MAA in B, DMF, and Py are summarized in Tab. 1. Composition of the copolymers calculated from the determined percentage of C, N, or from the 'H NMR spectra is expressed through the mole fraction, f, of the first comonomer in the copolymer; F denotes the mole fraction of the first comono- mer in the starting monomer mixture.

Tab.

1.

Res

ults

of th

e co

poly

mer

izat

ion

of s

tyre

ne (S

) with

met

hacr

ylic

acid

(MA

A) a

nd N,N-dimethyl-2-aminoethyl met

hacr

ylat

e (DAMA) a

nd o

f D

AM

A w

ith M

AA

in b

enze

ne (B

), D

MF,

or p

yrid

ine (

Py) a

t 50 "

C. F

andf

: m

ole f

ract

ion o

f the

firs

t com

onom

er in

the i

nitia

l pol

ymer

izat

ion

mix

ture

and

in th

e co

poly

mer

, res

pect

ivel

y; R

p: ra

te o

f cop

olym

eriz

atio

n in

mol

* 1-

1 * s-

l

F S-

MA

A

S-D

AM

A

DA

MA

-MA

A

fa)

R;16

fa)

R;16

fb)

Rp-16 f"

fb'

Rp

*1

6 fb'

Rp*l

d fb

) Rp

*16

f')

B PY

D

MF

B D

MF

PY

-

03

092

0,226

0,3

0,243

0,4

0,313

0,5

0,336

0,6

0,371

0,7

0,419

0,8

0,468

0-9

0,582

Cal

cula

ted

from

: a)

07

0 c

b, 070

N

c, NM

R

35,3

31,5

23,5

16,3

10,8

8,1

5.9

290

0,122

2.9

0,251

1,7

0,341

1,3

0,372

1,l

0,472

0,9

0,557

0.8

0,648

0,8

0,689

0,7

0,809

0,7

0,248

4,2

0,370

2.9

0,423

2,l

0,553

1,4

0,594

1,0

0,636

1.0

0,699

0,8

0,771

0.7

-

-

0.200

0,137

6,4

0,205

0,263

11,l

0,263

0,302

12,3

0,375

0,359

12,2

0,420

0,393

19,l

0,559

0,494

32,8

0,610

0,555

15,4

0,657

0,631

8,9

0,803

-

-

0,270

0,389

0,394

0,443

0,547

0,573

0,647

0,705

0,753

10.8

0,281

12,5

0,367

13,5

0,391

13,3

0,487

14,O

0,509

12,9

0,599

10,7

0,638

9,6

0,718

8.8

0,748

11,2

0,22

13,2

0,32

13,7

0.47

12,8

0,50

12,2

0,50

CI

11.6

0,70

10,9

0,65

T 10,5

0,61

??

9,7

0,79

b. P

The interaction of comonomers in the solution copolymerization. . . 1181

Characteristics of the copolymerization reactions:

For the pairs S-MAA and S-DAMA, R, decreases with increasing F, in accord- ance=) with the higher ratio of constants k:/& for MAA derivatives than for S. In B, the copolymerization S-MAA proceeded heterogeneously at a rate higher by an order of magnitude than in Py. In the copolymerization DAMA-MAA, R, reaches the maximum approximately at an equimolar ratio of the comonomers; at the same time, the maximum in B is more pronounced than in DMF and Py. With the exception of the maximum in B, R, of the pair DAMA-MAA in the solvents used is not very different, although the polymerization proceeded in B heterogeneously, and in DMF and Py homogeneously.

