Nickel-catalyzed polymerization which employs the coupling of isomeric dichlorobenzophenones is described. The polymerization utilizes inexpensive readily available monomers, 4,4-dichlorobenzophenone (4,4'-DCBP) and 2,5-dichlorobenzophenone (2,5-DCBP). The poly(4,4'-benzophenone) can be derivatized to be soluble during the synthesis by the use of a ketimine precursor that is subsequently hydrolyzed to give the target material. The polymerization of 2,5-dichlorobenzophenone yields a soluble derivative of poly(p-phenylene). The resulting polymers were characterized to confirm the composition, molar mass, and thermal properties. The Ni(O) catalyzed route proves to be facile and economically feasible and opens the way to a large variety of heterocyclic and phenyl-based homo- and copolymers

DeSimone, J.M.

Phillips, R.W.

Samulski, E.T.

Sheares, V.V.

Carolina Digital Repository

1.Isomeric Poly(benzophenone)s: Synthesis of Highly Crystalline Poly(4,4'.benzophenone) and Amorphous Poly(2,5-benzophenone),A Soluble Poly(p-phenylene) DerivativeR.W. Phillips, V.V. Sheares, E.T. Samulski, J.M. DeSimone*Departnment of ChemistryUniversity of North Carolina at Chapel HillKenan and Venable LaboratoriesChapel Hill, N.C. 27599-3290Abstract.Nickel-catalyzed polymerization which employs the coupling of isomericdichlorobenzophenones is described. The polymerization utilizes inexpensive readilyavailable monomers, 4,4-dichlorobenzophenone (4,4'-DCBP) and 2,5-dichlorobenzophenone (2,5-DCBP). The poly(4,4'-benzophenone) can be derivatized tobe soluble during the synthesis by the use of a ketimine precursor that is subsequentlyhydrolyzed to give the target material. The polymerization of 2,5-dichlorobenzophenoneyields a soluble derivative of poly(p-phenylene). The resulting polymers werecharacterized to confirm the composition, molar mass, and thermal properties. The Ni(O)catalyzed route proves to be facile and economically feasible and opens the way to a largevariety of heterocyclic and phenyl-based homo- and copolymers. Accesioji For ...NTIS CRA&IDTIC TABUn:urojitcect uJustific atior.............................................  .... .... ...Dist, ib!tioii IAvalabafity CodesDist IAaIai94-08960 PTT 10~94' 3 21- 0282Herein we describe a nickel-catalyzed polymerization which employs the couplingof bis(arylhalide)s as the polymer-forming reaction in a step growth polymerization ofisomeric dichlorobenzophenones. The reaction utilized has general applicability to thesynthesis of new processable engineering resins of superior thermal stability. Thesynthetic approach was first demonstrated by Colon et. al. I in the synthesis of biphenyl.They found that a Ni(O)-catalyzed system would quantitatively convert chlorobenzene tobiphenyl in short times at mild temperatures. It was thought that since the coupling of arylchlorides could be achieved in high yields, the possibility existed for the use of this catalystas a route to high polymer by coupling difunctional monomers. Poly(ether ether sulfone)s 2were chosen by Colon as the first system to be studied because they are generallyamorphous and soluble in dipolar aprotic solvents such as N,N-dimethylacetamide (DMAc)and 1-methyl-2-pyrrolidinone (NMP) at the relatively low temperatures (70 °C) required toproduce high polymer. Further studies of this system, 3 in addition to a variety ofpoly(arylene ether ketone)s, have been investigated by Ueda et al.4 Ueda utilized Ni(0)coupling of aromatic dichlorides containing ether-ketone structures to prepare highmolecular weight poly(arylene ether ketone)s. This method proved advantageouscompared with conventional methods because of the high rates and the mild conditions ofthe reaction.Recently, Percec extended the use of this catalyst system in an attempt to synthesizesoluble poly(phenylene)s. 5 Percec's efforts in the design of soluble materials werefocused on the polymerization of "crankshaft" type monomers. Specifically, they reportedthe synthesis of Ni(O)-catalyzed oligomerization of 4,4!"