Polystyrene-Supported Dimethylformamides as Phase Transfer Catalysts in Solid-Solid-Liquid System

Abstract

Polymer-supported dimethylformamides were prepared by copolymerization of N-methyl-N-(p-vinylbenzyl)formamide, styrene, and divinylbenzene with AIBN. These polymers displayed catalytic activity for the reaction of alkyl bromides with alkali metal thiocyanates and potassium acetate in a solid-solid-liquid triphase system, although the corresponding monomeric formamides were inactive. The catalytic activity depended remarkably on the copolymer composition. Further, the catalytic reaction was affected by some experimental parameters such as stirring speed, particle size, degree of crosslinking, and solvent. A plausible catalytic reaction mechanism consisting of collisional contact between the solid catalysts and reagents was proposed.     

Effects of the acid chain length and copolymer crosslinking on the acylation of N-hydroxysuccinimide copolymers with carbobenzoxyoligo-ϵ-aminocaproic acids

N-Hydroxysuccinimide-type soluble copolymer with styrene and three similar divinylbenzene (3–4 mole-%) crosslinked copolymers with styrene, N-vinylpyrrolidone, and N,N-dimethylacrylamide were prepared from their precursor copolymers of N-acetoxymaleimide. Acylation of these N-hydroxyl polymers with carbobenzoxyoligo-?-aminocaproic acids was conducted in dimethylformamide at room temperature by using dicyclohexylcarbodiimide as condensing agent. The soluble styrene copolymer was acylated in good conversions (76–89%) in every case (n = 1–3), whereas the acylation of the crosslinked copolymers decreased slightly from n = 1 to n = 2, and dropped suddenly to only small conversions (4.7–7.4%) with n = 3, showing a marked inhibitory effect of crosslinking when the acids became longer. The effect of the microenvironment of the polymer did not appear significant. All the acyl polymers, including the precursor polymers, yielded the corresponding cyclohexylamides when treated with cyclohexylamine.     

Preparation of Polystyrenes Containing Sulfonamide Moieties and Their Use as Phase Transfer Catalysts

Styrenes containing sulfonamide moieties such as N-methyl-N-(P-vinylbenzyl)methanesulfonamide and N,N-dimethyl-p-styrene-sulfonamide were prepared. The copolymerization parameters of these monomers were obtained from copolymerization with styrene under free radical conditions. Crosslinked polymers prepared by free radical terpolymerization of the sulfonamide monomer, styrene, and divinylbenzene served as phase transfer catalysts for the reaction of n-octyl bromide with sodium thiophenoxide in the toluene-water system. However, the corresponding monomeric sulfonamides were practically inactive. These polymer catalysts were stable even under strongly alkaline conditions, and the recovered catalysts were used without a significant loss in activity.     

Study of complexation between perrhenate ion and N-methyl-N-vinylacetamide and N-methyl-N-vinylamine copolymers in aqueous solutions by fast monolith high-performance liquid chromatography (HPLC)

Complexation between perrhenate ion and N-methyl-N-vinylacetamide and N-methyl-N-vinylamine copolymers in aqueous solutions was studied by high-performance liquid chromatography on monolith ultrashort columns. It was demonstrated that complexation has slow kinetics and strongly depends on the length of alkyl substituent.     

Miniemulsion polymerization of styrene using well-defined cationic amphiphilic comblike copolymers as the sole stabilizer

Well-defined, positively charged, amphiphilic copolymers containing long alkyl side chains were used as stabilizers in the miniemulsion polymerization of styrene. The copolymers were prepared by controlled free-radical copolymerization of styrene and vinyl benzyl chloride using either the reversible addition-fragmentation chain transfer method or TEMPO-mediated polymerization. The benzyl chloride moities were modified by two different long alkyl chain tertiary amines (N,N-dimethyldodecyl amine and N,N-dimethylhexadecyl amine) to yield the amphiphilic copolymers with vinylbenzyl dimethyl alkyl ammonium chloride units. Owing to their high structural quality, only a small amount of these copolymers was required to stabilize the latex particles (0.5–2 wt% vs styrene). Moreover, in the absence of any hydrophobic agent, the amphiphilic comblike copolymer preserved the colloidal stability of both the initial liquid miniemulsion and the final latex. Ill-defined, analogous copolymers were synthesized by conventional free-radical polymerization and in comparison, exhibited poor stabilization properties.     