Tab. 2. Copolymerization characteristia rl, rz, e,, ri calculated from e,, Q2 (symbols as in Tab. 1)

determined from data in Tab. 1 and ri,

Comonomers Solvent ‘1 ‘2 e, Qz Ml -hi12 cr; 1 (r’2)

SMAA B DMFQ PY

SDAMA Bn DMF

DAMA-MAA B(NMR) €3 (Yo N) B (calc.) DMF (Yo N) DMF (calc.) PY W R ) Py (qo N) PY W C . 1

< 0,05 0,53 0,46 f 0,05

0,54 0,37 f 0.04

0,35 f 0.08 0.20 f 0,05 ( < o m 0,35 f 0,06 (0,74) 0,37 f 0.04 0.36 f 0,06 ( O S )

0,75 f 0,06 0,45 0.64 f 0,06

0.35 0.20 f 0,03

0,67 f 0.14 0.60 f 0,05 (>4,2)a) 0.23 f O , 0 6 (1,15)b) 0.25 f 0,06 0.23 f 0,05 (1,42) c,

>1,01 >4.7 0,40 0,72 0,31 0.90

0,49 0.66 0,81 0,74

-0.71 1,05 -0,W 1,62

-0,78 0,58

-0,73 0,57

Calculated from: *) el = 0,49, Q, = 0.66; e, > l ,O l , Qz > 4,7. b, el = 0,81, Q1 = 0,74; e, = 0.40, Qz = 0.72.

el = 0,81, Q1 = 0,74;e, = 0,31, Q2 = 0.90.

The copolymerization parameters of the pairs S-MAA in B and Py, S-DAMA in DMF and DAMA-MAA in B, DMF and Py, thus determined and the Alfrey-Price copolymerization constants e and Q calculated therefrom are listed in Tab. 2; they were supplemented by the reported characteristics of the copolymerization S-MAA in DMF=), and S-DAMA in Bn. For the pairs S-MAA and DAMA-MAA, the values of the copolymerization parameter r, (= r-) are higher in B than in DMF and Py, while the parameter rl (=rs or rDm) is lower in B than in DMF and Py. The parameters of the pair S-DAMA in B and DMF differ little from each other. Of the ez data which ensue from the composition of the copolymer S-MAA the positive values seem to be the real ones, while in the calculation from the composition of the

1182 J. Lokaj, D. DoskoBlovB, F. HrabBk

copolymers DAMA-MAA the positive values are higher than 1,7, and therefore, the negative e, are held for the real ones.

Along with the experimentally determined copolymerization parameters r, , r, of the pair DAMA-MAA, Tab. 2 also contains the parameters r;, ri which were calcu- lated for the same pair from the e and Q constants of DAMA and MAA determined by the copolymerization of both monomers with S in the respective solvents. The r,, r, values differ more from r; , ri than for the pair N-methyl-N-phenyl-Zaminoethyl methacrylate-MAA 17).

Copolymerization diagrams:

Using the determined (r,, r2) and calculated (r; , ra values (Tab. 2), the experi- mental and hypothetical copolymerization diagrams were drawn in Fig. 1. They

1)S-MAA - - DMF (ref. 6 )

1 A /

C)DAMA - MAA 8 (NMR) u 6 (%N) A

- _ -

+

'I

'10 f

0 015 0 45

Fig. 1. Copolymerization diagrams of pairs S-MAA, S-DAMA and DAMA-MAA in benzene (B), DMF, or pyridine (Py) calculated using the determined copolymerization parameters (-, - - - , - * -) and the e and Q constants of comonomers (+); ( 0 , A , 0): experi- mentally determined composition of the copolymer; F and f: mole fractions of the first CO- monomer of the given pair in the starting polymerization mixture and in the copolymer, respec- tively

The interaction of comonomers in the solution copolymerization. . . 1183

demonstrate that the copolymers S-MAA and DAMA-MAA are enriched with acid more in B than in DMF and Py. The diagrams of the pairs S-DAMA in B and DMF are close to each other, and their shape suggests a considerable trend towards an alternating addition of the comonomers to the polymer radical. A similar trend is indicated - albeit more weakly - by the copolymerization diagrams S-MAA in DMF and Py, while in B the copolymers of this pair are enriched with acid over the whole range of F more than in DMF and Py.

