[ACS Symposium Series] Inorganic and Organometallic Polymers Volume 360 (Macromolecules Containing Silicon, Phosphorus, and Other Inorganic Elements) || Cationic and Condensation Polymerization of Organometallic Monomers

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  • Chapter 36

    Cationic and Condensation Polymerization of Organometallic Monomers

    Kenneth E. Gonsalves 1 and Marvin D. Rausch 2

    1Department of Chemistry and Chemical Engineering, Stevens Institute o f Technology, Hoboken, NJ 07030

    2Department of Chemistry, University of Massachusetts, Amherst, MA 01003

    1,1'-Bis(-aminoethyl)ferrocene was synthesized via a 6-step process starting with ferrocene. This monomer was then copolymerized with various aromatic and aliphatic diacid chlorides as well as with diisocyanates, leading to ferrocene-containing polyamides and poly-ureas having moderately high to low viscosities. The above monomer and 1,1'-bis(-hydroxyethyl)ferrocene were also utilized as chain extenders. Three types of isopropenylmetallocene monomers were synthesized and subjected to polymerization and copolymerization by cationic initiators: (1) isopropenylferrocene, (2) (5-isopropenylcyclopentadienyl)dicarbonylnitrosyl-molybdenum; and (3) 1,1'-diisopropenylcyclopenta-dienylstannocene, and related derivatives of each.

    There i s c u r r e n t l y considerable i n t e r e s t i n organometallic polymers, since polymers containing metals might be expected to possess prop e r t i e s d i f f e r e n t from those of conventional organic polymers. 1""^ Two major approaches to the formation of materials of t h i s type have involved the d e r i v a t i z a t i o n of preformed organic polymers with organometallic functions^ and the synthesis and polymerization of organometallic monomers that contain v i n y l s u b s t i t u e n t s > ^ For the t r a n s i t i o n metals, condensation polymerizations have also been in v e s t i g a t e d . However, the reactions have generally been conducted at elevated temperatures, and the r e s u l t i n g products have of t e n not been w e l l c h a r a c t e r i z e d . ^ * ^ Ferrocene-Containing Polyamides and Polyureas

    We now report a convenient method f o r the i n t e r f a c i a l polycondensa-t i o n of 1, 1-bis(3-aminoethyl)ferrocene (1) with a v a r i e t y of d i a c i d c h l o r i d e s and diisocyanates, leading to ferrocene-containing poly-amides and polyureas.9 In some instances, we have been able to observe f i l m formation at the i n t e r f a c e . Moreover, the polymerization reactions can be conveniently conducted at ambient temperatures i n contrast to e a r l i e r high-temperature organometallic condensation

    0097-6156/88/0360-0437$07.25/0 1988 American Chemical Society

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  • 438 INORGANIC AND ORGANOMETALLIC POLYMERS

    p o l y m e r i z a t i o n s , which f r e q u e n t l y l e d to undesirable s i d e r e a c t i o n s . We a l s o f i n d that the r e l a t e d monomer, 1,1 - b i s ( 3 - h y d r o x y e t h y l ) f e r r o cene (2) r e a c t s w i t h d i a c i d c h l o r i d e s and d i i s o c y a n a t e s to form ferrocene-containing p o l y e s t e r s and polyurethanes, r e s p e c t i v e l y . Monomers (_1) and (2) are shown i n Scheme I.

