SUPPL]~MENTO AL VOLUME XV, SERIE X N. 1, 1960 ])EL NUOVO CIMENTO 1 ° T r i m e s t r e

Crystal Structure of Isotactic Poly-alpha-Butene.

G . ~'~ATTA, P . CORRADISTI a n d I . W . B A S S I

Isti tuto di Chimica Indiistriale del Politecnico . Milano

(ricevuto il 26 Giugno 1959).

In these last years crystalline polymers of alpha-olefins were synthesized in the laboratory of Industrial Chemistry of the ~Iilan Polytechnic. ~ a n y of them, such as polypropylene and poly-alpha-butene, are expected to in- crease their importance because of the excellent physical properties they pos- sess, the low cost and the many foreseeable industrial applications. Their structure has been, therefore, the object of a broad investigation.

We shall refer, in this paper, on the results of our structure studies related to poly-alpha-butene. Preliminary results are outlined in a preceding letter to the Editor [lJ of Makromolek , u lare Chemie .

U n i t ceil. - The isotactic polymers of alpha-butene insoluble in ethyl ether

a)

b)

' ' i o ' i o

2 ~ o

Fig. t . - Powder spectra of crystalline poly-alpha-butene registered with a Geiger counter (Cu, Ka): a) modification 2; b)

modification 1.

prepared by the methods of stereo- specific catalysis of co-ordinated anionic type (TiC13~-AI(C2Hs)3) have a degree of crystallinity measured by X-ray methods [2] of the order of 60%.

Isotactic poly-alpha-butene shows two crystalline modifications [3]. One of them (modification 1), whose struc. ture is the object of this paper, appears the most stable one at room temperature; the other one (modifi- cation 2) is tha t occurring first, at the moment of crystallization, both from the melt and from solutions. The modification 2 is able to evolve in the most stable modification, at

a, m o r e or le,~,~ hig'h rt~t(,~ ~l(,('ordin~' to t:he, 1)rc('edi~l~' h i s t o r y of t h e s;lnlple :tnd to thc thel'nl~t] Ol" nle(.h~tllJ(.:/] tl'('~lrtnlcllt~ it lllldel'~'oc.~ (pries- sure, unidirectioual stretching). TI~e two form~ are character ized by n difrerent ident i ty period ~H~d, thu~, by ~ different s y m m e t r y of the chain. In Fig. 1 is shown, aS an example, the X- ray powder spectrum, registered with Geiger counter, of ~ sample of poly-a lpha-butene cooled f rom the melted s ta te

o o

. , ¢ 1:0 I =1

1040 ~ -rr lw I;~11 /

~ ~ r ?40 ,-~-vw 6~[t~' : ~ . 820 9 1 1 ~ --

900---- - -~ : 731

7~0 mWTo ~ 62~ m

~ - - l / " / 330 ,M-ww 421Jf'W r ~ / 5o~ ~t-s,stabl.

220 -~-vs 311 m

300 .~-vs 2"~ Vl

l / - - s i l l s ~ / eOB$[RV(O R[F'LCCTION (; ~*" lo t ~Lsisl-4~ ,

0 0

1=2

vw

~ w

v w

v w _

m s

m w

l : 3 ~ = 4

: silt.abs

w sisl,a bs vw

m .~w -vw

ms

fist abl .

1=5

I sisLabs.

~ t l a b $

llt.abs w

sist.al~.

Fig. 3. - Reciprocal lattice of poly-alpha-butene (interpretation of an electron diffraction spectrum of a drawn film of polymer).

without pressure a), (modification 2), and the powder spec t rum of the same specimen af ter submit t ing it, a t room tempera ture , to a pressure of 100 arm, for a few seconds b), (modification 1).

In the present s tudy, only the most s table modification will be considered. Fiber spectra have been taken in a cylindrical camera b y Cu, K ~ radiat ion.

The iden t i ty period along the axis of the chain is 6 . 5 0 ±0 .0 5 A . The photographs show numerous, sharp and, therefore, well resolved re-

flections (Fig. 2).

I t was possible to index all reflections b y the reciprocal la t t ice m e t h o d (Fig. 3), on the basis of a rhombohedra l uni t cell whose iden t i ty period a, referred to hexagonal axes, is (17.7 q -0 .1 ) • . The ( h k l ) reflections are pre- sent only when - - h + k q- l ~- 3n .

