Electrophilic Monomers Research Articles

Alkali-Promoted Tandem Polymerization of Nucleophilic Acetylide Monomers and Aldehydes toward Luminescent Polymeric Materials

Alkyne-based polymerizations have been an invaluable tool for the preparation of functional polymers. In the reported polymerizations, alkynes generally function as electrophilic monomers. Theoretically, ethynyl groups of monomers could also be used as nucleophiles, and the polymerization using an ethynyl group as the nucleophile should be developed further. In this work, a potassium tert-butoxide (t-BuOK)-promoted tandem polymerization of aromatic diynes and commercially available benzaldehyde, in which ethynyl groups were used as nucleophiles, was successfully developed. Under optimized conditions, this polymerization could produce polymers with good solubility, well-defined structures, high-weight-averaged molecular weights (Mw, up to 76,000), and yields up to 93% in as short as 15 min at room temperature. Moreover, thanks to their ethynyl vinyl carbinol moieties, the resultant polymers show the interesting luminescent property, and some are aggregation-induced emission (AIE)-active. Thus, the nucleophilic alkyne-based cascade polymerization not only provides a powerful tool for the preparation of functional polymers but also might inspire innovation in the area of polymer chemistry.

How to Fight Kinetics in Complex Radical Polymerization Processes: Theoretical Case Study of Poly(divinyl ether‐alt‐maleic anhydride)

AbstractProducts of free‐radical polymerization (FRP) are usually not regulated on the molecular scale, consisting of blocks obtained through the fastest kinetic scheme pathways. The side or kinetically restricted products can be a source of impurities in a complex FRP case, or possess new properties if isolated solely. FRP synthesis of poly(divinyl ether‐alt‐maleic anhydride), known as “DIVEMA”, serves as a polymerization example with such kinetic and thermodynamic complexities. Uncertainty in factors regulating polymer structure is a challenge in advancement “DIVEMA” derivatives toward medical practice. In‐depth investigation via quantum‐chemical and molecular mechanics methods unveils mechanistic aspects of polymer stereoisomerism and confirms possible isolation of thermodynamically or kinetically controlled products on a large data set. Strategies toward regulation of 5‐exo/6‐endo cycloisomerism are theorized and then studied via microkinetic modeling. Thermodynamically controlled products can be isolated utilizing lower monomer concentrations, in range of 10−3 to 10−1 m, and/or application of a complexing agent that is better to realize via solvents, capable of formation π‐ and σ‐radical complexes. Change of electrophilic monomer is proposed as an approach for designing more molecularscale adjustable copolymerization processes. Methodology, obtained results, and conclusions for “DIVEMA” can be valuable to control other FRP processes on the molecular scale, unlocking polymers with improved or new functionalities.

Dual Stimuli-Responsive Comb Polymers from Modular N-Acylated Poly(aminoester)-Based Macromonomers.

We report the synthesis of dual-responsive N-acylated poly(aminoester) (NPAE)-based comb polymers with varying molecular composition and monomer sequence via a combination of spontaneous zwitterionic copolymerization and redox-initiated reversible addition-fragmentation chain transfer (RRAFT) polymerization. NPAE macromonomers were synthesized from different nucleophilic (MN), for example, 2-ethyl-2-oxazoline (EtOx) or 2-ethyl-2-oxazine (EtOz), and electrophilic monomers (ME), for example, acrylic acid (AA) or 2-carboxyethyl acrylate (CEA), to tune the hydrophilicity and sequence of the systems. The latter was found to influence the thermal properties and stability of the respective comb polymers. Turbidity investigations in aqueous solution revealed a dual-responsive behavior of the comb polymers being responsive to both temperature and pH changes due to ω-carboxylic end groups of the NPAE-based macromonomers. Additional methylene groups in the NPAE backbone rendered the corresponding systems more hydrophobic and, hence, decreased the cloud point temperatures and, at the same time, increased the pH values (at constant temperature) at which the polymer phase separates from the aqueous solution.

