Synthesis and polymerization of various vinyl-type monomers containing the pyrrole ring

Vinyl-type monomers containing the pyrrole ring, such as 2-vinylpyrrole (2-VPyrr), N-(pyrrol-2-yl)methylacrylamide (PMA), N-methyl, N-(pyrrol-2-yl)methylacrylamide (MPMA), 2-allylpyrrole (2-AP), β-(pyrrol-1-yl)ethyl vinyl ether (PEVE), 2-diallyl-aminomethylpyrrole (DAMP), and 3-(2-pyrrolylmethyleneimino)propene-1 (PIP) were synthesized by various reactions involving characteristic properties of the pyrrole ring. Radical homopolymerizations and copolymerizations of these monomers were studied. In the homopolymerization of conjugated monomers such as 2-VPyrr and PMA, chain transfer to the pyrrole-containing monomer was remarkable but not degradative. The copolymerization parameters, that is, the values of r₁, r₂, Q₁, and e₁ of 2-VPyrr, were determined to be 0.066, 0.69, 5.53, and ?1.36, respectively in the copolymerization of 2-VPyrr (M₁) with MMA (M₂). The Q and e values of the monomers containing a heteroaromatic ring such as 2-vinylpyrrole, 2-vinylfuran, and 2-vinylthiophene were evaluated by the molecular orbital theory. The e value of PMA was found to be negative (?0.64) in the copolymerization with styrene, although e for acrylamide derivatives is generally positive. This may be explained by the intermolecular hydrogen bonding between the carbonyl group and NH group of PMA. That is, attraction or polarization of π-electrons in the vinyl group of PMA is weakened by such hydrogen bonding. From the results of copolymerization of 2-AP with various comonomers, the comonomers could be classified into three categories: class a monomers, in which both Q and e values are largely positive, can copolymerize with 2-AP; class b monomers, having small e values, homopolymerize and can not copolymerize with 2-AP; class c monomers, in which both Q and e values are small. The Q and e values of the comonomer must be largely positive in order to permit copolymerization with an allyl-type monomer.     

Equilibrium anionic polymerization of the isopropenyl monomers containing aromatic heterocycles

The anionic polymerization of three monomers, 2-isopropenyl-4,5-dimethyloxazole(I), 2-isopropenylthiazole(II), and 2-isopropenylpyridine(III), was studied in THF. These monomers produced red-colored living polymers on addition of sodium naphthalene or living α-methylstyrene tetramer as an initiator. It was observed that a considerable amount of monomer remained in the respective living polymer–monomer system, indicating that an equilibrium between the polymer and the monomer existed as in the case of α-methylstyrene. At lower temperatures, the conversion of the monomer to the polymer increased. The equilibrium monomer concentrations [M_e] were determined at different temperatures, and the heats (ΔH) and the entropies (ΔS°) of polymerization were obtained by plotting In(1/[M_e]) against 1/T as ΔH = ?9.4, ?6.8, and ?6.2 kcal/mole, ΔS°S = ?22.9, ?16.5, and ?16.6, eu for I, II, and III, respectively.     

Monodisperse Poly(triacetylene) Rods: Synthesis of a 11.9 nm Long Molecular Wire and Direct Determination of the Effective Conjugation Length by UV/Vis and Raman Spectroscopies

With 16 C−C double and 32 C−C triple bonds and a length of 11.9 nm, the hexadecameric poly(triacetylene) (PTA) of type 1 is currently the longest linear fully π-conjugated molecular wire that does not contain aromatic repeat units. A series of PTA oligomers 1 extending from monomer to hexadecamer was prepared by a rapid and efficient statistical deprotection–oligomerization sequence; the effective conjugation length at which saturation of molecular properties occurs was determined as n=10 (n=number of monomeric units) by both UV/Vis and Raman spectroscopies.     