-dichloroquaterphenyls. In spiteof the fact that the kink was introduced, molecular weight was still limited due to poorsolubility (<Mn> = 9.0 x 10 2 g/Mol).As is well known, poly(p-phenylene) (PPP) exhibits remarkable thermal stabilities.They have been considered for use in numerous thermally robust organic materialsincluding composites, lubricant additives and thermoset precursors for high performanceaerospace materials applications. The improvement of the solubility of poly(phenylene) hasbeen attempted by attaching lateral substituents.6,7 Appropriately substituted materialsshould be soluble and yet exhibit thermal properties comparable to that of PPP. Severalresearchers have examined the substitution of PPP via polymerization techniques other thanNi(0) catalysis to vary polymer properties. Schluter et.al.8P have described the palladium-catalyzed polymerization of alkyl-substituted poly(p-phenylene) derivatives. In somecases, degrees of polymerization of 30 to 50 could be achieved and solubility bemaintained. Tour has also investigated the substitution of a PPP backbone, but with thegoal of making thermoset precursors. 1O Specifically, they reported the functionalization of3brominated PPP with several alkynes. A tetrahydrofuran promoted polymerization ofbromo-lithiobenzene gave the polymer and subsequent replacement of the bromines withlkkynes led to the target materials. Novak has focused on the synthesis of water solublepoly(p-quaterphenylene 2,2'-dicarboxylate) via the palladium-mediated cross-coupling ofaryl halides and arylboronic acids. 11 The resulting polymers12 are rodlike polyelectrolytesthat have the unusual properties of water solubility, conformational rigidity, and chargedcharacter similar to biopolymers. More recently, Morrocco reported the physical propertiesof soluble poly(p-phenylene) derivatives. 13 The synthetic details were not disclosed, but itwas suggested that the "route involves relatively inexpensive materials". These substitutedpoly(p-phenylene)s were reported to be soluble in common organic solvents and exhibitnumerous interesting properties which make them candidates for high performanceapplications. Herein, we report the synthesis of isomeric poly(benzophenone)s usingNi(0) catalysts for the polymerization of inexpensive, readily available monomers, 4,4'-dichlorobenzophenone (4,4'-DCBP) and 2,5-dichlorobenzophenone (2,5-DCBP).The first polymerization was attempted using 4,4'-dichlorobenzophenone in N,N-dimethylacetamide (DMAc). Realizing that the 4,4'-DCBP would give a rigid, insolublematerial, polymerization was accomplished through a ketimine derivative-- a methodologyderived by McGrath et. al. 14 for the synthesis of amorphous poly(arylene ether ketone)s.For our purposes, the required ketimine functional dichloride monomer (1) wassynthesized by the treatment of 4,4'-DCBP with aniline in the presence of molecular sievesto give a bright yellow product in 50 % yield. After two recrystallizations from toluene,the purity of I was >99.9% by gas chromatography. The polymerization was thenperformed using the Ni(0) catalyst prepared from NiCI2 (0.3125 moles),triphenylphosphine (0.0093 moles), bipyridine (0.3886 moles) and zinc dust (0.0495moles) in DMAc. The monomer was dissolved in DMAc, added to the active catalyst (asevidenced by the deep red color) and stirred at 80 °C for 24 h. The resulting polymer(11) 15 was soluble in DMAc and gave an inherent viscosity of 0.25 dUg (NMP, 30 C).When this polymerization was repeated in 1-methyl-2-pyrrolidinone (NMP), an increase ininherent viscosity was seen (0.36 dUg ; NMP at 30 C) presumably due to the increasedsolubility in NMP. The amorphous polymer had a glass transition temperature of 225 °Cwith a 5% weight loss temperature in nitrogen at 558 *C. The amorphous prepolymer washydrolyzed in 10% hydrochloric acid solution to generate poly(4,4'-benzophenone) (III)which is completely insoluble presumably due to high levels of crystallinity. 16 The 5%weight loss temperatures in air and nitrogen were 510 °C and 560 °C, respectively(Figure 1).40+ H2N-QTolueneMolecular sieves (3A)2NCl -J -- a~Q- Cl (INiC12 , ZnTriphenylphosphinebipyridineDMAc2NC (Ihydrolysis0Synthesis of poly(2,5-benzophenone) not only increases the solubility of thepolymer compared with the poly(4,4'-benzophenone), but also changes the polymer5backbone to a substituted poly(p-phenylene). Synthesis of the monomer (IV) wasaccomplished by an aluminum chloride catalyzed acylation of benzoyl chloride and p-dichlorobenzene in a 1:1 ratio. The reaction was followed by TLC and completeconversion was seen after 3 h. Recrystallization from ethanol gave polymer grademonomer 17 (>99.9% purity by GC) that was analyzed extensively by a series of 2D NMRexperiments to verify the correct isomer and rule out the possibility of halogen exchangeduring acylation. Once 2D NMR experiments confirmed the structure, the 13C could beutilized to identify subsequent reaction products. 