Poly(arylene thioether)s containing 9,9′‐spirobifluorene moieties in the main chain: Masked dithiol‐based synthesis and excellent optical properties

AbstractPoly(arylene thioether)s (PTEs) containing 9,9′‐spirobifluorene moieties were synthesized in high yields from 9,9′‐spirobifluorene‐2,2′‐bis(N,N‐dimethylcarbamothioate) 4 as the masked dithiol and various difluoroarenes as electrophilic monomers. All PTEs showed high thermal stability: The 10% weight loss temperature as evaluated by thermogravimetric analysis was over 470 °C under both nitrogen and air atmospheres. The glass transition temperature estimated by DSC was in the range 210–270 °C. The PTEs showed high solubility in ordinary organic solvents, such as CHCl3, NMP, and THF. Most PTEs exhibited remarkably high refractive indices ranging from 1.69 to 1.73 at 587.6 nm, whereas no or little birefringence was observed for the PTEs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4192–4199, 2010

Novel Aromatic Polyimides Derived from 5′-t-Butyl-2′-pivaloylimino-3,4,3′′,4′′-m-terphenyltetracarboxylic Dianhydride with Potential Application on Gas Separation Processes

A new family of polyimides having two bulky groups in the central ring of a m-terphenyl moiety has been obtained. These polyimides have been synthesized by reaction of four commercial diamines with the electrophilic monomer, 5′-t-butyl-2′-pivaloylimino-3,4,3′′,4′′-m-terphenyltetracarboxylic acid dianhydride (PTPDA). This monomer has been obtained by a modern C−H-activated arylation method with good yield and purity. The attained polymers showed Tg values ranging from 300 to 430 °C, thermal stability >500 °C, and excellent solubility in a broad range of solvents, including tetrahydrofuran. Despite having an amide group, uptake of water was low and comparable to that of classical aromatic polyimides. Mechanical properties of polymer films were good enough to permit the use of these polyimides on gas separation applications at high pressures. Films obtained by casting offered a good balance of permeability and permselectivity with values close to the Robeson upper-bound, in particular for the O2/N2 gas pair.

Selective Synthesis of Poly(m-phenylene oxides) over Oxacalixarenes

We report a high yielding AA−BB type step-growth synthesis of poly(m-phenylene oxides) (mPOs) by nucleophilic aromatic substitution (SNAr) reactions. Previously, poly(mPOs) have proven difficult to synthesize, especially by SNAr, due to competing cyclooligomer (oxacalixarene) formation. We have found that the linear (polymeric) vs cyclic (oligomeric) product distribution is strongly dependent on the substitution pattern of the electrophilic monomer, and a model is described that predicts whether the reacting monomers will kinetically favor formation of poly(mPOs) or oxacalixarenes. The polycondensation reaction tolerates a range of functional groups on both reactive monomers, and the synthesized poly(mPOs) have high thermal and aqueous stability but are readily depolymerized in polar aprotic media.

Aromatic polyethers based on 3,5-dinitrodiphenylsulfone

Aromatic polyethers with phenylsulfone side groups were obtained via the reaction of aromatic nucleophile substitution using 3,5-dinitrodiphenylsulfone as an electrophilic monomer activated by meta-substituents. The polymers are characterized by solubility in a variety of organic solvents and by large intervals between the softening and thermal degradation temperatures, properties that determine their improved processability into articles.

Classical Metallocenes as Photoinitiators for the Anionic Polymerization of an Alkyl 2-Cyanoacrylate

The classical metallocenes, ferrocene and ruthenocene, dissolve readily in neat ethyl 2-cyanoacrylate (CA) monomer. The electronic spectra of the resulting solutions display a near-ultraviolet absorption band assigned as a charge-transfer-to-solvent (metallocene → CA) transition. Irradiation into this band causes the one-electron oxidation of the metallocene to the corresponding metallocenium cation accompanied by reduction of CA to its radical anion. Addition of the latter species to CA initiates the anionic polymerization of the electrophilic monomer. The progress of photoinitiated polymerization was monitored in real time by attenuated total reflectance infrared spectroscopy.

Benzoyl-Substituted Ferrocenes: An Attractive New Class of Anionic Photoinitiators

Spectroscopic, photochemical, and photoinitiation studies are reported for a series of monobenzoylferrocenes and 1,1‘-dibenzoylferrocenes. These nonionic metallocene complexes absorb strongly in the ultraviolet and visible wavelength regions owing to electronic transitions of mixed ligand field/charge-transfer character. Irradiation of the complexes in methanol results in ring−metal cleavage to yield a benzoyl-substituted cyclopentadienide carbanion and the corresponding half-sandwich iron(II) complex. This process occurs with an appreciable quantum efficiency (>0.30 at 546 nm) for 1,1‘-dibenzoylferrocenes; in contrast, monobenzoylferrocenes are appreciably less photosensitive. When the solvent is neat ethyl α-cyanoacrylate, the photogenerated carbanion initiates rapid anionic polymerization of this electrophilic monomer. Several factors that can influence the performance of benzoyl-substituted ferrocenes as anionic photoinitiators are considered.