    Monomers 1 and 2^ have been synthesized s t a r t i n g from ferrocene, u t i l i z i n g m o d i f i c a t i o n s of procedures o u t l i n e d p r e v i o u s l y by Sonoda and M o r i t a n i H and by Ratajczak et al.12 The intermediate d i a c i d , 1,1 f e r r o c e n e d i c a r b o x y l i c a c i d , was synthesized according to the more convenient procedure of Knobloch and RauscherA Monomer 1 was vacuum d i s t i l l e d p r i o r to use (bp 120C, 1 mm Hg). D e t a i l s of the s y n t h e t i c routes are given i n Scheme 1. I t should be emphasized that i n c o n t r a s t to previous ferrocene-containing monomers,13 and 2 p o s i t i o n the r e a c t i v e amino and hydroxyl groups two methylene u n i t s removed from the ferrocene nucleus. This feature minimizes s t e r i c e f f e c t s and a l s o enables _1 and 2_ to undergo the Schotten-Baumann r e a c t i o n r e a d i l y without the c l a s s i c a l -metallocenylcarbonium i o n e f f e c t p r o v i d i n g any constraints.14,15 Polyamide formation i s vigorous, exothermic, and instantaneous.

    I n t e r f a c i a l or s o l u t i o n polycondensation, w i t h or without s t i r r i n g , was the general procedure u t i l i z e d f o r the p r e p a r a t i o n of the polyamides and polyureas,la D e t a i l s are given i n Table I . An important p o i n t to be noted i s t h a t , i n the u n s t i r r e d i n t e r f a c i a l condensation p o l y m e r i z a t i o n of 1 w i t h sebacoyl c h l o r i d e or t e r e -p h t h a l o y l c h l o r i d e i n the organic phase and t r i e t h y l a m i n e as the proton acceptor, immediate f i l m formation took place at the i n t e r face. The polyamide f i l m s were removed a f t e r 1 h, d r i e d , and u t i l i z e d f o r t a k i n g e l e c t r o n micrographs.

    Attempts to o b t a i n molecular weights of these new i r o n - c o n t a i n i n g polyamides i n m-cresol s o l u t i o n have not- been s u c c e s s f u l , due to the very l i m i t e d s o l u b i l i t i e s of the m a t e r i a l s i n organic s o l v e n t s . S i m i l a r d i f f i c u l t i e s have p r e v i o u s l y been encountered i n the mole- ^ c u l a r weight dtermination of nylon 66 (polyhexamethyleneadipamide). However, the i n t r i n s i c v i s c o s i t y values greater than 1.0 f o r the polyamides obtained from 1_ and t e r e p h t h a l o y l c h l o r i d e or sebacoyl c h l o r i d e are comparable to i n t r i n s i c v i s c o s i t i e s of nylons having number average molecular weights between 10,000 and 18,000.16 -jhe low [] values obtained f o r the polyurethanes can be a t t r i b u t e d to premature p r e c i p i t a t i o n from s o l u t i o n and, i n the case of polymers obtained from _1 and TD1, to decreased r e a c t i v i t y imposed by s t e r i c e f f e c t s . 1 8

    19 The polyamides and polyureas e x h i b i t e d broad, intense N-H

    s t r e t c h e s around 3300 cm~l. A very strong carbonyl s t r e t c h i n g v i b r a t i o n was present at 1630 cm~l. The amide I I band was evident near 1540 cm"!. In a d d i t i o n , sp C-H s t r e t c h e s occurred around 3100 cm"! and asymmetric and symmetric sp^ c-H s t r e t c h e s at 2950 and 2860 cm~l, r e s p e c t i v e l y . The polyurethane showed the carbonyl abs o r p t i o n near 1700 cm"l and C-0 s t r e t c h e s i n the v i c i n i t y of

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  • 36. GONSALVES AND RAUSCH Organometallic Monomers 439

    C H 3 C 0 C 1 , A l C l ? ^ I * 5% NaOCl N | * C H 2 C 1 2 , 3 h a

    F

    f

    e

    v 0 5 0 C , 5 h F , e

    (58%) (75%)

    C 0 2 C H 3 ^ ^ - 6 2 0

    CH 3 OH, H 2 S O k ^ 1 L i A l H t , , Et20 ^ ^ ^ ^ ^ C 0 2 C H 3 ' 4 ^ C H 2 0 H

    (90%) (98%)

    ^ ^ ^ ^ - C H 2 C N ^ ^ 3 3 ^ C H 2 C H 2 N H 2 P C 1 3 , THF KCN, H 2 0 I L i A l H H , A 1 C 1 3 ^ 1 2 5 C , 2 h ( N 2 ) Th * y C ^ r W E c2 3 h > - = j = ^

    (85%) I (73%) 'NaOH

    E tOH,

    ^ I ^ L i A l H i + , THF ^ |

    H 2 C00H

    H 2 CH 2 OH

    H 2 CH 2 OH

    2 (70%) (98%)

    Scheme I .

