Polymer-supported analogues of t-butyl hypohalites. Preparation and applications in synthetic organic chemistry

Crosslinked polymer-supported analogues of t-butyl hypochlorite and t-butyl hypobromite were prepared and developed as a new class of recyclable solid-phase oxidizing and halogenating reagents. The preparation of these new reagents involved a three-step polymer-analogous reaction starting from styrene-divinylbenzene crosslinked polymer. A ketone functional group was introduced into the copolystyrene-2% divinylbenzene resin beads by a Friedel-Crafts reaction with bromoacetone. This functional group was then converted to a tertiary alcoholic function on the polymer support by a Grignard reaction with methylmagnesium iodide. The treatment of this tertiary alcohol resin with sodium hypochlorite or sodium hypobromite yielded the polymeric t-butyl hypochlorite or hypobromite. These hypohalites were estimated iodometrically. These reagents were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in high yields. They were also found to be suitable for halogenation of carbonyl compounds and amides. The spent polymeric reagent after the oxidation or halogenation step can be easily removed by filtration and can be regenerated many times by treating with the sodium hypohalite without any loss of capacity.     

Acrylate monomers from olefins via tertiary butyl hypochlorite

A variety of olefins were readily converted to acrylate monomers by combining them with t-butyl hypochlorite and acrylic or methacrylic acid at 25–65°C. The predominate product was the vicinal acyloxychloro derivative formed by addition at the olefinic double bond. By-products were the vicinal butoxychloro derivative and the still unsaturated chlorinated olefin. The main reaction was shown to occur by an ionic mechanism. 2-Chloro-1-methyl propyl methacrylate was isolated and identified as the main product of the reaction of 2-butene, methacrylic acid, and t-butyl hypochlorite. The crude olefin products readily homopolymerized and copolymerized with other vinyl monomers by incorporating free-radical initiators.     

Polymeric decontaminant 2 (N,N‐dichloropolystyrene sulfonamide): Synthesis,characterization, and efficacy against simulant of sulfur mustard

A polymeric decontaminant N,N‐dichloropolystyrene sulfonamide was synthesized by different steps from starting material polystyrene and followed by sulfonation, chlorosulfonation, and amidification. Halogeno‐sulfonamide was obtained by treatment of sodium hypochlorite with sulfonamide resin. It was characterized by FTIR, solubility, viscosity, DSC, and TGA techniques. Efficiency of this polymer as decontaminant was evaluated by reaction with 2‐chloro ethyl phenyl sulfide, a simulant of sulfur mustard (SM) at room temperature. This decontamination reaction was monitored by gas chromatography (GC) and products were identified by gas chromatography‐mass spectrometry (GC‐MS). The positive chlorine content of this polymer was checked by standard iodometry titration. The synthesized positive chlorine compound is observed to be a promising decontaminant against simulant of sulfur mustard, chiefly in the situation where use of aqueous medium such as acetonitrile : water (2 : 1) is precluded. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polyacenaphthylene supported t-butyl chromates: a new class of solid phase oxidizing reagents

Copolymers of acenaphthylene with divinylbenzene were functionalized by incorporating t-butyl chromate groups, and the resulting polymeric reagents were used to oxidize alcohols to carbonyl compounds. Primary and secondary alcohols were oxidized to the corresponding carbonyl compounds in quantitative yields. The extent of oxidation was found to depend on the various reaction parameters including the temperature, nature of the solvent, concentration of the reagent functions, duration of the reaction and the presence of catalyst. © 1998 SCI.     

