Study of the structure of phenolcarborane formaldehyde oligomers and polymers

Phenolearborane formaldehyde oligomers and polymers

1795

REFERENCES 1. Polimery v meditsino (Polymers in Medicine). Mir, 1969 2. A. A. TAGER, M. V. TSII2[POTKINA and D. A. RESHET'KO, Vysokomol. soyed. AI7: 2566, 1975 (Translated in Polymer Sei. U.S.S.R. 17: II, 2955, 1975) 3. J. L. BRASH, D. J. LYMAN, J. Biomed. Mater. Res. 3: 175, 1969 4. Q. SAMAK, Albumin-polyethylene Surface interaction. M. Engng. Thesis, Me Master U n i v . , Canada 1(,)75

.Polymer Science U.S.S.R. Vol. 22, No. 7, pp. 1795-1803, 1980 Printed in Poland

0032-3950/80/07 ] 7(.)5-00 $07.5O,'0 (¢~) 1981 Pergamon Pre~s Ltd.

STUDY OF THE STRUCTURE OF PHENOLCARBORANE FORMALDEHYDE OLIGOMERS AND POLYMERS* T . M. ABlCAMOVA, S. G. 2 ~ L L E K S E Y E V A , P . M. V A L E T S K I I , L. i . GOLUI~EN'KOVA, [. M. MAKAROVA, [. YA. SLO~tM, YA. (~. URMA~ a n(l A. N. SHAI;AI)AStI Seirnt.ific In(h~st.rial As.~()ciati~)u "Plastics'" ( P,cceivcd 12 .l~dy 1.()79)

NMI{ aud I1~ sp(,ct.roscopy were used t(, stu(ly tho c,,ml),,~ilion a~(t Sll'll(.lui.,~ ,*I" ptlenolearborane formahtchy(te oligom~rs, it was establislmd t h;~t. fra,_,m(,ltt s c()ttt .~mi,t._, (li- aud tetra-substituted b(~nzerl~ rings are (,nly fonn(~d ia t.h(~ ~)li.~om(~r arid m,~i~ll\" tetra-substitut(~d benzene rings, in ttm p(,lymq,r. It. was sh()wL~ that the pr[~sca(.~,()[' t h,.~,, fra~qn~Ilts eoutributcs to the formation ,)f a m , ) r ( , I'(~gllbl.l"sli['tlClUI'C l.ll;tll ilt i'.h[' (*;[r4t, ~ ,{" c(~v(~ntiortal pht+nol-ft)rmaldchy(h; ()li~zom+,t~. Using r('sttlis ,~t)t~i~(~d ~ .~t.rtt(.l~t,.. was l)l~)p()se(l f,)r ph¢,n(~lcarl)oran(• for~nal(h, hy(h.~ ,)li~(~m~.rs ~ ( l p()lym~.rs. |)OLYSrERS | ) a s c d On l ) h c n o l e a r b o r a l l ( ' f o r m a l ( l r h y ( h , olig()nl(,rs (PCI") ]1 ~l~()w U m l s u a l b e h a v i o u r a t h i g h t e m p e r a t u r e s 1.2, 3] m a n i i b s t e d irl l)r(>lollge(I h(:ats t a b i l i t y o f m a t e r i a l s b a s e d o n t h e l n 14], w h i c h (:()llsirmahiehyd(; p o l y m e r s . I t is t.lmrcil)r(~ (>f i n t e r e s t t o e x a m i n e in m o r e d e t a i l t h e s t r u c t u r e o f P C F i t s e l f a n d o f I ) r o ( h w t s (,t" solidiiication. Oligomers prepare(! in n-propyl a.lcohol with a molar ral.i(~ (,f 1,2-bis-(4-hydrox~l)h-nyl)carborane:formaldehyde of l :2.5 in the presence of 0-12 mole (PCF-0.12) ~tnd 0-20 moh~ NaOH (PCF-0.20) were examined. ~ldex

Molecular weight

PCF-O" 12 PCF-0"20

400-450 550-600

Pheuol hydroxyl content, °/o 12-15 6-8

Methylol group content, °/o 5-7 12-14

* Vysokomol. soyed. A22: No. 7, 1637-1644, 1980. t Determined from the temperature/deformation curve.

