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Modification of poly(acrylonitrile) via reaction with ti zr and hf dicyclopentadiene dichlorides.

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Die Angewandte Makromolekulare Chemie 25 (1972) 121-129 ( N r . 362)
From the University of South Dakota, Chemistry Department, Vermillion,
South Dakota 57069
Modification of Poly(Acrylonitri1e) via Reaction with
Ti, Zr, and Hf Dicyclopentadiene Dichlorides*
By CHARLESE. CARRAHERjr. and LONG-SHONG
WANG**
(Eingegangen am 6. Marz 1972)
SUMMARY:
The modification of poly(acrylonitri1e) was effected via formation of poly(acrylamideoxime) followed by condensation with Ti, Zr and Hf compounds.
Modification was effected utilizing generally the interfacial technique.
Thermal properties are reported. Initial degradation in the 200 to 350°C region
probably occurs via the formation of cyclic products whereas at temperatures
> 500 "C degradation in air occurs via oxidation of the remaining product.
ZUSAMMENFASSUNG :
Die Modifizierung von Polyacrylnitril wurde durch Bildung von Polyacrylamidoxim und nachfolgende Kondensation mit Ti-, Zr- und Hf-Verbindungen
durch Anwendung der Grenzfliichentechnik erzielt.
Die thermischen Eigenschaften dieser Produkte werden angegeben. Der anfiinglich bei 200 bis 350 "C erfolgende Abbau verlluft wahrscheinlich uber cyclische Produkte, wiihrend der Abbau oberhalb 50OoC in Luft durch Oxydation
des verbliebenen Produktes erfolgt.
I . Introduction
Much effort has been focused on the modification of polymers. This has been
reviewed1 .
We recently became interested in the modification of commercially available
polymers including metal atoms into the side chains of productsz-5. Two
straight forward pathways can be described for this to be accomplished. The
first is exemplified by work done by PITTMAN
and coworkers (for instance67 7),
where metal atoms are included in the monomer which is subsequently polymerized or copolymerized t o yield a chain having metal atoms included in its
side chain,
*
**
Portions presented at the 162nd National American Chemical Society meeting
m Washington, D. C.
Taken from thesis of L. Wang.
121
C. E. CARRAHERjr. and L.4. WANG
H
H
H H
\c=c/ +-c-c-I I
I I
H/
\x
H X
where X contains a metal.
The second approach, utilized in our laboratory, consists of fist forming the
polymer and then modifying the already formed polymer via reaction a t the
functional groups contained as pendant groups on the polymer chainz-5.
Much of our work has been the result of the belief that the chemical reactivity of such pendant groups should differ little from their reactivity if
included in a smaller molecule. Thus modification of polymers has closely
paralleled work done by us on the synthesis of polymers containing metal atoms
in the backbone of the chains8-13. Recently our work has been concerned with
the synthesis of Group IVB* containing polyesters, polyamines, polythioethers
and polyethers (for instance 1%13).
BL0MSTROMl4 and DoNARUMAl5 recently announced the synthesis of
poly(-0-acyl-amideoximes) as illustrated below :
HO-N
+
C-R-C
H2N/
/o
0
-(-0-N
A
-R-C
*
C-R-C
H~N/
C1/
\Cl
/N-OH
\
\NH2
b
0
/N-0-C-R-C-)I1
0
1I
\NHz
I
-(-R-C
/ N \
”\
C-R-C
C-)-
b-O/
\O-N/
I1
On heating I cyclodehydration occurred to yield poly(-l,2,4-0xadiazoles)
of form I1 which exhibited moderate thermal stability. These products were
reported to exhibit good hydrolytic stability in both acid and basic media and
good resistance to ultraviolet catalyzed oxidative attackla-19. We recently
synthesized analogous Group IVB products as illustrated below20. Work is
underway to determine if a product analogous to I1 is formed:
HO--N
HzN
*
N-OH
A
/
/C-R-c
\
NHz
CP
I
+ C1-M-Cl-
I
CP
Yp
-(-N
N-0-M-0-)-
A
C-R-C
/
HzN
/
\
NHz
III
IVB refers to the metals Hf, Zr and Ti which have 2 3d electrons.
122
I
CP
Modification of Poly(Acry1onitrik)
An extension of this work appeared t o be the modification of poly(acry1onitrile) as illustrated below. We now report this modification.
H
H
H H
I I
+ -(-c-c-)I 1
(>EN
H C
A
I I
-(-c-c-)I I
H
--
H
Cp2MC12
H
I I
-(-c-c-)-
I
I
H
C
/\
H2N N
H2N N
I
I
0-H
0
I
Cp-M-Cp
I
0
IV
I
H2N N
\/
C
I 1
-(-c-c-)I 1
H
H
H
2. Experimental
Dicyclopentadienylhafnium dichloride was used as received from Strem Chemicals
Inc. (Danvers, Mass.). Djcyclopentadienyltitanium dichloride and dicyclopentadienylzirconium dichloride were used as received from Alfa Inorganics (Beverly,
Mass.).