Use of polyethyleneimine dendrimer as a novel graded-modulus interphase material in polymeric composites

The effectiveness of polyethyleneimine (PEi) dendrimer as a novel graded-modulus interphase material in polymeric composites is discussed in the context of core (polystyrene)–shell (PEi) nanoparticles affecting the mechanical properties of epoxy. The dendrimer is grafted onto the surface of polystyrene (PS) particles via a free radical polymerization reaction of styrene monomers in a non-aqueous polar solvent with t-butyl hydroperoxide (TBHP) as initiator and mild heating. The effects of both particle loading and core/shell composition are investigated. The mechanical test results in all cases show an increase in both stiffness and fracture toughness or the ability of the polymer to resist crack growth, as opposed to the commonly seen trade-off between these properties in previously studied soft particles. SEM micrographs suggest that the crosslinks with epoxy in the dendrimer network, leading to a dramatic interface stretching as the core-to-shell ratio decreases, and the capability of the dendrimer to 'harden' PS particles by diverting cracks through them are responsible for the enhancements.     

Grafting of end-functionalized poly(tert-butyl acrylate) to poly(ethylene-co-acrylic acid) film

Poly(tert-butyl acrylate) (PtBA) was grafted to the surface of poly(ethylene-co-acrylic acid) (EAA) film and the pendant groups of the tethered PtBA were modified to create chemically tailored surface modifying layers. The carboxylic acid groups in the copolymer film served as the grafting sites for the covalent tethering of end-functionalized PtBA. The progression of these reactions was monitored using attenuated total reflectance (ATR)-FTIR and X-ray photoelectron (XPS) spectroscopies along with static contact angle measurements. By controlling the reaction conditions, the chemical functionality of the grafted layer ranged from tert-butyl ester (EAA-g-PtBA) to carboxylic acid (EAA-g-PAA) and was demonstrated by corresponding changes in wettability. The choice of PtBA as the tethered polymer allows for the subsequent substitution of the tert-butyl ester groups. To demonstrate, a novel procedure was used to replace the tert-butyl ester with N,N-dimethylethylenediamine (DMEDA) to form EAA-g-PDMEDA. These reaction schemes can be used to create tunable surface-grafted layers with various pendant group chemistries.     

Reactivity of t-butyl chromate resins with substituted α-phenylethanols: A kinetic study

Polystyrene and polyacenaphthylene supports were functionalized to generate a t-butyl chromate function and the resulting polymer-supported reagents were used for the oxidation of alcohols. They were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in quantitative yields. Oxidation of differently substituted α-phenylethanols was attempted for this purpose and the kinetics of oxidation reactions was studied. The reaction was found to be first order with respect to the substrate, the reaction being carried out with an excess of the t-butyl chromate reagent. The rate of oxidation was also found to be dependent on the nature of the substrate, concentration of the reagent function, and the nature and concentration of the acid catalyst used. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 799–804, 1998     

Allyl functionalized telechelic linear polymer and star polymer via RAFT polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene using bisallyl trithiocarbonate as a chain transfer agent (CTA) was studied. The polymerization exhibited first-order kinetics and the molecular weight increased linearly with increase of monomer conversion. Well defined allyl-functionalized telechelic polystyrene (PS), poly(tert-butyl acrylate) (PtBA) and corresponding triblock copolymers, polystyrene-b-poly(n-butyl acrylate)-b-polystyrene (PS-b-PnBA-b-PS) and poly(tert-butyl acrylate)-b-polystyrene-b-poly(tert-butyl acrylate) (PtBA-b-PS-b-PtBA) were prepared as characterized with GPC and NMR analysis. The allyl-end groups of the telechelic PS have been switched to 1,2-dibromopropyl groups quantitatively by bromine addition reaction, further substitution of the bromide with azide was also made. Furthermore, star PS with allyl-end-functionalized arms was synthesized by RAFT polymerization of divinyl benzene using allyl-functionalized PS as a macro-CTA via arm-first approach. Star polymer with a thiol-functionalized core was generated by aminolysis reaction of the star polymer and ethylenediamine. As a result, difunctionalized star polymer with allyl and thiol groups was obtained and was used as a stabilizer for the formation of gold nanoparticles.     

