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     

Polystyrene supported pyrazolinium Cr(VI) reagents: preparation and use in synthetic organic chemistry

Divinylbenzene (DVB) and ethyleneglycol dimethacrylate (EGDMA) crosslinked polystyrenes (2%) were functionalized to generate pyrazolinium chromate, chlorochromate and pyrazole–CrO₃ complex functionalities. These were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in high yields. The influence of solvent, temperature, catalyst and molar excess of the reagent in these oxidation reactions was investigated to find out the optimum conditions for effective oxidation reactions. EGDMA crosslinked polystyrene supported reagents showed higher reactivity in terms of functional group capacity and percentage yield. Also, chlorochromate reagent was found to be very efficient in oxidizing alcohols to carbonyl compounds. The spent polymeric reagent after the oxidation step can be easily removed by filtration and can be regenerated many times. © 1998 SCI.     

Solvent free oxidation of alcohols catalyzed by KMnO4 adsorbed on Kieselguhr

Efficient and selective oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones catalyzed by potassium permanganate supported on Kieselguhr reagent under solvent free conditions are reported.     

Functional monomers and polymers, 116. Asymmetric addition of n-butyllithium to aldehydes by chiral polymers and related compounds containing dimethylamino bornanol moieties

Asymmetric addition reaction of n-butyllithium to aldehydes was studied by using chiral polystyrene derivatives and chiral low molecular model compounds, both of which were derived from cis,endo-3-dimethylamino-2-hydroxybornane. The higher optical yields were achieved by using low molecular model compounds, and particularly the highest value was obtained in the case when ether was used as the solvent. The effect of reaction temperature, sort of the solvents and the molar ratio of the reagent to aldehyde on the asymmetric addition was also discussed.     

Influence of temperature,molecular weight,and polydispersity of polystyrene on interfacial tension between low‐density polyethylene and polystyrene

In this work, the influence of temperature, molecular weight, and polydispersity of polystyrene on interfacial tension between low‐density polyethylene (LDPE) and polystyrene (PS) was evaluated using the pendant drop method. It was shown that interfacial tension between LDPE and PS decreases with increasing temperature for all LDPE–PS pairs studied. The temperature coefficient (∂γ/∂T) (where λ is interfacial tension and T is temperature) was higher for lower molecular weight and larger polydispersity of PS. The interfacial tension between LDPE and PS at a temperature of 202°C increased when the molecular weight of polystyrene was varied from 13,000 to 30,000. When the molecular weight of PS was further increased, the interfacial tension was shown to level off. The effect of polydispersity on interfacial tension between PS and LDPE, at a temperature of 202°C, was studied using PS with a constant‐number average molecular weight and varying polydispersity. The interfacial tension was shown to decrease with increasing polydispersity. However, the influence of polydispersity was lower for PS of higher molecular weight. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2423–2431, 1999     

Influence of solvent contents on the rubber‐phase particle size distribution of high‐impact polystyrene

High‐impact polystyrene (HIPS) was prepared by the bulk or low‐solvent polymerization of styrene in the presence of dissolved rubber and characterized to measure the dispersed particle size of the rubber phase. Before preparation, the prepolymerization time was established by measuring the evolution of particle size distribution of the dispersed phase as a function of reaction time. The measurement technique by laser light scattering was found to be efficient enough not only to lead to the right prepolymerization time but also to predict rubber‐phase particle size distribution. Polymerization experiments were then conducted to investigate the effect of solvent contents on the particle size distribution of the rubber phase, in which ethylbenzene was introduced as a solvent at levels of 0, 3, 10, and 15%. As the solvent content increased, the size of rubber‐phase particles initially increased, reaching a maximum, and then decreased. It is speculated that a decrease in the molecular weight of the matrix, a decrease in the viscosity ratio between polybutadiene to polystyrene phases, and a change in rubber morphology all contributed to the change in the rubber particle size of HIPS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3672–3679, 2003     

Enantioface differentiation by using soluble chiral polymers having 2,3-exo-bornanediol groups

Soluble linear polymers containing 2,3-exo-dihydroxy-3-endo-p-tolyl-3-bornyl groups prepared by reaction of lithiated linear polystyrenes with (-)-2-exo-hydroxy-3-bornanone, are treated with lithium aluminium hydride to form complexes which can be used as reducing reagents. The highest enantioselectivity compared with those cases using crosslinked polystyrene as carrier and chiral low molecular weight compounds is achieved by linear polystyrene having chiral groups. The advantages of soluble polymer-bound chiral reagents are discussed. The effect of alcohols, the reaction temperature, the sort of solvents, and the molar ratio of the reagent to ketone on the asymmetric reduction is also discussed.     

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.     