54 G. N A T T A , P . C O R R A D I N I ~ l l d I . W . B A S S I

The choice of the possible space groups, from the systematic absence of (hOl) reflections with l=-2n-+-1, is restricted to R3c and R3c groups.

The experimental density is tha t expected if 18 monomeric units are pre- sent per unit cell. The R3v space group has just 18 equivalent points in ge- neral position, whilst 36 are those foreseen for the R-3c space group. The two space groups differ one from another according to the presence or to the absence of symmetry centers.

The R-3c space group may occur only if chains, with different polar orien- tation, (antic.lined), isomorphous to eavh other [4] are able to vicariate in a statistical way around the same threefold screw axis, whereas the R3c space group is possible only if the chains are able to arrange themselves in the crystal lattice, all having the same polar orientation (isoclined).

Anyway, only chains with threefold helical symmetry are allowed to be present in the unit cell; each right-handed polymer chain is surrounded by three left-handed chains and viceversa.

The monomeric units following one to another along the threefold helix must obviously have the same sterical conformation.

We have demonstrated that a regular helix type succession in a crystalline vin.yl polymer is possible only when the polymer is isotactic [5, 6].

Structure. The shape of the main chain of the polymer can be deduced from its threefold helical symmetry and from the knowledge of accepted data, con- cerning angles and distances between carbon-carbon single bonds. I t cor- responds to a succession of bonds alternately with trans and gauche confor- mations. The gauche conformations may be either right or left handed, thus generating, following the terminology introduced by B u ~ , (AB)3 or (AC)a enantiomorphous helical chains [7]. The angle between carbon-carbon bonds of the main chain, which may be deduced directly from the value of the identi ty period c, differs remarkably from the tetrahedral value and reaches 114 °.

The position of the ethyl side group was foreseen in such a way as to satisfy the principle of staggered bonds, and in order to realize suitable Van der Waals distances between different atoms of the same chain.

On the basis of these principles the shape of the chain of poly-alpha-butene remains univocally determined and is shown in Fig. 4.

The problem of determining the way of packing of the macromolecules between themselves has been faced by us both (I) through the consideration of significantly intense (hkO) reflections and (II) taking into account the prin- ciple tha t Van der Waals contacts between neighbouring carbon atoms of different ah~.in~ should not be lower than 4 A, in accordance with the current data of the most recent literature [8].

An outstanding equatorial reflection is that observed at a Bragg distance d~--1.27A. I t corresponds, however, to the possible superposition of two

('armor be dislin~'uishe(!

direction normal to its

rc[ie(.tions, the ( l l '2 0) :|ml tim ( 7 7 0) (rues, which in a tiber diagram.

Making' a fiber undergo a stron,,, pressare in a axis (crushing it under the wt~eels of a t r amw a y car), i t was possible to achieve a fu r ther or ientat ion of the crystallites.

The a axis becomes oriented perpendicular ly bo th ¢o the direction of the fiber axis c and to the direction a long which the pressure was applied. The double or ienta t ion is so good tha t the X- ray spectrum given b y the sample resembles tha t given by a single crys- tal. Thus, i t has been possible to us to ~ssign the (7 70) indices to the outs tanding reflection with d = 1.27 A.

The (7 7 0) s t ructure factor (which has the same analyt ical expression for the possible space groups R3e or R-ge) is so high, t ha t it demands tha t all the a toms of the independent s t ruc tura l unit scat ter nearly in phase. The (7 7 0) s t ructure-factor graph is shown in Fig. 5 [9]. The molecule, keeping into con- sideration also the Van der Waals contacts with the neighbouring molecules, remains compelled to assume the position drawn in the graph itself. I t is worth noticing, a t this point, t h a t the position held in the space by the independent s t ruc tura l uni t is such t h a t the Van der Waals contacts between different mole- cules are good even if we assume tha t statistical vicarianee of up and down molecules, a round the same threefold screw axis, occurs, as needed b y the R3c space group. In fact, a f ter sui tably choo.~ing the origin of z coordinates for the independent s t ructural unit, values of Van der Waals contacts between neigh- bouring molecules, packed according to the R3e space group, are obtained, all of t hem being greater t h a n 4~k and quite similar to those realized also in the /¢3c space group (Fig. 6). For the la t te r space group

( ' R Y : ~ T A J , ~ ' ] ' l ¢ [ ' ( "} [ I~ l ,~ | ) l" I , < ( / l ' ~ ( " l ' l ( ' ] ' ( ) I , ' , ~ A I , I ' I I ' X - I ~ I T I , ; \ E ;~,~

lh

Fig. 4 . - Conformation of poly-alpha-butene ma- cromolecule in the crys-

talline state.