Poly[N-(hydroxyethyl)ethyleneimine-co-phenyl succinic anhydride

Five copolymers from N-(hydroxyethyl)ethyleneimine as nucleophilic monomer and phenylsuccinic anhydride (PhSAn) as electrophilic monomer, were synthesized according to the spontaneous copolymerization concept. These copolymers were characterized by elemental analysis, FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The copolymer composition determined from the 1H-NMR spectra showed that the copolymers are not alternating. According to all the data, it was suggested a copolymer structure which includes ester and anhydride bonds. The molecular weights determined by vapor pressure osmometry ranged between 5.100 and 6.100 g/mol.

Novel non-alternating copolymers synthesized by spontaneous copolymerization of p -chlorophenylmaleimide with 2-methyl-2-oxazoline

The copolymerization of p-chlorophenylmaleimide (1) as electrophilic monomer with 2-methyl-2-oxazoline (2) as nucleophilic monomer without initiator in solution under different experimental conditions was investigated. Copolymers were characterized by FT-IR and 1H-NMR spectroscopy. The copolymer composition was determined from 1H-NMR spectra. Molecular weights ranged between 1700 and 5400 g/mol by vapor pressure osmometry.

Poly[N-(2-hydroxyethyl)ethyleneimine-co-(1,2,3,6-tetrahydrophthalic anhydride)] by spontaneous copolymerization

The copolymerization of 1,2,3,6-tetrahydrophthalic anhydride (THPhA) as electrophilic monomer and N-(2-hydroxyethyl)ethyleneimine1 Systematic name: N-(2-hydroxyethyl)aziridine. as nucleophilic monomer in acetonitrile without initiator was investigated. The copolymers show low incorporation of THPhA in the main chain and preferential incorporation in the side chain by esterification reaction of the hydroxymethyl group. On the basis of the spectroscopic data a copolymer structure is proposed.

Poly[N-(2-hydroxyethyl)ethyleneimine-co-(1,2,3,6-tetrahydrophthalic anhydride)] by spontaneous copolymerization

The copolymerization of 1,2,3,6-tetrahydrophthalic anhydride (THPhA) as electrophilic monomer and N-(2-hydroxyethyl)ethyleneimine1 Systematic name: N-(2-hydroxyethyl)aziridine. as nucleophilic monomer in acetonitrile without initiator was investigated. The copolymers show low incorporation of THPhA in the main chain and preferential incorporation in the side chain by esterification reaction of the hydroxymethyl group. On the basis of the spectroscopic data a copolymer structure is proposed.

Poly[N-(2-hydroxyethyl)ethyleneimine-co-(1,2,3,6-tetrahydrophthalic anhydride)] by spontaneous copolymerization

The copolymerization of 1,2,3,6-tetrahydrophthalic anhydride (THPhA) as electrophilic monomer and N-(2-hydroxyethyl)ethyleneimine as nucleophilic monomer in acetonitrile without initiator was investigated. The copolymers show low incorporation of THPhA in the main chain and preferential incorporation in the side chain by esterification reaction of the hydroxymethyl group. On the basis of the spectroscopic data a copolymer structure is proposed.

Transformation of the cationic growing center of poly(tetrahydrofuran) into an anionic one by bis(pentamethylcyclopentadienyl)samarium

Transformation of the cationic growing center of living poly(tetrahydrofuran) [poly(THF)] into an anionic one was achieved in high efficiency (62%) by the end-capping of living poly(THF) with potassium iodide followed by the reduction with bis(pentamethylcyclopentadienyl)samarium (Cp * 2 Sm), whereas the direct reduction with Cp * 2 Sm without the end-capping resulted in the formation of poly(THF) with pentamethylcyclopentadienyl group at the terminal. The increase in the molecular weight of poly(THF) after the reduction was observed, which indicates the presence of the dimerization of poly(THF) during the reduction. The polymerization of variety of electrophilic monomers including δ-valerolactone, 2-oxo-1,3-dioxane, and alkyl methacrylates with the macroanion provided good yields of the corresponding block copolymers consisting of both cationically and anionically polymerizable monomers.