t Tso n

45 65

1796

T. M. A.BRAMOV.~d a/.

To compare processes taking place during the sTcnthesis and solidification of phenolformaldehyde oligomers based on various bis-phenols and assign their spectra, an oligomer was synthesized from 2,2-bis-(4-hydroxypbenyl)propano and formaldehyde (BHPPF). Tiffs polymer was also prepared in n-propyl alcohol with a molar ratio of bisphenol:forma!dehyde of 1:2-5 in the presence of 0.20 mole NaOt[. PCF-0.12 and PCF-0.20 oligomers were solidified at a temperature of 250 °, BHPPF at 160° for 1 hr. ~H and 13C NMR spectra were obtained using a Bruker WH-90 spectrometer at frequencies of 90 and 22.63 Me/s, respechvely (Fourier transform). Acetone (with addition of deutero-acetone) or dioxano were the solvents. The numbers of build-ups ranged between 50 and 100 in IH I~IMR spectra and up to 35,000 in 13C NMR spectra. An internal standard, hexamethyldisiloxane, was used to obtain spectra, the chemical shift of which in relation to tetramethylsilano :,vas 0.05 p.p.m, for ~H NMR and 1.94 p.p.m, for ~3C NMR. IR spectra of oligomer powders and ]?CF polymers were obtained using a Hilger tI-800 spectrometer with a NaC1 prism in the range of 700-2800 cm-L Samples for testing were obtained by compression into pellets with KBr.

N M R spectra. T o s t u d y oligomer s t r u c t u r e , laC N M R spectra were o b t a i n e d of t h e oligomer itself and o f t h e initial bisphenol, 1,2-bis-(4-hydroxyphenyl)c a r b o r a n e (phenolcarborane). T h e c a r b o n s p e c t r u m o f p h e n o l c a r b o r a n e illustrated in Fig. l a consists o f five signals corresponding to the n u m b e r of various c a r b o n a t o m s 2

I1~)

3

(

H B~olllo

~3C N M R spectra were assigned b y c o m p a r i s o n with spectra of diphenylolp r o p a n e a n d o t h e r phenols [5]. T h e c a r b o n s p e c t r u m of PCF-0.20 oligomer (Fig. lb) in t h e a r o m a t i c region contains five basic signals, which a c c u r a t e l y agree w i t h signals of similar c a r b o n a t o m s o f the initial p h e n o l c a r b o r a n e . F u r t h e r m o r e , the s p e c t r u m contains signals o f m e t h y l o l groups a n d d i m e t h y l e n e ester bridges in the region o f 63-73 p.p.m. [6]. No signals are observed o f m e t h y l e n e o,o-CH~ bridges at 30.5 p.p.m. [7] in t h e s p e c t r u m o f PCF. T h e signal o f carbon a t o m s c o m b i n e d w i t h an O H group [8] is t h e m o s t sensitive to the t y p e o f s u b s t i t u t i o n of t h e benzene ring; this signal is d e n o t e d as C(1) in the spectrum. A s t u d y o f the C(1) signal shows t h a t t h e p e a k a t 159.83 p.p.m, corresponds to a n u n s u b s t i t u t e d benzene ring o f p h e n o l c a r b o r a n e a n d its area is ~50~/o of t h e entire area of t h e C(1) signal. T h e p e a k a t 157.57 p.p.m, shows a shift in relation to t h e peak o f an u n s u b s t i t u t e d benzene ring a t 2-26 p.p.m. Considering t h a t t h e ~aC N M R s p e c t r u m o f P C F does n o t contaSn signMs o f C H 2 bridge groups and t h a t according to results in t h e l i t e r a t u r e [6], t h e ortho, ortho-incroment for the OHCH2 s u b s t i t u e n t is 1.1 p.p.m., this shift m a y be assigned to t h e twofold i n c r e m e n t o f t h e C H s O H substituent.

Phenolearborano formaldehyde oligomers and polymers

1797

This suggests that the peak at 157.57 p.p.m, correspond.~ to the fragment Oil

l l() T{.,(" "e;\,,Cll~OIt /

the content of which is ~ 30 mole '!{) of +ill benzene rings of PC F. The peak at 156.55 p.p.m, may corresl)ond to the fragment 0It

OH

t

+ci,,-.o

~)

:l,°_.¢A~,_,. L~)

I

I

the content of which is ~ 2 0 mole <+)//oof all benzene rings. The position of peaks in the region of C2 and C3 atom signals confirms the assumption that substitution of the benzene ring takes place in the ortho-position. This is indicated by the absence of peaks in'the region of stronger field in relation to the C 2 signal of the initial phenolcarborane and the appearance of peaks in the weak field (shift by ~ 13 p.p.m.) in relation to the C 2 signal of phenolcarborane.

C3

Ct

C1

C:+ C5

b

!

170

,

,

I

140

,

,

•

II0

I

[

80

i

I

1

~, to.p.m. bO

Fie. 1. t3C NMR spectra of 1,2-bis-(4-hydroxyphenyl)carborano (a) and PCF oligomer (b).

