A n i s o t r o p y

o f

S e g m e n t s

U n i t s

o f

P o l y m e r

a n d

M o n o m e r

M o l e c u l e s

V . N . T s v e t k o v , L. N . A n d r e e v a , N . V . T s v e t k o v Institute of High Molecular Weight Compounds, Russian Academy of Sciences, St. Petersburg, Russian Federation

A. Introduction B. Tables of Anisotropy of Segments and Monomer Units of Polymer Molecules Table 1. Main-Chain Acyclic Carbon Polymers 1.1. Poly(dienes) 1.2. Poly(alkenes) 1.3. Poly(acrylic acid) and Derivatives 1.4. Poly(methacrylic acid) and Derivatives 1.5. Poly(acrylic acid) Derivatives with Mesogenic Side Groups 1.6. Poly(methacrylic acid) Derivatives with Mesogenic Side Groups 1.7. Vinyl Polymers 1.8. Poly(vinyl) Derivatives with Mesogenic Side Groups 1.9. Copolymers, Graft and Block Copolymers Table 2. Main-Chain Carbocyclic Polymers Table 3. Main-Chain Heteroatom Polymers 3.1. Poly(oxides) 3.2. Poly(esters) 3.3. Poly(amides) 3.4. Poly(peptides) and Nucleic Acids 3.5. Poly(phosphazenes) 3.6. Poly(siloxanes) Table 4. Main-Chain Heterocyclic Polymers 4.1. Poly(imides) 4.2. Poly(pyrromellitimides) 4.3. Poly(quinoxalines) 4.4. Poly(benzimidazoles), Poly(benzoxazoles) 4.5. Poly(saccharides) C. References

VII-745 Vli-746 VII-746 VII-746 VII-747 VII-747

A.

INTRODUCTION

Segmental anisotropy (a i — a2) of a chain molecule may be determined experimentally from measurements of flow birefringence in the solution of a polymer with a sufficiently high molecular weight, so that the conformation of its molecules would correspond to that of a Gaussian coil. For calculating (^ 1 — OL1) , Kuhn's equation was used (Ref. 1):

VII-748 VII-748 (Al) VII-749 VII-750 VII-751 VII-751 VII-752 VII-752 VII-752 VII-752 VII-755 VII-755 VII-755 VII-756 VII-756 VII-756 VII-756 VII-757 VII-757 VII-758 VII-760

where A r is the tangential flow stress (shearing stress), An is the observed flow birefringence of the solution, g is the velocity gradient, c and 77 are the concentration and the viscosity of the solution, respectively, [77] and [n] are intrinsic values of viscosity and flow birefringence of the solution, and 770 and n are the viscosity and the refractive index of the solvent. The value A n / A r = [n]/[rj\ may be called the shear optical coefficient. Another method of determining segmental anisotropy (which is seldom used) is through the measurement of stress birefringence in swollen polymers (74). The stress optical coefficient e = An/Ap (where Ap is the normal stress in the sample) determined experimentally is equal to AnjlAr (2), where An/Ar is also related to (a 1 - a2) * according to Eq. (Al). Data obtained by this method are marked in the table with the symbol sw. p. (swollen polymer). If the refractive indices of the polymer and the solvent are not equal, the experimental value of (OLi-Oi1) includes not only the intrinsic segmental (a\ -OL1), but also a part produced by the form effect (3,4). In this case the value a ] -OL1 may be calculated using (a 1 -OL1) and the theoretical equation for macro- and micro-form effects (3,4).