Spontaneous copolymerization of N-(2-hydroxyethyl)ethyleneimine with isatoic anhydride

The polymerization of isatoic anhydride (electrophilic monomer) with N-(2-hydroxyethyl)ethyleneimine (nucleophilic monomer) was studied in the absence of added initiator at different feed monomer concentrations, temperature, and time of copolymerization. The copolymers were characterized by FT-IR, 1H-NMR and 13C-NMR spectroscopy, and TGA. Based on spectroscopic data and copolymer composition, a copolymer structure was suggested.

Samarium poly(oxamide) polyanions as novel polymeric initiators. One-pot syntheses of graft copolymers

Samarium poly(oxamide) polyanions, formed quantitatively in situ by the reductive coupling polymerization of aromatic diisocyanates with samarium (II) iodide/hexamethylphosphoramide (HMPA) system, were directly used as the polymeric initiators in the graft polymerization with some electrophilic monomers. The graft polymerization of ϵ-caprolactone (CL) with several polyanions derived from bifunctional isocyanates, including tolylene 2,6-diisocyanate, o-tolidine diisocyanate and diphenylmethane diisocyanate, provided the corresponding graft copolymers in one-pot, indicating that the polyanion could work as a new type of reactive polymer. Several factors such as reaction temperature and time and the amount of HMPA and CL affected the behavior of the present polymerization system, and the graft copolymer was obtained quantitatively under the appropriate conditions. The results of the graft polymerizations of tert-butyl methacrylate and methyl methacrylate with the polyanion were also presented. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1381–1387, 1997

“Spontaneous Copolymerization ofp-Chlorophenylmaleimide with 2-Methylaziridine”

Abstract p-Chlorophenylmaleimide as an electrophilic monomer was copolymerized in the absence of initiator with 2-methylaziridine as nuclephilic monomer. The copolymers were characterized by elemental analysis, FT-IR, and 1H-NMR spectroscopy. The copolymer compositions were determined by chloro elemental analysis and 1H-NMR spectroscopy. 2-Methylaziridine is more reactive than p-chlorophenylmaleimide yielding statistical copolymers. Mn, determined by vapor pressure osmometry, varied between 3.000 and 6.700 g/mol.

Synthesis and characterization of copolymers from acrylic and methacrylic acid with 2‐methylaziridine by spontaneous copolymerization

Abstract2‐Methylaziridine (MAz) as a nucleophilic monomer and acrylic acid (AA) and methacrylic acid (MA), respectively, as electrophilic monomers were copolymerized in the absence of initiator at various feed ratios. Copolymers were characterized by elemental analysis, FT‐IR and 1H‐NMR spectroscopy. The monomer reactivity ratios were determined by the Fineman‐Ross and Kelen‐Tüdős methods. Values of r1 and r2 were found to be less than unity for MAz‐AA, and MAz‐MA, corresponding to random copolymers with the tendency to the alternance. For all the copolymers the thermal decomposition with 10% weight loss is higher than 430 K. The reaction order for degradation of all copolymers was zero. The kinetic parameters of the decomposition were determined for all copolymers.

Spontaneous copolymerization of phthalic anhydride with aziridine or 2-methylaziridine

Phthalic anhydride as an electrophilic monomer was copolymerized in the absence of initiator under various experimental conditions with aziridine or 2-methylaziridine as nucleophilic monomers. The copolymers by elemental analysis, i.r. and 1H-NMR spectroscopy were characterized and their specific viscosity was determined. The copolymer composition was determined by elemental analysis and compared with those obtained by 1H-NMR spectroscopy. Aziridine or 2-methylaziridine is incorporated preferentially in the copolymer when the feed ratio is richest in the nucleophilic monomer. According to the copolymer composition, the i.r. and the 1H-NMR spectra information, it was possible to suggest a copolymer structure. The MAz/PhAn copolymers have lower molecular weight than those Az/PhAn copolymers. The thermal degradation of the Az/PhAn and MAz/PhAn copolymers have been investigated using thermogravimetry in the temperature range 293–673 K. Most copolymers are stable until 387 K.