the mode of packing results independent of the choice of the origin along v. As shown in Fig. 7 if the space group is R3c, the ma~romolecules are iso-

d ined and each of them is surrounded by three enant iomorphous maeromole- cules and viceversa. On the other hand, should the space group be R3c (Fig. 8) each macromolecule is still surrounded by three enant iomorphous molecules and, fur thermore , reciprocally ant ic l ined macromolecules m a y vicariate in

a statistical way around each threefold screw t~xis. The foreseeable sta- tistical vieari~nee of antielined maeromolceules removes any pol~rit, y f rom

the e axis,

Fig. 5. - (7 7 o) structure factor graph of poly-alpha-butene, showing the position of the macromolecule (contours drawn at regular intervals: positive lines - - - - , zero

lines . . . . . . . . , negative lines . . . . . ).

A preliminary calculation of the s t ructure factors was performed for bo th

space groups. The agreement between calculated and observed structure-factors results

much be t te r for the centrosymmetr ical space group R3e. I t is possible to explain this result b y the assumption tha t the single crystals

of the polymer are composed of small blocks~ each of them being formed b y

reciprocally isoclined macromolecule[, and thus with a s y m m e t r y corres- ponding to the R3c space group. These blocks~ closely superposed in an anti- d ined way~ would simulate~ as far as the global diffract ion effects are con-

('I¢YHT,',,I, ~:'l'l~l'l 'rl'l I'1'; I)l" I>~i l ' '~(" l ' l ( ' I ' ( ) l , ' l ",IA)II~-I/I ' ' I ' I ' : 'NI'I ,)~

,,,,,rned, the s ta | i s l i ( ' a l s i t ua l i on

foreseeable on the basis of the

R3e spaee o'roup. A c, hoiee between the two space groups is thus ve ry difficult and would be critically de termined b y the dimensions of

the blocks. B y the signs result ing f rom the

calculat ion of the s t ruc ture factors of (h/c 0) reflections it was possible to obta in a Fourier project ion of the electron dens i ty (Fig. 9) which, though on one side confirmiag the substant ia l correctness of the as- sumed structure, on the other hand pointed out the fact t h a t the

Fig. 6. - Model showing isosterism of anticlined isomorphous macromo- leeules of poly-alpha-butene in the

crystal.

~2 ~ ) g A 2

~ _ "~>,~--; k , l . , l ~ l ,~

:' . . . . : ..... ~ ..~..:s." eAz

• . . . . . . ~-'~ :~ 1 , ~ .

......... "A2 SA2 ...... ..

........ . . . . . .:k.) L_~ . . . . . . " .......

..... ...~/.,~ ~?'....-- ........ V~z i ~hz ........

" - . . 1 1 . . o.

0

% %/~/"',~'-.% Z2 A ("~:" ," ', "Ct=(3 A ('3 .,~z v "%_ ~..~Y / 3/~z ", "~"%. 7/" 7/~z

~,,,~.-.~...~ " " " % , ", ',~ , ' . - . . . . £ " ~ ~ ", ~ ,' ..-, , . .E - ~ . . % . , " ~ /L>'==LJ B t:-)TA2 ",, // 7A2~ B ~)lt~2"x , // 1 1 ~ B L ) ~

o~ , . ',{ . ................. ~.,'_ .......................... -~__~

1Az , 1A2 s . / " " , 5 -" ........................ ?':,,i .............. :;-: ,-~- --_.f " ~ L _' _,P ,,' ~,',,. °=% _' .2 ,,, ,,,,,",, ~ 2..-~ ''~ T ~ , . , / ,, C ~ , , , / ',,

,, ,,~pW" ~ "%,, o 0

Fig. 7. -Pro jec t ion of the structure of poly-Mpha-butene on (0 01) for the/?3e space group.

. , ~ ( ; . ] N A ' I ' r r A , P . ( ' ( ) R I { A D I N I i l I l ( ] [ . I V . I / A S S 1

0 s,~ 2 ,o, .¢ 9,~ 2 / " ~ ' 0 ' ~ 9 , 4 2 ~, ~:;' ~/~2

,,,.

y,-,,, ..' :~, .. - . .~, .