Radical polymerization of metal-coordinated monomers with ligands of pyrrole-containing schiff bases

The copper complexes and the cobalt complex with the ligand of 3-(2-pyrrolylmethyl-enimino)propene-1 (PIP) or p-(2-pyrrolylmethylenimino)styrene (PIS) were synthesized and homopolymerizations and the copolymerization with styrene, acrylonitrile, methyl methacrylate and acrylic acid studied. In the polymerization of chelate monomers, inhibition of radical polymerization by the central metal ion was observed, but the chelate polymer could be obtained only if the initiator was present in higher concentrations in the feed. It is considered that the strength of inhibition depends on the electronic configuration of d-orbitals of the central metal ion. The initiation mechanism of the cupric chelate monomer may be reduction of the metal ion by the redox reaction with a primary radical via the intramolecular electron transfer through the π-conjugated system of the ligand prior to the propagation step. This mechanism was verified by studying the redox reaction of various copper complexes with DPPH. In the system of the copper complex containing PIS and acylic acid the alternating copolymer could be obtained at any mole fraction of monomer mixture in feed.     

Vinyl polymerization. 275. Polymerization of vinyl monomers photosensitized by tetramethyltetrazene

A study of the photopolymerization of vinyl monomers in the presence of tetramethyltetrazene (TMT) was made. TMT was found to act as an effective sensitizer. In the photopolymerization of vinyl monomers such as methyl methacrylate or styrene the rate of polymerization was expressed by the equation: R_p = k[TMT]^1/2[monomer]. The chain-transfer constant of TMT under ultraviolet irradiation was estimated to be 3.8 × 10^?2 for the above monomers. A linear correlation was found to exist between the reactivity of dimethylamino radical toward the vinyl monomers and e values for the corresponding monomers.     

Chain transfer constants for vinyl monomers polymerized in methyl oleate and methyl stearate

Chain transfer constants were obtained for styrene, methyl methacrylate, methyl acrylate and vinyl acetate, polymerized in methyl oleate and methyl stearate at 60°C. Transfer constants increased in the order: methyl methacrylate < styrene < methyl acrylate ? vinyl acetate in both solvents. Average values of the transfer parameters were: for methyl oleate, Q_tr = 2.04 × 10^?4, e_tr = 1.08; for methyl stearate, Q_tr = 0.373 × 10^?4, e_tr = 1.01. Indication that polar species predominate in the transition state is supported by the observed order of reactivity. The usual rate dependence appeared to be followed by all of the monomers except vinyl acetate, which was retarded, severely in methyl oleate. Transfer in methyl oleate was about 5.8 times greater than that found in methyl stearate for these four monomers. The internal allylic double bond of methyl oleate had about the same reactivity in transfer as had the terminal unsaturation in N-allylstearamide at 90°C. Rough estimates were obtained of the monomer transfer constants for the long side-chain homologs of these four monomers from the respective monomer transfer constants and the experimental transfer constants, corrected for transfer to the labile groups of the solvent. It was concluded that the rate of polymerization would determine in large measure the degree of polymerization for the reactive 18-carbon homologs but that the molecular weight of poly(vinyl stearate) and (oleate) will be regulated primarily by transfer to monomer.     

POLYROTAXANE WITH π-CONJUGATED PORPHYRIN AND POLYAZOMETHINE SYSTEMS PREPARED FROM A TYPE OF PORPHYRIN-DIALDEHYDE AND COMPLEX OF β-CYCLODEXTRIN WITH 1,4-PHENYLENEDIAMINE

The synthesis of 5,15-bis[4-(methoxycarbonyl)phenyl]-10,20-diphenylporphyrin (2) and its reduction to 5,15-bis[4-(hydroxymethyl)phenyl]-10,20-diphenylporphyrin (3), and so its oxidation to provide 5,15-bis(4-formylphenyl)-10,20-diphenylporphyrin (4) are reported. The copolymer possessing β-cyclodextrin (β-CD), π-conjugated porphyrin and polyazomethine systems was synthesized by the polycondensation of porphyrin-dialdehyde monomer (4) and β-cyclodextrin/1,4-phenylenediamine complex (5). The monomers and the copolymer were characterized by UV-Vis, 1H-NMR and IR spectra. Furthermore, 1H-NMR and FT-IR spectra confirmed locating the aromatic ring of 1,4-phenylenediamine molecule in the center of β-cyclodextrin cavity.     