The experimental copolymerization diagrams of the pair DAMA-MAA in DMF and Py are virtually identical and are therefore represented by a single curve (Fig. 1 (d)). The shape of the curve indicates an alternating character of the copolymeriza- tion. Fig. 1 (c) shows experimental copolymerization diagrams of the pair DAMA- MAA in B, calculated with the data on the copolymer composition determined by elemental analysis and ‘H NMR. The greatest difference infof the two diagrams is 0,06 and is caused by the difficult removal of MAA from the copolymers. At F > 0,4, the diagrams possess an alternating character, while at F < 0,4 the value o f f approaches F, and the comonomers are added to the propagating chain approxi- mately according to their concentration ratio in the monomer mixture.

Differences between the experimental and hypothetical copolymerization diagrams for the pair DAMA-MAA in B, DMF and Py (Fig. 1 (c) and (d)) are greater than for the pair N-methyl-N-phenyl-2-aminoethyl methacrylate-MAA”). The hypothetical diagrams of DAMA-MAA in DMF and Py are virtually identical.

The calculated compositions fo azeotropic monomer mixtures for the pair DAMA- MAA are 0,334 for B and 0,543 for DMF and Py.

Discussion

The alternating character of experimental copolymerization diagrams of S-DAMA in B and DMF (Fig. 1 (b)) is probably a consequence of the different e constants of both comonomers and of the relatively weak effect of both solvents on these constants. If the relative reactivity of double bonds of the comonomers were only a function of their e and Q constants, the copolymerization diagram of S-MAA should be similar, because the C=C bonds of isolated DAMA and MAA molecules have a similar character. This is the case only in the copolymerization S-MAA (Fig. 1 (a)) in DMF and Py, when the mutual association of carboxylic groups is weakened by the formation of associates of MAA with DMF and Py. In these, the C=C bond of MAA probably preserves its lower electron density compared to the C=C bond of S, as suggested by the mild alternating character of the diagram. In the copolymeriza- tion S-MAA in B, r, is smaller and r, is higher than in DMF and Py (Tab. 2). This means that MAA is added to the styrene radicals as well as to its own radical more readily in B than in DMF and Py, but that the copolymerization diagram of S-MAA in B preserves the character of alternating copolymerization (r, < 1, r, < 1). Such course - as mentioned earlier17) - could be explained by the addition of the hydrogen bonded dimer of MAA to the polymer radical. Chain propagation in this case would proceed assuming preferred cross addition of the comonomers and under

1184 J. Lokaj, D. Dosk4ovfi . F. Hrabfik

condition that the number of collisions between the polymer radical and double bonds of the acid associated to a dimer is the same as if the acid were in its monomer form, but each addition of the radical to a single double bond in the dimer would be followed by a reaction between the second double bond and the polymer radical. The rate of addition of the acid to the radical would be expressed by means of an equation in which the acid concentration would be multiplied with two. The same effect can be explained by assuming that, due to the association of functional groups on the monomer and on the propagating or inactive polymer chain, the local concentration of the given comonomer near the radical centre or on the surface of the polymer phase increases2-12, 16,24-26).

The fact that R, is higher by an order of magnitude in B than in Py at low F can be explained by a decrease in kt during the aggregation of macromoleculesz*x) which occurs earlier, when more MAA is present in the monomer mixture. The question remains open if also in this case the template effect is operati~e~’.~), which, e.g., in the polymerization of methyl methacrylate on the polymeric matrix is considerably reduced after the addition of the comonomer (styrene) 29).

The alternating character of the copolymerization diagrams of the pair DAMA- MAA in DMF and Py (Fig. I (d)) can be explained by the formation of hydrogen bonded associates from the solvents, DAMA and M A A 3 3 4 9 u ) in which the electron density on the C=C bond of the acid is higher compared with the C=C bond in DAMA. So far, no data are available to show whether with DMF or Py, present in excess with respect to DAMA, the concentration of associates of MAA with solvents was higher than that of hydrogen bonded associates of MAA with DAMA, or whether, due to the effect of the polar medium in DMF and Py, the equilibrium between the individual forms of the DAMA-MAA associate was shifted towards the ionic complex18*19) over the whole range of F:

H37 CH,=C-C-0-CH,-CH Nd+ -

2- I

0 CH3 II I

cH3 IT {

CH3 I CH3 I I1 0 CH3

CH2=C-C-0-CH NO-H + @O-C-C=CH2

Unlike DMF (donor number2)*) DN = 30,9) and Py (DN = 30,1), B (DN = 0,l) is a weak electron donor, and thus also a weak competitor with DAMA in the forma- tion of acidobasic associates. For this reason, in B in the case of DAMA-MAA (Fig. 1 (c)), the acidobasic associate of the comonomers both in the molecular and ionic forms, and the comonomer in excess can be regarded as the main polymerization com-

*) The donor number is defined as the molar enthalpy value for the reaction of donor @)with SbC4 as reference acceptor in a mol/l solution of dichloroethane2).