Anionic graft copolymerization of diene polymers with vinyl monomers

A mixture of homopolymer and graft copolymer was obtained by adding the monomer at 0°C to the polylithiodiene solution. Styrene, methyl methacrylate, and acrylonitrile were used as the monomers. Polylithiodienes were prepared by the metalation of diene polymers, i.e., polybutadiene or polyisoprene, with the use of n-butyllithium in the presence of a tertiary amine (N,N,N′,N′-tetramethylethylenediamine) in n-heptane. The graft copolymers were separated by solvent extraction and were confirmed by turbidimetric titration and elementary analysis. Oxidation of the polybutadiene–styrene grafts revealed that the molecular weight of the side chains was the same as the molecular weight of the free polystyrene formed. The grafting efficiency and grafting percentage were studied for polybutadiene–styrene graft copolymers prepared under various conditions.     

Hydrophobic interactions in the enantioselective solvolyses of optically active activated esters by imidazole-containing polymeric surfactants

Enantioselective solvolyses of optically active activated esters in the aggregate system of optically active polymeric surfactants containing imidazole and benzene moieties were performed. The catalyst polymers [copoly(MHis-DEVAB)] employed were copolymers of N-methacryloyl-L -histidine methyl ester (MHis) with N,N-dimethyl-N-hexadecyl-N-[10-(p-vinylcarboxanilido) decyl]ammonium bromide(DEVAB). In the solvolyses of N-carbobenzoxy-D - and L -phenylalanine p-nitrophenyl esters (D -NBP and L -NBP) by polymeric catalysts, copoly(MHis-DEVAB) exhibited not only increased catalytic activity but also enhanced enantioselectivity as the mole percent of surfactant monomers in the copolymers increased. The polymeric catalysts showed noticeable enantioselective solvolyses toward D - and L -NBP of the substrates employed. As the reaction temperature was lowered for the solvolyses of D - and L -NBP with the catalyst polymer containing 4.8 mol% of MHis, an increased reaction rate and enhanced enantioselectivity were observed. The coaggregate systems of the polymer and monomeric surfactants were also investigated. The case of a coaggregate system consisting of 70 mol% of cetyldimethylethylammonium bromide with polymeric catalyst showed maximum enantioselective catalysis, viz., k_cat (L )/k_cat(D ) = 6.68. The catalyst polymers in the sonicated solvolytic solutions were confirmed to form large ordered aggregate structure by electron microscopic observation. From these results, it is concluded that hydrophobic interaction in ordered aggregate structure plays an important role in enantioselective catalysis of optically active imidazole-containing polymers.     

Preparation and characterization of optically active polymers containing pendent and terminal chiral units via atom transfer radical polymerization

Optically active homopolymers and copolymers, bearing chiral units at the side chain and end chain, were prepared via atom transfer radical polymerization (ATRP) techniques. The well‐defined optically active polymers were obtained via the ATRP of pregnenolone methacrylate (PR‐MA), β‐cholestanol acrylate (CH‐A), and 20‐(hydroxymethyl)‐pregna‐1,4‐dien‐3‐one acrylate (HPD‐A) with ethyl 2‐bromopropionate as the initiator and CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalytic system. The experimental results showed that the polymerizations of PR‐MA, CH‐A, and HPD‐A proceeded in a living fashion, providing pendent chiral group polymers with low molecular weight distributions and predetermined molecular weights that increased linearly with the monomer conversion. Furthermore, the copolymers poly(pregnenolone methacrylate)‐b‐poly[(dimethylamino)ethyl methacrylate] and poly(pregnenolone methacrylate‐co‐methyl methacrylate) were synthesized and characterized with ¹H NMR, transmission electron microscopy, and polarimetric analysis. In addition, when optically active initiators estrone 2‐bromopropionate and 20‐(hydroxymethyl)‐pregna‐1,4‐dien‐3‐one 2‐bromopropionate were used for ATRPs of methyl methacrylate and styrene, terminal optically active poly(methyl methacrylate) and polystyrene were obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1502–1513, 2006     

