Polymerization by oxidation coupling. I. A study of the oxidation of 2,6-diphenylphenol to poly(2,6-diphenyl-1,4-phenylene ether)

The synthesis of poly(2,6-diphenyl-1,4-phenylene ether), by the oxidative coupling of 2,6-diphenylphenol has been studied. Procedures were found which demonstrated that polymers of very high molecular weight \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\overline M _n > 200{\rm 000; }\left[ \eta \right]_{{\rm CHCl}_{\rm 3} }^{25^\circ {\rm C}} > 1.1{\rm }{{{\rm dl}} \mathord{\left/ {\vphantom {{{\rm dl}} g}} \right. \kern-\nulldelimiterspace} g}} \right) $\end{document} could be made with a copper-amine catalyst system. A low nitrogen-to-copper ratio (1 N atom/Cu atom) was necessary to obtain the very high molecular weights under the conditions of these reactions. A variety of amines formed active catalysts; the effectiveness of mono- and bis- primary, secondary, and tertiary amines were compared. Effects of the type of copper halide, reaction temperature, desiccants, addition rates of 2,6-di-phenylphenol, and solvents were also examined. Samples of polymer were isolated at different times during the polymerization. Measurements of viscosity, osmotic pressure, light scattering, gel permeation, phenolic hydroxyl groups, and nitrogen content were made on various samples over a range of intrinsic viscosities of 0.05–0.59 dl/g. A very narrow molecular weight distribution was found for all samples. Hydroxyl endgroup analyses indicated that the concentration of phenolic endgroups per mole of polymer does not change during the polymerization. The presence of some side reactions is indicated by nitrogen analyses. The relationships between the intrinsic viscosity in chloroform at 25°C and M?_n and M?_w are: log [η] = ?3.97 + 0.72₇ log M?_n and log [n] = ?3.56 + 0.62₄ log M?_w.     

Poly(2,6-diphenyl-1,4-phenyl oxide): Characterization by gel-permeation chromatography,light scattering,and solution viscosity

Ten unfractionated poly(2,6-diphenyl-1,4-phenylene oxide) samples were examined by gel permeation chromatography (GPC) and intrinsic viscosity [η] at 50°C in benzene, by intrinsic viscosity at 25°C in chloroform, and by light scattering at 30°C in chloroform. The GPC column was calibrated with ten narrow-distribution polystyrenes and styrene monomer to yield a “universal” relation of log ([η]M) versus elution volume. GPC-average molecular weights, defined as M?gpc = \documentclass{article}\pagestyle{empty}\begin{document}$\Sigma w_i [\eta ]_i M_i /\Sigma w_i [\eta ]_i$\end{document}, w_i denoting the weight fraction of polymer of molecular weight M_i, were computed from the GPC and [η] data on the polyethers. The M?GPC were then compared with the weight-average M?_w from light scattering. The intrinsic viscosity (dl/g) versus molecular weight relations for the unfractionated poly(2,6-diphenyl-1,4-phenylene oxides) determined over the molecular weight range 14,000 ≤ M?_w ≤ 1,145,000 are log [η] = ?3.494 + 0.609 log M?_w (chloroform, 25°C) and log [η] = ?3.705 + 0.638 log M?_w (benzene, 50°C). The M?_w(GPC)/M?_n(GPC) ratios for the polymers in the molecular weight range 14,000 ≤ M?_w ≤ 123,000 approximate 1.5 according to computer integrations of the GPC curves with the use of the “universal” calibration and the measured log [η] versus log M?_w relation. The higher molecular weight polymers (326,000 ≤ M?_w ≤ 1,145,000) show slightly broadened distributions.     