{ . . . ~ . . : ~ ..;,-:~=Cie~')e.(')

S [~. ~2 '- / 7/~,..~ ^ ...~.----,..,,~ '., / ,~;,,..r--y~ .,.C.-,..A,,. ,o .~ . . . . . . . " '~z' o ~ :.j" ~ . " ~ o • . ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . . . . . . . . . . . . . . . . . . -o- . . . . . . . . . . . . . . . . . . . . . . . . . , ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . . . . . . . . . . . . . . : : ~

%.'~.%. A:~ .-#'- ." ;4~., " % . . " I i . M v . i # " .' % ',,. ~ .~ "%_ ~ . : ~ j ~ " "" .... I .. \ ..... ; ; \ ....

• .£,., \ ,, k \ :,~.... ~ .. ~¢/ ~.-:

.;.~., .7 ~ \",., . Z." ",~.

w. ~;i .... , • 0" , .-.

. • ~'--~ ~ ' ; ~ ' , ~ , - ~ ", :" x ' , . - . ' - - - ' , J ..... ' ' , - ."7,42

( ]

Fig. 8 . - Projection of the structure of poly-alpha-butene on (001) for the R-3e space group.

methy len i c carbon a t o m of the e thy l group (Ca in Fig. 10) does no t lay on the same plane on which 4 b y 4 the carbon a toms of the main chain (say for instance, as in Fig. 10, C~, C2, C1 C~) lay along the helix.

[ "",, j

< .........

f - - . . . . . . . . ) ', i . . . . . : . J . . . . . .'@ ~ # ' I t :j . . . . . . I t ~ ' ~ ' 1 i

\ , . / I

Fig. 9. - Poly-alpha-butene electron density proj ection on (0 01 ), calculated according to the R-3c space group (contours at intervals of 0.Se/i~2, the broken line is the 2e//l~ level).

( ' I ~ Y S T A I ~ S ' I ' I ~ I ' ( ' T U I ~ I , ] ~ t " I s O ' r A ( ' T I ( ' I ' t I [ , Y - A I A ' I I A - I ~ , U T | , ~ N E 5~)

In the original model, on the ( 'ontrary, the (.arbon a toms were a r ranged s tuggered on the same plane 5 by 5 ,~Fi,~,. 4).

I n fact , as it comes out f rom Fig. 10, :should one assume t h a t the C~C~C~ and C2C~C~ angles are 114 ° and t h a t the C~C2~'C3 and C.~2Cs angles cannot go down to values below the te t ra - hedral ones (109 ° 28') the discussed d i sp l acemen t can be justified a t once ,(Fig. 11).

This d isp lacement will general ly oc- Cur in each isotaet ie po lymer wi th threefold helix, g iven t h a t the C~C2C~b :and C2C~C2~ angles, Fig. 10, a long the chain , which m a y be calcula ted f r o m

24 ! t i

Fig. 10. - Model of the independent struc- tural unit of poly-alpha-butene showing .angles and distances between atoms

(C--C = 1.54 X).

Fig. l l . - Actual conformation of the poly-alpha-butene macromolecule in the crystalline state (side and end

views).

t h e observed iden t i ty periods, overcome in a n y case the t e t r ahed ra l values . A recalculat ion of the s t ruc ture factors was effected and showed a r e m a r k -

ab le i m p r o v e m e n t i n the accordance. The bes t a tomic co-ordinat~s found b y us are p lo t t ed in Tab le I , a n d the

resul ts of the calculation, including also hydrogen a toms, suppos ing the t em- p e r a t u r e fac tor to be B = 8.9 ~ are p lo t t ed in Table I I . The in t roduc t ion

(i0 G. NATTA, P. (Jt)RRA1)INI ~t~H~I I. ~V. BASSI

TABLt: I. Co-ordMates o] the atoms o] the ittdepettdetd structural ,uttit. (The atoms are marked according to Fig. 10; the hydrogen atoms index refers to the

carbon atom to which they ~re linked).

C1

C~ Ca C4

I-~ 1

I-I r

H~

H a,

HA H A , H4"

x/a y/b z/c

0.288 0.288 0.232 0.136

0.322 0.220 0.253 0.233 0.265 0.136 0.101 0.101

0.288 0.288 0.192 0.143

0.254 0.254 0.320 0.191 0.157 0.143 0.176 0.074

0.015 0.250 0.330 0.250

0.960 0.960 0.304 0.496 0.271 0.082 0.304 0.304

into the calculat ion of the cont r ibu t ion of the hydrogen a toms caused a t r u e i m p r o v e m e n t for some reflections (e.g. (330), (321), (403), (502)), whose cal- culated s t ruc ture fac tors devia ted a l i t t le f rom the observed value.

