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11
On the Influence of Side Chains in Molecules of Liquid..
Polymethyislioxanes on.their.Properties,H A.A.Zhdanov,
Andrianov, T.S.Vaksheeva, N.A.Polikanin and M.M.Levitskiy,
Plastic Materials, (No. 5) 19 (1964) -
The properties of polymethylphenylsiloxanes are usually .
dependent on the number of phenyl radicals in the polymer
chains (1)(2). The influence of position in these polymercci
chains, of the attached phenyl radicals and their side chains /
on the properties of the polyorganosiloxanes has, so far not be;en.
examined, even in the latest reports. There remains obscure
the question of what determines the properties of these polymers.,,
The position in the polymeric chains of the attached phenyl.
radicals or the overall ratio of 01q6Rit5 is shown (reflected); in
the properties ofthe.polymethylpheny snoxanes, with certain
definite ratios of CH3/C6H5 and closely paralleling molecular
weights- one chain bunt up Of dimethyl- and methylphenysiloxy
units and another of dimethyl- and diphenylsiloxy units.,."
The answer to this question can be found in the synthesis of,
appropriate polymers and a comparison of their properties which vas
the object of this work.
_ .
1. Polymers with regular ratios of dimethyl- and .methYlphenyl-
siloxy units were prepared by the reaction of disodium derivatives
of organosilanois and diorganodichlorosilanes which set up -
elemental chains by union (of the silanes) with loss of ONat
terminated by trimethylchlorosilane (3)(4).
2. Polymers, not having regulated chain composition, were
prepared by the hydrolytic condensation of a mixture of
dimethyldichlorosilane, methylphenyidichlorosilane and
trimethylchlorosilane in acid at about 500 to 600. O. with subsequent
action of 90% H2SO4. By this method. there was synthesized a
group of polymers of different relationships of methylphenyl- aad
dimethylsiloxy groups giving a mixture of homopolymers of average --
ratio 0H4(06H5 as, appropriate to the task in hand (5)(6).
Polymers not so regulated as to chains of dimethyl- and.diphenyisiloxy--
units were prepared by the hydrolytic condensation of dimethyl-
dichlorosilane, diphenyldichlorosilane and trimethylchlorosilane
with H2504 at 1000 C. with subsequent chain-grouping by the
action of 90% H2504.
STAT
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characteristics-of the Polymers
'No.c/14NA Mol Wt n20 Yield, cc Temp.of Formula of
200 1000 200? C4t,gea1ing Product
-
? ? ?
- -
18
2;32
1712
1;4980
?
398.2
36;62
12:20
..390
I n = 2 5c 5*, m
I
5c4
17
6,80
1988
1,4600
65.2
13140
4,45
5r 6
2
x7
15
9.80
2096
/.4482
63:0
16.50
6.00
.8,80
lx .4
x5
19
1:83
1905
1.5231
462:5
57.30
14.20
..320
4 x 3
x2
'
1
2,52
1750
15051
285.6
27.78
12:17
II n = 10, m
5
2
6. 69
2119
1.4613
96.4
18.56
9.12
-680
6
12
7
9.26
2185
14500
66.4
15.97
5.44
-910
4
16
6
1:88
1915
1.5240
551.4
39.06
11,24
:24 .
3
1?
2:80
1659
1:5051
590:0
45.27
10.5
,?,.337c)
III n = 4, m= 9=
13
6,32
2018
1.4671
/57,6
26.78
7.52
-67 0
3 15
11
9.68
2162
1.4482
98.1
18.26
6.84
2 18
10
1,86
1907
1.5215
1337.0
62.34
11.76
-200
6 9
Formula I
Formula II-
Formula III
H3
(C113)3Si0 ( 10)
6H5
(CH3)3S10 (
8-)
(CH3)3S10-
6H5
H3
10)
H3
OH3
1.0)0i(OH3)3
H3
6H5
10)n
6H5
H3
10;17ES1(CH3)3
6HS
H3
1.0 m-Si(OH3)3
H3
TRANSLATOR'S NOTE: The chief value of these data, with the verbal
explanations following (of somewhat confusing value) lies in their
relationship to brittle points or congealing points. PAS, in
terms, of AmerioanIF temperature readings, these become: ,
Sample No. 18
17
15
19
-38.20p
-99.40
-126.40
-25.60
1
-40:09
12
-34:60
2
-90,40
13
.-8p.60
7
-131.80
11
-115.60
6
-11.20
lp
-4.00
Any of the above values below -100? F are of considerable interest.