18 For this polymerization, we referred toColon's original paper in which he described the quantitative synthesis of biphenyl fromchlorobenzene. It was noted that the addition of an alkali metal salt to the reaction in one tothree equivalents decreased the total reaction time from 2 h to 20 minutes. Upon additionof one equivalent of sodium bromide to the polymerization and the use of an overheadstirrer, high molar mass polymer was obtained (V).6,AICI3Q_ C=Cl (IV)NiCI2 , ZnTriphenylphosphinebipyridineNaBrNMPQ({(5)The resulting light yellow material was characterized by a number of techniques ii order toconfirm composition and molar mass. The molar mass was analyzed by GPC giving a<Mn> = 12.4 x 103 g/mol19 (Figure 2). Poly(2,5-benzophenone) has a Tg = 219 °C and75% weight loss temperatures in air and in nitrogen of 496 "C and 495 "C, respectively(Figure 3).In conclusion, it is apparent that use of the Ni(O) catalysts in polymerization ofbis(aryl chloride)s leads to high molar mass polymers. In the case of poly(4 ,4'-benzophenone), the ketimine derivatized monomer gave increased solubilities resulting inhigher molar mass. The successful polymerization of 25-DCBP yields a soluble derivativeof poly(p-phenylene). Further work to increase the conversion, and therefore themolecular weight o the polymer in addition to more in-depth thermal analysis is underway.This Ni(O)-catalyzed polymerization is a facile and economically feasible synthetic routeand opens the way to a low temperature, mild reaction for a large variety of heterocyclicand phenyl-based homopolymers. Moreover, the ability to make a wide range ofcopolymers enables one to tailor make polymers that will be generally applicable forutilization as advanced materials.Acknowledgements.We would like to thank the National Science Foundation for a Young InvestigatorAward (JMD: 1992-1993) and a Presidential Faculty Fellowship (JMD: 1993-1997). Inaddition, we thank DuPont, Hoechst-Celanese, The Office of Naval Research for financialsupport. VVS also gratefully acknowledges financial support through a Kodak CorporateResearch Fellowship.References.1) Colon, I.; Kelsey, D.R. J. Org. Chem. 1986,51, 2627.2) Colon, I.; Kwiatkowski, G.T. J. Polym. Sci. Pt. A. 1990, 28, 367.3) Ueda, M.; Ito, T. Polym. J. 1991, 23, 297.4) Ueda, M.; Ichikawa, F. Macromolecules, 1990, 23,926.5) Percec, V.; Okita, S. J. Polym. Sci. Pt. A.. 1993, 31, 877.6) Kern, W.; Gruber, W.; Wirth, H.D. Makromol. Chem. 1960, 37, 198.7) Krigbaum, W.R.; Krause, K.J. J. Polym. Sci. Polym. Chem. Ed. 1978,16, 315.8) Rehahn, M.; Schluter, A.D.; Wegner, G.; Feast, W.J. Polymer 1989,30, 1060.9) Rehahn, M.; Schluter, A.D.; Wegner, G. Makromol. Chem 1990,191, 1991.10) Stephens, E.B.; Tour, J.M. Macromolecules 1993,25, 2420.811) Wallow, T.I.; Novak, B.M. J. Am. Chem. Soc. 1991, 113, 7411.12) Wallow, T.I.; Novak, B.M. Polym. Prepr. (Am. Chem. Soc. Div. Polym. Chem.)1992, 33, 1218.13) Baum, R. Chem. and Eng. News 1993, 30.14) Mohanty, D.K.; Lowery, R.C.; Lyle, G.D; McGrath, J.E. Int. SAMPE Symp.Exp. 1987, 32, 408.15) The polymer was isolated by hot filtration to remove the zinc and precipitation intoacetone to remove other remaining catalyst components.16) WAXS analysis of polymer (III) is currently underway.17) M.p. = 88.9 "C; MS, M+ = 251 g/mol.18) 13C NMR of 2,5-DCBP: 0140(C-1); a133(C-2); a131.1(C-3); a128.9(C-4);0129.2(C-5); a131.3(C-6); 4136.2(C-1 '); a130. 1(C-2'); a 128.8(C-3'); a134. 1(C-4'); a 128.8(C-5'); a 130. 1(C-6'); 0 190(C-carbonyl).19) Determined by using a Water 717 GPC in methylene chloride using polystyrenestandards.9Figure CaptionsFigure 1. Thermal gravimetric analysis (TGA) thermograms of poiy(4,4' benzo-phenone) (III) using a heating rate of 10 "C/min.Figure 2. Size exclusion chromatogram of poly(2,5-benzophenone) (V) in CH 2Cl2(I mLimin.) using a refractive index detector at 30 *C.Figure 3. Thermal gravimetric analysis (TGA) thermograms of poly(2,5-benzo-phenone) (V) using a heating rate of 10 *C/min.*• Z91CD In 0 ISI I I0m N/- -Cz uwci I nw 440 c- mz U.)on o4 w'i JJ U .0-- n" O -Iw - " I"CCDLIInI-Z4SEDECO)AUECD 0 N 'cm 0to"I~- toCLw'4ccc mcc 0.CCD0t

Isomeric Poly(benzophenone)s: synthesis of Highly Crystalline Poly(4,4'-benzophenone) and Amorphous Poly(2,5-benzophenone), a Soluble Poly(p-phenylene) Derivative

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Isomeric Poly(benzophenone)s: synthesis of Highly Crystalline Poly(4,4'-benzophenone) and Amorphous Poly(2,5-benzophenone), a Soluble Poly(p-phenylene) Derivative

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