Synthesis and characterization of original functional polymers of tetrafluoroethylene and 4,5,5‐trifluoro‐4‐ene pentyl acetate

The bulk radical copolymerization of tetrafluoroethylene (TFE) with 4,5,5‐trifluoro‐4‐ene pentyl acetate (FAc), initiated by tert‐butyl peroxypivalate to synthesize original, functionalized fluorinated poly(TFE‐co‐FAc), was investigated. FAc monomer was prepared from a five‐step process. The copolymerization was carried out in batch at different initial monomer molar ratios ([TFE]_o/[FAc]_o ranging from 95/5 to 10/90 mol %) and at different initiator concentrations (ranging between 0.075 and 1.100 mol % about the monomers) at 70 °C. All the experiments revealed the production of fluorooligomers as evidenced by an allylic‐transfer reaction from FAc. The microstructure of these copolymers (i.e., the molar percentage of both monomers in the copolymers) was assessed by ¹⁹F NMR spectroscopy. From the kinetics of copolymerization, two key characteristics were determined. First, the reaction order to the initiator (being 1.07) and that of FAc monomer (0.85) showed a heterogeneous character of the copolymerization and monomolecular chain‐transfer reaction to FAc. Second, from the Tidwell and Mortimer method, the reactivity ratios of both comonomers were determined, showing a tendency to alternance in a wide range of initial monomeric ratios (30/70–70/30): r_FAc = 0.20 ± 0.26 and r_TFE = 0.18 ± 0.15. Alfrey and Price's Q and e values of FAc were calculated by Greenley's technique [Q_FAc = 0.098 (from Q_TFE = 0.032) and e_FAc = 1.23 (vs e_TFE = 1.63)], indicating that FAc is a strong electron‐withdrawing monomer as TFE. The normalized monomer‐diad and triad fractions as a function of the polymer composition were obtained from the comonomer sequence‐distribution procedure. The average molecular weights and molecular weight distributions as well as the thermal properties (glass‐transition temperature and decomposition temperature) of the fluorocopolymers were assessed and are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1693–1706, 2004     

Copolymerization of ethylene with a homologous series of vinyl esters

The effect of the alkyl group on the relative reactivity of a homologous series of vinyl esters (2) has been studied with ethylene (1) as reference monomer, tert-butyl alcohol as solvent, at 62°C and 35 kg/cm². The experimental method was based on frequent measurement of the monomer feed composition throughout the copolymerization reaction by means of quantitative gas-chromatographic analysis. Highly accurate monomer reactivity ratios were estimated in a statistically justified manner by a nonlinear least-squares method applied to the integrated copolymer equation. The reactivity of the vinyl ester monomers towards an ethylene radical increased with decreasing electron-with-drawing ability of the ester group. All vinyl ester radicals considered turned out to have the same preference for their own monomer over ethylene (constant r₂ = 1.50). Reactivity ratios are discussed in terms of the Q–e scheme and the Taft relation. It appeared that chiefly polar factors contribute to the observed relative reactivity, while probably resonance stabilization only plays a minor part. Steric hindrance seems to impair monomer reactivity, only from vinyl pivalate on. Relative reactivities of the vinyl esters are compared with literature values, where other reference monomers have been used.     

