Bifunctional System Research Articles

Free‐radical polymerization of styrene with a binary mixture of symmetrical bifunctional initiators

AbstractThe kinetics of bulk styrene polymerization catalyzed by a binary mixture of symmetrical bifunctional initiators has been investigated. When the bifunctional initiators having different thermal stabilities are mixed, an unsymmetry in the initiator functions is formed in situ via propagation, chain transfer, and termination reactions. For the quantification of the polymerization kinetics, a kinetic model has been developed using the molecular species modeling technique. For various polymerization conditions, good agreements between the model predictions and experimental data have been obtained. It is shown that polymerization rate and molecular weight can be easily regulated under isothermal reaction condition by changing the initiator composition. A comparison of the detailed kinetic model with a simple kinetic model for monofunctional initiators has also been made to illustrate the molecular weight increasing effect of the bifunctional initiator system. © 1992 John Wiley & Sons, Inc.

A unique form of dental bilophodonty and a functional interpretation of peculiarities in the masticatory system of Arsinoitherium (mammalia, Embrithopoda)

The highly autapomorphic upper molar bilophodonty of the Oligocene mammal, Arsinoitherium (Embrithopoda) is an extreme form of dilambdodonty effected by lingual positioning of normally buccally situated cusps with reduction of lingual cusps. This effectively limits the molar dentition to a single phase shearing occlusal motion. Molar and premolar morphology is very different, premolars exhibiting high longitudinal ectolophs and typical two phase occlusal morphology. A double faceted mandibular condyle and angular discontinuity between lower molar and premolar dentitions is interpreted as a means of separating premolar from molar occlusion. A bifunctional masticatory system is proposed whereby efficient premolar occlusion is achieved only after a repositioning of the temporomandibular joint. Loss of phase II occlusion in the molars is compensated by maintenance of a crushing/grinding mode in the premolars. This coupled with the ability to maintain high occlusal pressures along the length of the mandible ex...

Hydrodechlorination of chloroaromatics: the use of a bifunctional homogeneous rhodium catalyst for the conversion of chloroaromatics into saturated hydrocarbons

The catalytic conversion of chloroaromatics into the corresponding saturated hydrocarbons is catalysed by a bifunctional homogeneous rhodium catalyst system generated from [(C5Me5)RhCl2]2 in the presence of an excess of NEt3 under 600 psi H2 at 75 °C (1 psi ≈ 6.894757 × 103 Pa).

Reaction and simultaneous diffusion in cellulose of reactive dyes containing a mixed bifunctional reactive system

The reaction with cellulose and simultaneous diffusion into cellulose for two reactive dyes containing a 4-chloro-2-(m-vinylsulfonylanilino)-1,3,5-triazinyl group were investigated at 40–80° C,pH 7-11 and ionic strength 0.3, using the cylindrical cellophane roll method. The experimental diffusion profiles of the active and fixed species were fitted with the theoretical profiles. The relationship between log k c (the pseudo-first-order rate constant of reaction with cellulose) and pH gave a straight line of unit slope below pH 10.5 for both dyes at 40, 60 and 80° C, the slope decreasing at pH values above 10.5. The surface concentration decreased with increase in pH for the red dye and remained nearly constant for the orange dye, whilst their diffusion coefficients were constant. Activation energies of the reaction with cellulose were 93–95 kJmol −1 and those of the diffusion into cellulose were 41–44 kJmol −1. These values are within the general range for vinylsulfonyl dyes, and the adsorption behavior of the dyes was similar to that of monochlorotriazinyl dyes.

A bifunctional vector system for controlled expression and subsequent release of the cloned gene product by phi X174 lysis protein-E.

A new bifunctional Escherichia coli cloning vector, pSB50, is presented. The plasmid allows controlled expression of a gene of interest under control of the lac promoter and the subsequent release of the cloned product by the use of bacteriophage phi X174 lysis protein-E, the gene of which is under control of the phage Lambda pL promoter. To ensure optimal repression of the Lambda pL promoter and the lac promoter in plasmid pSB50, E. coli strain UB89-1 was constructed which carries a chromosomal copy of the lambda cl857 repressor allele and the laclq1 allele, respectively. Here, we employ the E-based lysis system to release human prourokinase to the culture medium.

Mössbauer investigations of the Fe−Cu−Mn catalysts for Fischer-Tropsch synthesis

In the selective process of the syngas conversion to synthetic gasoline a bifunctional catalytic system has to be used. It was obtained by combination a Fischer-Tropsch catalyst with the HZSM-5 zeolite. The phase compositions of the precursor and the fresh catalyst were established as well as the optimum thermal treatment. The catalyst was reduced in pure H2 or in a H2+CO mixture. The influence of the reduction and reaction conditions on the catalyst structure was investigated.

Modeling of free radical polymerization of styrene catalyzed by unsymmetrical bifunctional initiators

A detailed kinetic model for the bulk polymerization of styrene initiated by unsysmmetrical bifunctional initiators is presented. When chain termination occurs via combination termination mechanism, 10 distinct polymeric species are identified for this initiator system according to the nature of polymer end units. It is shown that the unequal thermal decomposition characteristics of the labile groups in the bifunctional initiator system lead to the formation of polymers having considerbly higher molecular weight than those obtained by conventional monofunctional initiators or mixed initiator systems of those monofunctional initiators. It has also been found that high monomer conversion and high molecular weight can be obtained simultaneously within a short reaction time period by using the bifunctional initiators at high reaction temperature. This is due to the sequential decomposition of peroxides of different thermal stabilities distributed in various types of polymeric species.