The fac t t h a t t he i m p r o v e m e n t in t roduced b y the considerat ion of hydrogen, a toms is appreciable only for low angle reflections m a y be readi ly unde r s tood r because of the ve ry low diffracting power of hydrogen a t h igh 2 vg va lues . Moreover, the i m p r o v e m e n t is expec ted to be apprec iable only when a lmos t all hydrogen a toms are in phase coincidence one wi th another . The rel iabi l i ty i ndex calculated for observed and non-observed reflections up to d = 1 , 0 .k for 0, 1, 2, 3 layer lines results to be 0.23 and is one of the bes t values, unt i l now ob ta ined , for the s t ruc ture of a polymer . The corresponding Four ier pro jec t ion of the con- t en t of the uni t cell, a l ready shown in Fig. 9, presents different m a x i m a o f relat ive weight 2 : ½ : 1 in respect of the n u m b e r of a t o m s which are t r u l y projected herein. I n Tab le I I I also the values of the s t ruc ture fac tors cal- cula ted for the R3e space group for the same independen t un i t are g iven f o r compar ison with the observed ones. According to our opinion~ the resul ts ~re less good (R : 0.32).

The s t rue tu re of po ly -a lpha-bu tene shows a r e m a r k a b l e ana logy wi th t h a t of po lys tyrene on one side and of po lypropy lene on the other .

I n any case, the presence, a t the s~me t ime, in the uni t cell of enant io- morphous molecules is ac tua ted b y means of a glide plane wi th t r ans l a t ion along e (Fig. 12). I n the case of po ly -a lpha -bu tene and polys tyrene , the c rys t a l shows also the threefold s y m m e t r y pecul iar to the chain, con t r a ry to poly*

{ ' ] ¢ ' ~ 5 ' | ' . k ] , S ' I ' R I ' t ' T I ' R } ~ ; {)l" I : < I ) T A ( " | ' I { ' i * { } I , Y : A I : t ' I I A - I ; i ' T I ' ; X I ' ; (} [

"I'AH.I.: II . ('ompelri.~olt belwee~l calcld~tled ¢~td ob,~crred ,~lrl.'lttre ]<t~.lor,~ o/ iJoly-¢tlpIict- bHiellc ¢tccordit~y Io Ih¢' 1~'3c ,~lJ<tcc <jroltl~.

The b' o w~]ues co r re spond t<) t im s q u a r e root of lhe t o t a l i l l t e n s i l y diffra,(,led by l h e ffcneral (h ]," l) l a t t i ce pbme, a f t e r effe('tint~" t he co r rec t ions for t h e usua l a n g u l a r fac tors . In o rder to t ake in(o a c c o u n t t he different m u l t i p l i c i t y of re f lec t ions , zttl t h e c a l c u l a t e d

s t r u c t u r e f ac to r s excep t the (h 00), (h h 0) a n d (h 01) ones, were m u l t i p l i e d b y %/2. T h e n u m b e r s in to b r a c k e t s are t he va lues wh ich t h e s t r u c t u r e f a c to r s of n o n - o b s e r v e d reflec- t ions shou ld a s sume if t h e i r i n t e n s i t y were one ha l f of t h e lowest o b s e r v e d one. (Cu, K ~).

h k l

1 1 0 3 0 0 2 2 0 4 1 0 3 3 0 6 0 0 5 2 0 4 4 0 7 1 0 6 3 0 5 5 0

9 0 0 8 2 0 7 4 0 6 6 0

1 0 1 0 9 3 0 8 5 0

1 2 0 0

7 7 1 0 4 0

9 6 0 1 3 1 0 1 2 3 0

8 8 0 1 1 5 0 1 0 7 0 1 5 0 0 1 4 2 0 1 3 4 0

9 9 0

1 1

2 1

2 s in

0.174 0.301 0.347 0.460 0.521 0.602 0,626 0.695 0.758 0.796 0.869 0.903 0.919 0.967 1.042 1.057 1.085 1.140 1.204

1.216

1.253 1.311 1.357 1.379 1.390 1.422 1.485 1.504 1 . 5 1 5

1.544 1.564

0.355 0.432 0~497

Ft.

