The synthesis and study of carborane-containing polyphosphazenes

0032-3950/801092180-08507.50[0

Polymer Science U.S.S.R. Vol. 22, No. 9, pp. 2180-2187, 1980 Printed in Poland

© 1981 Pergamon Prems Ltd.

THE SYNTHESIS AND STUDY O F CARBORANE-CONTAINING POLYPHOSPHAZENES* V. V. KORSItAK, A. I. SOLOMATINA,•. I. BEKASOVA, M. A. AXDRWYEVA,

Y~,. G. BVT,rCHEVA, S. V. Vn~OGRADOVA,V. N. KALn~n~ and L. I. ZAKHARKnV Organometallie Compounds Institute U.S.S.R. Academy of Sciences

(Received 18 July 19~9) Polymer-analogue reactions were used for the first time to synthesize carboranocontaining polyphosphazenes from polydichlorophosphazono (PCPA) and various earborane-containing nuc]eophilcs. The largest chlorine substitution by earboranyl groups was found not to exceed 50%. The thermal and chemical properties of the earborane-containing polyphosphazeno have been shown to depend on the nature of the groups surrounding the main chain of the polymer. The hexachlorocyclotriphosphazeno reactions with m-carborano derivatives yielded carboranylcyclotriphosphazones for the first time.

AN improvement of the heat resistance of polyphosphazenes was sought in studying the effect of carborane group insertions in to the polymers [1, 2]. The carborane-containing polyphosphazenes were produced by a nucleophilic substitution of the chlorine atoms in polydichlorophosphazene (PCPA) with the mono-lithium derivatives of o - a n d m-carboranes LiOCsH4Ctt2C--CtI ,

LiC--CCstts,

BloHlo

LiOCH~C--Ctt,

BloHlo

LiCBtoHioCH,

BloHlo

"

a n d also the monomercapto-m-carborane tISCB I oH~oCI-I. The feasibility of these compounds reacting with PCPA was first examined on the hexachlorocyclotriphosphazene (HCP) reactions with the mono-lithium and mono-mereapto:derivatives of m-carborane as examples. The lastnamed was used as a complex with triethylamine. The solvents used for these reactions were aromatic hydrocarbons or ethers and a slight excess of the carborane-eonraining reagent. CI

//

B

C1 P

R

V

P

\

N

N

N

-1- 6BX

f

\

--6(C~Hs)N.HCI C1/ P ~

/"

R N

N

in which X ~ L i or H, R------CBloHloCH or SCBloHloCH. *Vysokomol. soyed. A22: No. 9, 1988-1994, 1980. 2180

N

Study of carborane-containing polyphosphazones

2181

T h e synthesis conditions a n d t h e characteristics of the r e a c t i o n p r o d u c t s are listed in T a b l e 1. T h e best solvents for these reactions, judging f r o m t h e Clc o n t e n t p r e s e n t in t h e c a r b o r a n y l c y c l o t r i p h o s p h a z e n e s , were TI-IF a n d o-xylene. T.~BLE

] . TB-E S Y N T H E S I S COI~DITIONS

AND

THE

CHARACTERISTICS

OF T H E

CARBOI~A.NY.~-

CYCLOTRIPHOSPHAZENES

(1 : 6"2 molar ratio of HCP : carborane) Carborane derivative

Conditions of synthesis T°

solvent

HCB10HloCSH'NE% o-xylene benzene THF LiCBIoHloCH

o-xyt(~ne

benzene diothyl other THF

Yield, %

Chlorine content, %

Tm *, °C

4 6 4.5

97 83 73

0"80 5'43 0"89

121"* not doter. 114

4 5 6

37 57 43

1.97

5"55 19"54

62-63*** 68-70 63

time~

hr

60 80 20 60 80 0-20

* The Tm o f m-carborane derivatives w a s determined from the thermomechanical curve (0-8 kg/cm~ stress, !°C/min termperature gradient). A capillary was used for the mecapto-carborane. ** Molecular weight of 1150 was determined eryoseopically in benzene (calculated for HCBIoHloCS)6PsN,--1186). *** l~Iolecular weight of 480 was determined ebullioscopieaUy in ethanol (calculated for HCBIaH~AChP,1%- 993).

