Thermotropic liquid crystalline polymers. II. Polymers with amino acid fragments in the side chains

Thermotropic Liquid Crystalline Polymers. 11. Polymers with Amino Acid Fragments in the Side Chains V. P. SHIBAEV, R. V. TAL’ROZE, F. 1. KARAKHANOVA, and N. A. PLATE, Polymer Chemistry Department, Faculty of Chemistry, Moscow State University, Moscow, USSR

Synopsis The comblike polymers, poly(Nf-methacryloyl-N~-acyl) derivatives of L-lysine, which contain amino acid fragments and long sequences of methylene groups in the side chain, were synthesized. This article, which is based on x-ray data, differential thermal analysis, and optical microscopy, describes the structure of these polymers and their properties. I t also shows that the combination of anisodiametric side groups with a “rigid” matrix of main chains leads to a liquid crystalline structure of examined polymers.

INTRODUCTION The preceding article1 dealt with an approach, which we have adopted, to obtaining thermotropic liquid crystal polymers and copolymers chemically linking mesogenic cholesterol groups (Chol) to the side chains of comblike polymers based on polymethacryloyl-w-aminocarbonicacids: -CH2-C(CH3)-

I

CO-NH-

(CH&-C-

P

OChol

where n varies from 2 to 11. It showed, in particular, that replacement of cholesterol by other substituents such as the -H, -CH3, n-(CHd&H3, and - C H 2 - 0 arranged at the side branch ends precludes the liquid crystalline state and polymers do not exhibit liquid crystalline properties.1,2 In other words, the layered ordering that occurs in these polymers and is determined by the interaction of the side aliphatic chains is not sufficient for a liquid crystalline phase to be formed. Obviously the principal role is played by the arrangement and type of interaction of various groups and substituents in the aliphatic branches. As another step in the development of methods of producing and studying the structure and properties of polymer liquid crystalline systems and in an attempt to reveal the regularities and conditions leading to a liquid crystalline state in comblike polymers that contain functional groups in the side chains we have synthesized poly(N‘-methacryloyl-Na-acyl)derivatives of L-lysine (PML-n).* These comblike polymers contain amino acid fragments and long sequences of methyiene groups in the side chain of the following general formula: * n is the number of carbons atoms in the n-alkyl group. Journal of Polymer Science: Polymer Chemistry Edition, Vol. 17, 1671-1684 (1979) 01979 John Wiley & Sons, Inc. 0360-6376/79/0017- 1671$01.OO

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SHIBAEV ET AL. CH, -CH2-

I

C-

I CO-NH--(CH,),-CH

COOH

I

where R = n-C,HI5, n-C9H19, n-C,,H,,,

-NH-COn-C,,H,,,

R, and n-C,,H,,.

Earlier we published preliminary data on the liquid crystalline structure of some homopolymers of the foregoing homologous series of polymer^.^,^ Presented in this article are detailed results of the synthesis and study of the structure and properties of monomers (ML-n) and polymers of N'-methacryloyl-N"-acyl derivatives of L-lysine with different alkyl radical length.

EXPERIMENTAL MATERIALS Studies of L-lysine hydrochloride manufactured by Reanal were conducted and commercial grade thionyl chloride, whose boiling temperature interval of the collected fraction was 75-8OoC, ng = 1.5326, was distilled. Aliphatic acids, namely, caprylic, capric, palmitic, and stearic acids of pure grade and behenic acid manufactured by Schuchardt, were used without additional purification. Chlorides of aliphatic acids were obtained by heating a mixture containing 0.1M of a corresponding acid and 0.12-0.15M of freshly distilled thionyl chloride in a water bath for 3-4 hr. Subsequent separation of the products resulted. SYNTHESIS OF MONOMERS N'-methacryloyl-Na-acyl derivatives of L-lysine (ML-n) were obtained as follows:

7%

CH,=COCl

[ NH,-(CH,),-CH(NH,)-CCOO],CU

(I)

H S

[ HLC=C(CH,,)-CO-NH-(CH,)4-CH(NH,)-COO~Cu

-

(11)

RCOCl

CH,=CtCHJ-CO-NH-(CH2),-CH(NH,)COOH (111)

CH~=C(CH,J-CO-NH-(CH~)~-CH-NH-CO-R

I

COOH where R = n-C7Hlrr n-C,H,,,

(N) n-C,,H,,, n-C,,H,,,

and n-C,,H,,.

