Synthesis of Polydiacetylenes from Novel Monomers Having Two Diacetylene Units Linked by an Arylene Group

Polymer Journal, VoL 33, No. 2, pp 182-189 (200 I) Synthesis ofPolydiacetylenes from Novel Monomers Having Two Diacetylene Units Linked by an Arylene Group Hiroshi MATSUZAWA, Shuji OKADA, Abhijit SARKAR, Hiro MATSUDA,* and Hachiro NAKANISHI Institute for Chemical Reaction Science, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan *National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba 305-8565, Japan (Received September 14, 2000; Accepted October 19, 2000) ABSTRACT: Three novel monomers 4BCMU4A(Ar) with chemical structures of R-C=C-C=C-Ar-C=C-C=C-R, where R=-(CH 2 ) 4-0CONHCH 2 COOC 4 H 9 and Ar= 1,4-phenylene (Ph) or 2,3,5,6-tetrafluoro-1,4-phenylene (PhF) or 4,4'biphenylene (Biph), were synthesized. 4BCMU4A(Ph) was found to be stable for solid-state polymerization, although 4BCMU4A(PhF) and 4BCMU4A(Biph) could be polymerized by UV or y-ray irradiation. The polymerization for two polymerizable monomers was investigated in detail mainly by solid-state 13 C NMR. The polymerization of 4BCMU4A(PhF) and 4BCMU4A(Biph) took place by 1,4-addition reaction at one of the butadiyne moieties in the monomer to give singlechain-type polydiacetylenes with the respective butadiynylaryl moiety as a side chain and ladder-type ones were not obtained. High crystallinity was confirmed for these polymers by X-Ray diffraction. Polydiacetylene obtained from 4BCMU4A(PhF) was found to be dispersed in organic solvent. Visible absorption spectra of this polymer in dispersion state with different compositions of solvents and in amorphous state were investigated in comparison with the spectrum in the crystalline state. KEY WORDS Bis(butadiynyl)arene I Solid-State Polymerization I Polydiacetylene I Polydiacetylenes (PDAs) are a unique class of nconjugated polymers obtainable by solid-state 1,4addition polymerization of diacetylenes (DAs). 1• 2 The polymerization is usually stimulated by UV or y-ray or annealing. Since the reaction is topochemically controlled, the reactivity of DAs is greatly affected by packing in crystals. 3 In fact, when those DAs in crystals have stacking distance d of adjacent molecules in the array of about 5 A and angle l/J between the DA rod and stacking axis of about 45°, 1,4-addition polymerization occurs (Scheme 1). Since molecular packing in crystals is determined by the substituents attached to the DA moiety, the substituents affect the reactivity of the DAs by physical disposition rather than chemical nature. In this connection, much research has been performed to explore the relationship between structure and reactivity ofDAs. 1 - 4 PDAs are important for topochemical polymerization studies. Much research on physical properties of PDA such as electrical, 5 chromic, 6 and nonlinear optical (NLO) properties, 7 which originate from its quasi-one dimensional n-conjugated backbone structure, has been undertaken. Especially, third-order NLO properties of PDAs have attracted interest. 8 - 10 To achieve larger X( 31 on PDA, several PDAs have been proposed and synthesized with tailor-made molecular design by the following two ways. One is the extension of n-conjugation system and the other is increase of n-conjugated polymer backbone density _II - 19 For the extension of n-conjugation, the introduction of n-conjugated substituents directly attached to the PDA backbone seems indispensable. 15 Direct attachment of aromatic 16 or acetylenic 17 substituents to the polymer backbone for the single-chain PDAs is effective to modify the electronic structure of the polymer backbone resulting in enhancement of %( 31 • 18 •19 For increase of n-conjugated polymer backbone density, ladder-type PDAs as shown in Scheme 2 are promising, because n-conjugation density is at least almost doubled 182 simply due to increase in PDA backbones per monomer unit when the monomer molecular length is fixed. Thus, we synthesized several monomers for the ladder-type PDA having an inner substituent (X) between two DA moieties with outer substituents (R). 11 - 14 We designed and synthesized three novel monomers with 1,4-phenylene or 2,3,5,6-tetrafluoro-1,4-phenylene or 4,4'-biphenylene as inner substituents X and alkoxycarbonylmethylurethane (AU: -( CH 2 ) 4 -0CONHCH 2 COO-(CH 2 ) 4-H) groups as outer substituents R in the present work. The AU group was selected because hydrogen bonding between AU groups in adjacent monomers is expected to form rigid crystalline structure, resulting in smooth solid-state polymerization. If both butadiyne moieties of these monomer can be polymerized, the ladder-type PDA in Scheme 2 with n-conjugation between two polymer backbones may be produced. Even if only one butadiyne moiety in a monomer is polymerized to give single-chain-type PDAs, n-conjugation effect of ! R R R R d hvor 1'1 R qJ Diacetylene monomer Polydiacetylene Scheme 1. Polymerization scheme of DA monomers. When the condition for monomer array in solid state is satisfied, where the distanced and angle qJ are about 5 A and 45°, polymerization occurs at 1,4-position to give PDA. Synthesis ofPolydiacetylenes from Novel Monomers ' ' R R X R'' X R First step """" -....o: "'"R Second step R ' R R "'"-- -....-:: -....o:R R' R X -....-:: R "'"- -....o:R R Single-chain-type PDA Monomer Scheme 2. R Ladder-type PDA Polymerization scheme of monomers with two DA moieties modified by an inner linkage X and two outer substituents R. \.#Br HO'\ 2 ________ _ KOH CuCI, i-PrNH 2 #"' Pd(PPh3)2CI2 1-Ar-1 40L4A(Ar) Et 3N, CuCI 5a,5b,5c HO 6a,6b,6c Ar= _#R 0 7 pyridine _#' R 4BCMU4A(Ar) Sa,Sb, Sc -o- * F. F F F (Ph): Sa, 6a, Sa (PhF): 5b, 6b, 8b -o-o- (Biph): 5c, 6c, Be H 0 R 0 Scheme 3. Synthetic scheme for 4BCMU4A(Ar) monomers. the aromatic substituents to polymer backbone improve optical properties compared with conventional PDAs. This paper reports the synthesis of the monomers mentioned above, and mechanisms of polymer formation as well as structures of the polymers. We used various techniques such as solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and powder X-Ray diffraction (XRD). Absorption spectra were used to characterize the polymers. Since one of the polymers forms dispersion in organic solvent, absorption properties for this dispersion state were studied. EXPERIMENTAL Scheme 3 shows the synthetic route of investigated monomers 8a-8c, abbreviated as 4BCMU4A(Ar). Solvents and reagents in this work were purified according to standard literature techniques. 2° Commercially availPolym. J .• Vol. 33, No.2, 2001 able 5-hexyn-1-ol (Lancaster), 1,4-diiodobenzene (Kanto Chemical), 1,4-diiodo-2,3,5,6-tetrafluorobenzene, 4,4'diiodobiphenyl (Aldrich) and butyl isocyanatoacetate (Tokyo Kasei Kogyo) were used as obtained. Preparation of 5,7-octadiyn-1-ol4 was carried out according to a similar procedure reported earlier. 21 Purification of the synthesized compounds was d (...truncated)