Charge transfer and dispersion interaction stabilization of the D2h isomer of O4

The results of some minimal basis set valence bond calculations, with an antibonding midbond molecular orbital (π_m*) included, are reported for the D_2h isomer of O₄. The in-plane π_m*←π* excitations describe the charge transfer from each monomer, while the π*←π excitations on each monomer partially describe the intermolecular dispersive attractions. It is found that the charge-transfer interactions by themselves are insufficient to stabilize the S=0 spin D_2h dimer of O₄ relative to two O₂ monomers when a correction is included for basis set superposition error. The inclusion of both the charge transfer and dispersion terms yields an estimate of 14 cm⁻¹ for the binding energy (D_e) at an equilibrium separation (R_e) of 3.29 Å. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 129–134, 1998     

Copolymerization of new pyrazolone-containing monomers with certain vinyl comonomers

The polymerization ability of two new pyrazolone-containing monomers—3-methyl-1-phenyl-4-crotonoyl-pyrazolone-5 ( Cr ) and 3-methyl-1-phenyl-4-(3′-phenyl-acryloyl) pyrazolone-5 ( Cy )—was investigated. The monomers were obtained by acylation of 3-methyl-1-phenyl-pyrazolone-5 with crotonyl chloride or cinnamoyl chloride, respectively. It was established that the two monomers do not homopolymerize either under the action of ionic and radical initiators nor with γ-rays (doses between 2 and 10 MRad). In contrast to this, the two monomers copolymerize with other vinyl comonomers. Copolymers of Cr and Cy with methacrylic acid (MAA), methyl methacrylate (MMA), and Styrene (St) were synthesized by radical copolymerization. The molecular weights of the polymer products obtained were in the 10,000–65,000 range. It was established that the molecular weight characteristics of the copolymers were affected by the concentration of the pyrazolone-containing monomer and by the chemical nature of the solvent used. The copolymerization of Cr and Cy with MAA was investigated in detail in order to evaluate the relative activity of the new monomers during copolymerization. The reactivity ratios (r) were calculated by three different methods with good agreement. The values obtained for the monomer pairs are: r_MAA = 0.61 ± 0.01, r_Cr = 0.04 ± 0.01; r_MAA = 0.64 ± 0.05, r_Cy = 0.02 ± 0.02. The Q/e values for Cr and Cy were determined using the reactivity ratios of both monomers.     

Reactivity ratios for copolymerization of vinyl chloride with 2-methylpentyl vinyl brassylate by computerized linearization

A computerized version of the Fineman-Ross linearization procedure was used to determine reactivity ratios for copolymerization of vinyl chloride (monomer 1) and 2-methylpentyl vinyl brassylate (monomer 2). From differential refractometry data for the products of low-conversion copolymerization, the procedure gave r₁ = 1.06 and r₂ = 0.234. The ratios computed from chlorine contents of the same products were r₁ = 1.10 and r₂ = 0.239. The polarity factor (e₂) and general monomer reactivity (Q₂) calculated for monomer 2 from these ratios were, respectively, ?0.95 to ?0.98 and 0.032–0.033. The interquartile range for the copolymerization of a mixture of 60% monomer 1 and 40% monomer 2 was 1.4%. These values suggest that from suitable proportions of reactants, sufficiently homogeneous distribution of monomers can be achieved in copolymers of vinyl chloride and 2-methylpentyl vinyl brassylate to offer the possibility of effective internal plasticization.     

Molecular orbital study of the Q–e scheme in free radical copolymerization

Molecular orbital calculations were used to study free radical polymerization. Calculations show that the monomer is activated during the reaction and the pi bond becomes a diradical. The radical on the carbon that is about to form the new bond is called the e radical in this article. The other is the Q radical. For different monomers it is shown indirectly that changes in the energies of formation of the Q and e radicals are related to changes in the Q and e terms in the empirical Q–e scheme of Alfrey and Price. The polar effect in the Q–e scheme involves the e-radical, unpaired electron density. Specifically, the Q–e sum (e_x + e_y) is correlated with the e radical spin density. Also the e term is correlated with the electron density on the unsubstituted carbon of the monomer. The relationship of the Q radical to the adjacent substituent is shown by correlating ln Q values with the energy of addition of a hydrogen atom to a monomer. These relationships give theoretical meaning to the Q–e terms and allow calculation of Q and e values from molecular orbital properties for small monomers.     