( ML-n)

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The cupric complex of L-lysine (I) was obtained by the method described in ref. 5; that is, by heating equimolar amounts of L-lysine hydrochloride and cupric subcarbonate in an aqueous solution for 2 hr. The solution was then filtered and the product was precipitated with dioxane. L-lysine copper complex (I) was acylated according to ref. 6. Drops of the three- to fourfold excess of chloride of methacrylic acid in absolute ethyl ether were slowly added to a 10%aqueous solution (I) cooled to 4°C. The pH value of the reaction mixture was maintained equal to 8-9 by adding a 2N solution of NaOH. The solution was then slowly brought to room temperature and the precipitate was separated (11),thoroughly washed with water to remove the chlorine ions completely, and dried in uacuo. N*-acyl derivatives of L-lysine (111) were obtained from (11) by flushing the suspension with hydrogen sulfide (111)in a water-methanol mixture for 3-4 hr.7 The black precipitate that resulted was filtered and the clear solution was evaporated on a rotary evaporator. The products obtained were dried in uacuo.

N* -methacryloyl-Na-acyl derivatives of L-lysine (ML-n) were obtained as follows: 0.05M of chloride of a corresponding acid in absolute ethyl ether was added in drops to a water-alkali solution of 0.01M of (111). The reaction was, conducted with vigorous stirring at a temperature no higher than 35°C; pH 8-9 was maintained by constantly adding a 2N solution of sodium hydroxide. After the reaction was over the mixture was acidulated with hydrochloric acid to pH 1.0-1.5. At the same time, when chlorides of caprylic and capric acids were used, the mixture was separated into two layers, whereas in chlorides of palmitic, stearic, and behenic acid a white precipitate settled out. The resulting layer or precipitate was washed, first with water to remove the chlorine ions completely, then with warm ether to remove the aliphatic acids produced in the hydrolysis of their chlorides. It should be noted that the process of obtaining compounds ML-7 and ML-9 with simultaneous formation of monomers is accompanied by polymerization, which is the reason why it is almost impossible to separate these monomers in their pure form. In addition, for comparative structural analysis of the ML-17 monomer and the corresponding homopolymer, a hydrogenated monomer, namely, Ne-isobutyroyl-N"-stearoyl-L-lysine (IBL-171,was synthesized by interaction between the L-lysine copper complex (I) and isobutyroylchloride. All intermediate and end products of synthesis (I-IV), as well as IBL-17, were separated and identified by elemental analysis and infrared (IR) spectro~copy.~,~ TABLE I Elemental Analyses of Polymers of PML-n Found

Calculated

(%)

(%)

Polymer

C

H

N

C

H

N

PML-7 PML-9 PML-15 PML-17

62.87 64.67 67.98 69.54

9.19 9.48 10.87 10.73

7.71 n.49 5.70 6.02

63.53 65.21 68.24 70.00

9.41 9.78 10.55 10.89

8.23 7.60 5.92 5.85

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SHIBAEV ET AL.

POLYMERIZATION PROCEDURE Samples of PML-n were obtained by radical polymerization of the corresponding monomers in chloroform a t 75OC in an inert atmosphere for 5-6 hr with benzoyl peroxide as the initiator. The results of elemental analysis of some of the polymers obtained are given in Table I.

METHYLATION OF MONOMERS AND POLYMERS To change the chemical nature of the polar groups and examine the effect of this change on the processes of structure formation, monomers (ML-n) and polymers (PML-n) were methylated with diazomethane, by which, in accordance with the following reaction, appropriate methylated derivatives, MML-n and PMML-n, were obtained:

CH 3

I

CH,=C-CO-NH-(CH,),-CH

/

NH-CO-R

\ CmY,

(MML-n) where R = C, ,H,, and C, 7H35.