- - 69 + 87 - - 1 1 0 - - 14 - - 4

+ 33 - - 24 + 1 + 33

- - 2

- - 2 0

- - 2

+ 1 + 17

- - 14 + 2

- - 22 - - 1 1

- - 8

- - 2

+ 35 + 14 - - 5 + 8

- - 1

- - 3

- - 11 + 8 + 2 - - 1 + 1

5

q-- 152 - - 39 + 32

35

Fo.

92 105 127

13 (2)

40 23 (3) 31 (3) 17 (3) (3) 18 16 (4)

21 14 (4)

28

17 (4)

< 6 (4) (4) 10

6 (4) (4) (4) (4)

175 40 22

h k l

4 2 1 - 5 1 1 4 3 1 6 1 T 5 3 1 - 6 2 1 5 4 1 7 2 1 - 8 1 1 6 4 1 - 7 3 1

9 1 8 3 1 9 2 1 7 5 1 - 8 4 1

1 0 2 i 7 6 1

9 4 1 0 3 1

8 6 ~ 9 5 1

1 2 1 i - 1 1 3 1

8 7 1 1 2 2 1 1 0 5 1 1 1 4 1

9 7 i -

1 3 2 1 2 4 1 -

2 s in v ~ Ft.

0 .580 ~ 18 0.606 -{- 67 0.654 8 0.701 2 0,741 6 0.761 0.818 0.854 0.889 0.905 0.922

0.985 33 < q - 1

1.016 + 1 1.045 1.O73 ~ 1 1.087 ~ 22 1.140 - - 5 1.155 ~ 3

÷ 9 1.181 24

14

1.205 1.242 1.254 1.278 1.301 1.325 1.337 1.347 1.369 1.413 1.424

1.434 1.466

+

+

- - 41 - - 5

+ 1 + 37 + 7

- - 5

- - 3 3

- - 22 + 6 + 2 + 1

11 - - 4

- - 1

+ 10 - - 1 ÷ 1 - - 10

÷ 9 < - k l

62 (;. NATTA, P. CORRAD1NI and I. "~V. BASSI

TABLE I I (continued).

h k l

1 4 1 1 13 3 }

9 8 1 1 6 1 2 5

1 0 2 0 2 1 3 1 4 0 3 2 5 0 4 2 5 1 4 3 5 6 7 2

5 3 6 2 2 5 4 ~ 8 0 2 7 2 2 8 1 2 6 4 2 7 3 ~

9 1

8 3 2 1 0 0 ~

9 2 2

8 4 1 1 0 2 1 0 2 2

7 6 2

I 1 1 1 0 3 ~

8 6 2

sin 0

1.477

1.497

1.516 1.536

0.481 0.512 0.540 0.594 0.618 0.642 0.688 0.710 0.730 0.771 0.809

0.845

0.863 0.914 0.930 0.946 0.978 0.993 1.020

1.066

1.094 1 . 1 0 8

1.121 1.148

1.I61 1.200 1.212 1.224

1.248

1.273 1 . 3 0 8

Ft .

- - 1

1

2 2

+ 3 1

54 20

+ 28 -4- 17 + 12 -4- 12

2 -4- 21

12 -4- 3

- - 29 + 1

I7 + 17

- - 11 - - 4

- - 2 0

- - 6

- - 9

+ 4 + 1 + 11

13 + 7 + 5 - - 1

+ 1 - - 4

10 + 9 <=4-1 + 5 - - 6 + 5

10 + 8 < + 1

- - 9

~'ao.

(6)

( 6 )

( 6 )

( 6 )

t rsh

11 26 12

8

14 (3) 17 15 (3) 22

15

12 (4) 22 (4)

< 7 (4) (4)

14

(5) (5) (5)

(5) < 8 < 8

9

(5) 10

h k l

9 5 ~ 1 2 1 2

1 1

2 2

2 2

4 1 3 3

3 3 5 2

4 4

7 1

6 3

5 5

7 4 oo;} 6 6

l O I ~ }

1 0 1

9 3

2 sin

1.319 1.350

0.731

0.787

0.843

0.878

0.944

0.991

1 . 0 3 5

1.064

1.120

1.159

1.198

1.259

1 . 2 7 t

1.295

Ft .

- - 4

3

28 39

+ 28 7

10 + 7

33 34

+ 8 9

13 + 9

2 2

< - - I + 3

i 3

+ 1

- - 1

+- 21

- - 1

+ 5

- - 5

- - 1 6

- - 1

+

+

+

+

4

21

16

3 3

1

5 7

5 6

6 1

4 5

3

Fo.

