Homo- and copolymerizations of 3-(N-carbazolyl)-1-propyne and its homologues by Mo and W catalysts

Summary 3-(N-Carbazolyl)-1-propyne polymerized with MoCl₅- and WCl₆-based catalysts to produce a polymer in high yields. The MoCl₅ and MoCl₅-n-Bu₄Sn catalysts were the most effective (the systems solidified immediately after initiation of polymerization with these catalysts). The product polymer was a yellow solid insoluble in any solvent. Copolymerization of the present monomer with tert-butylacetylene by MoCl₅-n-Bu₄Sn produced a copolymer; it had a high molecular weight (M _w 350,000), completely dissolved in toluene, CHCl₃ etc, and formed a free-standing film by solution casting. -N-Carbazolyl-1-hexyne and-1-octyne produced toluene-insoluble polymers with WCl₆-Ph₄Sn.     

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     

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.     

1,2‐Polymerization of 1,3‐butadiene with Cr(acac)3‐alkylaluminum catalysts

The polymerization of butadiene (Bd) with chromium(III) acetylacetonato [Cr(acac)₃]‐trialkylaluminum (AlR₃) or methylaluminoxane (MAO) catalysts was investigated for the synthesis of 1,2‐poly(Bd). The polymerization of Bd was found to proceed with Cr(acac)₃‐AlR₃ (R‐Me, Et, i‐Bu) catalysts to give poly(Bd) with a high 1,2‐vinyl content, but highly isotactic 1,2‐poly(Bd) was not synthesized. The Cr(acac)₃‐MAO catalyst gave a polymer consisting of low 1,2 units. The effects of the Al/Cr mole ratios on the polymerization of Bd with the Cr(acac)₃‐AlR₃ catalysts were observed. With an increase of Al/Cr mole ratios, the isotactic (mm) content of the polymer increased but the 1,2‐vinyl contents decreased. The effects of the aging time and temperatures of the catalysts on the polymerization of Bd with the Cr(acac)₃‐AlR₃ catalysts were also observed, and the lower polymerization temperature and the prolonged aging time were favored to produce the 1,2‐vinyl structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1621–1627, 2000     

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.     

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.     

Investigation of the structure of poly(p-chlorophenyl glycidyl ether) by the 13C n.m.r. technique: tacticity and addition isomerism

The p-chlorophenyl glycidyl ether was polymerized in the presence of Al(OiPr)₃, ZnCl₂, SnCl₄, BuOK, KOH and by the Al(OiPr)₃ZnCl₂ 1:1 initiator system. Analysis of the ¹³C n.m.r. spectra of the poly(p-chlorophenyl glycidyl ethers) obtained has made it possible to determine their tacticity and the content of the head-to-tail and head-to-head linkages in the polymer chain.     

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.     

Synthesis and properties of poly(phenylacetylene)s with pendant imino groups

Summary Polymerization of phenylacetylenes containing imino groups with a variety of transition metal catalysts was investigated. The monomers employed were N-(4-ethynylbenzylidene)aniline (1), N-(3-ethynylbenzylidene)aniline (2), N-(4-ethynylbenzylidene)-2,6-diisopropylaniline (3), N-(4-ethynylbenzylidene)-4-hexylaniline (4), N-(4-ethynylbenzylidene)butylamine (5), and N-(4-ethynylbenzylidene)octylamine (6). All of the monomers smoothly polymerized with [(nbd)RhCl]₂-Et₃N to give polymers in excellent yields, whereas no polymerization took place with W, Mo, and Fe catalysts. The produced polymers were orange to red solids and soluble in common organic solvents except for poly(1). UV-vis spectra of the polymers indicated that the main chains possess a similar degree of conjugation to that of poly(phenylacetylene). However, the stability of polymer backbone toward oxidative cleavage in solution remarkably improved, which is contributed by the electron-withdrawing character of imino groups. Received: 24 August 1999/Accepted: 29 September 1999     

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 of complex architectures of comb block copolymers