Nitroxide‐mediated controlled radical polymerizations of styrene derivatives

Several (protected) amine and alcohol functionalized styrene monomers were synthesized via readily accessible synthetic routes. The controlled radical copolymerization of these functionalized styrene monomers with styrene was performed using two alkoxyamines, namely N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl) hydroxylamine (MAMA‐SG1) and N‐tert‐butyl‐N‐(2‐methyl‐1‐phenylpropyl)‐O‐(1‐phenylethyl)hydroxylamine. The copolymers obtained showed low polydispersities, controlled molecular weights, and a random topology. The thermal properties of the polymers were determined with differential scanning calorimetry. All polymers were amorphous and showed glass transition temperatures between 40 and 111 °C. Deprotection of the copolymers afforded amine or alcohol pendant polystyrenes which were readily functionalized with isocyanates. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Acyloin condensation by polymer supported thiazolium salt: Relation between the catalytic activity and the degree of quarternization

Thiazolium salt polymers were synthesized by the quarternization of thiazole polymers by alkyl halides. It was found that these polymers had high catalytic activities for the acyloin condensation of furfural. The catalytic activities of thiazolium salt polymers increased as the degree of quarternization decreased. This tendency was observed both in the polar solvents such as MeOH and in the nonpolar solvents such as dioxane. From the results of the acyloin condensation catalyzed by more hydrophobic polymer catalyst PTS⁺–St (which had styrene unit instead of free thiazole unit) and CnPTS⁺ (which had a long alkyl chain around the active site), it became clear that the hydrophobicity and the steric hindrance around the active site greatly affected the catalytic activity.     

Synthesis and characterization of N-substituted 1,4,5,6-tetrahydropyrimidine containing functional polymers as SO2 and CO2 sorbents

Novel vinyl monomers containing 1,4,5,6-tetrahydropyrimidine were prepared by the reaction of N-substituted-1,3-diaminopropane with N,N-dimethyl-formamide dimethylacetal, which gave 1-alkyl or aryl substituted 1,4,5,6-tetrahydropyrimidines, Alkylation of the tetrahydropyrimidine derivatives by chloromethylstyrene produces the N-methyl-N′-vinyl benzyl-1,4,5,6-tetrahydropyrimidinium chloride in high yields. These monomers were readily polymerized in dimethylformamide by AIBN at 80°C. Homopolymers and soluble linear copolymers were prepared and copolymerization parameters were rationalized. Further, insoluble terpolymers prepared from these monomers, styrene and divinylbenzene were tested for the sorption of the weakly acidic gases gave excellent results. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2411–2420, 1997     

Catalytic systems Me2SiCp*NtBuMX2/(CPh3)(B(C6F5)4) (MTi,XCH3, MZr,XiBu) in copolymerization of ethylene with styrene

Catalytic activity of Me₂SiCp*N^tBuMX₂/(CPh₃)(B(C₆F₅)₄) [MTi, XCH₃ (1); MZr, X=ⁱBu (2)] systems in the ethylene/styrene (E/S) feed was examined. Experimental data revealed high activity for the catalytic system (1) for copolymerization ethylene with styrene, whereas the system with enhanced catalytic activity for ethylene homopolymerization (2) was temporarily blocked in the styrene presence yielding, even at high styrene content, homopolyethylene as the final product. Properties of thus obtained polymers were analyzed. Catalytic system (1) occurred very sensitive to S/E ratio in the comonomers feed. The 10‐fold acceleration for ethylene consumption was shown in two experimental sets conducted at S/E = 1.3 ratio, 1 bar, and 7.5 bar ethylene pressure, respectively. The consequent enhancement in S/E ratio resulted in slowing down both ethylene consumption and catalyst deactivation rates. Atactic polystyrene was formed at high styrene content with the catalyst (1). Catalytic system (1) allowed design of products with the highest styrene content (20 mol %) at low ethylene pressure, moderate temperature, and high S/E ratio. The apparent activation energy estimated from the initial rates of ethylene consumption was 54.6 kJ/mol. Analysis of apparent reactivity factors (r_E = 9 and r_S = 0.04; r_E × r_S = 0.4) and ¹³C‐NMR copolymer spectra revealed an alternating tendency of the comonomers for active center incorporation. DSC measurements showed considerable decrease of melting points and crystallinity even for copolymers with low styrene content. The catalyst produced relatively high–molecular weight copolymers (140–150 kg/mol) even at 80°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1083–1093, 1999     