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. dharaoteristiopolymers-were-isoIated from the mixtures by
distillation at 1.mm-2 mm and at temperatures upto 2400, as shown
in the tables. The formulae of these polymers were assigned on
the basis of anaylses._ - - -
Results of the Study of the Properties of Liquid
Polymethylphenylsiloxanes
A study and comparison follow of the detailed properties of the
polymers. -" -
1. Evaporation experiments (1 .g.) of a thin layer (0.5 mm) at
2500 and 300? O. in air..
?
As shown in Figure 1, it will be seen that evgporation of the
pblymers-is practically ,constant anddoes-not depend on a regular
chain Structure but only on the sum.total-of a number of methyl
dnd phenyl radicals. - kcertain.rise in evaporation of the
irregular polymer with high diphenyl content (as sample No.?12)
and No. 10, 0113/005 2.8 and 1..6) St 250? G. is explained iy
the volatility of certain components ot the polymeric mixture
and not by a lowering of the thermooxidative resistance.
Evaporation %
IQ
ratio. CH4005
Figure 1, comment: points from all compounds are near or
equally near these curves.
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?
2, Therthooxidative Resistance at 2500 C. by passage across a
volume of polymer of 100 c.c. of air at constant speed under controlled
cooling,, is shown in Figure 2, is also shown to be practically
constant for the polymers with given chains of dimethyl- and
methypheny1s1loxy units, but related to molecular weight and the
cH3 C6H5 ratio.
60
Change in
Viscosity
Time, hours
Figure 2, Change in viscosity pf polymethylphenylsiloxanes with
calculated chain structure,during thermooxidative treatment at
250? C. Ratios CHVCAHn: I 1.83-1.88, II 2.32-2.80,
III 6.32-6.80, IV .25-g.68
From Figure 2, two points may be brought out (among them)
that viscosity of polymers with diphenylsiloxy units in the
chain and a CH/06H5 of 9.68 (curve 4) change in the thermooxidative
process to a considerably smaller value than the viscosity of the
polymers (without thermooxidation).
In all polymers with a ratio CH3/005 of 6.32-6.80 (curve 3)
(Figure 2), the viscosity after thermooxidation change is less
than with polymers with a larger phenyl content. The reason for
this phenomenon will be examined later.
3. Thermosetting of the polymers (Figure 3) shows straight line
relationships in correlation with their methyl and phenyl radical
contents. Regular ratios of dimethyl- and methylphenylsiloxy
units to diphenylsiloxy units in the chain are practically of no
influence in this category, as is shown by substitution of
methylphenylsiloxy units by diphenyisiioxy units in two cases of
the four. Polymers with maximum and minimum maintained
diphenyisiloxy unitd are more adaptable for thermosetting at
10? C. and above as compared with other polymers.
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MIR
-4, The RelatiOn-between-ViScosity. and-TemPerature:.(Figure 4)
in polyMers with detinite--(regular). and-irregular ratios of .
dimethyl and methylphenyisiloxy units. In -the chain is identical
as far as any definite-significance to viscosity is concerned.
The greatest slope is with a small amount of phenyl radicals
(Curve 4), 0H31U6K5 9.26-9.68.
-20?
Temperature
of
Hardening
-1000C
0 10
ratio CH3/C6H5
(points pertaining to different compounds show almost no
deviation from the line)
Figure 3 'Relation Between Temperature of Hardening of the
Polymethylphenylsiloxanes with Different Structural Ratios
"3/06H5
Polymers with diphenyisiloxy units show high absolute
viscosities (Figure 4 and Table) and the relation to temperature is
reflected somewhat by the large banking curyes in the region
of low temperatures (the amounts of viscosities of these polymers
is marked in Figure 4 by figures pertaining to the numbered curves).
7263
Viscosit
(loglic)
-500 +2000
I 0H3/06H5 1.83-1.88, II 2.32-2.80, III 6.32-6.80, IV 9.26-9.68
Figure 4
\
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?
? At temperatures, above +1500 C. the value of the viscosity
and the character of the curve of all (of these) polymers are
practically the same.
The indices of refraction, n-20 D (table) of comparable polymers
are close (for four polymers of prectically the same molecular
weight they are identical).
Discussion of Results
The fundamental properties of liquidd,W-hexamethylpolymethyl-
phenylsiloxanes with-regular and irregular ratios of dimethyl.-- and - -
methylphenylsiloxyl units in the chain are practi6ally the same in
(the realm of) viscosity with respect to the number of methyl radicals
and the number of phenyls and of comparable molecular weights.
These properties depend in the main on the size of the ratio
CH4/C6H5 and are not dependent on the structure of the main
molecular chain.
