Polymerization and polymer properties of (2-methyl-5-tert-butylphenyl)acetylene: steric effects of the ring substituents

Summary (2-Methyl-5-tert-butylphenyl)acetylene (2Me5tBuPA) polymerized in the presence of MoCl₅-n-Bu₄Sn catalyst in 1,4-dioxane to give a high molecular weight polymer . Not only MoCl₅- but also WCl₆-based catalysts were effective. The polymer obtained was a dark brown solid, soluble in organic solvents such as toluene and CHCl₃, and formed a freestanding film by solution casting. The onset temperature of weight loss of the polymer in air was 260 °C. Its oxygen permeability coefficient was 43 barrers, which is twice that of natural rubber. Differences from the results (usually lower molecular weight, not film-forming, and thermally less stable) of both poly(phenylacetylene) and poly[o-methylphenyl)acetylene] are attributable to the synergistic steric effect of the o-methyl and m-tert-butyl groups.     

Living metathesis polymerization of (p-n-butyl-o,o,m,m-tetrafluorophenyl)acetylene by MoOcl4-n-Bu4Sn-EtOH (1:1:1)

Summary Possibility of living metathesis polymerization by Mo catalysts was examined for (p-n-butyl-o,o,m,m-tetrafluorophenyl)acetylene, which has two fluorine atoms at both ortho positions. The MoOCl₄-n-Bu₄Sn-EtOH (1:1:1) catalyst yielded a polymer with narrow molecular weight distribution ( ), but the corresponding MoCl₅-based catalyst did not formed such a polymer. With the former catalyst, the number-average molecular weight of polymer increased in direct proportion to monomer conversion, while the molecular weight distribution remained narrow; this proves the livingness of the polymerization. The optimal conditions for the living polymerization were [n-Bu₄Sn]/[MoOCl₄]=∼1.0, [EtOH]/[MoOCl₄]=0.5–1.5, and temperature≤30 °C. n-Butyl acetate and acetone as well as EtOH were effective as third catalyst components.     

Polymerization of 1-butyne and isopropylacetylene by transition metal catalysts and geometric structure of polymers

Polymerization of 1-butyne and isopropylacetylene was studied using MoCl₅, WCl₆, and two Ziegler catalysts [Fe(acac)₃-Et₃Al, Ti(On-Bu)₄-Et₃Al]. 1-Butyne was polymerized in high yields with WCl₆ and Fe(acac)₃-Et₃Al to give a yellow, air-sensitive polymer. The cis content of poly(1-butyne), evaluated by ¹³C n.m.r., was about 80% irrespective of polymerization conditions. Isopropylacetylene was polymerized well by any of MoCl₅, WCl₆, and Fe(acac)₃-Et₃Al; the polymer formed was a light yellow air-sensitive powder. The cis content of poly(isopropylacetylene) varied from 65% to 90% according to polymerization conditions. Substituent effects on polymerization and polymer structure are discussed.     

Polymerization of propynes bearing diphenylamino or indolyl groups

Summary Nitrogen-containing acetylenic monomers including 3-(N,N-diphenylamino)-1-propyne (DPAP), N-(2-propynyl)indole (PI), 2-methyl-N-(2-propynyl)indole (2-MePI) and 3-methyl-N-(2-propynyl)indole (3-MePI) polymerized in the presence of various transition metal catalysts. Poly(DPAP) was obtained with WCl₆, MoCl₅, Rh and Fe catalysts, and its weight-average molecular weights (M _w) reached 140x10³. Polymerization of PI and 2-MePI by Rh and Fe catalysts gave good yields of high molecular weight polymers with M _w of 340x10³ and 640x10³, respectively. Polymerization of 3-MePI by WCl₆- and MoCl₅-based catalysts resulted in a soluble polymer (M_w= 52x10³), whereas the use of Rh and Fe catalysts led to the formation of an insoluble polymer. All the polymers exhibited cutoff wavelengths around 450–500 nm, meaning the moderate to fair conjugation along the polymer backbones. Received: 24 June 1998/Accepted: 5 August 1998     

Synthesis and properties of polyacetylenes containing carbazolylmethyl groups

Novel acetylene monomers containing carbazolymethyl groups, 3,5-bis[(3,6-di-t-butyl)carbazolylmethyl]-1-ethynylbenzene (1), 3-(3,6-di-t-butyl)carbazolylmethyl-1-ethynylbenzene (2), and 4-(3,6-di-t-butyl)carbazolylmethyl-1-ethynylbenzene (3) were synthesized, and polymerized with [(nbd)RhCl]₂-Et₃N, Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃], and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 1600 to 115,000 were obtained in 18%-quantitative yields. The UV-vis absorption band edge wavelengths of the polymers obtained with W catalyst were longer than those of the Rh-based polymers. The photoluminescence quantum yields of the W-based polymers were 1.1-3.1%, while those of the Rh-based ones were 0.18-4.1%.     