1798

T.M. ABm,,MOVAe~ a/.

The NMR spectrum of phenolcarborane

AB Bl0]ll0 contains an AA'BB' type quartet of protons of the aromatic ring. A broad signal with J=-3.8 p.p.m, corresponds to the proton of the hydroxyl group. Signals of protons combined with boron atoms are considerably widened and are only observed with considerable magnification. The NMR spectrum of a PCF oligomor (Fig. 2) indicates that methylene bridges are absent from PCF oligomer (shift for o,o'-CH2 bridge is 3.9-4.0 p.p.m. [9]) and the signal in the region of -~4-5 p.p,m., according to ~H NMR results for resol phonolformaldohydo oligomors may correspond to methylol groups-,CH2OH and CH2--O--CH 2 bridges [7]. The ortho-incremont for methylol groups,

'

8

7

I

I

6'

i

I

5 Fie. ~ PMR spectrum of PCF oligomers.

,

[

4 ~p.p.m.

according to results previously obtained [10J, is 0.07 p.p.m. The proton signal of the aromatic ring therefore consists of quartet AA'BB' of unsubstituted rings, as iu the spectrum of the initial phenolcarborane and a singlet of di-substituted rings according to results of the carbon spectrum of a PCF oligomer. Since increments of methylol groups are slight, the singlet of di-substituted rings is not displaced in practice in relation to the initial position of the AA' part of the quartet. From the NMR spectrum of the oligomer and results of the 13C NMR spect r u m it was established t h a t on average there are about two methylol or methyl,ene ester groups per benzene ring. A study of PCF-0-12 oligomers by NMR spectroscopy shows that they contain structural fragments similar to PCF-0.20. The polymer based on PCF-0.12 oligomer is an infusible but largely soluble p r o d u c t (gel-fraction being 15-18% and molecular weight of the sol fraction, ~2000), whereas the PCF-0.20 oligomer under the same conditions forms a

Phenylcarborane formaldehyde oligomers and polymers

1799

practically insoluble (gel-fraction representing 95-97~o ) and infusible product. Results of NMR spectra of the sol-fraction show that CHs bridges are formed in the product and methylol groups and dimethyleno ester bonds completely disappear. All this suggests that the solidification of the PCF-0.12 oligomer results in the formation of a slightly branched polymer which retains solubility. IR spectra. Results of I R spectroscopic studies of oligomers show satisfactory correlation with results of NMR investigations. I R spectra of PCF oligomers were interpreted according to results in the literature [11-14] and using spectra of BHPPF and monomers as follows: !,2-bis(4-hydroxyphenyl)carborane, 1,2-bis-(4-hydroxybenzyl)carborane and 1,2-bis(hydroxymethyl)carborane. Absorption bands at 840, 1480 and 1510 cm -1 are typical of various substitutions of the benzene ring: at 840 cm -I the band corresponds to out-of-plane vibrations of the 1,4-substituted benzene ring; at ]510 cm -~, to deformation vibrations of the 1,4- and 1,2,4-substituted benzene ring; at 1480 cm -~ the b~nd corresponds to deformation vibrations of the 1,2,4,6substituted benzene ring The absorption band al. 2600 cm -~, correspon(ting to bond-stretching vibrations of the B - - H carhorane group [Ill and bands observed in spectra of model compounds at [075, S3~) and 730 cm '~ [12], the intensity of which is retained during soliditication, ('orre,sf)ond to vibrations typical of the earborane nucleus. A band at 730 cm -~ (l)ond-.~tretehiug vibrations of the carborane group) was selected a.s internal slan(tard, th(" intensity of which remains unchanged in a wide range of temt)eratllr(~. in sl)eetra o!" P( 'F (d"~)ligomers (Fig. 3) bands are observed which are typical of 1,4- an(l 1,2,4,6-sul)stit ut ions. The absence of 1,2,4-substitutions from the region of 825 cm-L in both PCF oli~omers proves the (,onstancy of the into,nsit.y of the band contour at 830 cm- t, t yl)i~.al el" vibrations of the carborane nucleus. The absence of a noticcal)le absorl)lion band related to 1,2,4,6-substitntions in the 860-880 ('m -t region on the basis of ~,x~unining spectra of model comt)ounds may be explaine(l t)v a h)w cocfli(:ient (~I' absorption of a tetra-substituted 1)enzcne ring. The existem.e in 1he PCF structure of oligomers of only (ti- and tetra-substitutcd fragments is, al)l)arently , due to the, strong electron-acceI)tor action of the carborane nu(.leus, (.ontrolling the fi)rmation of methylol derivatives, as observed (luring the intera~tion of formaldehyde wiih ehloro- and nitrophenols in an alkaline medium [15, 16]. The second oft~m-position of the benzene ring is activated as a result of the intramolecular hydrogen bond [I7], which contributes to the formation of ortho,qrtho-dimethylol derivatives of phenolcarborano [18]

/ 0 I

H2C

11 -.