T h e I R - s p e c t r a o f t h e p r o d u c t s c o n t a i n e d the 2600 cm - f a b s o r p t i o n line t y p i c a l for the B H - b o n d valence oscillations p r e s e n t in the c a r b o r a n e ring. According to the elemental analysis given below, this s u b s t i t u t i o n was practically quantitative. Elemental analysis (HCB~oHloCS)ePsNs: (found/calculated value) (HCBI~I10C) 6PsNa : (found/calculated value)

C

H

B

P

S

N

C1

12-53 5"68 54.04 6"06 16.21 3"33 0"80 12-14 5.60 54"68 7"83 16.21 3"54 15.26 i4.49

6"25 50.10 10.18 6"69 65"24 9.34

3"86 1.87 4.22

T h e alp N M R - s t u d y of the m e r c a p t o - m - c a r b o r a n y l - s u b s t i t u t e d cyclotrip h o s p h a z e n e showed t h e s p e c t r u m t o contain only a single n a r r o w signal w i t h a chemical shift o f + 3 0 mag. "div. One assumes t h a t t h e c o m p o u n d contains P - a t o m s o f o n l y a single t y p e . T h e Cl-atoms s u b s t i t u t i o n in t h e P C P A b y c a r b o r a n y l g r o u p s was carried o u t a t m o l a r ratios of i : 1, 1 : 2 a n d 1.25 u n d e r t h e same conditions as used for t h e h.c.p. T h e solvent was T H F owing t o t h e b e t t e r solubility o f t h e p o l y m e r s in it. T h e p r o d u c t s got in t h e P C P A r e a c t i o n w i t h t h e lithium d e r i v a t i v e o f phenylo - ~ r b o r a n e a n d t h e m o n o 4 i t h i u m d e r i v a t i v e o f m-carborane h a d a composition which could n o t be established owing to t h e i r instability. W h e r e the m e r c a p t o - m -

V.V. KORSH~

2182

a[.

carborane, the o-carboranyl methylate of lithium or the o-carboranylmethyt phenolate of lithium were used at a 2 or 2.5 molar ratio per base-mole of PCPA~ the yields of the carborane-substituted polyphosphazenes reached 60-70%. The largest chlorine substitution was 500/o and this can be explained by the sterie effects of the carborane substituents. The same results were got when the bulky n.ucleophiles, especially phenols [3], steroids or dyes [4] were used as substituents. The result of the PCPA reaction with lithium-o-carboranyl methylate was a reaction product practically devoid of chlorine. It seems to hydrolyze during extraction and yields a polymer containing the o-carboranylmethoxy groups together with hydroxyl ones, as indicated by the elemental analysis (Table 2, polymer 2). The reaction at a 1 : 1 molar ratio gave an almost quantitative yield but the Cl-substitution in the original PCPA did not exceed 20%. The remaining Cl-atoms could be substituted by organic or organo-metallic substituents as shown in t h e synthesis of poly-(o-earb0ranylmethoxy) or-(tetrafluoropropoxy) phosphazenes (Table 2, polymers 4 and 5). Such polymers were produced in T H F at 20-22°C by the consecutive Cl-atom substitution in PCPA for o-carboranylmethoxy- or tetrafluoropropoxy groups, without any prior isolation of the first-stage product: Cl [--P-----N--In + LiOCH2C--CH .+LiOCH2CF~CF2H I

CI

~

BloHlo

-2LiCl

-

-

OCH2CF,_,CF2H =N~ ,,

OCHoC--CH

BloHjo The elemental analysis a n d the properties of these polymers are given in Table 2; they were white or slightly yellow powders with an intrinsic viscosity of some samples reaching 3 dl/g in THF. The resistance to chemicals and heat of these polymers depended on the group types surrounding the main chain. Those with mercapto-m-carboranyl or o-carboranylmethoxyl groups in the branches had residual Cl-atoms which were hydrolyzable during isolation (Table 2, polymer 2). The Cl-atoms present in polychloro(o-carboranylmethylphenoxy) phosphazene resisted hydrolysis as evident from the elemental analysis of these polymers (Table 2). The larger hydrolytic stability of this polymer when compared with the mercapto-m-carboranyl- or o-carboranylmethoxy derivatives seems to be due to a more remote position of the electronaccepting carboranyl group from the P-atom in the first-named. The poly-organocarboranyl phosphazenes are more resistant to hydrolysis, but even these showed some property changes when stored in air. For example, the [tl] of the polytetrafluoropropoxy-o-carboranylmethoxyphsophazene changed on air storage in 5 months from 3.0 to 2.2 dl/g, although th~ amount of polymer remained the same.