For determining a\ — Ot2, it is preferable to use the "matching" solvent in which the increment of index of the polymer, dn/dc, is equal to zero The tables give the intrinsic segmental anisotropy, a i — a 2 , obtained directly from measurements in the "matching" solvent, as well as the (a\-a2)* values including the form effect. The corresponding figures are marked with the symbol *. In some of the reviewed works in which measurements were carried out in "nonmatching" solvents, the segmental anisotropy was calculated on the basis of the theory of the form effect (3,4). In these cases the figures are marked with the symbol **. Intrinsic segmental anisotropy of the polymer chain in various solvents, even in the absence of the form effect, may differ owing to a "specific" effect of the solvent (see, e.g., poly(vinyl acetate)) (5-11). "Specific" effect may probably includes phenomena such as a change in the type of rotation of the side groups (5,6,8,12), a change in the polarizability of its bonds, and the short-range ordering of the solvent molecules (11). Principal values which effect the intrinsic segmental anisotropy of the chain are the anisotropy of the monomer unit and the equilibrium rigidity of the chain. The Kuhn segment with the length A is the measure of the equilibrium rigidity of the chain. If the chain adopts the conformation of the Gaussian coil, then we have A = (r2)/L, where L is the complete length of the extended chain and (r 2 ) is the mean square end-to-end distance. Also, a\\—a± is the difference between the polarizabilities of the monomer unit in the parallel and perpendicular directions of the chain. Values of a ^ —a^ presented in the table were calculated from

Many rigid-chain polymers have been investigated in the molecular-weight range in which their molecules exhibit a conformation intermediate between the rodlike conformation and the Gaussian coil. The best model for these polymers is the wormlike chain. Under these conditions the shear optical coefficient An/Ar varies with the molecular weight M of the polymer and is given by the equation (100) (A3) where B = (4n/45kT)(n2 4- I)1Jn, (71 - 72) is the mean value of the wormlike chain optical anisotropy, (h2) and (Zi4) are the mean square and fourth degree end-to-end distance of the wormlike chain. For the wormlike chain, the value of (71 - 7 2 ) as a function of the reduced chain length x = 2L/A is given by the equations

(A4)

According to Eqs. (A3) and (A4) the limit values of An/Ar for wormlike chains are as follows: at x —* 0, (An/Ar)0 = B(^i — 7I)JC —> 0 as for a thin rod, and at x —> 00, (An/Ar)^ x = B(a\ — Ct2) as for a kinetically flexible Gaussian coil. The dependence of An/Ar on M for the wormlike chains given by the Eqs. (A3) and (A4) may be approximated (100,101) by a linear relationship (A5) between the inverse values {An/Ar)" and M~[\

(A2) where A is the length of the monomer unit in the chain direction. For cellulose esters, a\\ —a\_ and correspondingly, a i — a 2 depend on the degrees of substitution (DS), which are also given in the table. For heterocyclic polycondensation polymers, the term "monomer unit" means the repeat unit of the polymer chain.

(A5) where MQ is the molecular weight of the repeat unit of the chain. If the experimental dependence of {An/Ar) ~ on \/M is plotted, the slope of the straight line obtained makes it possible to calculate Aa = a^ —a±, and its intercept with the ordinate gives ct\ -Qt2.

B. TABLES OF ANISOTROPY OF SEGMENTS AND MONOMER UNITS OF POLYMER MOLECULES TABLE 1. MAIN-CHAIN ACYCLIC CARBON POLYMERS Polymer

(a Il - a ;)

(fljj - a )

Solvent

xl02scm3

xl025cm3

Benzene, sw. p. Carbon tetrachloride, sw. p. sw. p. Cyclohexane, sw. p. Toluene, sw. p. /;-Xylene, sw. p.

61.3-63 53.5* 55.2* 57.3 72 86.9

Refs.

1.1. POLY(DIENES) Poly (butadiene) \A-cis

30.8 31.7* 33.9 42.6 51.4

52-54 53 54 53 53 53

TABLE 1. cont'd Polymer

Solvent

Poly(butadiene) \A-trans

Benzene sw. p. Carbon tetrachloride, sw. p. sw. p. Cyclohexane, sw. p. Toluene, sw. p. />Xylene, sw. p. a-Bromonaphthalene Carbon tetrachloride Chlorobenzene Dichloroethane cx-Methylnaphthalene Tetrachloroethylene Toluene p-Xylene Benzene Squalene, sw. p. Benzene

Poly(chloroprene)

Poly(isoprene) cis trans

1.2.