Aromatic poly(amic acids): Fundamental structural studies

Aromatic poly(amic acids) derived from pyromellitic dianhydride and 4,4′,-diaminodiphenyl ether were characterized by dilute solution techniques. Number-average molecular weights M?_n of 13 samples ranged from 13,000 to 55,000 (DP 31–131). Weight-average molecular weights M?_w of 21 samples ranged from 9,900 to 266,000. The ratio M?_w/M?_n was between 2.2 and 4.8. Heterogeneous polymerization yielded higher molecular weight polymer than homogeneous polymerization. The molecular weight could be varied systematically by control of stoichiometric imbalance. Use of very pure monomers and solvent gave polymers of relatively high number-average molecular weight (～50, 000) and the most probable molecular weight distribution M?_w/M?_n = 2. Impure monomers and/or solvent resulted in lower number-average molecular weight (M?_n ? 20,000–30,000) and wider distributions (M?_w/M?_n = 3–5). The Mark-Houwink relation obtained was [η] = 1.85 × 10^?4M?_w^0.80 The exponent is characteristic of moderately extended solvated coils. The unperturbed chain dimensions (r₀² /M)^1/2 were 0.848 A., and the steric factor σ was 1.24 which is close to the limiting value of unity for an equivalent chain with free internal rotations. The sedimentation constant–molecular weight relation was S₀ = 2.70 × 10^?2M?_w^0.39. This exponent is consistent with the Mark-Houwink exponent.     

Association of polyacrylonitrile prepared by low-temperature,solution polymerization with an organometallic catalyst

The weight-average molecular weights of polymers of acrylonitrile prepared by a free-radical initiator and an organometallic catalyst have been determined by lightscattering measurements in N,N-dimethylformamide, dimethyl sulfoxide, and dimethylacetamide at 25°C. and in dimethyl sulfoxide at 140°C. The apparent molecular weights of the polymers prepared with the NaAlEt₃S(i-Pr) catalyst in DMF at ?78°C. (referred to as high-melting polymers) changed from 54,800, 82,700, and 480,000 when measured in DMF at 25°C. to 36,000, 41,600, and 225,000 when measured in DMSO at 140°C., whereas the molecular weights of the free-radical polymers remained unchanged. Furthermore, from results obtained in DMSO at 140°C., The intrinsic viscosity–molecular-weight relationships were found to be identical for the high-melting and the free-radical polymer and in substantial agreement with an equation reported by Cleland and Stockmayer. The apparent decrease in molecular weight of the high-melting polymer from 25 to 140°C. indicates rather clearly that the high-melting polymers are associated in DMF at 25°C. The “aggregates,” even though present only at low concentrations, raised the weight-average molecular weight markedly but affected the number-average molecular weight only slightly, thus giving a high M?_w/M?_n ratio. It appears likely that when temperature and solvent are such that association does not occur, linear PAN's will have approximately the same intrinsic viscosity–molecular weight relationship (subject of course to slight change by polydispersity). The often reported abnormal molecular weight of samples prepared by solution polymerization especially at low temperatures, may be attributed to branching, or to an association, as reported here. The nature of association of PAN in dilute solution is also discussed.     

Polymerization of vinyl chloride with organolithium compounds. V. Fractionation and solution properties of high molecular weight poly(vinyl chloride)

A sample of high molecular weight poly(vinyl chloride) (PVC) was fractionated by classical precipitation fractionation and gel-permeation chromatography (GPC) on a preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, and by the GPC method. The measured weight-average molecular weights M?_w, intrinsic viscosity [η], and polydispersity index M?_w/M?_n values were used for the determination of the Mark-Houwink equation, [η] = KM^a, for PVC in cyclohexanone (CHX) at 25°C valid for molecular weights from 100,000 to 625,000.     

Polymerization of 2‐pentene with Ni(II) α‐diimine complex/M‐MAO catalyst and structure of the polymer