(5: (6:

not tab

not n h

25

6

< 6

< 7

19

<' ~'~~'I'+~ S T I < I ( ' I ' t . ' R I ' ] ( )F I+'<+)TA('I 'I< ' I+(kLY-AI+PIIA+I+TVI'I+~NJ ̀ ] ~i3

h k 1 2 sin v~

8 5 3 / 1.34I

8 5

11 2 1.407

7 7

- - 8

10 + 5

- - 2

+ 9 < - - 1 9

< + 1

Fo.

I0

h k 1 2 s i n t~

,04:} 10 4 °°;/

9 6

1.438

1.489

+

+ +

F~.

1

3 3 3

7 6

(5)

(5)

• -

y " ( - ) ~" -,~ -¢~ v -,,,~,--~,~/~ z

7 f " i " ~ . .

Fig. 12. - Pro jec t ion on (001) and on a p lane para l le l to t he e axis of two fac ing enan t io - morphous macromolecules .

( i ~ (~. N A T ' ] ' A ~ 1 ' . C t ) I ~ R A I ) ] S I , q l l ( l I . i V . | ~ , A S S I

propylcnc, for which it is impossible to get a good fillin~" of space in this way (Fig. 13).

I t is worth noticing tha t 1,2 isotactic po lybutad iene shows ~ s t ruc ture • closely analogous to tha t of poly-alpha-butene, differing only for the orien- t a t i o n of the lateral group and for small differences in the length of the

~2

,o/,z

~ 2

'l/t2

~ 2 %2

" / t 2 " - ~ ~ o/12

10/12 4/I l

~2 ~2

/ /~/i2 ~2 "/,2 ~.-S-~,Ol "/~ 5,;,2 2/'2i'i~E~l ~

t/~ 2 -'3/~

( ~ _ s/12 I V~

~2 712

L , i .

:Fig. 13. - Comparison between the packing realized by poly-alpha-butene and poly- propylene macromolecules in the crystals.

axis [lOJ. A similar s t ructure is shown b y po lyv iny lm~hy le the r , whose X - r a y diagram is closely similar to t ha t of poly-alpha-bute~a. May be t h a t Jn this case the molecu les are somewhat more closely assembled since the

T.x I:l,l,: 111

( ' H ' I : - I ~ l , ~ , ' l ' I ~ | ' l " l l I~1': I ~ l I > , ) ' [ ' A ( ' T I I " I ' . I I , ~ - ' ~ [ , I H I ~.-I~1 ' I ' E N I ' : ( ) 5

('Oml.tri.~ott bc lwcc , c~d~..laled a . d ob.~et'ccd .~ l r ,H ,m ' f.,'l.r.,~ 0/ I . d g - a l p h a - b , l c , c accord i , f f Io Ihc l}3c .~'p~,'c g r o , p .

(For lh, ' m(,anin~" of F,. and o l o. see Table 1I. l I= : S.2 ~t:).

1 3 2 4 3 6 5 4 7 6 5 9 8 7 6

10 9 8

12 11

7 10 9

13 12

8 11 10 15 14 13

9

1 0 O 0 2 0 1 0 3 0 O 0 2 0 4 0 1 0 3 0 5 0 O 0 2 0 4 0 6 0 1 0 3 0 5 0 O 0 2 o°} 4 0 6 0 1 0 3 0 8 0 5 0 7 0 O 0 2 0 4 0 9 0

1 1 1 i - 2 1 2 1 1 1 3 1 1 7 3 ] 2 1 4 1

F~. i ! ~o. h k 1

69 94

106 38

4 34 29

1 44

4 21

9 7

25 15

6 24 14 10

38

16 7 9 5 3

12 10 3 3 2 7

155 65 34 28 99 10

8 7

76 7

• j _ •

115 7 131 8 159 6

17 7 (2) 6 51 9 29 8 (3) 38 (3) 21 (3) (3) 25 2O (4) 26 18 (4)

35

22 (4)

< 8 < 5

(4) 13

8 (4) (4) (4) (4)

219 5O 28 19 88 (3) (4) (4) 48 (4)

I

Fo. I Fo. . . . . i . . . . . _ . . . . .