MEASUREMENTS The structure of monomers and polymers was studied by x-ray technique with CuK,, radiation. X-ray patterns were obtained with a URS-55 apparatus and a special setup based on a Rigaku Denki microfocus tube that permits recording of x-ray diffraction patterns at both wide and small anglesg The x-ray patterns were converted to an optical image by an electron optical converter and photographed. Phase transitions were examined by differential thermal analysis (DTA) with a Derivatograph apparatus. Optical studies of structural changes in monomers and polymers were conducted with a MIN-8 optical polarizing microscope equipped with a hot stage. Photos were taken with a Zenit-3M camera mounted on the microscope tube by a micro attachment. RESULTS AND DISCUSSION Structure and Properties of Long-Chain Monomers The synthesized homologs of Nf-methacryloyl-N"-acyl derivatives of L-lysine (ML-n) are low molecular analogs of respective comblike polymers, which makes it essential to study the structure of these monomers as systems modeling the side-group orientation ordering of the PML-n series.

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First of all it should be pointed out that all monomers of the ML-n series are easily crystallizable, but the type of crystalline cell depends on the conditions of crystallization. Table I1 shows the values of interplanar spacings d which correspond to the most intensive x-ray maxima of monomer specimens obtained from their solutions in chloroform. It follows from Table I1 that all ML-n samples are characterized by close values of interplanar spacings in the wide scattering angle (spacings d4-d6). Comparison of the obtained values of d 4 - d ~ with published data for crystalline n-paraffins that contain an odd number of carbonslOJ1suggests that crystallization of ML-n monomers from solutions occurs in a combination-type lattice which includes triclinic and rhombic forms (modification I). Crystallization of ML-17 and ML-21 monomers from a melt results (see Table 11) in a different crystalline modification that corresponds to hexagonal packing of molecules (modification 11). Comparison of long spacings d l for monomers of the ML-n series in modifications I and I1 with a theoretically calculated molecule length has made it possible to establish their one-layer packing; that is, in monomers crystallized from a solution one-layer packing of molecules in the crystal prevails with an oblique position of molecules in the layers ( amodification).12J3 Crystallization of polymers from the melt leads to the straightening of molecules in a hexagonal cell, which is confirmed by the values of cll which coincide with the calculated molecule length. In this case the arrangement of molecules in layers corresponds to modification.12J3 An increase in the length of the alkyl radical brings about a decrease in the melting point in a series of examined monomers (Table 11). This regularity seems to be inconsistent with the published data,14according to which the melting point increases with the number of carbons in a homologous series of n-paraffins and their derivatives. However, considering that the presence in ML-n homologs of such polar groups as -CO-NHand -COOH makes a major contribution to the energy of intermolecular interaction, we can account for the above-mentioned regularity by a decrease in this interaction as the length of the aliphatic substituent increases. It should be noted that a relationship between the melting point and n , similar to that found by us, was observed15 for the series of N-na1kylamides. TABLE I1 Interplanar Spacings and Melting Temperatures of ML-n and MML-n Monomers Modification I Interplanar spacings

Modification I1 Interplanar spacings

(A) di dz d3 d4 d5 ds Monomer f 1 f 0.3 f 0.1 f 0.05 f 0.05 i 0.04 ML-13 ML-15 ML-17 ML-21 MML-15 a

20 23 27 30 23

11.1 12.3 13.1 14.9 12.3

... 6.2 6.7

... 6.4

4.67 4.85 4.67 4.79 4.80

4.23 4.25 4.27 4.27 4.25

3.78 3.75 3.78 3.80 3.78

T, ("C) fl

114 106 608and90b 6EPand 74b

(A) di dz d3 d4 f 1 f 0.3 f 0.3 f 0.04

36 38

Temperature a t which crystals melt into an optically anisotropic liquid. Temperature of transition of the anisotropic melt to a n isotropic one.

13.3 14.5

8.5 8.4

4.19 4.19

SHIBAEV ET AL.