/ 0 I

'//'(~"~I

II

..

/

11

0

CH~

]800

T. M. ABRAMOVA e~ al.

G

S b

I

I

I

I

!

__

I

d

I

28

2O

}

I8

16

lq

IZ

10

9

8

7

V • I0-~ cm -f

FIG. 3. I R spectra of PCF-0.12 (a) and PCF-0.20 (b) oligomers and polymers based on t h e m (c, d), respectively.

Phonolcarborane formaldehyde oligomers and polymers

1801

I R spectroscopy made it also possible to study the structure of insoluble (solidified) products, wlfich cannot be analysed by NMR. A comparison of spectra of oligomers and PCF polymers (:Fig. 3) shows an intensity reduction in the absorption bands at 845 and 1510 cm -~ corresponding to ~dbrations of the 1,4-substituted benzene ring and ~n intensity increase of the band at 1485 cm -~, typical of vibrations of the 1,2,4,6-substituted benzene ring. •The v~riation of the optical density ratio of absorption bands of.oligomers and PCF polymers is tabulated. Tabulated data indicate t h a t a polymer based on PCF-0.12, wlfich retains tfigh solubility after heat treatment, contains much fewer tetra-substituted benzene rings, tyl)i(.al of ~ three-dimensional structure than the i)olymer hased on PCF-0.20. The optical density ratio corresponding to this substitution (D~4s~,/D:ao) for a PCF-0.12 polymer is 0.55. For PCF-0.20 a larger number of tetra-substituted structures are formed (Dlt.~/D:3o:--l.2), which ~ccounts for the formation of ~ regular three-dimensional network. It also follows from t.hc Table that substitution only takes place in the ortho-po,~ition during soliditlcation. I n filet, tbr structure containing ~ 1,2,4-substitnted l)enzenc ring (which, the sam(; way as wilh 1,4-substitution, alJsorbs in ihc region of 1510 cm -a) no equality seems to exist in th(~ va.ri~!ion of optical density ratios I)ar,~o 'rod D~.zs~ on transition from the oligomer to the 1)olymcr. Amdysing results of sl)eetros('opi(~ investigations and results of determining mol(~eul~u' weight and lhe nunlber of nmthylol groups it may be assmncd that tho l?(Jl.," oligomer contains the following products

C!I?~II ]' ('"

I::)

CH20II

i

III ':

(: "'< IDIO['

' ]0 I '~':III" , / I'(: "

:: II:':

-)

II ~ } ] '

I I

CII201 f

Ct t.~011

!

11o-(i )

c:, \ / ¢:__/" ~_.j

C!T._,Otl Bl,,llla II

I CIT.,OTt

(,,it , IlO

c I Cll;:OIt

,: -- :--\/ [~ollv, I[I

the approximat(; contents of which may be as follows: 1 - - 3 0 - 4 0 , I I - - 1 0 , I I I - -

40-50% I R spectroscopic investigations of PCF polymers indicate t h a t the mechanism o f solidification of those oligomers is similar to the mechanism of synthesis and in the cazo of PCF-0.20 oligomors produces a considerable n u m b e r of orttw,ortho-

1~)2 OPTICAL

T.M. AB~OVA ¢~ a/. DENSITY RATIO

OF

ABSORPTION BANDS

OF

Sample PCF-0.12 PCF-0.12 PCF-0.20 PCF-0.2D

oligomer polymer oligomor polymer

PCF OLmO~aRS AND

D.5 D,so

Dl,s6

3-15 2.1

0"35 0"55 0"7 1.2

D78o

1.75

1.1

L~OL~gRS e

Dmo D,,. 2-4 1.6 1.25

0.75

* The optical density of bands a t 1510, 1485, 845 and 730 cm -x was determined using the base line method, in parallel with the abscissa at wave lenght~ of 1500, 1475 and 860 cm-~ (Fig. 3a).

disubstitutod phonolcarborane dorivativos. Bearing in mind also that tho polymor is practically froo from 1,2,4-substituted fragments of the bonzono ring, which disrupts structural rogularity, tho most likoly motol of structurally solidified P C F may be: OH