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  • 440 INORGANIC AND ORGANOMETALLIC POLYMERS

    Table I. Polycondenstion Reactions between 1,1f-Bis(3-amino-ethyl)ferrocene (1) and (3-hydroxyethyl)ferrocene (2) with Diacid Chlorides and Diisocyanates

    monomer ( M ^ (M 2)

    process (base used)

    % yield dL/g e

    i a terephthaloyl chloride (CI^Cl^ UI b(Et 3N) 72 1.50 i a sebacoyl chloride (CCl^) UI (Et3N) 85 O.37 i a sebacoyl chloride (CCl^) UI (NaOH) 39 O.59 i a sebacoyl chloride (CCl^) I b (Et3N) 51 1.09 i a adipoyl chloride (CCl^) UI (Et3N) 47 O.53 1 terephthaloyl chloride(CH 2C1 2) S b (Et3N) 45 O.80 2 terephthaloyl chloride

    (m-xylene, reflux) S (pyridine) 51 O.16

    2 TDI (Me2S0, 115 C) S 46 O.20 i a TDI (CHC13) UI 58 O.16 1 TDI (CHC13) S 53 O.10 1 MDId S 67 f

    Monomer in aqueous phase bUI, unstirred interfacial S, solution I, Stirred interfacial CTDI: tolyene 2,4-diisocyanate (80%) +2,6, isomer (20%) dMDI : methylenebis(4-phenylisocyanate) 6 Intrinsic viscosity determined in m-cresol at 3?C ^insoluble in m-cresol 1220 and 1280 cm ^. Similar absorptions were present in the poly-ester. The polyamides and polyureas are thus assessed to have structures outlined in Scheme II. Model Compounds. Further elucidation of these polymer structures was done by synthesizing model analogs.

    20 It has been demonstrated by Hauser and coworkers that 3-amino-

    ethylferrocene (_3) undergoes reactions typical of the amino func-tional group.

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  • 36. GONSALVES AND RAUSCH Organometallic Monomers 441

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  • 442 INORGANIC AND ORGANOMETALLIC POLYMERS

    They showed that _3 afford e d a p i c r a t e on being t r e a t e d w i t h s a t u r ated a l c h o h o l i c p i c r i c a c i d and formed N,N,N-trimethyl - 3-ferrocenyl-ethylammonium i o d i d e on being t r e a t e d w i t h methyl i o d i d e . 3-Amino-eth y l f e r r o c e n e (3) was synthesized by a m o d i f i c a t i o n of the l i t e r a ture method^O and was c h a r a c t e r i z e d by elemental a n a l y s i s , IR and -4i NMR spectroscopy. Following the procedure of Pittman et a l . , ^ 1 the methiodidide of ,-dimethylaminomethylferrocene was converted to f e r r o c e n y l a c e t o n i t r i l e by r e f l u x i n g w i t h sodium cyanide i n de-oxygenated water. The l a t t e r compound was then reduced to the amine _3 w i t h L 1 A I H 4 . In order to i s o l a t e pure _3, i n s t e a d of passing hydrogen c h l o r i d e gas i n t o an ether s o l u t i o n of 3,^ 6N H2SO4 was used. The p r e c i p i t a t e d ferrocenylammonium s u l f a t e was f i l t e r e d under n i t r o g e n and t r e a t e d w i t h aqueous sodium hydroxide to o b t a i n the f r e e amine _3 i n the organic l a y e r . Pure 3-aminoethylferrocene (3) was obta i n e d i n 70% y i e l d by d i s t i l l a t i o n under*vacuum (b.p. 120C/1 t o r r ) .