Poly(acrylonitri1e) wm prepared using a slurry method aa described in 21. It exhibited a limiting viscosity number of 8.2 (dl/g) which corresponds to a weightaverage molecular weight of 1.1 x 106 a s determined by light scattering. Solution
characterization was performed in dimethylformamide. Poly(acry1onitrile) was converted to poly(acry1amideoxime) via reaction at the nitrile with hydroxylamine.
Poly(acrylonitri1e) (50 g) in dimethylfomamide (500 ml) was added to a 1 1 threenecked flask equipped with a thermometer, condensor and stirrer. The reaction
mixture was brought to 75OC and maintained there for the remainder of the reaction. Hydroxylamine hydrochloride (1.5 mole) and sodium carbonate (0.7 mole)
were added to the flask. After three hours the reaction mixture wm filtered to remove insoluble salts. The filtrate was added to 1 1 of methanol and filtered. The
solid was washed with portions of methanol and dried. The infrared spectrum of the
product exhibited no band about 2250 cm-1 characteristic of the nitrile group.
Modification was effected utilizing the interfacial technique. Briefly, aqueous solutions of poly(acry1amideoxime)containing added base were added to rapidly stirred solutions containing a solvent which is immiscible with water containing the
Group IVB reactant. The product precipitated from the reaction mixture. The solid
was separated by suction filtration and washed repeatedly with water. It was then
dried and weighed.
123
C. E . CARRAHERjr. and L.3. WANG
Polymerizations were conducted in a one pint Kimex Emulsifying Jar fitted on
top a Waring Blendor (Model 1043). The screw cap lid of the Kimex Jar was fitted
with a “gas outlet” (which consisted of a glass tube fitted through a cork placed
through a hole in the jar lid) and separatory funnel. A fuller description of the
equipment is given elsewhere22.
From knowledge of the amount of unreacted poly(acry1amideoxime)and weight
of product it is possible to determine the amount of Group IVB moiety included in
the polymer. The amount of unreacted polymer was determined as follows. The
aqueous phase and aqueous washings were collected and dried under vacuum to
dryness. The resulting solid was washed with water to dissolve the salts present
but not the polymer since it takes several hours for poly(acry1amideoxime)to dissolve under these conditions. The remaining solid was dried and weighed. I n some
instances unreacted and hydrolyzed Group IVB material was recovered to determine
the amount of Group IVB moiety incorporated. The amount incorporated by both
methods agreed closely with one another.
The products are insoluble in all solvents tried. This is expected if the products
are crosslinked.
Thermal Gravimetric Analysis was conducted employing a 950 duPont TGA.
Differential Scanning Calorimetry was carried out employing a duPont 900 DSC
cell fitted on a duPont 900 Thermal Analyzer Console. A linear baseline compensetor was used with the DSC cell to insure a constant energy baseline. A Mettler
H20T semimicro balance was employed for DSC sample weighings. Measurements
were obtained on samples contained in open aluminum cups to allow the free flow
away from the solid of volatilized gases thus more closely simulating the conditions
under which TGA studies were conducted. A flow rate (of both air and nitrogen) of
about 0.3 1 per min gas was employed for both DSC and TGA studies. The samples
were ground to aid in obtaining reproducable samples.
Infrared spectroscopy was performed using KBr pellets for both liquids and
solids as described elsewhere utilizing both the Beckman IR-10 and Perkin-Elmer
237-B Spectrophotometers. Spectra were in agreement with the inclusion of the
Group IVB moiety. I n particular spectra of the polymers all contained bands about
820,1010-1025 and 144&1450cm-1 characteristic of the Cp-n-ring; 3120-3070 cm-l
assigned to the C-H stretching in the n-Cp groups; around 1630-1650 em-1 characteristic of the C=N group (unreacted, indicating the presence of at least some
unreacted C=NOH units); 1580-1600 cm-1 characteristic of polar C=N bonds, in
particular the C =N-0-M
unit; and a broad band in the 3200 to 3500 cm-1 region
characteristic of amines23. 24.
3. Discussion and Results
The modification of poly(acry1onitrile) is general for Group IVB organometallic of t h e form CpZMC12 (Table 1). The products presumably are crosslinked as expected and as evidenced by their insolubility in all solvents tried.
Yield increases with time over the range studied (Table 1).
The structural analysis of condensation products of poly(acry1amideoxime)
with Group IVB halides is not straightforward. Previous polycondensations
124
Modification of Poly(AcrylonitriEe)
Table 1. Yield of precipitated polymer as a function of Group IVB reactanta9d.
b
Group IVB
Reactant
Stirring Time
CpzTiClz
CpzTiClz
CpzTiClz
CpzTiClzC
CpzZrClz
CpzZrClz
CpzHfClzb
30
60
Yield
(YO)
35
53
56
56
47
59
180
180
30
60
30
34
Reaction conditions : Poly(acry1amideoxime) (0.00125 mole repeating units, i. e.