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94?000 were obtained in 20-98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV-vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.     

Microstructure of polyphenylacetylene obtained by MoCl5 and WCl6 type catalysts

Summary The microstructure of polyphenylacetylenes prepared with MoCl₅ and WCl₆ catalysts under different reaction conditions was determined by 200 MHz ¹H-NMR spectroscopy. Cis, trans and cyclohexadiene sequences were evidenced in all polymers. Two mechanisms are responsible for the polymer microstructure: isomerization prior to double bond formation, and thermal isomerization after double bond formation. When trans sequences are formed mainly through the first mechanism, the polymer is almost void of cyclohexadiene structural units and its molecular weight is very high. This can be explained through a unimolecular termination mechanism, i.e., intramolecular cyclization of the cis-polymer chain end. The control of polyphenylacetylene microstructure by these two mechanisms explains why a cis-cisoidal polymer could not be obtained by using MoCl₅ or WCl₆ catalysts. Dedicated to Prof. H.-J. Cantow in honor of his 60th birthday     

Synthesis, thermal stability, light emission, and fluorescent photopatterning of poly(diphenylacetylene)s carrying naphthalene pendant groups

Naphthalene (Nap)-containing poly(diphenylacetylene)s with different spacer lengths (-{C₆H₅CC[C₆H₄O(CH₂)_mO-Nap]}_n-; P1(m), m = 4, 6, 8) are synthesized. The monomers are prepared by etherifications of 1,m-dibromoalkanes with 1-naphthol and 1-(4-hydroxy)phenyl-2-phenylacetylene and are polymerized by TaCl₅-n-Bu₄Sn and WCl₆-Ph₄Sn catalysts. Whereas the tantalum-based catalyst gives insoluble products in low yields, the tungsten-based catalyst furnishes soluble polymers with high molecular weights (M_w up to 5.0 × 10⁴) in satisfactory yields (up to 62%). The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, PL, and EL analyses. All the polymers are thermally stable: while the polymers lose 5% of their weights at ∼420 °C under nitrogen, no decreases in molecular weights are found after they have been annealed at 200 °C for 2 h in air. When their THF solutions are photoexcited, the polymers emit strong green lights with high efficiencies (up to 98%). No significant shifts in the photoluminescence spectra are observed when the polymers are cast into thin solid films, suggestive of little involvement of aggregative or excimeric emission. A multilayer EL device with a configuration of ITO/P1(8):PVK/BCP/Alq₃/LiF/Al is constructed, which emits a green light of 520 nm with a maximum external quantum efficiency of 0.16%. The spectral stability is outstanding: no recognizable change is observed in the EL spectrum when the device current is raised. Irradiation of a film of P1(8) through a mask photooxidizes and quenches the emission of the exposed regions, resulting in the formation of two-dimensional luminescent photopatterns.     

Synthesis and photoluminescence property of polyacetylenes containing liquid crystalline side groups

A series of new side-chain liquid crystalline (LC) polyacetylenes containing 4-(trans-n-alkylcyclohexanylcarbonyloxy)phenyl 4-alkynyloxybenzoate side groups were synthesized by using [Rh(nbd)Cl]₂, WCl₆ and MoCl₅ as polymerization catalysts. The synthesized polymers were characterized by differential scanning calorimetry, optical microscopy and X-ray diffraction measurements. The monomers showed a nematic phase while all polymers revealed the nematic, smectic A and smectic C phases. X-ray diffraction measurements proved that all the polymers show an interdigitated bilayer structure. The optical properties of the polymers were investigated by UV-vis and photoluminescent spectroscopies. The polymer films emitted green-blue photoluminescence at about 500 nm.     

Synthesis, characterization, and high gas permeability of poly(diarylacetylene)s having fluorenyl groups

Diarylacetylenes having fluorenyl groups and other substituents (trimethylsilyl, t-butyl, bromine, fluorine) (1a-1) were polymerized with TaCl₅-n-Bu₄Sn. Monomers 1a-l produced high molecular weight polymers 2a-l (M_w 5.1 × 10⁵-1.3 × 10⁶) in 12-59% yields. All of the polymers were soluble in common organic solvents, and gave tough free-standing membranes by the solution casting method. The onset temperatures of weight loss of polymers 2a-l in air were over 400 °C, indicating considerably high thermal stability. All the polymer membranes showed high gas permeability; e.g., the oxygen permeability coefficient (PO₂) of 2a was as large as 4800 barrers. Membrane 2d possessing two fluorine atoms at meta and para positions of the phenyl ring showed the highest oxygen permeability (PO₂ = 6600 barrers) among the present polymers.     