Polymerization of 2‐pentene with [ArN?C(An)C(An)·NAr)NiBr₂ (Ar?2,6‐iPr₂C₆H₃)] ( 1‐Ni) /M‐MAO catalyst was investigated. A reactivity between trans‐2‐pentene and cis‐2‐pentene on the polymerization was quite different, and trans‐2‐pentene polymerized with 1‐Ni /M‐MAO catalyst to give a high molecular weight polymer. On the other hand, the polymerization of cis‐2‐butene with 1‐Ni /M‐MAO catalyst did not give any polymeric products. In the polymerization of mixture of trans‐ and cis‐2‐pentene with 1‐Ni /M‐MAO catalyst, the M_n of the polymer increased with an increase of the polymer yields. However, the relationship between polymer yield and the M_n of the polymer did not give a strict straight line, and the M_w/M_n also increased with increasing polymer yield. This suggests that side reactions were induced during the polymerization. The structures of the polymer obtained from the polymerization of 2‐ pentene with 1‐Ni /M‐MAO catalyst consists of ? CH₂? CH₂? CH(CH₂CH₃)? , ? CH₂? CH₂? CH₂? CH(CH₃)? , ? CH₂? CH(CH₂CH₂CH₃)? , and methylene sequence ? (CH₂)_n? (n ≥ 5) units, which is related to the chain walking mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2858–2863, 2008     

Excluded volume study of a sulfonate-containing polyelectrolyte in salt solutions

Chain characteristics of a linear sulfonate-containing homopolymer, sodium poly(3-methacryloyloxypropane-1-sulfonate), in aqueous salt solutions (ionic strength, C_s = 0.01N to 5N NaCl) have been investigated by light scattering and intrinsic viscosity. The molecular weight (M?_w)–viscosity relation can be well described by the Mark–Houwink and the Stockmayer–Fixman equations. The coil is highly expanded even in the most concentrated NaCl solution (6N), and no 1:1 electrolyte was found to precipitate this polymer. A linear relation was observed between the viscosity expansion factor, α^3η, and (M?_w/C_s)^1/2. Examination of the data in terms of theories for excluded volume and hydrodynamic interaction suggests that the coil experiences dominant hydrodynamic interaction, corresponding to a nondraining coil, and the second virial coefficient and coil expansion at high C^s can be correlated by the Flory–Krigbaum–Orofino equation. Results for this polymer are compared with those for other polyelectrolytes, and are discussed in terms of chain structure, flexibility, and hydrophobicity.     

Synthesis of polysiloxanes containing trifluoroethylene aryl ether groups: The effect of promoters

Polysiloxanes with high molecular weight (M_n > 100 000, M_w/M_n < 2.2) containing various quantity of trifluoroethylene aryl ether groups were prepared by anion ring opening polymerization (AROP) in the presence of promoters including N,N‐dimethylformamide (DMF) and N‐methyl pyrrolidone (NMP). The structures of monomers and polymers were characterized by FTIR and NMR. It was found that the addition of promoter could significantly increase the polymerization rate, decrease the polymerization temperature, and increase the molecular weight of the polymer. When DMF as the promoter, the optimal conditions for polymerization were as follows: The polymerization temperature is 100°C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 160:1. The optimal conditions for polymerization using NMP as the promoter were as follows: The polymerization temperature is 75°C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 70:1, which indicated that NMP is more effective on AROP than DMF. Thermogravimetric analysis (TGA) showed that the polymer has good heat temperature resistance. Differential scanning calorimetry (DSC) showed that the introduction of NMP in bulk polymerization could improve the randomness of polymer structure, which leads to the disappearance of crystal peak and improve the low temperature resistance of polymer.     

THE MOLECULAR WEIGHT AND ITS DISTRIBUTION OF 1, 2-POLYBUTADIENES PREPARED WITH MOLYBDENUM CATALYST SYSTEMS

The study on the molecular weight and its distribution of 1, 2-polybutadienes prepared with MoCl_4OR-i-Bu_2AlOR' catalyst systems has been carded out by viscosity and GPC methods. 1, 2-Polybutadienes with (?)=1.2-2.0can be obtained with these catalyst systems at 30—70℃. There is a linear relation between the (?) and the polymerization temperature. It was found by extrapolation that these catalyst systems may possibly initiate a living polymerization at the temperature near 18℃. The molecular weight of the polymers can be regulated either by polymerization temperature or by adding polar compounds such as allyl halides.     