The synthesis of comb block copolymers by ring opening metathesis polymerization (ROMP), ring opening polymerization (ROP), and atom transfer radical polymerization (ATRP) is described. Block copolymers were synthesized by the ROMP of oxanorbornene and norbornene monomers followed by hydrogenation of the olefins along the backbone. One block of these diblock copolymers possessed initiators either for the ROP of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione or the ATRP of butyl acrylate. The synthesis and characterization of comb polymers with arms composed of poly(lactic acid) and poly(butyl acrylate) are described. These polymers had well-defined peaks in the size exclusion chromatography spectra which indicated that no homopolymers were synthesized. A comb block copolymer with polymeric arms of poly(styrene-b-vinylpyridine) is described. Vinylpyridine was polymerized from a comb polymer with poly(styrene) arms by ATRP at high dilution of the comb polymer.     

Synthesis and properties of polyacetylenes carrying N-phenylcarbazole and triphenylamine moieties

Novel acetylene monomers containing N-phenyl-substituted carbazole (Cz) and triphenylamine (TPA) groups, namely, 3-ethynyl-9-phenylcarbazole (1) and p-(N,N-diphenylamino)phenylacetylene (2) were synthesized, and polymerized with several Rh-, W-, and Mo-based catalysts. Poly(1) and poly(2) with high number-average molecular weights (15?500-974?000) were obtained in good yields (77-97%), when [(nbd)RhCl]₂-Et₃N (nbd = norbornadiene) was used as a catalyst. The polymers exhibited UV-vis absorption peaks derived from the Cz and TPA moieties at 250-350 nm and polyacetylene backbone above 350 nm. The UV-vis absorption band edge wavelengths of the polymers were longer than those of the corresponding monomers. Poly(2) exhibited a UV-vis absorption peak at a longer wavelength than poly(1) did, which indicates that poly(2) has main chain conjugation longer than that of poly(1). The molecular weights and photoluminescence quantum yields of the polymers obtained by the polymerization using [(nbd)RhCl]₂-Et₃N were larger than those of the Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃]-based counterparts. The cyclic voltammograms of the polymers indicated that they had clear electrochemical properties; the onset oxidation voltage of poly(1) was higher than those of N-alkyl-substituted Cz derivatives. The polymers showed electrochromism and changed the color from pale yellow to blue by application of voltage, presumably caused by the formation of charged polaron at the Cz and TPA moieties. The temperatures for 5% weight loss of the polymers were around 350-420 °C under air, indicating the high thermal stability.     

Polymerization of 1,3-butadiene with VO(P204)2 and VO(P507)2 activated by alkylaluminum

The oxovanadium phosphonates (VO(P₂₀₄)₂ and VO(P₅₀₇)₂) activated by various alkylaluminums (AlR₃, R = Et, i-Bu, n-Oct; HAlR₂, R = Et, i-Bu) were examined in butadiene (Bd) polymerization. Both VO(P₂₀₄)₂ and VO(P₅₀₇)₂ showed higher activity than those of classical vanadium-based catalysts (e.g. VOCl₃, V(acac)₃). Among the examined catalysts, the VO(P₂₀₄)₂/Al(Oct)₃ system (I) revealed the highest catalytic activity, giving the poly(Bd) bearing M_n of 3.76 × 10⁴ g/mol, and M_w/M_n ratio of 2.9, when the [Al]/[V] molar ratio was 4.0 at 40 °C. The polymerization rate for I is of the first order with respect to the concentration of monomer. High thermal stability of I was found, since a fairly good catalytic activity was achieved even at 70 °C (polymer yield > 33%); the M_n value and M_w/M_n ratio were independent of polymerization temperature in the range of 40-70 °C. By IR and DSC, the poly(Bd)s obtained had high 1,2-unit content (>65%) with atactic configuration. The 1,2-unit content of the polymers obtained by I was nearly unchanged, regardless of variation of reaction conditions, i.e. [Al]/[V], ageing time, and reaction temperature, indicating the high stability of stereospecificity of the active sites.     