    A suspension of 3-aminoethylf errocene (_3) i n deoxygenated water, c o n t a i n i n g an excess of sodium hydroxide, was found to form a yel l o w p r e c i p i t a t e immediately on being shaken v i g o r o u s l y w i t h one equival e n t of pure t e r e p h t h a l o y l c h l o r i d e i n dry benzene. Elemental analys i s and an IR spectrum i n d i c a t e d the y e l l o w p r e c i p i t a t e to have the s t r u c t u r e h_ ( y i e l d 100%) .

    In _3, the amino f u n c t i o n a l group i s two methylene u n i t s removed from the ferrocene nucleus. I t appears from the instantaneous and q u a n t i t a t i v e formation of 4_ from _3 that t h i s feature minimizes s t e r i c e f f e c t s and a l s o enables _3 to undergo the Schotten-Baumann r e a c t i o n r e a d i l y without the c l a s s i c a l -metallocenylcarbenium i o n e f f e c t s p r o v i d i n g any c o n s t r a i n t s . ^ The IR spectrum of 4^ showed the c h a r a c t e r i s t i c N-H s t r e t c h at 3320 cnTMs), the amide 1 (carbonyl) s t r e t c h a t 1625 cm" 1(s), the amide I I (N-H) s t r e t c h at 1540 c m " l ( s ) , and the amide I I I band at 1310 cm~ 1(m). In a d d i t i o n , c h a r a c t e r i s t i c absorptions of the f e r r o c e n y l group were evident at 1100 and 1000 cm"l ( i n d i c a t i n g an unsu b s t i t u t e d c y c l o p e n t a d i e n y l r i n g ) and at 800 cm~l.

    In a d d i t i o n to the above r e a c t i o n , 1 , l ' - b i s ( 3 - a m i n o e t h y l ) -ferrocene (3) was reacted w i t h two equivalents of benzoyl c h l o r i d e

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  • 36. GONSALVES AND RAUSCH Organometallic Monomers 443

    i n the presence of t r i e t h y l a m i n e . A product (5) whose i n f r a - r e d spectrum c l o s e l y resembled that of 4_ was obtained.

    As before, an N-H s t r e t c h was observed at 3325 cm ( s ) , the amide I at 1650 c m _ 1 ( s ) , amide I I at 1550 c n T ^ s ) , and amide I I I at 1325 cm"l(m) .

    I t i s w e l l e s t a b l i s h e d that primary amino-functional groups, p a r t i c u l a r l y a l i p h a t i c ones, react instantaneously w i t h isocyanates to form ureas at ambient temperature. Indeed t h i s was observed when -aminoethy1ferrocene (3) and f r e s h l y d i s t i l l e d phenylisocyanate were shaken v i g o r o u s l y . A yellow p r e c i p i t a t e separated out immedia t e l y . Elemental a n a l y s i s and an IR spectrum of the product i n d i c a t e t h i s compound to have the s t r u c t u r e 6^.

    Fe

    The c h a r a c t e r i s t i c absorptions of the urea group were evident i n the IR spectrum: -NH s t r e t c h 3320 cm~ 1(s); amide I 1625 cnT^m); amide I I 1560 cm" 1(s); amide I I I 1240 cnT^m). The y i e l d of 6^ was again q u a n t i t a t i v e . When the diamine 1 was s i m i l a r l y reacted w i t h phenylisocyanate, a y e l l o w p r e c i p i t a t e was observed immediately. The IR spectrum of t h i s product (7) was s i m i l a r to that of 6. The -NH s t r e t c h occurred at 3300 cm"~l(s) and the carbonyl absorption at 1630 cm"" 1(s). The amide I I band occurred at 1550 cm~"l(s,br) and the amide I I I at 1260 ^).