Study

of carbonme-containing

polyphosphazenes

i -

I

-

-

‘

-

-

5

-

-

-.

i -

-

1: 3

s -

V. V. KO~m~K et al.

2184

The viscosity changes also occur in the solutions of these polymers; the rate of change was larger and varied in various solvents. In T H F for example it was 3.0 dl/g, in acetone 4.3 dl/g and in ethanol 7.4 dl/g; after a 1 week storage of the polytetrafluoropropoxy-o-carboranylmethoxyphosphazene it dropped to 2.2, 2.8 and 4.4 dl/g respectively. The [~] of the poly-o-carboranylmethoxyphosphazene changed from 1.7 to 0.32 dl/g after 1 week storage in ethanol. mole Gases, base-mole.AT

100

t

l.G~lO-2

80

ea

20

: qO0

\t 600

800 T o

1 - TGA curves, 2, 3--gas analysis curves (2--H=, 3--CH4) for the polyphosphazene l--N----P(OCHaCFsCF~I) (OCHaC--CH)]s in argon using a 5°C/min heating gradient.

The dynamic TGA study of the polymers showed a 5% weight loss in air to take place at relatively low temperatures (Table 2). High temperature thermal and thermal-oxidative resistance is however imparted by the carborane groups; The coke residue after heating such polymers at 500-600°C in air was 35-80°,/o and was in some cases as high as 100% in helium, while the original PCPA and its organo-derivatives had completely decomposed at 500-75°C [5]. The TGA of the polytetrafluoropropoxy-o-ca~boranylmeth0xY phosphazene (Table 2, polymer 4) in an argon atmosphere at 300-400°C, when combined with chromatography of the gaseous products (see Figure) showed that the only gaseous product was hydrogen (in practice); the latter was characterized by three liberation peaks and was accompanied at 310-400°C by an large weight reduction of the polymer. Responsible for this hydrogen liberation in this temperature range was evidently the carborane ring. All of the polyrn'er remained stable at 400°C and at a 47~/o level up to 900°C. In addition to the main gas liberated, i.e. hydrogen, in the 400-900°C range,

Study of carb0rane-containing polyphosphazenes

218.~.

• a small methane quantity was liberated: at 400-660°C; these gases are probably due to a severer conversion of the o-carboranylmethoxy group. The secondary reaction during such heat treatment evidently caused some crosslinking which ultimately gave rise to more heat-resistant structures. The polytetrafluoropropoxy-o-carboranylmethoxy-phosphazene (Table 2, polymer 5) was used to show that a reduction of the boron content, and thus of the carborane groups, did not affect the 5% weight loss temperature, b u t the coke residue was lower at 500-600°C when compared with that of the similar P C P A containing a larger amount of the o-carboranylmethoxyl groups (Table 2, polymer 4). One can conclude from our results that the investigated carborane reagents can be placed in the following series with respect to their effect on resistance t o high temperatures: HSCB~Ig0CH < HOCHzC--CH < HOC~H,CHgC--CH