(«||

x 10 2S cm 3

71 70.4 58.1* 61.1* 57.3 81.6 101 110* 33 64 39 99 * 46 67 88 48 53.1 49

~«±)

37.4

36.3* 33.1* 48.6 60.2

30.5 31

Refs. 52 53 55 53 53 53 53 11 11 11 11 11 11 11 11 52 56 52

POLY(ALKENES)

PoIy(I-butene) atactic isotactic PoIy(I-decene) isotactic PoIy(I -dodecene) Polyethylene) PoIy(I-heptene) isotactic PoIy(I-hexadecene) isotactic Poly(l-hexene) atactic isotactic Poly(isobutene)

Poly( 1-octadecene) isotactic PoIy(I-octene) isotactic PoIy(I-pentene) isotactic Poly(diphenylpropylene) Polypropylene) atactic

isotactic Poly(l-tetradecene) isotactic

1.3.

(«-I - « i )

x 10 2 5 c m 3

Toluene Toluene Toluene Toluene Tetralin, xylene Decalin Toluene Toluene Toluene Toluene Benzene, chlorobenzene, tetrachloroethylene, m-xylene Carbon tetrachloride Decalin /7-Xylene Toluene Toluene Toluene Bromoform Benzene, xylene Carbon tetrachloride Decalin Toluene Carbon tetrachloride Toluene

33.4 25.2 -82.5 - 120 60 30 -24.5 -205 to-213 12.1 -6.5 45-59 35 30 69 -257 -39 8.0 9.3 80 45 30 30 55 30 -176 -171

13 13 13 13 14 14 13 13 13 13 11,14,15

3.5

3.5

11 14 11 13 13 13 13 16 14 17 14 13 17 13 13

POLY(ACRYLIC ACID) AND DERIVATIVES

Poly(acrylic acid) - , sodium salt Poly(H-butyl acrylate)

Poly(cetyl acrylate) Poly(cholesteryl acrylate)

Dioxane 0.0012MNacl, pH 7 Water, pH 6.1 Benzene Decalin Toluene Decalin Toluene Benzene

~-0.5** 20** -4**to-flO** - Ii -17.8 -10.1 -6.5 -141 -164 - 360

^-0.1**

18

- 1-5 -1.9 -1.1 -0.9 -6.5 -7.5 - 16

19 20 21 21 20 22 21 23

References page VII/760

TABLE 1. cont'd Polymer

Solvent

Poly(decyl acrylate)

Decalin Toluene Benzene, sw. p. Bromobenzene, sw. p. Bromoform, sw. p. Dibromoethane, sw. p. Dimethylformamide, sw. p. Benzene Toluene

Poly (ethyl acrylate)

Poly(methyl acrylate) Poly(octadecyl acrylate) Poly(octyl acrylate)

1.4.

(aH - « ± ) x 10 2S cm 3

Decalin Toluene Decalin Toluene

-74 -95 3.0 10** -37** - 1 4 ** -11** 17 16 26 - 190 -232 - 57.4 -47.9

Benzene Benzene Benzene Benzene Bromobenzene o-Toluidine Dioxane 0.1 M NaCl Benzene 0-Toluidine Dimethylformamide Ethyl alcohol Water Benzene Carbon tetrachloride Methanol 0.002 M HCl 0.012M NaCl, pH 7 0.0012 M NaCl, pH 7 Water Dibromoethane Benzene Benzene Tetrabromoethane Benzene Carbon tetrachloride o-Toluidine Bromobenzene

-14 -2.0 2.1 19.3 - 90 -230 180 * 370* - 160 — 160 1.0 - 6.0 ** -6.0** -40 - 9.7 50 * 150* 150 * 400 56 *-300 * — 77 2.0 25 -60 -47 -12.5 - 103 -10.5