Polymer‐Supported Bisacetoxybromate(I) Anion –‐An Efficient Co‐Oxidant in the TEMPO‐Mediated Oxidation of Primary and Secondary Alcohols

A polymer‐bound reagent for the efficient oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in the presence of a catalytic amount of 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO) is described. The oxidation process is particular mild and allows one to prepare aldehydes with α‐chirality without racemization. This also includes the synthesis of α‐aminoaldehydes. In most cases, work‐up of this heavy metal‐free oxidation is achieved by simple filtration followed by removal of the solvent. Insight into the role of the bromate(I) anion in the oxidation process was gained from the TEMPO‐mediated oxidation of benzaldehyde in the presence of the hypochlorite anion loaded on an anion exchange resin.     

Synthesis of isopropenylbenzyl‐terminated macromonomers and preparation of polymer brushes by anionic homopolymerization

Isopropenylbenzyl‐terminated polystyrene (PS) macromonomers were synthesized by anionic addition in a two‐stage process using styrene and 1,4‐diisopropenylbenzene (DIPB) in benzene. The reaction products of polystyryl anions with DIPB provided PS macromonomer possessing less than two isopropenylbenzyl groups at the propagating end under the condition of being in hydrocarbon solvent at 25°C (ceiling temperature) because of the anionic equilibrium nature. Subsequently, anionic homopolymerization of such macromonomers was carried out in tetrahydrofuran (THF) at ?78°C using anionic initiators to prepare the polymer brushes. The conversion of polymer brushes was very low (ca. 5%). Moreover, the degree of polymerization (DP) was less than 50. The low concentration of propagating chain ends seemed to affect the formation of polymer brushes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87:1790–1793,2003     

Dynamic mechanical properties of polystyrene‐block‐poly[ethylene‐co‐(ethylene‐propylene)]‐block‐polystyrene triblock copolymer/hydrocarbon oil blends

Blend systems of polystyrene‐block‐poly(ethylene‐co‐(ethylene‐propylene))‐block‐polystyrene (SEEPS) triblock copolymer with three types of hydrocarbon oil of different molecular weight were prepared. The E″ curves as a function of temperature exhibited two peaks; one peak at low temperature (? ?50°C), arising from the glass transition of the poly[ethylene‐co‐(ethylene‐propylene)] (PEEP) phase and a high temperature peak (? 100°C), arising from the glass transition of the polystyrene (PS) phase. The glass transition temperature (T_g) of the PEEP phase shifted to lower temperature with increasing oil content. The shifted T_g depended on the types of oil and was lower for the low molecular weight oil. The T_g of PS phase of the present blend system, were found to be constant and independent of the oil content, when molecular weight of the oil is high. However, for the lower molecular weight oil, the T_g of the PS phase also shifted to lower temperatures. This fact indicates that the oil of high molecular weight is merely dissolved in the PS phase. The E′ at (75°C, at which temperature both of PEEP and PS phases are in glassy state, was found to be independent of oil content. In contrast, at 25°C, at which temperature the PEEP phase is in rubbery state, the E′ decreased sharply with increasing oil content. This result indicates that the hydrocarbon oil was a selective solvent in the PEEP phase. It mainly dissolved in the PEEP phase, although slightly dissolved into the PS phase as well, when molecular weight of oil is low. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Formation of microcapsules of medicines by the rapid expansion of a supercritical solution with a nonsolvent

The rapid expansion from a supercritical solution with a nonsolvent (RESS‐N) was applied to the formation of polymeric microcapsules containing medicines such as p‐acetamidophenol, acetylsalicylic acid, 1,3‐dimethylxanthine, flavone, and 3‐hydroxyflavone. A suspension of medicine in carbon dioxide (CO₂) containing a cosolvent and dissolved polymer was sprayed through a nozzle to atmospheric pressure. The pre‐expansion pressure was 10–25 MPa, and the temperature was 308–333 K. The polymers were poly(L ‐lactic acid) (molecular weight = 5000), poly(ethylene glycol) (PEG; PEG4000, molecular weight = 3000; PEG6000, molecular weight = 7500; and PEG20000, molecular weight = 20,000), poly(methyl methacrylate) (molecular weight = 15,000), ethyl cellulose (molecular weight = 5000), and PEG–poly(propylene glycol)–PEG triblock copolymer (molecular weight = 13,000). The solubilities of the polymers as coating materials and these medicines as core substance were very low in CO₂. However, the solubilities of these polymers in CO₂ significantly increased with the addition of low molecular weight alcohols as cosolvents. After RESS‐N, polymeric microcapsules were formed according to the precipitation of the polymer caused by a decrease in the solvent power of CO₂. This method offered three advantages: (1) enough of the coating polymers, which were insoluble in pure CO₂, dissolved; (2) the microparticles of the medicine were encapsulated without adhesion between the particles because a nonsolvent was used as a cosolvent and the cosolvent remaining in the mixture was removed by the gasification of CO₂; and (3) the polymer‐coating thickness was controlled with changes in the feed composition of the polymer for drug delivery. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 742–752, 2003     