Polymer-bound ethylenediamine–borane reagent: A new class of polymeric reducing agent

A polymer-supported ethylenediamine (EDA)–borane reagent was prepared under mild reaction conditions. The reagent was found to be efficient and selective in the reduction of aldehydes to the corresponding alcohols in high yields at room temperature. The polymeric reagent was prepared on a Merrifield resin and on a 1,6-hexanediol diacrylate-crosslinked polystyrene resin (HDODA–PS). HDODA–PS was prepared by suspension polymerization and chloromethylated by a Friedel–Crafts reaction. The preparation of the polymer-bound EDA–borane reagent involves a series of polymer analogous reactions, such as amination of the chloromethyl resin, conversion to amine hydrochloride, and, finally, complexation with sodium borohydride. The reagent exhibited good chemoselectivity in the reduction of aldehydes. The reduction reactions were carried out with a 2 molar excess of the polymeric reagent. In the competitive reduction of a 1:1 molar mixture of benzaldehyde and acetophenone, benzaldehyde was selectively reduced to benzyl alcohol. The spent resin could be recycled by treating with sodium borohydride. The recycled resin was used several times without much loss in chemical reactivity and mechanical stability. The HDODA–PS resin was found to be more efficient than was the Merrifield resin in the preparation of the reagent as well as in the reduction reactions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 593–600, 2001     

A comparison of the oxidizing ability of polystyrene‐supported linear and cyclic polyoxyethylene bound permanganates

The grafting of linear and cyclic polyoxyethylenes into DVB‐crosslinked chloromethylpolystyrene was carried out by treating with polyethyleneglycol (PEG₆₀₀). The complexations of crosslinked polystyrene‐supported linear and cyclic polyoxyethylene with permanganate functions were carried out. With this reagent, primary alcohols and secondry alcohols were converted to aldehydes and ketones and aldehyde to acid. The polymer acts as a reservoir of permanganate functions and releases them slowly as the substrates are being used up. The effect of solvent, molar excess of reagent, time, and temperature on oxidation behavior were investigated by choosing benzoin to benzil conversion as the model reaction. The linear polymeric reagent has greater reactivity than the cyclic polymer due to the greater availability of the reactive sites in the linear polymer than the cyclic polymer. Polymeric reagent could be used in excess to get a good yield without causing any separation problems and over oxidation products. The reagents have advantages of easy separation, regeneration and reuse. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1897–1905, 2005     

Preparation of a New Polystyrene Supported-Ethylenediaminediacetic Acid Resin and its Sorption Behavior toward Divalent Metal Ions

A new polystyrene-supported ethylenediaminediacetic acid resin has been synthesized through a reaction between the amination of the commercially available 4-chloromethyl polystyrene polymer with ethylenediamine and the subsequent carboxymethylation with monobromoacetic acid, using ethylenediamine as spacer. The chelation behavior of this resin toward the divalent metal ions Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺ in aqueous solutions was investigated. Batch equilibration experiments were carried out as a function of contact time, pH, amount of metal-ion, and polymer mass. The amount of metal-ion uptake of the polymer was determined by using atomic absorption spectrometry (AAS). Results of the investigation revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Cu²⁺ and that the metal-ion uptake follows the order: Cu²⁺ > Zn²⁺ > Ni²⁺ > Pb²⁺. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed.     

Influence of microstructure on dynamic mechanical behaviour of polymeric composites with complex inclusions

The dynamic mechanical properties of polymeric composites composed of crosslinked poly(n-butyl methacrylate) continuous-phase and crosslinked polystyrene dispersed phase with poly(n-butyl methacrylate) occlusion have been examined. The composite samples were prepared by mixing and swelling of the crosslinked polystyrene particles obtained by emulsifier-free emulsion polymerization, with n-butyl methacrylate and crosslinker, then photopolymerizing at the desired temperature. The composite microstructure was varied by either changing the crosslink density of polystyrene, and temperature of swelling and polymerization, or using different sizes and contents of polystyrene particles. The tan δ peak positions of composite samples are found to be dependent on morphological characteristics as well as the properties of the dispersed phase while the peak height seems to be dependent on the effective volume of dispersed phase composed of polystyrene and poly(n-butyl methacrylate) occlusions. Special attention has been paid to the comparison among composite, homonetworks, and bulk IPN samples that are expected to have the identical structure with the complex dispersed phase of the composite samples. © 1993 John Wiley & Sons, Inc.     