Fundamental studies on cationic polymerizations: Molecular weights and molecular weight distributions of polyisobutylenes produced by γ-irradiation (free ions) and chemical catalysis (ion pairs)

The molecular weights (M?_n, M?_v, and M?_w) and molecular weight distributions of polyisobutylenes synthesized by γ-irradiation in the range 29 to ?78°C have been determined. The plots of log M?_n, log M?_v, and log M?_w versus 1/T are linear and parallel (E_M? = ?6.3₆ ± 0.5), and M?_w/M?_n ≈ 3.0 ± 0.5 over this temperature range. The viscosity-average molecular weights of polyisobutylenes obtained by γ-irradiation were compared with those of polymers prepared by BF₃, EtAlCl₂, and AlCl₃. It is found that, at the same polymerization temperature, the M?_v of radiation-induced polyisobutylenes, which propagate by free carbonium ions, is significantly higher than those synthesized by the Lewis acids, which probably propagate via ion pairs. The implications of these findings are discussed, and it is concluded that the counterion in the proximity of the growing cation impedes propagation to a greater extent than it does the competing process of chain transfer to monomer.     

Generalized Universal Molecular Weight Calibration Parameter in GPC

Abstract

In this report we show by experimental and theoretical investigations that the commonly used GPC universal calibration parameter, the intrinsic viscosity multiplied by the weight average molecular weight ([η] M^w) is incorrect. The error which can arise by using [η] M to calculate the molecular weight across the GPC chromatogram for nonuniformly branched polymers [poly(vinyl acetate) and low density polyethylene] and copolymers with compositional drift, could be very large. We also show conclusively that the number average molecular weight M_n is the correct average to use for the universal calibration parameter. We therefore recommend that our general universal Calibration parameter [η] M_n be used for calculating the molecular weight across the chromatogram for all polymer systems (linear and branched homopolymers, copolymers with or without compositional drift and for polymer blends).     

Molecular weight distribution and stereoregularity of polypropylenes produced with VCl4–AlEt2Cl catalyst

Dependences of the molecular weight distribution and stereochemical regulation of the polypropylenes produced with VCl₄–AlEt₂Cl catalyst on the polymerization temperature were examined. The molecular weight distributions of the polymers obtained at temperatures below ?40°C were unimodal and narrow (M _w/M _n ≤ 2). The molecular weight distributions obtained at higher temperatures (above ?21°C) were bimodal with one narrow distribution and one wide one (M _w/M _n > 2), and the polymer fraction of the wide distribution increased with the polymerization temperature. The fractional amount of ? (CH₂)₂? groups in the polymers, which corresponds to tail-to-tail linkage of two propylene units, increased to a maximum at ?21°C followed by a gradual decrease with the polymerization temperature. The production of isotactic polymers was confirmed at temperatures above ?21°C. From these data, it is concluded that only the homogeneous form of the catalyst system is responsible for the polymerization at temperatures below about ?21°C while the heterogeneous form appears and catalyzes the polymerization together with the homogeneous one at temperatures above ?21°C.     

Studies on reactions of the N-phosphonium salts of pyridines. XIV. Wholly aromatic polyamides by the direct polycondensation reaction by using phosphites in the presence of metal salts

Poly-p-benzamide of high molecular weight (η_inh = ～ in H₂SO₄) was obtained by the direct polycondensation reaction of p-aminobenzoic acid (p-ABA) by means of diphenyl and triaryl phosphites in N-methylpyrrolidone (NMP)-pyridine solution containing lithium and calcium chlorides. Molecular weight of polymer varied with the amount of these salts, showing maximum values at the concentration of about 4 wt-% of LiCl or about 8 wt-% of CaCl₂ in the reaction mixture. The reaction temperature at around 80°C gave a polymer of the highest viscosity. The polycondensation reaction was also affected by monomer concentration, solvents, and tertiary amines like pyridine. Similarly, aromatic polyamides with high molecular weight (η_inh values up to 1.34 in H₂SO₄) were prepared from isophthalic acid and aromatic diamines, whereas terephthalic acid gave only low-viscosity polymers.     