OH

I

I

-0-=.-_0._ I 0 i

T

C

C

[ ) B'Hlo

\ B l o Hlo

/

C

C

I

I

I

OH

OH

0It

I

l

[

Hlo

_()_ I OH

OH

I C

I C

I'Bl°III° / C [

] "Bl° / Hlo C '1

OH

C )B10

0tI

Phenolcarborane formaldehyde oligomers a n d polymers

1803

The regularity of the PCF polymer structure formed, as well as the effect of the carborane nucleus, apparently, contribute to a marked extent to the increase of heat-stability of phenol-carborane formaldehyde polymers, compared with conventiona] phenol-formaldehyde resites. Translated by E. SEMERE

REFERENCES 1. G. A. KOLOMOYETS, L. I. GOLUBENKOVA, P. M. VALETSKH, S. Y. VINOGRADOVA,

V. I. STANKO and V. V. IKORSHAK, Plast. massy, No. 2, 19, 1974 2. P. M. VALETSKII, T. M. ABRAMOVA, L. I. KOMAROVA, L. I. GOLUBENKOVA, V. 1. STANKO and S. V. VINOGRADOVA. Tezisy dokladov IV Vsosoyuznoi konfer(mt.~ii "Stareniye i stabilizatsiya polimerov" (Ageing and Stabilization of Polymers), Tashk~,zlt, 1976 3. A. I. AKSENOV, G. A. KOLOMOYETS, L. I. GOLUBENKOVA, P. M. VALETSKII. V. I. STANTKO, S. V. VINOGRADOVA and V. V. KORSHAK, l)okl. AN SSSR 227: ~)03. 1976 4. M. G. LUR'YE, D. A. KARDASHOV, A. P. PETROVA, P. M. VALETSKII, L. I. GOLUBENKOVA and G. A. KOLOMOYETS, Tezisy clokladov na I I konferentsii "Fcnolformal'degidnyye smoly i klei na ikh esnove (Phenolformaldehyde Resins and Adhesives). Tallin, 1976 5. G. LEVI and G. NEL'SON, Rukovodstvo po yadernomu magnitnomu rezonansu ugleroda-13 d l y a khimikov-organikov) (Handbook of Nuclear Magnetic Resonance of ('arben-13 for Organic Chemists). Mir, 1975 6. A. J. J. de BREET, W. DANKELMAN, W. G. B. HUTSMANS and J. de WIT, Angew. Makromolec. Chemic 62: 7, 1977 7. $. C. WOODBREY, H. P. HIGGINBOTTOM and H. M. CULBERTSON. J. Polymer Sei. A3: 1079, 1965 8. M . I . SILING, Ya. G. URMAN, I. V. ADOROVA. S, G. ALEIK.qEYEVA, O. S. MATYUKHINA and I. Ya. SLONIM, Vysokomol. soyed. A19: 309, 1977 (Translated in Polymer Sci. U.S.S.R. 19: 2, 358, 1977) 9. M. I. SIL1NG, O. S. MATYUKHINA, O. A. MOCHAI~VA, V. P. PSHENITSYNA a n d I. Ya. SLONIM, Vysokomol. soyed. A l l : 1943, 1969 (Translated in Polymer Sei. U.S.S.R. 11: 9, 2215, 1969) 10. $. BEEBY, S. STERNHELL, T. HOFFMANN-OSTENHOF, E. PRETSCH and W. SIMON. Analyt. Chem. 45: 1571, 1973 11. L. A. LEITES, L. Ye. VINOGRADOVA, V. N. KALININ and L. I. ZAKHARKIN, lzv. A N SSSR, set. khim., 1016, 1968 12. L. A. LF.ITES, L. Ye. VINOGRADOVA, V. T. ALEKSANYAN and S. S. BUKALOV, Izv. AN SSSR, ser. khim., 2480, 1976 13. N. I. MAKAREVICH, N. I. SUSHKO, A. I. IVANOV and T. I. GLAZOVA, Zh. prikl. spektroskopii 18: 671, 1973 14. L. M. SVERDLOV, M. A. KOVNER and Ye. P. KRAINOV, K o l e b a t e l ' n y y e spektry mnogoa t o m n y k h molekul (Oscillatory Spectra of Polyatomic Molecules). Nauka, 1970 15. F. UOI~ER, F o r m a l ' d e g i d (Formaldehyde). Goskhimizdat, 1957 16. R. W. MARTIN, The Chemistry of Phenolic Resins, New York, 1956 17. K. HULTZCH, Chemie der Phenolh~rze, Berlin, 1950 18. M. I. SILING, V sb. K h i m i y a i tekhnologiya vysokomolekulyarnykh soyedinenii (Chem i s t r y and Technology of High Molecular Weight Compounds). 11: 125, Nauka, 197T p