Synthesis of a cis-rich,living poly[(o-methylphenyl)acetylene] by use of the MoOCl4-n-Bu4Sn-EtOH catalyst

Summary Polymerization of (o-methylphenyl)acetylene (o-MePA) by MoOCl₄-n-Bu₄Sn-EtOH catalyst in toluene at 0°C provided a cis-rich living polymer; cis 77%, M _w/M _n=1.21. The polymerization at -30°C gave results similar to those for 0°C, whereas the polymer obtained at 30°C exhibited a broader molecular weight distribution (MWD) and a lower cis content. Among several organotin compounds, only n-Bu₄Sn was effective for the living polymerization of o-MePA. The bulkier the alkyl group of alcohols as the third catalyst component, the broader the MWD of the polymer, while the geometrical structure was not affected by the alcohols.     

Metathesis copolymerization of chlorine-containing acetylenes with NBE catalyzed by MoCl5-n-Bu4Sn

Summary In the copolymerizations of 1-chloro-1-octyne (ClOc) and 1-chloro-2-phenylacetylene (ClPA) with norbornene (NBE) by MoCl₅-n-Bu₄Sn in toluene at-20°C, both comonomers were consumed simultaneously. The GPC curves of the copolymerization products were unimodal and identical irrespective of the RI and UV (290 nm) detectors. The¹³C NMR spectra of the products exhibited the presence of cross-propagating sequences. From these results, it is concluded that the copolymerization products are copolymers and not mixtures of homopolymers. The monomer reactivity ratios were: r_ClOc=0.69, r_NBE=6.4; r_ClPA=1.0, r_NBE=3.1. The more electron-donating the ring substituent of CiPA, the more reactive the ClPA in copolymerization with NBE.     

Novel Neodymium-Based Ternary Catalyst, Nd(Oi-Pr)3/[HNMe2Ph]+[B(C6F5)4]-/i-Bu3Al, for Isoprene Polymerization

Summary Polymerization of isoprene was investigated by using a novel ternary catalyst system composed of neodymium(III) isopropoxide (Nd(OiPr)₃), dimethylphenylammonium tetrakis(pentafluorophenyl)borate ([HNMe₂Ph]⁺[B(C₆F₅)₄]^-; borate), and triisobutylaluminum (i-Bu₃Al). The mole ratios of borate and aluminum compounds to Nd catalyst significantly affected the polymerization behavior. Both yield and cis-1,4 content of polyisoprene decreased in the case of [borate]/[Nd] < 1.0, while at [borate]/[Nd] > 1.0 the formation of multiple active species resulted in the polymer showing bimodal peaks in GPC. When the [Al]/[Nd] ratio was lower than 30, the polymer yield sharply decreased, whereas the cis-1,4 content became relatively low with use of a large excess of Al ([Al]/[Nd] > 50). Thus, the optimal catalyst composition was [Nd]/[borate]/[Al] = 1/1/30, which gave in > 97% yield polyisoprene with high molecular weight (M_n2×10⁵) and relatively narrow molecular weight distribution (M_w/M_n2.0) and mainly cis-1,4 structure (90%).     

Phosphonated poly(1,6-heptadiyne) derivatives prepared by metathesis polymerization for nonlinear optics

Summary Poly(triethyldipropargylphosphonoacetate) (TDPA), poly[(tetraethyl dipropargylmethylenediphosphonate) (TDMDP) were prepared by metathesis polymerization using transition-metal catalysts. MoCl₅-based catalyst systems were more effective for the polymerization of these monomers than WCl₆-based catalyst systems. Resulting polymers exhibited good solubility in common organic solvents and could be easily cast on glass plates to give thin films. Third-harmonic Maker fringe technique was used to measure third-order nonlinear susceptibility,x ⁽³⁾, for thin film of poly(TDPA). Thex ⁽³⁾ was evaluated to be 3.4x10^-11 esu at incident wavelength of 1.907m.     