Synthesis of poly(styrene‐block‐tert‐butyl acrylate) star polymers by atom transfer radical polymerization and micellization of their hydrolyzed polymers

A series of poly(styrene‐block‐tert‐butyl acrylate) heteroatom star block copolymers having various block lengths were prepared by atom transfer radical polymerization (ATRP), using an “as synthesized” cynurate modified trifunctional initiator. The structure of the star polymers was confirmed by the characterization of the individual arms resulting from hydrolysis. Amphiphilic poly(styrene‐block‐acrylic acid) star copolymers were further synthesized by hydrolyzing PtBA blocks using anhydrous trifluoroacetic acid. The characterization data are reported from analyses using gel permeation chromatography, infrared, ¹H and ¹³C NMR spectroscopies. The stable micelle solution was prepared by dialyzing the solution of these polymers in N,N‐dimethylformamide against deionized water. The temperature‐induced associating behavior of these amphiphilic star polymers were studied using dynamic laser light scattering spectroscopy. The hydrodynamic diameter of both micelles and unassociated chains were obtained in the same solution using light scattering cumulant's calculation method. The homogeneity and the size distribution of the micelle population in the solution were determined using centrifuge/sedimentation particle size distribution analyzer. Field emission scanning electron microscope was used to visualize the size of the micelles formed and the micellar aggregates. The influence of the temperature on the viscosity of the micelle solution was studied using an Ubbelohde viscometer. Thermodynamics of micellization of these block copolymers were also investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6367–6378, 2005     

Aminimides. XII. Synthesis,homo- and copolymerization studies of trialkylamine N-acryloyl or N-methacryloyl glycinimides and β-aminopropanimides

Some representative examples of a new family of aminimide monomers, i.e., trialkylamine N-acryloyl or N-methacryloyl glycinimides and β-aminopropanimides have been prepared and studied. These are the first examples of a possible large family of primary aminimide monomers. With radical initiators, the acryloyl and monosubstituted methacryloyl monomers readily homopolymerize. The disubstituted methacryloyl aminimides do not homopolymerize under the same conditions. All of the new monomers copolymerize with styrene, methyl methacrylate, and n-butyl acrylate. The various polymers were characterized by IR, DTA, TGA, GPC and inherent viscosities. When heated (160°C) the polymers liberate amine and crosslink in the presence of active hydrogen moieties to give resins with carbamate, urea, allophonate, etc., residues. When no active hydrogens are available during heating, polymers can be prepared with pendent primary isocyanate groups. This preliminary work shows these monomers to be highly useful for preparing a wide variety of reactive copolymers.     

Multifunctional ATRP initiators: Synthesis of four‐arm star homopolymers of methyl methacrylate and graft copolymers of polystyrene and poly(t‐butyl methacrylate)

Tetrakis bromomethyl benzene was used as a tetrafunctional initiator in the synthesis of four‐armed star polymers of methyl methacrylate via atom transfer radical polymerization (ATRP) with a CuBr/2,2 bipyridine catalytic system and benzene as a solvent. Relatively low polydispersities were achieved, and the experimental molecular weights were in agreement with the theoretical ones. A combination of 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated free‐radical polymerization and ATRP was used to synthesize various graft copolymers with polystyrene backbones and poly(t‐butyl methacrylate) grafts. In this case, the backbone was produced with a 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated stable free‐radical polymerization process from the copolymerization of styrene and p‐(chloromethyl) styrene. This polychloromethylated polymer was used as an ATRP multifunctional initiator for t‐butyl methacrylate polymerization, giving the desired graft copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 650–655, 2001     

Photodegradation behavior of tert-butyl vinyl ketone polymers and copolymers with styrene and α-methylstyrene

Photodegradation behavior of atactic and isotactic polymers of tert-butyl vinyl ketone (t-BVK) and its copolymers with styrene and α-methylstyrene was studied in dioxane as a solvent at room temperature. The quantum yield of main-chain scission of atactic poly(t-BVK) was found to be larger than that of isotactic poly(t-BVK) and atactic poly(methyl vinyl ketone). From the Stern-Volmer plots on the quenching study of atactic poly(t-BVK) with naphthalene and 2,5-dimethyl-2,4-hexadiene, it was found that 60–70% of its photochemical reaction underwent main-chain scission from the triplet state. It was also found that the increase in t-BVK contents of both copolymers accelerated the photodegradation, and the copolymer with styrene was more photodegradable than that with α-methylstyrene. These results seemed to suggest that the main-chain scission of these vinyl ketone polymers and copolymers proceeded through a Norrish type II photoelimination mechanism.     