Polystyrene-bound dioxirane: a new class of recyclable oxidising reagent

Polystyrene-bound dioxirane containing a five-methylene spacer arm between the polymer matrix and reagent function has been prepared and investigated as a new class of recyclable oxidising reagent for various organic substrates. The new reagent was found to oxidise alkenes to epoxides, pyridines to N-oxides and amines to nitro compounds in near-quantitative yields. The spent reagent could be regenerated to the dioxirane resin by a simple reaction without considerable loss in reactivity.     

Synthesis and properties of a liquid oligomeric cyanate ester resin

A multiple aromatic ether-containing cyanate ester resin system with high thermal stability and superb processability has been developed. The oligomeric monomer was prepared via a hydroxyl-terminated intermediate synthesized from a modified Ullmann synthesis with bisphenol A and 1,3-dibromobenzene in the presence of potassium carbonate and a catalytic amount of a copper (I) complex in N,N-dimethylformamide. The hydroxyl-terminated intermediate was end-capped with the cyanate moiety by reaction with cyanogen bromide and triethylamine in dry acetone resulting in a resinous material at ambient temperatures. The thermo-oxidative and water absorption properties were determined for the new cyanate ester polymer as well as its flexural strength, flexural modulus and Rockwell hardness. Mechanical tests were also conducted on the commercially available 2,2′-bis(4-cyanatophenyl)isopropylidene cyanate ester resin to investigate the effect of introducing an oligomeric spacer between the terminal end groups on the properties of the material.     

Influence of spacer groups on grafting ability,curing ability,and film properties of water-based radiation curable latexes

Film-forming polystyrene/poly(n-butyl acrylate-co-glycidyl methacrylate) [PS/P(BA-co-GMA)] core–shell latex particles were prepared via a two-stage emulsion polymerization procedure using a PS latex seed. A delayed addition of GMA was used to locate the functional epoxy groups near the surface of the particles. The surface-bound epoxy groups were used as grafting sites for unsaturated carboxyl functional monomers having the unsaturated groups and the carboxylic group separated by 1, 5, or 10 oxyethylene units. Grafting and curing characteristics and film properties after irradiation were investigated as a function of the number of oxyethylene units. A BA-GMA [P(BA-co-GMA)] copolymer was used as a model system for the core–shell latex particles for quantification of the grafting reactions. The grafting was demonstrated by FTIR and ¹H-NMR spectroscopy. The effects of crosslinking was studied by thermal mechanical analysis and dynamical mechanical analysis. Differential photocalorimetry was also used for evaluation of the curing ability. It was demonstrated that the reagent having five oxyethylene units in the spacer group was grafted onto the polymer backbones to a larger extent than the other two reagents, and a more thoroughly cured film was obtained upon irradiation. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 897–906, 1998     

Styrene polymerization with a macroinitiator having siloxane units

Block copolymers containing segments of poly(dimethylsiloxane) (PDMS) and polystyrene were synthesized. Dihydroxy terminated PDMS M_n 2500 g/mol, was reacted with an ali-phatic diisocyanate (isophorone diisocyanate) and an aliphatic hydroperxide (t-butyl hy-droperoxide). The resulting polymeric peroxycarbamate having siloxane units (a new mac-roinitiator) was used as free radical initiator for vinyl polymerization of styrene. Formation of block copolymers was illustrated by several characterization methods such as chemical and spectroscopic analysis, fractionation, and GPC. Mechanical and thermal characterization of the copolymers were made by stress–strain tests and DSC. The surface properties and the morphology of the block copolymers were investigated by contact angle measurements and SEM. © 1996 John Wiley & Sons, Inc.     