1676

At the same time an increase in the length of the aliphatic part of molecules results in specific properties exhibited by monomers in this series. If crystalline ML-15 and ML-17 are transforming an isotropic liquid a t a temperature above the melting point, ML-21 melts in a number of stages. The thermogram of ML-21 reveals two endothermic transitions between 60 and 90°C (Fig. 1,curve 1). The first peak corresponds to the melting of crystals which yield an opalescent fluid that, a t a temperature above 90°C, becomes a clear isotropic melt. The calculated value of the enthalpy of fusion ( A H f )for ML-21 a t the first transition is equal to 22 cal/g; the enthalpy of fusion a t the second transition is insignificant, being equal to 4-5% of AH a t the first transition. The results of optical polarization microscopy indicate that in the temperature range of 60-90°C ML-21 behaves like a bright, colorful specimen which demonstrates a small, birefringent spherulite pattern [Fig. 2(a)]. The x-ray pattern of ML-21 in this temperature range has two diffraction maxima: an amorphous halo in the 4.6-4.8-w region and a small-angle maximum that corresponds to the molecule length that disappears a t temperatures above 90°C [Fig. 2(a) and (b)]. Thus the x-ray analysis, DTA, and optical microscopy data suggest that the ML-21 monomer exhibits liquid crystalline properties in this temperature range. Comparative structural analysis of monomers of the ML-n series has shown that liquid crystalline properties are exhibited by compounds of this series only at a definite length (n = 21) of the aliphatic part of the molecule. In other words, it can be assumed that a major role in realizing the liquid crystalline state is played by the interaction energy ratio in the polar and nonpolar parts of the molecule. If this assumption holds true, chemical modification of the polar group or “head” of a monomer, which does not form a liquid crystalline phase, could result in the liquid crystalline state formation. To verify this assumption we synthesized two compound groups. First, by methylation of one of the monomers (ML-15) we transformed carboxyl groups to ester groups with the result that the role of hydrogen bonds in

65

- T% 50

60

70

80

90

f80

UO

Fig. 1. Thermograms of ML-21 (l),ML-15 (21, and IBL-17 (3).

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Fig. 2. Optical microphotograph of the mohomer ML-21 (crossed polarizers) a t 70°C (a), x-ray patterns of the same sample a t wide (b), and small (c) angles obtained a t 80°C with the aid of an electron optical converter.

intermolecular interactions was reduced. As a consequence the melting point of the monomer was also reduced (from 114°C for ML-15 to 68OC for MML-15, Table II), and the liquid crystalline state became possible in a smaller number of methylene groups than for ML-21. This was corroborated by the presence of two endothermal transitions at 68 and 74OC on the thermogram of MML-15 (Fig. 1, curve 2) and by the optical anisotropy that appeared in this temperature range [Fig. 3(a)]. Second, the polar “head” was chemically modified by synthesizing a low molecular analog of a polymer, N‘-isobutyroyl-N*-stearoyl-L-lysine (IBL-17), which differed from the ML-17 monomer by the absence of a double bond. In this case as well IBL-17 exhibited liquid crystalline properties in the 65-98°C range. Figure 1 (curve 3) represents a thermogram of IBL-17 and Figure 3(b) shows its microphotograph. Thus examination of the structure of monomers of the ML-n series has revealed that some monomers and their derivatives manifest liquid crystalline properties. The possibility of realizing a liquid crystalline state in the examined compounds is determined by the length of the aliphatic portion and the energy ratio of dipole and van der Waals interactions of molecules.

Structure and Properties of Poly(N‘-Methacryloyl-Na-Acyl) Derivatives of L-Lysine In contrast to the series of comblike polymers examined earlier, namely, poly(n-a1kylacrylate)s(PA-n) and poly(n-alkylmethacry1ate)s (PMA-n),16which

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SHIBAEV E T AL.