Preparation of high‐molecular‐weight poly(N‐vinylcarbazole) by the photoinduced low‐temperature solution polymerization of N‐vinylcarbazole in 1,1,2,2‐tetrachloroethane

For the preparation of high‐molecular‐weight (HMW) poly(N‐vinylcarbazole) (PVCZ) with a narrow molecular weight distribution, N‐vinylcarbazole (VCZ) was solution‐polymerized in 1,1,2,2‐tetrachloroethane (TCE) at ?20, 0, and 20°C with photoinitiation. The effects of the polymerization temperature and the concentrations of the polymerization solvent and photoinitiator on the polymerization behavior and molecular parameters of PVCZ were investigated. A low polymerization temperature with photoirradiation was successful in obtaining HMW PVCZ with a smaller temperature rise during polymerization than that for thermal free‐radical polymerization by azobisisobutyronitrile (AIBN). The photo‐solution‐polymerization rate of VCZ in TCE was proportional to [AIBN]^0.45. The molecular weight was higher and the molecular weight distribution was narrower for PVCZ made at lower temperatures. For PVCZ prepared in TCE at ?20°C with a photoinitiator concentration of 0.00003 mol/mol of VCZ, a weight‐average molecular weight of 920,000 was obtained, with a polydispersity index of 1.46, and the degree of transparency converged to about 99%. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2391–2396, 2003     

Efficient and Selective Aerobic Alcohol Oxidation Catalyzed by Copper(II)/2,2,6,6,‐Tetramethylpiperidine‐1‐oxyl at Room Temperature

A simple and efficient copper(II)/2,2,6,6,‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐catalyzed aerobic oxidation of both primary and secondary benzylic, allylic, and aliphatic alcohols to their corresponding aldehydes and ketones at room temperature using the copper(II) complex [Cu(μ‐Cl)(Cl)(phen)]₂ as the Cu(II) source is reported. The conversion of both electron‐rich and electron‐neutral benzyl alcohols is smooth and faster than those of electron‐deficient ones. The chemoselectivity of a primary benzyl alcohol over the secondary alcohol is also observed. Alcohols regarded as difficult substrates for oxidation due to their coordinating ability with transition metal catalyst such as 4‐(methylthio)benzyl alcohol and 3‐pyridinemethanol are also oxidized easily. In addition, a lignin model alcohol is oxidized to the corresponding aldehyde in excellent yield. Conversions of benzylic and allylic alcohols are faster as compared to those of aliphatic alcohols in accordance with their C_α H bond strengths. A plausible mechanism of the TEMPO‐based catalytic cycle is proposed.     

Transition phenomena of polymers in mixed solvents in the vicinity of theta conditions: Effect of preferential adsorption

Viscosimetric measurements were obtained with the ternary systems polystyrene/dioxane/methanol, polystyrene/benzene/methanol and poly(methyl methacrylate)/dioxane/cyclohexane, changing the solvent mixture composition at constant temperature. The polystyrene and poly(methyl methacrylate) systems exhibit a transition phenomenon with solvent-mixture composition in which the polymer is just above the theta condition. In the case where two theta conditions occur ((θ-intra, θ-inter) the transition point is closely related to the intramolecular theta conditions. Moreover the intramolecular theta conditions vary with the molecular weight in the region of molecular weights where the preferential adsorption also varies. This variation induces a variation of the transition point with molecular weight which obeys a formula analogous to that giving the variation of the preferential adsorption with molecular weight.     

Swelling of crosslinked polyacrylates in isotropic and anisotropic solvents

The purpose of this study was to examine the swelling and deswelling of photochemically crosslinked poly(n‐butylacrylate) networks in isotropic and anisotropic solvents. The phase diagrams were established in terms of composition and temperature for five isotropic solvents, acetone, cyclohexane, methanol, tetrahydrofuran, and toluene, and two low‐molecular‐weight nematic liquid crystals, 4‐cyano‐4′‐n‐pentyl‐biphenyl and an eutectic mixture of cyanoparaphenylenes. Networks were formed by ultraviolet curing in the presence of 0.5 wt % difunctional monomer (hexane diol‐di‐acrylate) and 0.5 wt % photoinitiator (Darocur 1173). Immersion in excess solvent allowed us to measure the solvent uptake by weight and to determine the size increase by optical microscopy in terms of temperature. We calculated weight and diameter ratios considering the swollen‐to‐dry network states of the samples. Phase diagrams were analyzed with the phantom network model according to the Flory–Rehner theory of rubber elasticity, and for the anisotropic solvents, modeling was supplemented with the Maier–Saupe theory of nematic order for free energy. The polymer–solvent interaction parameter was deduced as a function of temperature, but the values were in discrepancy with Fedors's model of solubility parameters, which overestimated the interaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1–9, 2004     