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     

Polymerization of butadiene with Co(acac)3–(i-Bu)3Al–H2O catalyst

The polymerization of butadiene in toluene using Co(acac)₃–(i-Bu)₃Al–H₂O catalyst system was studied. Presented are the effects of the addition order, aging time, and composition of catalysts on rates, polymer microstructure, and molecular weights. The polymerization was found to be initiated by the Co(acac)₃-hydrolized aluminum alkyl complex. The chain propagation proceeds according to a first-order reaction with respect to monomer and active species and is a strong function of Al/H₂O with an optimum ratio of 1.0, but independent of Al/Co. The nature of polymerization seems to change as Al/H₂O increases from less than 1 to greater than 1. Transfer reaction is significant. From the kinetic data it was found that the termination reaction is most likely to be by combination.     

Soluble neodymium chloride 2-ethylhexanol complex as a highly active catalyst for controlled isoprene polymerization

Soluble NdCl₃·3EHOH (2-ethyl hexanol) in hexane combined with AlEt₃ is highly active for isoprene polymerization in hexane. The NdCl₃·3EHOH/AlEt₃ has higher activity than the typical binary catalyst NdCl₃·3ⁱPrOH (isopropanol)/AlEt₃ and ternary catalyst NdV₃ (neodymium versatate)/AlEt₂Cl/Al(i-Bu)₂H. The molecular weight of polyisoprenes can be controlled by variation of [Nd], [Al]/[Nd] ratio and polymerization temperature and time. The NdCl₃·3EHOH/AlEt₃ catalyst polymerized isoprene to afford products featuring high cis-1,4 stereospecificity (ca. 96%), high molecular weight (ca. 10⁵) and relatively narrow molecular weight distributions (M_w/M_n = 2.0-2.8) simultaneously. More importantly, some living polymerization characteristics were demonstrated: (a) absence of chain termination; (b) linear correlation between M_n and polymer yield; (c) increment of molecular weight in the ‘seeding’ polymerization. Though some deviation from the typical living polymerization such as molecular weight distribution is not narrow enough and the line of M_n and polymer yield does not extrapolate to zero, controlled polymerization with the current catalyst can still be concluded.     

Reversible coordinative chain transfer polymerization of isoprene and copolymerization with ε-caprolactone by neodymium-based catalyst

Coordinative chain transfer polymerization (CCTP) of isoprene was investigated by using the typical Ziegler–Natta catalytic system [Nd(Oi-Pr)₃/Al(i-Bu)₂H/Me₂SiCl₂] with Al(i-Bu)₂H as cocatalyst and chain transfer agent (CTA). The catalyst system exhibited high catalytic efficiency for the reversible CCTP of isoprene and yielded 6–8 polymer chains per Nd atom due to the high chain transfer ability of Al(i-Bu)₂H. The narrow molecular weight distribution (M_w/M_n = 1.22–1.45) of the polymers, the good linear relationship between the M_n and yield of the polymer, and the feasible seeding polymerization of isoprene indicated the living natures of the catalyst species. Moreover, the living Nd-polyisoprene active species could further initiate the ring-opening polymerization of polar monomer (ε-caprolactone) to afford an amphiphilic block copolymer consisting of cis-1,4-polyisoprene and poly(ε-caprolactone) with controllable molecular weight and narrow molecular weight distribution.     

Geometrical structures in solution and solid phase of poly(propargyl ester)s prepared by using a [Rh(norbornadiene)Cl]2-cocatalyst