Anionic polymerization of caprolactam. XLIII. Relationship between osmometric molecular weight,viscosity, and endgroups of a polymer

For unfractionated anionic polymers, the following relationship between the osmometric molecular weight and intrinsic viscosity is valid: M?_n = 13200[η]^1.115 (cresol), or M?_n = 13000[η]^1.021 (93.8% H₂SO₄). A comparison of the osmometric and viscometric data with the number of endgroups of a polymer confirmed the finding that under certain conditions, moderately branched molecules can be formed; the above parameters depend on the type of the activator used.     

Synthesis and dilute solution properties of branched poly(benzyl methacrylate) using na-clay supported aqueous-phase catalysis

The supported aqueous-phase catalysis (SAPC) using hydrated interface has been used to synthesize branched polymers (star and graft) of benzyl methacrylate (BnMA) via atom-transfer radical polymerization (ATRP) in the presence of Na-clay supported catalyst in anisole at ambient temperature. The propagation of star poly(BnMA)s using diPENDTA-Br₆, as hexa-functional initiator is confined at the hydrated interface between the support and the liquid medium as evident from the obtained polymers that are catalyst contamination-free, and exhibited moderately narrow molecular weight distributions (M_w/M_n ≤ 1.33). The hexa-functionality of synthesized stars is verified by ¹H NMR, the measurement of their intrinsic viscosity ([η]), and radius of gyration (R_g). The polymerization was also recycled up to 5 times to produce star PBnMAs with high initiator efficiency. The star polymers prepared using hydrated Na-clay supported is compared with star prepared using covalent silica supported catalyst system. The star polymer obtained from covalently supported catalyst gave broad M_w/M_n and poor initiator efficiency. The polystyrene-graft-PBnMA (PS-g-PBnMA) copolymer is also prepared using hydrated Na-clay supported catalyst system in anisole at ambient temperature. The graft-copolymer had narrow M_w/M_n and was confirmed using ¹H NMR and atomic force microscopy. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2225–2237     

Dilute solution characterization of polyfluoroalkoxyphosphazenes

Results from the dilute solution characterization of polyfluoroalkoxyphosphazenes in Freon ether (E2) solutions are reported. Anomalous viscosity data suggest that polymer aggregation sometimes occurs in E2 and may be caused by the presence of relatively few anomalous polar groups on the polymer backbone. Since small amounts of acetone added to the E2 solutions inhibit aggregate formation, samples are also characterized in an E2-acetone mixed solvent. Light scattering and osmometry indicate that E2 and E2-acetone (9.09% by volume) are theta solvents for the polymers. High molecular weights (M?_w < 3 × 10⁶) and unusually broad molecular weight distributions (M?_w/M?_n < 16) are found. One polymer is fractionated by extracting solutions in 1,1,2-trichloro-1,2,2-trifluoroethane with acetone. Although the samples are highly polydisperse, intrinsic viscosities correlate with number-average molecular weights satisfying the Mark-Houwink relation with the exponent a ≈ 1/2. The z-average mean-square radius of gyration increases linearly with molecular weight so that 〈S²〉_g/M?_w ≈ 0.098. Because of the large polydispersity and unknown form of the distribution function, a quantitative interpretation of characterization results relating dilute solution parameters to polymer skeletal structure is not possible. The tentative conclusion is that the fluoroalkoxy-substituted phosphazene polymers are relatively linear and therefore that the broad distribution of molecular weights must be due to some polymerization mechanism other than branching.     