Bead‐to‐fiber transition in electrospun polystyrene

The morphological transition, namely bead‐to‐fiber transition, of electrospun polymer was examined for polystyrene, with its molecular weight ranging from 19,300 to 1,877,000 g/mol. Tetrahydrofuran and N,N‐dimethylformamide were used as solvents to examine the effects of solvent properties on the morphological variations. Polymer molecular weight and solvent properties had a significant effect on the morphology of beads as well as fibers. Observation of fiber diameter and its distribution suggested that the effect of molecular weight and solvent may be independent. The critical concentrations at which incipient and complete fibers were observed were found to decrease significantly with molecular weight, as can be expected. The effect of solvents on these critical concentrations was minimal for moderate to high‐molecular‐weight (>100,000 g/mol) solutions. For low‐molecular‐weight solutions, the transition occurred at concentrations much lower than those predicted by a model, based exclusively on chain entanglements. Rapid solidification of jet which is expected to occur with concentrated solutions may play a vital role in establishing stable fibers during electrospinning. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Design and applications of a solid-phase oxidizing reagent consisting of a crosslinked polystyrene matrix and a t-butyl hypochlorite function separated by a trimethylene spacer

A crosslinked polystyrene–supported solid-phase analogue of t-butyl hypochlorite containing a trimethylene spacer group between the polymer matrix and the t-butyl hypochlorite function was prepared and used as a recyclable oxidizing reagent for alcohols. The synthetic route to this new polymeric reagent involved a seven-step polymer-analogous reaction starting from styrene-divinyl benzene 2%-crosslinked polymer. A β-ketopropionic acid function was introduced into the polystyrene matrix by Friedel–Crafts reaction with succinic anhydride. The keto function in the resulting polymer (2) (capacity, 3.57 meq of COCH₂CH₂COOH/g) was converted to the methylene group by Clemmensen reduction using zinc amalgam and HCl. The carboxyl function in the product polymer (3) was converted to the acylmalonic ester function by malonic ester synthesis through the reaction of the polymeric acid chloride (4) with ethoxymagnesium diethylmalonate. The polymeric acyl malonic ester (5) was decarboxylated to yield the 2-oxopentyl polystyrene resin (6). This on Grignard reaction with methyl magnesium iodide followed by hydrolysis afforded the polystyrene derivative with the t-butyl alcohol function separated by three methylene groups (7) . The t-butyl alcohol resin (7) was converted to the corresponding hypochlorite resin (8) by reaction with sodium hypochlorite. The resin was found to have a capacity of 2.84 mmol Cl/g by iodometric analysis. The capacities of the resins 2–8 were determined from the weight changes in the corresponding conversions and verified by quantitative determination of the functional groups. This new hypochlorite was found to oxidize alcohols to carbonyl compounds in 85–98% yield. The oxidizing efficiency of this new reagent was found to be significantly greater than those of the reagents containing only one spacer and no spacer between the reagent function and the polymer support. The presence of a 3-methylene spacer also facilitated the hypochlorite formation step significantly.     

Structural modification of expandable polystyrene. I. Copolymerization with α‐methylstyrene

Conventional expandable polystyrene (EPS) was modified by the preparation of copolymers containing 1.0, 2.5, and 5.0% α‐methylstyrene. Increasing the glass‐transition temperature of EPS was the aim of this work. Copolymeric expandable polystyrene (CEPS) samples were characterized with various techniques. ¹H‐NMR spectroscopy was used for the determination of the composition, and gel permeation chromatography was used for the determination of the molecular weights and molecular weight distributions. Differential scanning calorimetry showed that the glass‐transition temperatures of the CEPS samples increased with increasing α‐methylstyrene contents. The prevention of the collapse of the EPS cells was observed in scanning electron microscopy images of the inner portions and outer surfaces of the CEPS samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 609–614, 2003     

Friedel-Crafts反应制备乙酰化聚苯乙烯型载体

通过Friedel Crafts酰基化反应制备了功能化乙酰基聚苯乙烯(PS)载体. 该载体经Mannich反应胺化后可替代氯甲基树脂制备的胺基树脂用作酶的固定化载体及制备离子交换树脂. 此法避免了氯甲基树脂生产中使用氯甲醚等致癌物质及多取代、二次交联等副反应的问题. 考察了反应时间、催化剂和酰基化试剂用量、溶剂体系及溶剂用量等对PS乙酰化反应的影响,优化了反应条件,制得乙酰基PS最大担载量可达5.9 mmol/g,并在此范围内可定量获得预期担载量的乙酰基PS载体.