. Notable above is a divergence from this conformity for some
polymers with diphenylsiloxyl units (change in viscosity with
thermpoxidation, thermosetting, dependence of viscosity on
temperature and absolute viscosity-in-the region of low temperatures)
entailing.moderately large intermolecular force interaction between
phenyl radicals of different chains of molecules relatively, one with
other. This is particularly noticeable in the viscosity of the
polymers at 200, 1000 and 2000 (table). At 2000 C., the difference in
viscosity of all comparable polymers is not noticeable from a
practicable point of view but at 200 their viscosities differ by
1.5 to 2.0 fold. There is a probability, at lower temperatures
(below 50 0 C.) that structural viscosity controls viscosity and
is conditioned on the dimensions of the molecule while at a rise
in temperature, structural viscosity has little influence.
These phenomena apparently tie in with the fact that polymers
with a ratio CH3 6H5 of 6 show significantly less change on
thermooxidation (Fisgure 2) than those polymers with a high phenyl
content.
In certain cases, there would be a lesser effect on
structural viscosity from a change in the thermooxidatiye process
as far as concerns phenyl radicals, arranged over a considerable
distance from each other in the polymeric chain with (consequent)
little interaction. However, there is a certain probability
attached to the shielding of methyl radicals during thermooxidation.
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It remains to-examine the cause of the small influence of the
structure of the molecular chain of liquid polymethylphenylsiloxanes
on their properties.
When-we speak of distinctive-properties of regalar.and irregular
polymers, we have in mind that side groups are present in definite.
organic content with regard to the main polymeric chain. This
stipulates a close packing of the chain,_ good opportunity for the
formation,of crystals or of some-sort of crystallization and as- a
consequence a rise in temperature of-soft04ng and _mechanical hardening.
of the regular polymers. Thus the condition is possible only with
polymers-with iong:_cbal;ns which may not freely move (rotate) relatively.
We are considering polymers with comparable short chains (molanular
weights around 2000), liquids at a wide range of temperatures. With
these cases there is an opportunity for great freedom of lateral
rotation of groups and sections of the chain and even transference
or shift of chains, relatively, with resulting heat fluctuations.
In liquid short chain polymers it could be neither physical positions
of lateral groups in space near the main chain nor stability of the
crystalline formations involving nrighboring chains (two chains) nor
the stability of the chains as set up. The molecular chain of the
polymer could easily be_rolled up as a spiral or straightened out
again to take some (other) desired configuration.
It is natural that with these liquid polymeric systems in
which the dimensions of the molecule include numerically equal or
nearly equal groups and atoms of comparable molecules of the same
type, but with groups arranged in the different chains and having
freedom of rotation and slight displacement of the organic groups,
that these properties reach some stage of equilibrium. In the
overall, the mixture in which this is observed properly makes use of
a fairly homogenedfid volume if the forces are uniformly steady,
elastic and uniformly diffused in intermolecular space, for example
using acids, freely run in at uniform speed to a given density onto
a packed uniform chain.
The form then, of short chain liquid polymers with uniform
chain composition and molecular weights, with regular chain
structures, is apparently without greatly varying influence on its
properties- this is confirmed by the present work.
The difference in properties in these systems could be related,
as seen, apparently, to temperature variations or to the limits set by
brittle points.
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? - --
Some exceptions from these rules are observed in the cases
of polymerswwith diphenylsiloxy units; with bonds so arranged
with two phenyl radicals on one atom of silicon, the probability
is that the intermolecular interaction between several groups in
the chain is increased. In these cases it could be that there
would appear, in addition, a strong, "intermingling" of aromatic
groups with the result that the symmetry of two sequences of
groups would lead to an increase in the energy of intermolecular
interaction.
Bibliography
1. C.M.Murphy, C.E.Saunders and D.C.Smith, Ind. Eng. Chem., 42
2462 (1950)
2. C.M.Murphy, I.B.Romans, N.A.Zisman, Trans. Am. Soc., Mech.
Eng., 71 561 (1949)
3. M.B.Sonievskii, L.A.Chistyakova, D.V.Nazarova and
V.V.Kirillina, Plastic Materials, (No. 10) 17 (1962)
4. M.B.kboleyskii, L.A.Chistyakova, V.V.I,cirillina and
D.V.Nazarova, USSR Patent 141 155 (1961), Byulleten Izobreten4i
(No. IS) (page not giiFen)(1961)
5. M.A.leinovskaya, M.V.Sobolevskii, T.A.Krasovskaya and
N.M.Zharkova, Plastic Materials, (No. 9) 19 (1962)
6. V.A.p.rgin, G.L.Slonimskii, Short Essay on the Physical
Chemistry of Polymers, Izv. MGU (1966)
7. P.P.Kobeko, Amorphous Materials, Izv. Akad. Sci. USSR (1952)
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