Propargyl esters, HCCCH₂OCOC_nH_2n+1 (1: n = 3, 2: n = 5, 3: n = 9, and 4: n = 13), were polymerized using a [Rh(nbd)Cl]₂ catalyst and cocatalyst in an appropriate solvent at 0 °C and 40 °C. Number average molecular weights, M_n of the resulting polymers, poly(1)–poly(4), were 8000–54,000, and its dispersities (M_w/M_n)s and the yields were estimated to be 1.6–3.6 and ca. ～99%, respectively. These polymers were soluble in CHCl₃, CH₂Cl₂, and THF, and insoluble in CH₃OH and DMF. The amines, e.g., 2,6-dimethylpyridine and triethylamine worked well as the cocatalysts for the polymerization to give the yields, 93% and 88%, respectively. Further N,N-diethylaniline gave the maximum in cis%, 74%, although pyridine, aniline, pyrrole or imidazole did not work effectively. Remarkable line broadening phenomenon, LBP observed in the ¹H NMR spectra of poly(1) and poly(2) prepared at 0 °C or 40 °C, and poly(3) prepared at 40 °C was correlated with the polymerization temperature and the radical concentration generated in the polymer. The LBP was interpreted by the dipole–dipole interaction between the protons in the polymer and unpaired electrons due to carbon radicals generated by the rotational scission of the cis CC bonds during the polymerization. Their UV–vis spectral shape of poly(1)–poly(4) depended on the polymerization temperature and/or the alkyl chain length in the polymer. The XRD powder patterns of poly(3) prepared at 0 °C, and poly(4)s prepared at 0 °C and 40 °C showed layer crystal structures with a slightly bent herringbone confirmed by molecular mechanics calculation. The λ_max values of poly(4) prepared at 40 °C in methanol showed 317 nm and 340 nm in the solution and on the alumina, respectively.     

Synthesis and photoluminescence properties of heterocycle-containing poly(disubstituted acetylene)s

The metathesis polymerizations of disubstituted acetylenes containing heterocycles such as thiophene, furan, benzo[b]thiophene, and benzothiazole were examined using NbCl₅, TaCl₅, and WCl₆. Thiophene-containing monomers polymerized to afford relatively high-molecular-weight polymers in moderate yields. Benzo[b]thiophene-containing monomers also polymerized to give polymers with relatively high molecular weights. On the other hand, furan- and benzothiazole-containing monomers exhibited low metathesis polymerizability, and the polymerizations did not provide high-molecular-weight polymers. Poly(1-hexyl-2-arylacetylene)s having heterocycles [poly(1a) and poly(3a), Scheme 1] emitted blue-colored lights, and the emission maxima were around 480 nm. Heterocycle-containing poly(1-phenyl-2-arylacetylene) [poly(1b)] and poly(1-fluorenyl-2-arylacetylene) [poly(3d)] showed green-colored and yellow-colored emissions, and the emission maxima were 520 and 540 nm, respectively. The emission wavelengths of poly(disubstituted acetylene)s having heterocycles were almost the same as those of the corresponding poly(disubstituted acetylene)s without heterocycles. However, heterocycle-containing polymers showed high fluorescence quantum yields compared to the corresponding polymers without heterocycles. Diarylacetylene polymers showed emission red-shifts between the solution and cast film, while the emission maximum of poly(1-hexyl-2-phenylacetylene) [poly(1a)] in the cast film was almost the same as that in the solution. Benzo[b]thiophene-containing poly(1-(4-trimethylsilylphenyl)-2-phenylacetylene) [poly(3b)] and poly(1-(9,9-dimethyl-2-fluorenyl)-2-phenylacetylene) [poly(3d)] afforded the free-standing membranes because of their high molecular weights. The oxygen permeability coefficient (PO₂) of poly(3b) was as large as 1400 barrers. Poly(3d) showed higher gas permeability, and its PO₂ was 5300 barrers.     

The effect of trivalent metal nitrates on the properties of dental cements made from poly(acrylic acid)

Addition of either Al(NO₃)₃ or Fe(NO₃)₃ to zinc polycarboxylate and glass polyalkenoate dental cements has been shown to cause an acceleration to their setting reactions. In the case of Fe(NO₃)₃, the reaction was so fast that cements could not be mixed, but Al(NO₃)₃ had a less severe effect, and cements containing various amounts of this additive were prepared. Their compressive strength at 24 h was lower than for the original cements, with zinc polycarboxylate being more affected than the glass polyalkenoate. Both cements are made from poly(acrylic acid), and infrared spectroscopy showed that both Al(NO₃)₃ and Fe(NO₃)₃ form adducts with this polymer, the interaction of aluminum with the polymer being significantly different from that of the iron (III) species. The binding by Al(NO₃)₃ was also shown to reduce the pH of a poly(acrylic acid) solution. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2353–2359, 1998