Fig. 3. Optical microphotographs of MML-15 at 7OoC (a) and IBL-17 at 75OC (b) (crossed polarizers).

crystallizes under all conditions, is the phase state of polymers of the PML-n series, which with side-chain lengths are 10-12 carbons or more depends to a great extent on the conditions of treatment. If PML-7, PML-9, and PML-13 are amorphous polymers, regardless of the conditions of crystallization, and, according to x-ray analysis data, feature only layered packing of the side chains,s polymers of the same series with longer branches can be obtained in an amorphous or crystalline state. Table I11 lists values of interplanar spacings for polymers of the PML-n series, calculated from x-ray patterns. The diffraction maxima in wide scattering angles (d4-ds) are indicative of crystallization of comblike PMLs due to packing the methylene groups in the hexagonal cell, characteristic of PA-n and PMA-n.16 To obtain crystalline PML-n with side-chain lengths n = 15,17, however, certain crystallization conditions are required. Removal of the solvent (e.g., chloroform) from polymer solutions by evaporation results in amorphous polymer films. Crystallization requires solvent-precipitant systems. The precipitants, according to experimental evidence, are acetone and methanol for PML-17 and trifluoroacetic acid (TFAA) for PML-15. This particular feature of polymers of the PML-n series is probably the result of formation by amide and carboxyl

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TABLE 111 Interplanar Spacings, Melting Temperature, and Enthalpies of Fusion of Comblike PML-n and PMML-n Polymers Interplanar spacings

(A)

T,

d2

d3

d4

d5

d6

Polymer

di f1

f 0.5

f 0.5

f 0.04

f 0.02

f 0.02

PML-15 PML-17 PML-21 PMML-17 PMML-21

34 37 42 38 42

...

...

18.6 21.4 19.0 21.3

12.6 14.2 12.8 13.7

4.19 4.19 4.16 4.19 4.17

2.43 2.41 2.40 2.43 2.40

2.08 2.08 2.08 2.08

...

("C) fl

Uf (cal/g)

32 34 56 46 66

... 5.0 11.8 10.0

...

groups of intra- and intermolecular hydrogen bonds, which are responsible for the rigidity of the attachment bridge of a side chain to the main chain and create steric hindrances for packing the side branches. Solvents like methanol or TFAA take an active part in the formation of hydrogen bonds with macromolecules, whereby the number of hydrogen bonds in intermolecular interactions decreases, thus leading to crystallization of polymers. In this case, however, the values of AH, (Table 111)are small and, as calculations show, the average number of crystallizing CH2 groups is only 2-3 CH2 groups for PML-17, that is, twice as small as that of the number of crystallizing methylene groups of PMA-n with the same length of side aliphatic chain. Thus comblike polymers with functional groups in the side chains crystallize with hexagonal packing of the methylene chains, but because of the conformational distortions introduced into this packing by amide and carboxyl groups the structure of PML-n polymers is characterized by a considerable degree of imperfection. Nevertheless, all crystalline polymers of the PML-n series, as well as their methylated analogs, PMML-n, feature layered ordering, which is indicated by the presence of a few small-angle x-ray maxima on their x-ray patterns (Table 111). The value of long spacing d l is related to the length of the side chain of the polymers examined, and the presence of small-angle x-ray maxima d:! and d ~ , which are the second and third orders of d are indicative of one-layer packing of the side chains of PML-n macromolecules. The fact that the values of interplanar spacings for PML-n and methylated PMML-n polymers coincide permits an assumption of the identity of the crystal structure of these polymers. Analysis of small-angle x-ray texture diagrams of oriented PMML-r2 polymers suggests that their side chains extend at right angles to the main chain axis (Fig.

4). In spite of the identical packing of macromolecules in the PML-n and PMML-n polymers (see Table 111),substitution of ester groups for carboxylic is conducive to a smaller fraction of intra- and intermolecular hydrogen bonds, which facilitates crystallization of the methylene chains, and is corroborated by a slight increase in the melting point as well as an increase in AHf in the transition from polymers of the PML-n series to PMML-n polymers (Table 111). Particular attention should be paid to the fact that melting and crystallization of the aliphatic side branches of PML-n take place a t temperatures below the glass temperature of the main chains of their macromolecules,which corresponds

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SHIBAEV ET AL.