The interaction of comonomers in the solution copolymerization. . . 1185

ponents. It is probable, at the same time, that the electron density of the C=C bond of MAA in the complex will increase c~nsiderably~~), while the C=C bond of the complex-bound DAMA is not essentially different from the C=C bond of DAMA and MAA in excess. At F > 0,5, benzene solutions of DAMA-MAA contain an associate of the comonomers and free DAMA. Different electron densities of the C=C bonds in the complex-bound MAA and in the complex-bound and free DAMA will lead to alternating MAA and DAMA basic units at the end of the propagating radical, and hence to a higher MAA content in the copolymer than in the monomer mixture (right- hand half of Fig. 1 (c)). At F < 0,5, benzene solutions of DAMA-MAA contain the associate of the comonomers and MAA in excess, partly perhaps also bound to the 1 : 1 associate of the comonomers18*19). Electron densities of the C=C bonds in the complex-bound MAA are probably higher than in MAA in excess and in the complex- bound DAMA. The radical of the complex-bound MAA will possess approximately the same reactivity towards MAA in excess and the complex-bound DAMA, and the radicals of free MAA and bound DAMA will preferentially react with the complex- bound MAA. Hence, the probability of the addition of DAMA and MAA to the polymer complex-bound MAA radical will correspond to the concentrations of the complex and of free MAA in the monomer mixture, and the diagram will approach a diagonal (left-hand half of Fig. 1 (c)).

The hypothetical copolymerization diagram of DAMA-MAA in B (Fig. l(c)) corresponds to an ideal copolymerization, because a higher relative reactivity of MAA follows from the composition of the copolymers S-MAA and S-DAMA, due to the hydrogen bonded association of carboxylic groups. On the other hand, however, the actual composition of the copolymers DAMA-MAA formed in benzene is not identical with the hypothetical copolymerization diagram, because DAMA and (MAA), were not the reacting compounds, as this was the case in the copolymeriza- tions with S. In a benzene solution of DAMA-MAA, the comonomer associates, the character of which varies with the comonomer react predominantly. The hypothetical copolymerization diagram of DAMA-MAA in DMF and Py (Fig. 1 (d)) approaches the diagonal. This means that the relative reactivities of S towards the associates of MAA with DMF and Py and towards DAMA are close to each other. At the same time, the slightly preferred addition of MAA by the two radicals should suggest that dimerization of MAA is not completely suppressed in solutions of S-MAA in DMF and Py. On the contrary, the alternating character of the determined DAMA-MAA copolymerization diagram indicates that also in solutions of DMF and Py there is a difference in electron densities on the C=C bonds of DAMA and MAA bound in associates of DAMA with MAA, or of MAA with DMF and Py.

The copolymerization diagram of the pair N-methyl-N-phenyl-2-amhoethyl meth- acrylate-MAA in B, experimentally determined earlier I*), resembles the hypothetical copolymerization diagram of DAMA-MAA in B (Fig. 1 (c)). This is obviously due to the fact that the interaction between carboxylic acids and aromatic tertiary amines is much weaker than that with aliphatic tertiary amines'*). For the same reason, differences between the experimental and hypothetical copolymerization diagrams of the pair DAMA-MAA in B are much greater than those observed for the pair N-methyl-N-phenyl-2-aminoethyl methacrylate-MAA I,).