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  • 444 INORGANIC AND ORGANOMETALLIC POLYMERS

    Segmented Poly(ether urethane) Films Containing Ferrocene Units i n the Hard Segments

    Segmented poly(ether urethanes) were synthesized from polypropylene g l y c o l (PPG) and 4,4 Methylene-bis(phenyl-isocyanate) (MDI), using l , l f - b i s ( $ - a m i n o e t h y l ) f e r r o c e n e (1) and 1,1 T-bis(-hydroxyethyl)-ferrocene (2) as chain extenders.

    Synthesis of Polyurethanes. In the "prepolymer method" employed i n t h i s study, MDI (2 equivalents) and PPG (1 equivalent) were reacted at 60C i n the presence of 1% d i b u t y l t i n d i l a u r e a t e as c a t a l y s t , i n the melt. The course of the polymerizations was followed spectro-s c o p i c a l l y by observing the i n t e n s i t y of the ^NCO peak i n the IR (Scheme I I I ) .

    MDI i t s e l f e x h i b i t s a strong NCO peak at 2260 cm ^. A f t e r the above r e a c t i o n had proceeded f o r 30 min, a small a l i q u o t was withdrawn from the r e a c t i o n v e s s e l and i t s IR spectrum recorded. I t showed a strong absorption at 2260 cnT^ c h a r a c t e r i s t i c of the NCO group. S i m i l a r l y , a f t e r 60 min the absorption f o r NCO was s t i l l strong. The prepolymer thus obtained had r e a c t i v e NCO groups. When t h i s prepolymer was cured i n a vacuum oven f o r 12 h at 60 C, the r e s u l t i n g m a t e r i a l also e x h i b i t e d a strong broad absorption at 2245 cm~l. Likewise, a s i m i l a r prepolymer allowed to cure at ca. 20C i n a i r showed the above absorption. Thus i n a l l cases, the prepolymer possessed r e a c t i v e isocyanate end groups.

    A f t e r the MDI and PPG had reacted to form the prepolymer, 1 (1 equivalent) i n dry DMF was added as the chain extender. The re a c t i o n was then continued at ambient temperature, ca. 20C, f o r 3 h followed by curing at 20C f o r 24 h i n vacuum. No isocyanate group absorption was observed i n the IR spectrum of the block poly(urea urethane) polymer (BPUla). A l t e r n a t i v e l y , the curing was also c a r r i e d out at 60C i n a vacuum oven f o r 24 h. No isocyanate group absorption was observed i n the IR spectrum of t h i s polymer (BPU1). However, the d i f f e r e n c e i n curing procedures produced dark brown f i l m s having d i f f e r e n t s o l u b i l i t i e s . The former was soluble and the l a t t e r i n s o l u b l e i n DMF.

    The complete disappearance of the NCO peak i n the IR spectra of these dark-brown translucent f i l m s i s a good i n d i c a t i o n that comple t e chain extension or cure had occurred. In the l a t t e r case,

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  • 36. GONSALVESANDRAUSCH Organometallic Monomers 445

    DMF,60eC/3 h

    viscous residue

    cured at 60eC f o r 24 h

    No NCO peak in IR

    (BPUR2)

    (MDI)

    +

    CH-

    rr-H>-CH--CH2- r^OH (PPG)

    Dibuty l t i n d i laurea te 60 e C, Melt -1

    c m

    -IL-* VNC0: 2260 (s) 30 mi

    30 min

    PREPOLYMER c m

    - ^ V N C 0 M2260 (s)

    1730 (s)

    20*C/3 h

    cured a t 20eC f o r 24 h

    No NCO peak in IR

    (BPUla)

    No NCO peak in IR (BPU1)

    cured at 60C f o r

    24 h

    Scheme I I I .

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  • 446 INORGANIC AND ORGANOMETALLIC POLYMERS

    however, the i n s o l u b i l i t y of the f i l m i n DMF a l s o i n d i c a t e s that b i u r e t branching and c r o s s l i n k i n g could have occurred on c u r i n g at 60C f o r 24 h, as might be a n t i c i p a t e d .