High-molecular-weight poly(p-phenyleneterephthalamide) by CaCl2 promoted direct polycondensation with thionyl chloride in N-methylpyrrolidone

The direct polycondensation of terephthalic acid and p-phenylenediamine hydrochloride (PPD.2HCl) with thionyl chloride was found to be significantly promoted in N-methylpyrrolidone (NMP) by dissolved CaCl₂ and tertiary amines. The inherent viscosity of the polymer obtained varied with the amount of CaCl₂ and tertiary amines added. The reaction, when effectively promoted by CaCl₂, proceeded homogeneously in the early state of polycondensation, and then resulted in a highly swollen gel. CaCl₂ had to be present in the PPD.2HCl/tertiary amines/NMP solution as well as in the TPA/SOCl₂/NMP mixture for the polycondensation to proceed to high molecular weight. Complexes of CaCl₂, PPD.2HCl, and tertiary amines in NMP similar to the well known complex, CaCl₂ · nNH₃ (n = 2, 4, 8) was proposed to facilitate the polycondensation.     

Cationic polymerization of α-methylstyrene in dichloromethane initiated with system 2,5-dichloro-2,5-dimethylhexene-BCl3. II. Continuous addition of monomer into initiator,quasiliving polymerization

A slow continuous addition of dichloromethana solutions of α-methylstyrene (α-MeSt) into a dichloromethane solution of 2,5-dichloro-2,5-dimethylhexane (DDH) with BCI₃ (initiating system II) prepared in advance resulted, in the temperature range between ?20 and ?40°, in a quasilving polymerization of α-MeSt. At ?20°C and a 100% conversion a polymer with a very narrow molecular weight distribution is formed, M?_w/M?_n - 1.1. Quasiliving polymerization of α-MeSt has not been achieved with freshly prepared dischloromethane solutions of DDH with BC₃ (initiating sytem I), or with solutions of BCI₃ alone (initiating system III). Polarity of the polymerization medium affected molecular weight distribution (MWD) of the polymer, and the polydispersity index decreased with decreasing polarity. MWD of the polymer samples were studied by the GPC method, the structure of poly (α-methylstyrene) (Pα-MeSt) was investigated by the ₁H-NMR analysis     

Schiff base as a novel kind of catalyst for reversible complexation‐mediated radical polymerization of methyl methacrylate

Two kinds of Schiff base, N,N′‐dibenzylidene‐1,2‐diaminoethane (NDBE) and N,N′‐disalicylidene‐1,2‐diaminoethane, have been found as efficient organic catalyst for reversible complexation‐mediated radical polymerization (RCMP) of methyl methacrylate (MMA) for the first time. The polymerization results show obvious features of “living”/controlled radical polymerization. Well‐defined and low‐polydispersity polymers (M_w/M_n = 1.20–1.40) are obtained in RCMP of MMA catalyzed by Schiff base at mild temperature (65–80°C). Moreover, Schiff base also exhibits a particularly high reactivity for RCMP of MMA with in situ formed alkyl iodide initiator. The polymer molecular weight and its polydispersity (M_w/M_n is around 1.20) are well controlled even with high monomer conversion. Notably, when the dosage of azo initiator is same as the dosage of iodine, the polymerization could also be realized in the presence of NDBE. The living feature of synthesized polymer is confirmed through the chain extension experiment. In short, Schiff base is a kind of high‐efficient catalyst for RCMP and reverse RCMP of MMA, which can be one of the most powerful and robust techniques for polymer synthesis. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1653–1663     

Atom Transfer Radical Polymerization of Styrene Using Multifunctional Iniferter Reagents as Initiators

Summary: Two multifunctional iniferters, 1,4-bis-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (BDCIB) and 1,3,5-tris-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (TDCIB), were successfully synthesized and used as initiators to initiate the polymerization of styrene in the presence of a CuBr/PMDETA complex. The polymerization results demonstrated that the kinetic plots in all cases were first-order to the monomer, the molecular weight of the polymers increased linearly with the monomer conversion; meanwhile, the molecular weight distribution of the polymer was kept to a very low value (M_w/M_n ≤ 1.35). Furthermore, the measured molecular weights were very close to the calculated values, which indicated the high efficiency of the initiator for the polymerization of styrene. The effect of catalyst concentration and initiator concentration was not obvious and the influence of polymerization temperature was apparent, and the polymerization rate increased with the polymerization temperature. The results of chain-extension and ¹H NMR analysis proved that the polymer obtained was capped with diethylthiocarbamoylthiy (DC) group.