\/

BloHlo

\/

BgoHlo

EXPERIMENTAL

Starting materials. The HCP was recrystallized from petroleum ether and then vaceuumsublimated; Tm = 111-112"5°C (112-114°C in the literature [6]). The PCPA were synthesized as described by Andreev a n d co-workers [3]. The monomereapto-m-carborane was produced from the mono-lithium compound with sulphur; Tm=207-208°C (201-202°C according to the literature [7]). The o-earboranyl-methano| and -methylphenol were produced by known methods [8, 9]. The triethylamine was purified b y t r e a t m e n t with benzoyl chloride a n d was then distilled over sodium in an argon atmosphere; b.p. = 89°C [10]. The T H F was treated with KOH, the distilled, first over K O H a n d then over Na; b.p.=63"5°C (65°C/751 m m H g according to the literature [11]). Triethylamine-monomercapto-m-carborane complex. HCCBI~I10CSH.N(C~Hs)v To 1-6 g of HCB10HIoCH~0 {0.0090 mole) dissolved in 20 ml benzer~e add 0.92 g (0.0090 mole) o f triethylamine, simmer the mixture 3 hours, evaporate the solvent at 40-50°C while applying a suction p u m p attached to the water tap. This produced 2.38 g of a white crystalline compound with T m = l l 7 ° C at a 95~o theoretical yield. Elemental analysis, ~o: 12-45 S, 38.83 B; CsH~TB~e-NS. 11-55 S, 3.8-98 B theoretical. Hexa-(mercapto-m-carboranyl)cyclotriphosphazene. To a solution of 3.98 g (0.0143 mole) of HCCBI~I10CSI=I.I~(C,Hs)3 in 15 ml T H F add dropwise 0.8 g (0.0023 mole) H C P at 20°C while mixing (as solution in l0 ml TI-IF). Mix for another 4.5 hours at 20°C and filter off the produced (C2Hs)31~.HC1, then evaporate the solution. Wash the solid residue 4 times with petroleum ether to remove any mlreacted reagents and dry to constant weight a t ll0-130°C/1 mmHg. The yield was 97~/o of theoretical as a white powder which w a s soluble in m a n y organic solvents (THF, acetone, benzene, chloroform, and o~hers). Its additional purification was carried out b y reprecipitation from the T H F solution with water; the yield was then 73~o and the T~-~ ll4°C. Hexa-m-carboranyl-cyclotriphosphazene. To a suspension of 1-89 g (0.1257 mole LiCBIoH10CH in 150 mole of o-xylene and dropwiso 7 g (0-0201 mole) t t C P in 40 ml o-xylene at 60°C, then gradually raise the temperature in 1 hour to 100°C and keep it 4 hours at t h i a temperature. Filter off the sediment and wash 3 times with absolute ethanol. Preeipitate~ the ethanol solution with water, then dry the precipitate at 100°C]I m m H g to constant.

2186

V . V . KORSHAK St a/.

weight. The product weighed 7.4 g and was a white powder. The yield was 37% of theoretical; [NP (CBloHIoCH),]3, Tm----62-63°C. The earboraaxe-containing polyphosphazenes were synthesized in a 4-necked flask with a spherical bottom; it was fitted with a stirrer, a drop funnel, a condenser and an inlet for argon. Polychloro-mercapto-m-carboranyl-phosphazene. To 1.0 g (0.0085 mole) of P C P A in 50 ml T H F add dropwise 5.5 g (0.0191 mole) of the triethylamine complex of mercapto-m-carborane at 20°C while mixing; continue mixing for 4 hours. Filter off the triethylamine hydrochloride sediment and pour the filtrate into water. Reprecipitate the recovered polymer with water from its T H F solution, and redissolve in T H F and then precipitate again with petroleum ether. Vacuum-dry the polymer at 30-40°C to constant weight. The yield of 1,72 g is 75~/o of theoretical for the compound [--N==PC1 (SCB10H10CH)],. The characteristics o f the polymer (polymer 3) are listed in Table 2. Polychloro:o-carboranylmethylphenoxy-phosphazene. T o a 0.29 g P C P A solution in l0 ml of T H F add dropwise the benzene solution of LiOC6H4CH2C--CH, prepared from 1.25 g

\/

BloHlo (0"005 mole) of HOC6H4CH~C--CH and 0-32 g (0.0050 mole) of C4H,Li. Mix at 20°C for

%/

B10Hlo 5 hours, filter off the LiC1 sediment, evaporate the solvent under v a c u u m (from water tap) and precipitate the residue with water from the T H F solution, afterwards from T H F with petroleum ether. The product of 0.49 g was a white powder, the yield 60% of t h a t oalculated for [--N~-P(C1) (OC6H4CH,--C--CH)],. The characteristics of this product (polymer 1)

\/

B10H10 are listed in Table 2. Other polychloro- add poly(hydroxy)-carboranyl-phosphazenes were produced by the same method.. Poly-tetrafluoropropoxy-o-carboranylmethoxy-phosphazene. To a lithium alcoholate-hydroxymethyl-o-earborane solution in T H F , prepared from 2-1 g (0.0120 mole) hydroxymethyl-oe a r b o r a n e and 0.75 g (0.0117 mole) C6HgLi add dropwise at 20°C a solution of 1-16 g (0.010 base-mole) of P C P A in 20 ml of T H F , mix for 2 hours and then add 1.6 g (0.0120 mole) of LiOCH2CF2HCF~ in 5 rnl T H F and mix at 20°C for another 4 hours. Isolate the polymer and purify it as described in the previous methods. The product weighed 3.43 g and was a pale-yellow powder. The yield was 98% of theoretical for a compound of formula [--I~T=P (OCH2CF2CF2I-1) (OCHaC~4~H)]n. Its characteristics (polymer 4) are contained