0.108 g) with NaOH (0.00250 moles) in 50 ml water, condensed with the organometallic reactant (0.00125 moles) in 50 ml CHC13 with a stirring rate of 17,500
rpm (no load) at 25°C.
[bid a except employing 0.000625 moles of CpzHfClz in 25 ml CHCb and 0.000625
moles of poly(acry1amideoxime)and 0.00125 moles of NaOH in 25 ml HzO.
[bid a except with the CpzTiClz is in 50 ml HzO.
Mole-% inclusion of CpzM moiety is in the 40 to 50% range. Inclusion of one mole
of CpzMClz for every two amideoxime units (structure given as IV) would represent 50 yo inclusion.
with hydrocarbon acid chlorides were reported t o occur a t the N-OH rather
than the NH2 group49 5. The authors have not been able to find satisfactory
proof of this. It is possible t h a t reaction could occur at the NH2 as well a s the
N-OH group. This would offer the possibility of at least the below (as well
as the N-OH product) units being present in the condensation product. Such
aminations are known. In a recent
H H
I
-c-c-
H H
I
I I
-c-c-
\&-AI
R-M-RI
I
R
R
(V)
(VI)
work of ours we have prepared products of the below (VII) form where
M
== Ti25.
CP H
I
1
-M-N-R-N-
I
CP
H
I
(VII)
125
C . E. CARRAHERjr. and L.-S. WANG
I n the present situation we have not been able to differentiate between reaction
a t each site. The insolubility of the products make it impossible to conduct
NMR studies of the products. ELOYand Co-workers26 report the formation of
both acylated products in the study of acyl derivatives of formamideoxime.
Under one set of conditions the ratio of (VIII)/(IX)was about 3/1.Thus it is
proper to consider the products contain a mixture of the NOH and NH2
reacted products with a major portion of the product containing 0-acylamideoxime units as illustrated in form (IV).
H
HO--N=C-NHz
I
+ Br-
a - i - C l -
Br- ~ - ! - N = c H - - s t I l +
(VIII)
It is also possible that the products contain units of form (X)where reaction
occurred a t both the NOH and NH2 sites in one amidoxime unit. This was
evaluated in previous studies by us using sulfonyl and phosphorus mono- and
dihalides and found not to occur49 5. For the present we can assume structures as (X) as unimportant:
H H
I I
-c-cI I
' /.
H
R3M-N
/\c N-0-MR3
(X)
The active organometallic moiety in interfacial systems has not yet been
identified but in the aqueous solution syntheses the active species has been
established for other systems studied by us to be the Cp2M+2 solvated moiety.
The products are isolated as solid materials which can be ground to powders.
Products where M = Ti are rust colored, M = Zr are white and M = Hf from
a light to dark brown. The products are electrostatic in that they are affected
by electrical charges. For instance, a charged nylon comb when brought near
the products causes the products to ,,jump" to the comb.
DSC and TGA thermograms for M = Ti, Zr and Hf products are reproduced
in Fig. 1 and 2. All of the products show moderate to good thermal stabilities
(with respect to weight loss as a function of temperature) with stability being
better (or equal to) under a nitrogen purge.
126
Modification of Poly(Acrylonitri1e)
A1 R
80
0
3llO
600
TEMPERATURE
I200
900
(OC)
Fig. 1. TGA thermograms of condensation products of poly(-0-acylamideoximes)
with CpnTiClz -, CpzZrClz ----, and CpzHfCl2 ....... at a heating rate of
20°C per minute in air, with a gas flow rate of about 0.3 lpm.
%W.
NZ
........... ......
... .........
Loss
40 -
............. ....
'..
0
3im
600
9(W
.....
120
TEMPERATURE ( O C )
Fig. 2. As Fig. 1 except the measurements were obtained in nitrogen.
The products undergo small weight losses beginning around 70 "C and
continuing until about 250 for M = Ti and 350°C for M = Zr and Hf a t which
points occur an accelerated weight loss of about 8 to 10%. I n addition the
TGA and DSC thermograms (for a constant M) are identical in air and nitrogen
up t o about 400°C. The products undergo an endothermic reaction in the region
of 70 "C to 200 "C and then undergo an exothermic reaction in the 200-300 "C
region for M = Ti and 280-350°C region for M = Zr and Hf. Heteroatomed
polymers often undergo exothermic degradation via two common modes, i. e.
crosslinking and oxidation. If reaction occurs via an exothermic pathway in
air but not in nitrogen the degradation is probably occurring via an oxidative
pathway. If degradation occurs via the same exothermic energy mode in both
air and nitrogen, then the degradation is probably occuring via the formation
of crosslinks. The exotherms observed in the 200-350°C region are then
probably occurring via the formation of crosslinks.