Tailor‐made biomimetic random copolymers for medical applications

Biospecific copolymers were synthesized by random substitution of a preformed polymer with suitable chemical groups or by random copolymerization of suitable functional monomers. Such polymers contain arrangements of the chemical functions that mimic natural biospecific sites. The probability of occurrence of such arrangements will depend on the average composition of the copolymer. Two examples of such bioactive copolymers are presented. Some O‐[(N‐benzylcarbamoyl)methyl]dextrans (DMCB) exhibit an inhibitory effect on the growth of human breast cancer cell lines. Its derivatives, associated or conjugated to sodium phenylacetate (NaPA), were found to have a strong antitumoral activity on malignant human melanoma 1205LU. Preliminary in vivo tests on nude mice are performed. Adhesion of Staphylococcus aureus to biospecific random polystyrene derivatives or acrylic terpolymers carrying sulfate and carboxylate groups is hindered in a composition‐dependent way. In addition, a correlation between the bacterial adhesion and proliferation has been evidenced. As a result, biospecific random copolymers endowed with both bacteriophobic and bacteriostatic activities were synthesized.     

Facile synthesis and catalytic activity of well‐defined amphiphilic block copolymers based on N‐vinylimidazolium

Well‐defined amphiphilic block copolymers, poly(styrene)‐b‐poly(N‐vinylimidazole) (PS‐b‐PVim), were successfully synthesized by macromolecular design via interchange of the xanthates/reversible addition–fragmentation chain transfer (RAFT) polymerization. The structure of the copolymer based on Vim can be well controlled, and the molecular weight distribution was relatively narrow (PDI = 1.24). The size and morphology of the aggregates of the amphiphilic copolymers were investigated by dynamic light scattering and transmission electron microscope, the results implied that the uniform spheroidal micelles consisting of PS core and PVim corona were assembled, and the catalytic activities of PS‐b‐PVim for the hydrolysis of p‐nitrophenyl acetate at different temperatures were also investigated by high‐performance liquid chromatograph (HPLC); the catalytic activities of diblock copolymers were prominently improved compared with that of PVim homopolymers. Moreover, the catalytic activities of the copolymers followed the Arrhenius behavior in the wide experimental temperature range. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and polymerization of N-[N′-(α-methylbenzyl)aminocarbonyl-n-alkyl]maleimide

Two types of optically active N-[N′-(α-methylbenzyl)amino/carbonyl-n-alkyl]maleimides (MBAC) were synthesized from maleic anhydride, 6-amino-n-caproic acid (or 12-amino-n-dodecanoic acid), and (R)-(+)-α-methylbenzylamine. Radical homopolymerizations of MBAC were performed in several solvents at 60 and 110°C for 24 h to give optically active polymers. Radical copolymerizations of MBAC were performed with styrene (ST) and methyl methacrylate (MMA) in dioxane at 60°C. The monomer reactivity ratios and the Alfrey-Price Q-e values were determined. Chiroptical properties of the polymers and copolymers were investigated. © 1995 John Wiley & Sons, Inc.     

Asymmetric interaction of optically active polymers with asymmetric small molecules. IV. Effect of hydrophobic groups on asymmetric interaction

In order to investigate the mechanism of the asymmetric interaction between optically active polymers and small molecules, optically active copolymers of N-acrylyl L-amino acids(N-acrylyl-L -phenylalanine, N-acrylyl-L -tryptophan, and N-acrylyl-L -leucine, respectively) and N,N′-hexamethylene diacrylylamide were synthesized, and interaction of these polymers with the optical isomers of phenylalanine and tryptophan was investigated. In the interaction of these acidic polymers with amino acids performed at pH 5.0, significant difference in amount of adsorption between the D and L isomers of amino acids were observed, and the L form of amino acids was adsorbed preferentially. The interaction between optically active small molecules was also investigated: these results showed a similarity to the results for interaction between optically active polymers and amino acids. In some instances of asymmetric interaction the influence of hydrophobic interaction between a polymer and substrate was clearly perceived. The stereoselective effects on the asymmetric interaction are discussed.