Reactivity and Characterization of the Radical Copolymerization of Itaconic Acid with Some Conventional Monomers

Abstract

Radical copolymerizations of itaconic acid (IA) with acrylamide (Am), N-vinyl pyrrolidone (NVP), ethyl methacrylate (EMA), and methyl methacrylate (MMA) were carried out in dioxane in the presence of azobisisobutyronitrile as the initiator at 65°C. The monomer reactivity ratios (r ₁, r ₂), Q, and e for IA with the four monomers were determined. The reactivity ratios show a tendency toward alternation, while the Q and e of IA indicate that it is an electron-accepting monomer. The polymers obtained were characterized by FT-IR, x-ray diffraction, intrinsic viscosity, and thermal stability measurements.     

Electrochemical reduction potential of n-type π-conjugated polymers

The ease of reduction of π-conjugated poly(p-phenylene)-, poly(naphthalene-2,6-diyl)-, and poly(naphthalene-1,4-diyl)-type polymers is determined by the electron accepting properties of the recurring aromatic units. Linear relationships hold between reduction potentials (E_red) of the π-conjugated poly(arylene)s and electron affinities (EA) of the recurring arylene units: E_red = ρEA + a. A ρ value of 0.85 ± 0.02 is found for the three types of polymers investigated. © 1996 John Wiley & Sons, Inc.     

Ferrocene-containing polymers. II. Radiation-induced copolymerizations of ferrocenylmethyl methacrylate with styrene,methyl methacrylate,and ethyl acrylate

Ferrocenylmethyl methacrylate (FMMA) was copolymerized with styrene (St), methyl methacrylate (MMA), and ethyl acrylate (EA) in benzene solution at 25°C by γ radiation. The reactions proceeded by a free radical mechanism, and monomer reactivity ratios were derived by the Tidwell–Mortimer method for St(M₁)–FMMA(M₂), r₁ = 0.35 and r₂ = 0.46; for MMA(M₁–FMMA)(M₂), r₁ = 0.85 and r₂ = 1.36; for EA(M₁)–FMMA(M₂), r₁ = 0.36 and r₂ = 3.03. The Q and e values of FMMA determined from copolymerization with St were 0.97 and 0.55, respectively. Terpolymerization of a MMA–FMMA–EA system based on the Alfrey–Goldfinger equations was studied. This is a typical terpolymerization system in which reactivities of the monomers obey the Q–e scheme. Comparing the results obtained here with those previously reported for other monomers, we concluded that FMMA is one of the most highly reactive monomers among alkyl methacrylates.     

Dinuclear Pd(II) and Pt(II) compounds bearing a bridging π-conjugated moiety: synthesis and reactivity toward alkynes and isocyanides

Abstract

Dinuclear Pd(II) halides that contain bridging π-conjugated groups, trans,trans-[(PR₃)₂(X)Pd–Y–Pd(X)(PR₃)₂] (X?=?Br; YH₂ = terpyridine, fluorenone, benzil, benzthiadiazole), were prepared by the oxidative addition of corresponding dihalo π-conjugated reagents to [Pd(styrene)(PR₃)₂]. Similar reactions involving dihalobenzil, dihalobithiophene, or dihaloterthiophene afforded dinuclear Pt(II) halides containing bridging π-conjugated groups. Additionally, when the dihalosilole derivatives {2,5-dibromo-1,1-dimethyl (or diphenyl)-3,4-diphenylsilole} reacted with [Pd(styrene)(PR₃)₂], mono or dinuclear Pd(II) complexes bearing a dimethyl (or diphenyl)-3,4-diphenylsilole group were obtained. π-Conjugation extension reactions of dinuclear bithiophene-bridged Pd(II) halides with HC≡C–R {R?=?SiPh₃, C(O)OMe} in the presence of CuI and HNEt₂ led to the unexpected formation of bis(acetylide) Pd(II) complexes of the form, [Pd(C≡C–R)₂(PR₃)₂] and bithiophene. In contrast, treatment of the dinuclear Pd(II) halides with two equiv of organic isocyanide resulted in isocyanide insertion into the Pd???C bonds to afford π-conjugation-extended dinuclear Pd(II) compounds bearing a π-conjugated moiety.     