127
C. E. CARRAHERjr. and L.-S. WANG
END0
lAT
EX0
..............
.......2:....
,: ............ -_.......
....
.. ..
..: .:..
.: ..
i:
N2
....._
.. ..
i )AIR
:.i
..
i .
L
,
300
TEMPERATIJRE("C,
Fig. 3. DSC thermograms taken on samples weighing about 0.00100 g a t a heating
rate of 20°C per min with a gas flow of about 0.3 lpm. Sample designations
are the same as given in Fig. 1. The Y-axis sensitivity was l.O"C/inch in air
and 0.1 "Clinch in nitrogen. The Y-axis divisions represent one inch each.
The A T = 0 line is designated by a straight line. Lines below the A T = 0
line represent exothermic transitions whereas lines above represent endothermic transitions.
The thermograms in air and nitrogen become markedly different around
400 "C. Highly exothermic reactions are occurring around 500 "C for M = Zr,
525 "C for M = Hf and 550 "C for M = Ti in air but not nitrogen. This then is
probably due to oxidative degradation of the remaining moiety.
The two lower temperature transitions may result from the formation of
stable cyclic compounds similar to those described in the introduction for the
linear poly(0-acylamideoximes). No further rapid degradation occurs in nitrogen to 1200 "C. This is still under study.
The modification of poly(acry1onitrile) via initial formation of poly(acry1amideoxime) followed by condensation with Group IVB organometallic
reactants of the form Cp2MC12 resulting in the inclusion of the Cp2M moiety has
been accomplished for the first time.
1
2
E. FETTES
(Editor), "Chemical Reactions of Polymers", Interscience Pub., New
York, 1964.
C. CARRAHERand L. TORRE,
J. Polym. Sci. A-1 9 (1971) 975.
128
Modification of Poly(Acry1onitrik)
C. CARRAHERand J. PIERSMA,
Makromol. Chem. 152 (1972) 49.
C. CARRAHERand L. WANG,Makromol. Chem. 152 (1972) 43.
5 C. CARRAHER,J. PIERSMA,
and L. WANG,Amer. Chem. SOC.Div. Org. Coatings
Plast. Chem. Pap. 31 (1971) 254.
6 C. U. PITMAN,
J. Polym. Sci. A-1 5 (1967) 2927.
7 C. U. PITMAN,
Tetrahedron Lett. 1967, 3619.
8 C. CARRAHER
and D. WINTER,Makromol. Chem. 141 (1971) 237; 141 (1971) 251.
9 C. CARRAHER
and R. DAMMEIER,
Makromol. Chem. 141 (1971) 245.
10 C. CARRAHER,
Macromolecules 4 (1971) 263.
11 C. CARRAHER
and G. SCHERUBEL,
J. Polym. Sci. A-1 9 (1971) 983.
1 2 C. CARRAHER,
Amer. Chem. SOC.Div. Org. CoatingsPht. Chem. Pap. 31 (1971)
3
4
330; 31 (1971) 338.
16
C. CARRAHERand R. NORDIN,J. Polym. Sci. A-1 10 (1972) 521.
U. S. P. 3044994 (1962), Du Pont de Nemours and Company, Wilmington
Del., Invs.: D. BLOMSTROM.
L. DONARUMA,
J. Org. Chem. 26 (1961) 577.
Y.IWAKURA,
K. UNO,Y. IMAI,
and M. AKIYAMA,
Makromol. Chem. 95 (1966)
17
V. KORSHAK,E. KRONGANZ,
and A. RUSENOR,Dokl. Akad. Nauk SSSR 166
18
M. AKLYAMA,
Y.IWAKURA,
S. SHIRASHI,
and Y. IMAI,
J. Polym. Sci. B 4 (1966)
19
C. OVERBERGER
and F. FUJIMATO,
J. Polym. Sci. B 3 (1965) 735.
C. CARRAHERand R. FRARY,
in preparation.
W. SORENSON
and T. CAMPBELL,Preparative Methods of Polymer Chemistry,
Interscience Publ., New York, 1961, p. 168-171.
C. CARRAHER,J. Chem. Educ. 46 (1969) 314.
C. RAO,Chemical Applications of Infrared Spectroscopy, Academic Press, 1963,
p. 245-281.
J. SALZMANN,
Helv. Chim. Acta 51 (1968) 903.
C. CARRAHERand P. Lessek, Eur. Polym. J., in press.
F. ELOY,R. LENAERS,and C. MOUSSEBOIS,Helv. Chim. Acta 45 (1962) 437.
13
14
15
275.
(1966) 356.
305.
20
21
22
23
24
25
26
129
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