Selective conjugation of soybean esters to increase hydrogenation selectivity

Polyunsaturated fatty acid methyl esters of soybean oil (MeSBO) were selectively conjugated as a means of increasing the linolenate selectivity of various homogeneous and heterogeneous hydrogenation catalysts. Kinetics of the conjugation reaction in various solvents indicated that linolenate conjugated 5–8 times faster than linoleate. Selective conjugation of MeSBO with potassiumt-butoxide in dipolar solvents resulted in an increase in linolenate hydrogenation selectivity to 7–8 with Ni and Pd heterogeneous catalysts, and to 7–10 with homogeneous and heterogeneous chromium carbonyl catalysts.Trans-unsaturation in the hydrogenated products was only 1–3% with the chromium carbonyl catalysts, in contrast to 30–39% with the heterogeneous metal catalysts. Triglycerides were readily converted to partial glycerides andt-butyl esters with the potassiumt-butoxide reagent. Presented at the AOCS North Central Section Symposium, March 1980.     

三相相转移催化法精制粗间二硝基苯

以氯甲基聚苯乙烯树脂分别与三甲胺、三乙胺、三丁胺、三乙醇胺、吡啶5种叔胺反应,制备了不同的聚合物三相相转移催化剂,并用于间二硝基苯精制,考察了催化剂、氢氧化钠、甲醇的用量及催化剂种类对邻、对二硝基苯转化率的影响,得到了适宜的精制工艺条件为:m(粗间二硝基苯)∶m(甲醇)∶m(NaOH)∶m(聚苯乙烯吡啶树脂)=1∶0.8∶0.1∶0.12,反应温度76～78℃,反应时间2 h。在该条件下,邻对二硝基苯的转化率在99.5%以上,精制后的间二硝基苯经色谱分析后其色谱纯度达99.8%,间二硝基苯的收率在99%左右,聚苯乙烯吡啶树脂催化剂可重复使用7次以上。     

Esterification on solid support by surface‐initiated ring‐opening polymerization of ε‐caprolactone from benzylic hydroxyl‐functionalized Wang resin bead

Biodegradable poly(ε‐caprolactone) (PCL) was formed on benzylic hydroxyl‐functionalized Wang resin surface by surface‐initiated ring‐opening polymerization (SI‐ROP). The SI‐ROP of ε‐caprolactone was achieved first by treating Wang resin with Tin(II) 2‐ethylhexanoate [Sn(Oct)₂] to form Tin(II) complex, and then followed by polymerization of ε‐caprolactone in anhydrous toluene at 60°C. Thus, the polymer‐grafted Wang resin was characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), optical microscopy (OM), and field‐emission scanning electron microscopy (FE‐SEM). The FTIR spectroscopic analysis of polymer‐grafted Wang resin (Wang‐g‐PCL) reveals the formation of ester linkage between PCL and hydroxyl‐terminated Wang resin. The DSC thermogram shows melting peak corresponding to PCL polymer on Wang resin surface. Thermogravimetric investigation shows increase in PCL content on the Wang resin surface in terms of percentage of weight loss with increase in reaction time. The formation of polymeric layers on the Wang resin surface can be directly visualized from OM and SEM images. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and Structural Analysis of Branched-Chain Derivatives of Methyl Oleate

As part of a project to develop new value-added industrial applications for cottonseed oil (such as biodiesel, fuel additives, and lubricants), studies were conducted on the synthetic conversion of oleic acid to branched-chain fatty acid esters. In these studies, methyl oleate was brominated in the allylic position and subsequently treated with organocuprate reagents to produce novel branched-chain derivatives (methyl, n-butyl, phenyl). Original reaction conditions afforded only the branched methyl derivatives as major products. Modification of reaction conditions (lower temperature, less organocuprate reagent) afforded predominantly the desired n-butyl and phenyl derivatives and minimized products resulting from attack on the ester functionality. Details of the syntheses, characterization (especially by NMR), and the properties of the products (with emphasis on low-temperature properties) are discussed.