Fig. 4. Small-angle x-ray diagrams of an oriented PMML-21 (the primary beam is normal to the fiber axis).

to a temperature range of 90-100°C.8 Figure 5, which represents the results of DTA and refractometry, vividly illustrates the phase transition in PML-17, which corresponds to the melting of crystallites formed by the side chains of macromolecules. X-ray analysis data also demonstrate that the polymer becomes amorphous a t temperatures above the melting point. The crystal x-ray maximum at 4.19 A is replaced by diffuse scattering in the 4.6-4.8-A region, although the small-angle reflection d l remains, even above the melting point, up to the temperature of chemical decomposition of the polymer. Hence the combination of two types of structural unit in the macromolecules of comblike PML-n polymers results in independent behavior between side and main chains. In this case the hydrogen bonds are responsible for the rigidity of the main chains and elevated glass temperatures of the polymers, whereas the van der Waals interaction of the methylene branches ensures crystallization of the side groups. At temperatures exceeding the melting point of the branches (i.e., in what can be regarded as melts) polymers of the PML-n series are characterized by an ordered structure. However, unlike the previously examined melts of PA-n, PMA-n, etc., also characterized by an ordered arrangement of branches,16 the high degree of ordering in the “melts” of amorphous polymers of the PML-n series (at n = 15, 17,21) is manifested by unusual optical properties.

1.56‘

L5P 4.522-

1.50.

AT

I

4.48

.I I

eb L

4b T60 80 T

Y

Fig. 5. Refraction index versus temperature (1)and thermogram (2) of a PML-17 sample.

THERMOTROPIC LIQUID CRYSTALLINE POLYMERS. I1

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Optical Properties Examination of films of crystalline PML-17 and PML-21 between crossed polarizers has revealed a crystalline structure typical of crystallizable comblike polymers of the PA-n and PMA-n series16 (Fig. 6 ) . Of particular interest is a study of these samples at a temperature above their melting points. Figures 7(a) and (b) represent optical microphotographs of PML-17 and PML-21 films taken a t temperatures much higher than their melting points. As can be seen in Figure 7, these polymers are characterized by the presence of a peculiar “feathered,” optically anisotropic structure. A similar optical picture is observed when the polymer samples are cooled and, without being crystallized, pass to a glass state. It should be pointed out that despite the presence of these structural formations their x-ray patterns resemble those of amorphous polymers. There is a broad diffuse maximum in wide scattering angles and an intensive small-angle maximum. What, then, is responsible for the optical anisotropy in amorphous films of the examined comblike polymers? In the foregoing we have considered the possible causes of liquid crystalline properties in monomers and some of their derivatives that contain anisodiametric molecules with functional groups. In polymers of the PML-n series there is an ensemble of long-chain molecules united by the backbone chain. It can be assumed that the packing of long side chains in a rigid polymer matrix formed by the main chains of macromolecules is responsible for the liquid crystalline structure that occurs in a solid polymer. In this case optical anisotropy prevails while the main chains are sufficiently strongly linked; that is, in the glass and viscoelastic state up to the temperature of their chemical decomposition. For polymers of the PMML-n series, characterized by lower glass temperatures, the temperature region of disappearing birefringence is 125-135°C; that is, within the limits of the fluid state of PMML-17 and PMML-21. Obviously, when a polymer passes to a fluid state, the intermolecular interaction becomes so weak that the liquid crystalline structure is destroyed and the optical anisotropy disappears. These results provide additional support for the important

Fig. 6. Optical microphotograph of a PML-17 crystal film a t 25OC (crossed polarizers).

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SHIBAEV ET AL.

Fig. 7. Optical microphotographs of PML-17 (a) and PML-21 (b) films a t 90°C (crossed polarizers).

Fig. 8. Optical microphotograph of a PML-21 film obtained from a polymer solution in a chloroform-TFAA mixture.

role of the interaction of cholesterol groups in the earlier cholesterol-containing polymers and copolymers in which the liquid crystalline structure exists in the fluid state as well. The appearance of optical anisotropy in films of PML-n and PMML-n depends, to a large measure, on the method of treatment of the polymers; for example, polymer films obtained by evaporation of the solvents (e.g., chloroform) from their solutions remain optically isotropic over the entire temperature range up to the chemical decomposition temperature. If, on the other hand, films are