Polymerization behaviour of 2,5-dimethylene- 2,5-dihydrofuran

Spontaneous homopolymerization of 2,5-dimethylene-2,5-dihydrofuran (DDF) was studied. The polymerization rates in two different initial monomer concentrations of DDF were analyzed with the first-order and second-order kinetics, and the homopolymerization of DDF was found to obey the first-order kinetics. The Arrhenius plot of the apparent rate constants at 30, 40, 50, and 60° gave an overall activation energy of 68.0 kJ/mol for the polymerization of DDF. From the comparison of the apparent rate constants at –78° and the time (the so-called half-life time) to decrease in half the monomer concentration for DDF with the corresponding values for p-xylylene (QM), DDF was found to be a less reactive monomer than QM. The copolymerizations of DDF with vinyl monomers such as acrylonitrile (AN), α-chloroacrylonitrile (CIAN), diethyl fumarate (DEF), and fumaronitrile (FN) were carried out in chloroform at 50° in the presence of AIBN to obtain the monomer reactivity ratios r₁(DDF) = 30.0 ± 3.0 and r₂ (AN) = 0 for the DDF-AN system, r₁ (DDF) = 1.55 ± 0.2 and r₂(CIAN) = 0 for the DDF-CIAN system, r₁(DDF) = 3.88 ± 0.2 and r₂(DEF) = 0 for the DDF-DEF system, and r₁(DDF) = 2.41 ± 0.1 and r₂ (FN) = 0 for the DDF-FN system, respectively. As the monomer reactivity ratios of r₂ for all systems were zero, Q and e values of DDF were calculated from the combination of two r₁ (DDF) values of any two copolymerization systems to be the 7.64 to 6.63 ×10²¹ range for Q and the –0.70 to –6.31 range for e, indicating that DDF is a highly conjugative and electron-donating monomer. © 1995 John Wiley & Sons, Inc.     

π-Conjugated Macrocycles Bearing Angle-Strained Alkynes

Angle-strained alkyne-containing π-conjugated macrocycles are attractive compounds both in functional materials chemistry and biochemistry. Their interesting reactivity as well as photophysical and supramolecular properties have been revealed in the past three decades. This review highlights the recent advances in angle-strained alkyne-containing π-conjugated macrocycles, especially their synthetic methods, the bond angles of alkynes (∠_sp at C≡C−C), and their functions. The theoretical and experimental research on cyclo[n]carbons and para-cyclophynes consisting of ethynylenes and para-phenylenes are mainly summarized. Related macrocycles bearing other linkers, such as ortho-phenylenes, meta-phenylenes, heteroaromatics, biphenyls, extended aromatics, are also overviewed. Bond angles of strained alkynes in π-conjugated macrocycles, which are generable, detectable, and isolable, are summarized at the end of this review.     

Synthesis and physical properties of π-conjugated metallacycle polymers of cobalt and ruthenium

Recent studies on two types of π-conjugated metallacylce polymers are reviewed. Reaction of CpCo(PPh₃)₂ with conjugated diacetylenes afford poly(arylene cobaltacyclopentadienylene) and that of CpRuBr(cod) does poly(arylene ruthenacyclopentrienylene)s in ambient conditions. Regioselectivity of the former metallacycling reacion is not perfect (at most 80% of the 2,5-diaryl selectivity) but that of the latter is satisfactory (∼100% of the 2,5-diaryl selectivity) for the formation of π-conjugated structure. Electrochemical oxidation of the cobaltacyclopentadiene polymer and reduction of the ruthenacycle polymer occur facilely and quasi-reversibly by the contribution of metal d-orbitals. Physical properties in undoped (neutral) and doped (charged) sates show the behavior of electronic band structure derived from the organic π-conjugated main chain strongly coupled with the metal d-orbitals. This affords, for example, photoconductivity in the neutral form of the cobaltacylopentadiene polymer and ferromagnetic interaction in the reduced form of the ruthenacyclopentatriene polymer.