    The above prepolymer on treatment w i t h 2_ as the chain extender i n dry DMF d i d not proceed at ambient temperature. The mixture had to be heated to 60C f o r 3 h before the r e a c t i o n was complete. A f t e r c u r i n g at 60C f o r 24 h, the y e l l o w , t r a n s l u c e n t block polyurethane f i l m (BPUR2) again showed the absence of the NCO peak i n the IR spectrum i n d i c a t i n g that c u r i n g had been complete. The f a c t that a higher temperature had to be used i n the case of 2_ as the chain extender compared to 1. i s i n keeping w i t h the lower order of react i v i t y of d i o l s w i t h d i i s o c y a n a t e s as compared to diamines w i t h d i i s o c y a n a t e s .

    On the b a s i s of t h e i r i n f r a r e d s p ectra the polymers BPUla and BPUR2 were assessed to have the s t r u c t u r e s 8 and 9_ r e s p e c t i v e l y , as given i n Figure 1.

    Polymer BPUla showed the c h a r a c t e r i s t i c NH s t r e t c h at 3350 cm 1 along w i t h the corresponding amide I and I I absorptions at 1735(s)_^ and 1530 (br) cm"1 r e s p e c t i v e l y . A carbonyl absorption at 1650 cm was a s c r i b e d to the urea group i n t h i s polymer. A strong C-O-C (br) peak at 1100 cm"1 and CH s t r e t c h e s at 3050, 2940, and 2860 cm"1 were a l s o observed. The polymer BPUR2 al s o showed the c h a r a c t e r i s t i c NH s t r e t c h at 3300 cm"1 and the amide I and I I absorptions at 1720 (s) and 1530 (s) cm"1, r e s p e c t i v e l y . Again the C-O-C s t r e t c h was observed at 1100 cm"1 and the CH s t r e t c h e s at 3050, 2940, and 2860 cm"1. These c o r r e l a t i o n s compare w e l l w i t h the IR spectra of s i m i l a r segmented polyurethanes. "

    The i n c l u s i o n of _1 as an i n t e g r a l part of the polyurethane system was confirmed i n the s y n t h e s i s of BPUla. A f t e r the r e a c t i o n had been completed, the mixture was poured i n t o excess d i e t h y l ether, r e s u l t i n g i n a yellow g e l a t inous p r e c i p i t a t e . The y e l l o w viscous m a t e r i a l was separated and allowed to cure at ambient temperature f o r 24 h. The r e s u l t i n g t r a n s l u c e n t yellow f i l m was s o l u b l e i n DMF. The amount of i r o n determined by elemental a n a l y s i s i n t h i s sample was 1.1% (4% f e r r o c e n e ) . Thus the IR s p e c t r a , elemental analyses, as w e l l as p r e c i p i t a t i o n procedure f o r BPUla a l l point towards the i n c l u s i o n of 1 i n the polyurethanes v i a chemical l i n k a g e , and not by j u s t mere p h y s i c a l compounding. The percentage of i r o n i n the other polyurethanes, BPU1 and BPUR2, were determined to be approximately 1.9 and 1.2%, r e s p e c t i v e l y , c o r r e s ponding to 6.7% and 5% ferrocene u n i t s i n the copolymers.

    The molecular weight d i s t r i b u t i o n (MWD) of the l i n e a r polyurethanes were determined by GPC. The solvent used was THF and the instrument c a l i b r a t e d _ b y narrow MWD polystyrenes. Polymer BPUla had an M of 56,000 (M :12,500); and BPUR2 M of 97,000 (M :9,100). w w Mass Spectrometry. Mass spectrometric (MS) a n a l y s i s has been u t i l i z e d f o r polymer and copolymer s t r u c t u r a l i d e n t i f i c a t i o n ^ . Recently Dussel et a l . 2 5 u t i l i z e d pyrolysis-MS to c h a r a c t e r i z e

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    In Inorganic and Organometallic Polymers; Zeldin, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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