(a\\ ~ « i ) x 10 2S cm 3 -3.7 -4.7 0.36 1.2** 4.5** ~ 1.7** -1.7** 2.5 1.9 3.6 - 6.6 -8.0 - 4.3 -3.6

Refs. 21 21 24 24 24 24 24 20 21 20 21 21 21 21

P O L Y ( M E T H A C R Y L I C ACID) AND DERIVATIVES

Poly(«-butyl methacrylate) atactic isotactic Poly(terf-butyl methacrylate) atactic isotactic Poly(p-te/t-butylphenyl methacrylate) Poly(p-carbethoxy-Af-phenylmethacrylamide) Poly(p-carboxyphenyl methacrylate) Poly(cetyl methacrylate) Poly(p-chloro-/V-phenylmethacrylamide) Poly(glycol methacrylate) Poly(hexyl methacrylate) Poly(methacrylic acid) -, sodium salt Poly(p-methylcarboxy-phenyl methacrylate) Poly(methyl methacrylate) atactic isotactic Poly(P-naphthyl methacrylate) Poly(octyl methacrylate) Poly(Af-phenylmethacrylamide) Poly(phenyl methacrylate)

—2.1 -0.3 0.3 3.0 - 7.5 -23 8.0* - 8.9 — 20 0.18 -1.1** -1.1** -4.6 -1.1

- 7 0.3 3.5 -8.5 -5.9 - 1.6 - 13 -1.5

25 26 20 20 22,28 40 35 35 29 40 30 30 30 31 31 32 32 33 33 34 35 38 38 4 31 31 40 4

1.5. POLY(ACRYLIC ACID) DERIVATIVES WITH MESOGENIC SIDE GROUPS

Tetrachloroethane

- 520 *

100

Tetrachloroethane

-520*

100

TABLE 1. cont'd C« H — « JL) Polymer

Solvent

x 10 2S cm 3

(flu-aj x 10 2S cm 3

Refs.

Tetrachloroethane

-630*

100

Tetrachloroethane

- 810 *

100

Tetrachloroethane

-800*

100

Tetrachloroethane

-450*

-19*

100,102

Tetrachloroethane

-510*

-21

100,102

Benzene

- 300 *

- 15 *

100,103

1.6. POLY(METHACRYLIC ACID) DERIVATIVES WITH MESOGENIC SIDE GROUPS

Carbon tetrachloride

- 445 *

- 18 *

100,105

Dimethylformamide

- 240 *

100,106

Tetrachloroethane

-500*

100

-320*

36,100

Benzene

-370*

100,107

Dioxane

- 1200*

100,106

Dimethylformamide/ toluene (1/1)

Carbon tetrachloride

- 600 *

- 40 *

100,108

Carbon tetrachloride

- 2700 *

- 110 *

100,109

Carbon tetrachloride

- 2350 *

100

References page VII/760

TABLE 1. cont'd Polymer

Copolymer with cetylmethacrylate mol% 70/30 50/50

Solvent

(«i| ~ a L) 10 2 5 cm 3

Refs.

Benzene Bromoform Chloroform Carbon tetrachloride Tetrahydrofuran Benzene/heptene (52/48), (66/34)

- 1600* -1000* - 1400* - 2700* -890* -4200*

Carbon tetrachloride Carbon tetrachloride

-1050* - 680 *

-44* - 28 *

100,93 100,93

Benzene

-3000*

-150*

100,111

Chloroform

- 4900 *

- 100 *

100,111

Carbon tetrachloride

Dioxane

Tetrachloromethane

1.7.