2 ] 5 1 1 53 4 ] 19 3 1 6

1 37

3 1 11 9 2 1 1 7 5 ] 3 8 4 1 26

10 2 ] : 6 7 6 1 5

11 1 1 / 9 4 l / 27

10 3 1 13 8 6 ~ 8 9 5 1 4

12 1 ~ 18 1 1 3 1 5

8 7 1 4 1 2 2 1 4 1 0 5 T 12 1 1 4 1 4

9 7 1 2

1 3 2 16

1 2 4 1 2 1 4 1 1 2 13 3 1 /

9 8 1 / 5 i161 5 1 2 5 1 2

1 0 2 62 2 0 2 26 2 1 2 35 3 1 2 18 4 0 3 16 3 2 3 12 5 0 2 2 4 2 2 22 5 1 2 13 4 3 3 21

(4) 47 (4) (4)

35

(5) (5) (5) 24 (5) (5)

29

(5) (6) (6)

< 1 1 < 7

(6) (6) 14 (6) (6)

19

(6) (6)

(6)

(6) (6)

n o t calc. 13 32 15 10 17 (3) 21 19 (3)

5 - Supplemenfo al Nuovo C~menfo.

66 ~:. NATTA. 1'. ( ' O I ( R A I ) I N I ~lIl([ I . "4 . I ' A S S I

TABLE I l l (continued).

Fo.

8 7 8 6 7 6 9 8

10 9 7 8

l l 10

7 9

l l 10

8 9

12

l ~ z Fo.

6 1 2 35

5 3 20

6 2 3 12 5 4 3 9

0 2 24 2 2 9 1 ~ 12 4 2 6 3 3 7

5 3 / 18 1 21 3 2 6 0 2 6 2 2 1 5 2 | 4 5 / 15

0 2 3 2 2 6 6 2 9

1 I1

3 2 <I 6 2 10 5 2 4 1 2 4

1 71

2

28

19

15 (4) 28 (4)

< 9 (4) (4)

18

(5) (5) (5)

< 1 0

< <

(5) 10 10

11

(5) l g (5) (6)

n o t ta lc .

n o t calc.

31

h k l Fo.

3 3 3 [ I 3 3 3J i 22

52_3 / 5 ~ 3 J 6

4 4 17

7 1 7

6 3 3 1 6 a af ~4 5 5 3 / 5 551 s 8 2 3 [ 8 2 3J 17

7 4 15

6 6 14

1 0 1 11

9 3 6

8 5 19

1 1 2 7 7 11

7 7

10 4 4

9 6 10

Fo. I k ___

8

9

< 8

< 9

24

(4)

19

(5)

l 0

(5)

(5)

13

< 1 1

(5)

(5)

allowed Van der Waals contacts between CH8 and O are expected to be lower, with regard to the correspondent contacts between methyl and methylene groups.

R E F E R E N C E S

[1] G. NA~TA, P. CORRADINI a n d I. W. BASSI: Makr. Chem., 21, 240 (1956). [2] G. NATTA, P. CORRA])I~I a n d M. CESARt: Rend. Ace. Naz. Lineei, (8), 22 11

(1957); G. NATTA a n d I . W. BASSI: u n p u b l i s h e d d a t a .

( I : " , < ' l ' X I , < ' l l t l ' ( ' r [ I H I : (hi" I ; ' - ( ) T X ( " I I ~ ' I q I I , ' X - " , I , I ' I I X I~l I I : N l : qi7

13 1 (;. NwrT:X. ]'. (',)l¢l¢,xm×I and I. \V. Bxss , : I,'e,d. .I,~'. .Y~l:. Lim. , i . 19 Is)..~-q)4

[4] In~. Tab. ~ r l~:',~'limmung con Ari,~l~H/.~h'u/,h~ren: 1, 24:L 264 (BerliN. 1,~351. [5] G. NAT'rA: l ,evture h(hl a | lhe 133rd Nat ional Mee|in:,Z,' of the American ('l,e-

mieal Sociely, S. Fram.iseo, Apri l 13-18 (1958). [6] G. NATTA and e . (~,OtCRA1)]NI: S u p p l . Nuo~'o Ci,metdo, 15, 9 (1960). p. 13, 14. [7] C. IV. B u x N : ])roe. Roy. Soc., A 180, 67 (1942); P. (~()R[tADINr and [. PAs(4uo~,-:

Rend. Acc. Naz . Lincei, 19, (8), 453 (1955). [8] It. A. STUART: Die Physik der Hochpolymeren, 1, 160 (Berlin, 1952). [9] W . L . BRAGG and H. LIPSON: Z. Krist. , 95, 323 (1936).

i l0] G. NATTA, P. CORRADINI ~nd I. W. BASSI: Rend. Ace. Naz. Lineei, 23, (8), 363 (1957).