Stereoregular fluoropolymers: 5. The ring-opening polymerization of 2-trifluoromethylbicyclo-[2.2.1]hepta-2,5-diene

2-Trifluoromethylbicyclo[2.2.1]hepta-2,5-diene undergoes metathesis ring-opening polymerization under the influence of the initiators WCl₆/(CH₃)₄Sn, MoCl₅/(CH₃)₄Sn, OsCl₃, RuCl₃, IrCl₃ and ReCl₅. Analysis of the infrared and high-field ¹³C-n.m.r. spectra of the different polymers leads to the following conclusions: the Mo based initiator gives predominantly trans-vinylene units; the Re based system shows the greatest tendency towards stereoregulation and gives predominantly cis-vinylenes; and the other catalysts are unselective in this respect. 2-Trifluoromethylbicyclo[2.2.1]hepta-2,5-diene is more readily polymerized than its 2,3-bis(trifluoromethyl) analogue; both monomers display no vinylene stereoselectivity with the very reactive W based initiator, whereas with both Mo and Ru based initiators the disubstituted monomer displays significantly greater trans-vinylene selectivity.     

Synthesis and properties of poly(diphenylacetylenes) having ether linkages

Summary Polymerization of 1-phenyl-2-(p-phenoxyphenyl)acetylene (p-PhODPA), 1-phenyl-2-(p-methoxyphenyl)acetylene, and 1-phenyl-2-(p-n-butoxyphenyl)acetylene was examined. These monomers polymerized with TaCl₅-n-Bu₄Sn to give methanol-insoluble polymers in over 60% yields. Poly(p-PhODPA) was a yellow solid completely soluble in toluene, CHCl₃, etc., and its weight-average molecular weight was about 1.0x10⁶ or higher. This polymer was thermally very stable (the onset temperature of weight loss in TGA in air was 420 °C). Its oxygen permeability coefficient (P o ₂) was 37 barrers (P o ₂/P n ₂ 2.2) and similar to that of natural rubber. In contrast, the other two polymers did not completely dissolve in any organic solvent, and their thermal stability was lower.     

Polymerization of propiolic acid and its derivatives catalysed by MoCl5

The polymerization of propiolic acid by group VI and VIII transition metal catalysts was investigated. MoCl₅, which was the most active among the catalysts examined, provided poly (propiolic acid) in over 80% yields under favourable conditions. The polymer formed was a water-soluble tawny powder, and its molecular weight was low ($\text{η}{}_{\mathrm{<mtext>sp</mtext>}}\text{C}\text{0.04–0.05}\text{dl g}{}^{\mathrm{?1}}$). The polymer structure,

was confirmed by the i.r. and ¹³C n.m.r. spectra and elemental composition. Some derivatives of propiolic acid (methyl propiolate, acetylenedicarboxylic acid, and phenylpropiolic acid) also produced coloured powdery polymers in the presence of MoCl₅-based catalysts.     

Synthesis and properties of copolymers from diphenylacetylene having a hexaphenylbenzene moiety

Summary Copolymerization of diphenylacetylene having a hexaphenylbenzene group, 1-[p-(pentaphenyl)phenyl]-2-phenylacetylene (1), with a few other diphenylacetylene derivatives (i.e., diphenylacetylene, 1-phenyl-2-[p-(trimethylsilyl)phenyl] acetylene, 1-phenyl-2-[p-n-octylphenyl]acetylene, (2a–c, respectively) and properties of the formed copolymers were investigated. No polymer was obtained in homopolymerization of 1 with TaCl₅-n-Bu₄Sn catalyst owing to steric hindrance. On the other hand, copolymerization with 2a–c proceeded at various feed ratios to give copolymers in moderate yields. Copoly(1/2a) (feed ratio 25/75) was soluble in toluene and CHCl₃ and its weight-average molecular weight (M _w) was ca. 31×10⁴ and relatively high. Copoly(1/2b) and copoly(1/2c) (both feed ratios 5/95) were soluble in common organic solvents, and had a large M _w up to ca. 1×10⁶. These copolymers were yellow to orange solids. Oxidative cyclodehydrogenation of hexaphenylbenzene groups in copoly(1/2a) was attempted in order to convert them into more conjugated groups. Received: 24 January 2000/Accepted: 17 February 2000     

Metathesis ring opening polymerization of 5,6-dimethylenebicyclo[2.2.1]hept-2-ene

5,6-Dimethylenebicyclo[2.2.1]hept-2-ene ( I ) polymerizes in the presence of the two-component ring opening metathesis polymerization (ROMP) initiators WCl₆/(CH₃)4Sn and MoCl₅/(CH₃)4Sn. The product polymers were insoluble in all of many solvents investigated and are presumably cross-linked. The product polymers were investigated by IR and solid state ¹³C NMR spectroscopy, which established that the material consisted predominantly of poly(1,4-(2,3-dimethylene-cyclopentylene)vinylene) ( II ). A possible alternative route to II via thermal dehydrochlorination of poly(1,4-(2,3-bis(chloromethyl)cyclopentylene) vinylene) ( IV ) was also examined.