1186 J. Lokaj, D. DoskoEilovA, F. Hrabfik

’) G. A. Ham, “Theory of Copolymerization”, in “Copolymerization”, ed. by G. A. Ham,

2, V. Gutmann, “The Donor-Acceptor Approach to Molecular Interactions”, Plenum Press,

3, R. Kerber, Makromol. Chem. 96, 30 (1966) 4, H. Herma, Faserforsch. Textiltech. 18, 328 (1967)

A. F. Nikolaev, V. M. Gal’perin, Vysokomol. Soedin., Ser. A, 9, 2469 (1967) 6, Yu. D. Semchikov, A. V. Ryabov, V. N. Kashaeva, Vysokomol. Soedin., Ser. B, 10, 57

(1 968) 7, V. Hynkovh, E. KniakovA, F. Hrabhk, Proceedings “Polymers 71”, p. 41, Scient. Tech.

Union Chem. Ind., Rakovsky Str. 108, Sofia 1971; Chem. Abstr. 81, 169947~ (1974) ’) K. Plochocka, H. J. Harwood, Polym. Prepr., Am. Chem. SOC., Div. Polym. Chem. 19,

240 (1978) 9, 0. Sosanwo, J. Lokaj, F. HrabAk, Eur. Polym. J. 18, 341 (1982)

lo) N. Slavnitskaya, Yu. D. Semchikov, A. V. Ryabov, D. N. Bort, Vysokomol. Soedin., Ser.

Chapt. 1, Interscience Publishers, John Wiley and Sons, Inc., New York 1966

New York, London 1978

A, 12, 1756 (1970) S. Ali-Miraftab, A. Chapiro, Z. Mankowski, Eur. Polym. J. 17, 259 (1981)

12) F. HrabAk, M. BezdEk, V. Hynkovh, J. SvobodovA, Makromol. Chem. 183,2675 (1982) 13) A. M. North, Polymer 4, 134 (1963) 14) J. A. Seiner, M. Litt, Macromolecules 4, 316 (1971)

K. Hayashi, P. A. Marchese, S. Munari, S. Russo, Chim. Ind. (Milan) 56, 675 (1974) 16) A. A. Kumecov, S. N. Novikov, A. N. Pravednikov, Vysokomol. Soedin., Ser. A, 22,2390

(1980) 17) M. BezdEk, V. Hynkovh, F. Hrabhk, Makromol. Chem. 184, 1967 (1983) l’) T. Duda, M. Szafran, Bull. Acad. Pol. Sci., Ser. Sci. Chim. 26, 207 (1978) 19) A. A. Samoilenko, A. I. Serebryanskaya, N. N. Shapetko, A. I. Shatenshtein, Zh. Obshch.

m, F. Hrabfik, J. Lokaj, Eur. Polym. J. 15, 701 (1978) 21) R. M. Joshi, S. G. Joshi, J. Macromol. Sci.-Chem. 5, 1329 (1971)

Khim. 50, 1387 (1980)

R. Korus, K. F. O’Driscoll, in “Polymer Handbook”, ed. by J. Brandrup, E. H. Immergut, J. Wiley, New York 1975, 2nd ed., Ch. 11, pp. 45 A. V. Ryabov, Yu. D. Semchikov, N. N. Slavnitskaya, Vysokomol. Soedin., Ser. A, 12,553 (1970) G. Burillo, A. Chapiro, Z. Mankowski, Eur. Polym. J. 18, 367 (1982)

25) G. G. Cameron, J. Cameron, Polymer 14, 107 (1973) 26) H. B. Lee, D. T. Turner, Polym. Prepr., Am. Chem. SOC., Div. Polym. Chem. 18, 539

27) D. N. Koetsier, Y. Y. Tan, G. Challa, J. Polym. Sci., Polym. Chem. Ed. 18, 1933 (1980)

29) K. F. O’Driscoll, I. Capek, J. Polym. Sci., Polym. Lett. Ed. 19, 401 (1981) M, T. A. Alfrey, Jr., C. G. Overberger, S. H. Pinner, J. Am. Chem. SOC. 75, 4221 (1953)

(1 977)

V. S. Rajan, J. Ferguson, Eur. Polym. J. 18, 633 (1982)