\/

BIoHlo in Table 2. The thel~nal decomposition was followed on a " S e t a r a m " electronic balance with a simultaneous analysis of the gaseous decomposition products. This work was carried out by I. V. Zhuravleva and Yu. I. Tolchinskii and the authors here record their thanks to t h e m

Translated by K. A. ALLEN REFERENCES 1. H. STRUSZCZYK, P o l i m e r y - - t w o r z . wielkocz~steczk. (Polish) 23: 77, 1978 2. R. E. SINGLER, G. L. HAGNAUER and N. S. SCHNEIDER, Po l y m er News 5: 9, 1978 3. M. A. ANDREEVA, E. G. BULYCHEVA, E. A. LYUBAVSKAYA, G. L. SLONIMSKH et al., Vysokomol. soyed. A21: 48, 1979 (Translated in Polymer Sci. U.S.S.R. 21: 1, 55, 1979) 4. H. R. ALLCOCK, T. J. FULLER, K. TATSUMURA and J . L. SCHMUTZ, Polymer Preptints 19: 92, 197~

Thermal degradation of polyisobutylono

2187

5. G. ALLEN, C. J. LEWIS a n d S. M. TODD, Polymer 11: 44, 1970 6. S. M. ZHIVLrKHIN, V. V. KIltEEV, V. P. POPILIN a n d G. S. KOLESNIKOV, Zhur. Neorg. Khim. 15: 1220, 1970 7. L. I. ZAKHARKIN a n d G. G. ZHIGAREVA, Zhur. Neorg. Khim. 36: 886, 1966 8. L. I. ZAKHARKIN, V. A. BRATTSEV and V. I. STANKO, Zhur. Org. Khim. 45: 789, 1975 9. L. I. ZAKHARKIN, B. N. KALININ, V. K. SHITIKOV and V. V. KORSHAK, Russian Authors' Cert. 445284, 1974; Byul. Izobret., No. 7, 1976 10. V. V. KORSHAK, S. V. VINOGRADOVA and V. A. VASNEV, Vysokomol. soyed. A10: 1329, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 6, 1543, 1968) 11. H. BOHME and W. SCHL~RHOFF, Chem. Ber. 84: 28, 1951

Polymer Science U.S.S.R. Vol. 22, No. 9, pp. Printed in Poland

2187-2192, 1980

0032-3950/80/092187-06$07.50/0 © 1981 Pergamon Press Ltd.

THE INITIATED T H E R M A L D E G R A D A T I O N OF POLYISOBUTYLENE A N D ITS COPOLYMERS IN TRICHLOROBENZENE SOLUTIONS* Z. A. SADYKHOV

and

S. R . KULIEVA

S. M. Kirov State University, Azerbaidzhan

(Received 19 July 1979) A q u a n t i t a t i v e thermal dogr~lation method at 110-140°C initiated b y eumyl peroxide has been developed for polyisobutyleno (PIB) and its copolymers with styrene and p-chlorostyreno in trichlorobonzene. The degradation rate of the central radical (P~ -~ degrad.) and the rate of dimethylphonylcarbinol accumulation ( R O ' + P H -~ -* R O H + P ~ ) a t 120°C has been found in the initial stage do be a linear function of the initiation rate. There exists a strict linoarity between the ratio of the initiation to the degradation rate eel/coa and the inverse value of the polymer concentration l/[PHI when coi=const. This confirms the suggested kinetics of the initiated thermal degradation in an inert medium.

T~E poly-olefm pyrolyses, especially of polyisobutylene (PIB) have been studied in some detail [1]. Sangalov and co-workers [2] had shown that salt complexes of the type ]Ke[C2HsA1C18] catalyze the thermal degradation (TD) of PIB at 350-360°C. The yield of the light TD products (up to the pentamer) increased on initiation. The viscosity of the PIB solution was also found to drop noticeably in the presence of various initiators [3] at ll0°C. * Vysokomol. soyed. A22: No. 9, 1995-1999, 1980.