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cast from a solution with the addition of precipitants (CH30H, TFAA), they are optically anisotropic a t temperatures below glass temperature and in the viscoelastic state (Fig. 8). Evidently, here, as in monomers, the interaction energy ratio in the polar and nonpolar portions of a molecule is predominant. Compounds such as CH3OH and TFAA, because of their ability to form hydrogen bonds, can link specifically with the polar parts of a macromolecule, thereby acting as precipitants for the polymer as a whole. Thus specific solvation affects the energy of intra- and intermolecular interaction and makes it possible for the liquid crystalline state to occur. It seems that the introduction of such solvents as TFAA or CH3OH prevents the formation of intermolecular hydrogen bonds that disturb the intramolecular ordering of side chains and is conducive to the formation of anisotropic structures. A detailed analysis of the possibilities of formation of anisotropic structures responsible for a liquid crystalline order in polymers with side anisodiametric groups is made in ref. 17.

CONCLUSIONS Thus polymers of the PML-n and PMML-n series are typical representatives of the class of comblike polymers that features a specific structure determined by the combination of two types of structural unit in a single macromolecule.16 At the same time, the pronounced diphilic nature of the macromolecules of these polymers is the main reason why such systems occupy a particular place among comblike polymers. The existence of two types of interaction, namely, hydrogen bonds, between functional groups, as well as dispersion forces between methylene branches, results in microsegregation in PML-n and PMML-n homopolymers. As a consequence regions that show a tendency to molecular rearrangements and phase transitions typical of low molecular liquid crystals are formed. These regions result from the ordering of side anisodiametric groups that tend to form liquid crystals, whereas stabilization of the structure is due to its being formed by a matrix of “rigid” main chains. Because the glass temperatures of polymers exceed the melting points of the regions formed by side chains, the processes of crystallization and melting occur in the microregions inside a glasslike matrix that permits molecular rearrangements only within the limits of these regions. This structure exists in a broad temperature range above the melting point of the crystallites formed by side chains. In the same temperature range the entire system is characterized by optical anisotropy that manifests itself as birefringent regions, which suggests that we are dealing with a liquid crystalline state of the polymers examined.

References 1. V. P. Shibaev, Ya. S. Freidzon, and N. A. Plat&,J . Polym. Sci.Polym. Chem. Ed., 17, 1655 (1979). 2. V. P . Shibaev, Ya. S. Freidzon, and N. A. PlatB, Vysokomol. Soedin., in press. 3. F. I. Karakhanova, V. P. Shibaev, and N. A. Plat&,Uzb. Khim. Zh., No. 6,56 (1974). 4. V. P. Shibaev, R. V. Tal‘roze, F. I. Karakhanova, A. V. Kharitonov,and N. A. Plat& Dokl. Akad. Nauk SSSR, 225,632 (1975). 5. M. Bergmann, L. Zervas, and W. F. Ross, J . Biol. Chem., 111,245 (1935). 6. K. Schloegel and H. Fabitschoewitz, Monatsh. Chem., 84,937 (1953). 7. H. Morawetz and H. Ladenheim, J. Phys. Chem., 60,1357 (1957). 8. F. I. Karakhanova, thesis, 1975.

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9. M. I. Butalov, Ya. V. Genin, V. I. Gerasimov, A. M. Dorfman, and D. Ya. Tsvankin, Prib. Tekh. Eksp., 1,199 (1972). 10. A. Mueller, J. Chem. SOC.,2043 (1923). 11. D. Lutz and Z. Witnauer, J. Polym. Sci., 23,31 (1964). 12. A. Mueller, J. Chem. SOC.,123,3153 (1923). 13. A. I. Kitaigorodsky, Organicheskaya Kristallokhimiya, Acad. Sci. USSR Publishing House, Moscow, 1955. 14. T. Malkin, in Progress in the Chemistry of Fats and Lipids, London, 1952, Vol. 1. 15. I. A. Turner and E. C. Linghafer, Acta Crystallogr., 8,549 (1955). 16. N. A. Plat6 and V. P. Shibaev, J . Polym. Sci. Macromol. Rev., 8,117 (1974). 17. V. P. Shibaev and N. A. Plat6, Vysokomol. Soedin. Ser. A, 19,923 (1977).

Received October 31,1977 Revised December 28,1977

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