(«U ~ « i ) xl025cm3

-40* - 1 K)*

36 36 36 37,100 36 36

-117*

100,109

-90*

100,109

- 180* -250*

153 153

VINYL POLYMERS

Poly(acrylonitrile) PoIyO?-chlorostyrene) Poly(2,5-dichlorostyrene) Poly(3,4-dichlorostyrene) Poly(a-methylstyrene) Poly(/>methylstyrene) atactic isotactic Poly(2,5-dimethylstyrene) Poly(2-methyl-5-vinyl-/V-butylpyridinium bromide) Poly(2-methyl-5-vinyl-pyridine) Poly(2-methyl-5-vinyl-pyridinium chloride) Poly(styrene) atactic isotactic Poly(vinyl acetate)

Dimethylformamide Bromoform Bromoform Tetrabromoethane Tetrabromoethane Bromoform Bromoform Bromoform 0.01 M NaCl 0.1 M NaCl Bromoform 0.1 M HCl Bromoform Bromoform Acetone sw. p. Benzene sw. p. Bromobenzene. sw. p. Bromoform sw. p. Carbon tetrachloride sw. p. Chlorobenzene Chloroform sw. p. Cyclohexanone Dichloroethane

- 23 -230 -265 -300 -133 — ) 47 - 140 -180 - 900 * -270* - 260 - 300 * - 145 - 224 -20** _37** 4.0-5.9 5.1** 9.4** - 20 ** -18.7** - 16 -26 -25.2 14** -34.9** -24 - 17.9 -23 -36 - 39

-1.8 -35 -30 -25 -17 — 20 - 19 -25

- 29 - 18 — 23 -5.3** -5.3** 0.5 to 0.8 0.75** 1.3** -2.7** - 2.0 -3.6 1.75** -2.6** -3.0 -2.9 -4.5 - 4.9

4 41 41 15 128 42 42 41 43 43 44 45 46,41 46 7 10 6,8,9,11 10 10 7 10 9,11 6 10 11 6 9,11 10 9,11 11 11

TABLE 1.

cont'd

Polymer

Solvent Tetrabromoethane sw. p. Toluene

Poly(vinyl butyral) Poly(vinyl butyrate) Poly(vinyl chloride) Poly(vinyl cinnamate) Poly(p-vinylnaphthalene) Poly (vinyl propionate)

Poly(4-vinylpyridine) Poly(4-vinylpyridiniurn chloride) Poly(vinylpyrrolidone) Poly(vinyl stearate)

sw. p. o-Xylene sw. p. Chloroform Toluene/phenol (79/21) Benzene Carbon tetrachloride Chloroform Tetrahydrofuran Bromoform Tetrabromoethane Bromoform Benzene Carbon tetrachloride Chloroform Toluene Bromoform 0.1 M HCl 0.05 M HCl Benzyl alcohol Carbon tetrachloride

(«0-ax) xl02Scm3 -25** -33** -46.4** 10 13.5 19 9.4** 2.0 9.8** 81 173 - 8.0 - 36 -48 40 - 420 — 430 - 440 —4.4 —31 -40 1.3 -240 - 260 * -440* — 75 —130

(a\\~aL) 25 cm3

fxl0

-3.1** -6.6** 1.25 2.0 1.3** 0.25 1.4**

- 35 — 30 - 20 to - 30

-22 - 10 —4.7

Refs. 11 7 10 9,11 8 6 10 9,11 10 11,47 11,47 11,47 11,47 11,47 48 49 4 39 11,47 11,47 11,47 11,47 50 50 50 4 51

1.8. POLY(VINYL) DERIVATIVES WITH MESOGENIC SIDE GROUPS Poly[4-(4-nonyloxy-benzamido)styrene]

Benzene

-2500*

-100*

100,104

1.9. COPOLYMERS, GRAFT AND BLOCK COPOLYMERS Poly(acryl amide-comethacrylic acid ether)

R = -C 2 H 5 ;X- = - C r nmol%= 0 6 30 69 80 100 Poly(p-(4-cetoxybenzoxy)-phenyl methacrylate-co-cetyl methacrylate)

mol% 81/19 60/40 59/41 22/78 15/85 8/92 4/96

0.001 M NaCl

Water

2.5* 15 35 * 90 * 80 * 40 *

Carbon tetrachloride

157

93

-2000* -920* 540* -400* -277* -180* -16* References page VII/760

TABLE 1. cont'd Polymer

Solvent

Poly(methyl methacrylate-a>/?-r