Kinetics of bulk styrene polymerization catalyzed by symmetrical bifunctional initiators

The kinetics of bulk styrene polymerization catalyzed by symmetrical bifunctional initiators [2,5-dimethyl-2,5-bis(benzoyl peroxy) hexane] is studied. Being characterized by the presence of two peroxide groups of equal thermal stabilities, this bifunctional initiator system shows complex initiation, propagation, and termination reaction pathways. The kinetic model for bulk styrene polymerization with the bifunctional initiator is presented and compared with experimental data. The experimental data indicate that the model is quite satisfactory in describing the polymerization rate and polymer molecular weights for bulk styrene polymerization catalyzed by the symmetrical bifunctional initiator.

Steady state behavior of a continuous stirred tank reactor for styrene polymerization with bifunctional free radical initiators

Steady state behavior of a continuous stirred tank reactor is analyzed for styrene polymerization with bifunctional free radical initiators. Compared with polymerization by monofunctional initiators, the bifunctional initiator system produces polymers of significantly high molecular weight at high monomer conversion. This is due to the presence of multiple labile peroxide groups having distinctively different thermal decomposition characteristics. The steady state reactor model analysis indicates that five unique regions of steady state behavior are present in a parameter space with reactor residence time as a bifurcation parameter. It is also shown that a broad range of polymer properties can be obtained by judiciously choosing the reactor operating conditions with the bifunctional initiator.

Modeling of free‐radical polymerization of styrene by bifunctional initiators

AbstractA detailed kinetic model for the bulk styrene polymerization initiated by symmetrical diperoxyester bifunctional initiators is presented. When chain termination occurs via a combination termination mechanism, six distinct polymeric species are identified in accordance with the nature of the polymer end units. It is shown that the unequal thermal decomposition characteristics of the peroxides of the bifunctional initiator system lead to the formation of polymers having considerably higher molecular weight than those obtained by the monofunctional intiator systems. It has also been found that high monomer conversion, high molecular weight, and narrow molecular weight distribution can be obtained simultaneously by using the bifunctional initiators at high reaction temperatures. This is due to the reinitiation and propagation of inactive polymers carrying undecomposed peroxides. The molecular‐weight‐increasing effect of the bifunctional initiator is more pronounced at high reaction temperatures. The new possibilities of increasing the monomer conversion and controlling the polymer molecular weight properties more effectively through the use of bifunctional initiators are discussed.

ChemInform Abstract: HOMOLOGATION OF METHANOL BY A BIFUNCTIONAL SYSTEM COMPOSED OF COBALT, IODINE, AND HETEROGENEOUS RUTHENIUM CATALYSTS

Chemischer InformationsdienstVolume 16, Issue 49 Preparative Organic Chemistry ChemInform Abstract: HOMOLOGATION OF METHANOL BY A BIFUNCTIONAL SYSTEM COMPOSED OF COBALT, IODINE, AND HETEROGENEOUS RUTHENIUM CATALYSTS T. MATSUZAKI, T. MATSUZAKISearch for more papers by this authorY. SUGI, Y. SUGISearch for more papers by this authorH. ARAKAWA, H. ARAKAWASearch for more papers by this authorK. TAKEUCHI, K. TAKEUCHISearch for more papers by this authorK. BANDO, K. BANDOSearch for more papers by this authorN. ISOGAI, N. ISOGAISearch for more papers by this author T. MATSUZAKI, T. MATSUZAKISearch for more papers by this authorY. SUGI, Y. SUGISearch for more papers by this authorH. ARAKAWA, H. ARAKAWASearch for more papers by this authorK. TAKEUCHI, K. TAKEUCHISearch for more papers by this authorK. BANDO, K. BANDOSearch for more papers by this authorN. ISOGAI, N. ISOGAISearch for more papers by this author First published: December 10, 1985 https://doi.org/10.1002/chin.198549123AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue49December 10, 1985 RelatedInformation

Platinum, barium and platinum-barium catalysed gasification of graphite in steam and CO 2

The concept of forming a bifunctional catalyst system for the gasification of carbon was investigated using controlled atmosphere electron microscopy. Platinum and barium were chosen as the catalyst components and their effect has been studied, both in separate and combined forms, on the gasification of graphite in steam and CO 2. Platinum was found to operate in both systems primarily by the channelling mode but was not very active and was susceptible to deactivation at temperatures 900 °C in a steam environment. This deactivation phenomenon is believed to arise from carbon deposition or precipitation during the reaction. In contrast, previous studies have shown that barium is a relatively active catalyst for both these reactions and operates predominantly by the edge recession mode. The mixed platinum-barium catalyst only exhibited channelling activity, but the intrinsic rate indicated that it probably functions as a true bifunctional catalyst with barium increasing the oxygen reactivity, and platinum the carbon reactivity. The results of this study demonstrate the potential of multicomponent catalysts in which the components are selected by their ability to enhance the rate of one particular step in the reaction scheme.

Selective transfer of 1-hexylcarbamoyl-5-fluorouracil into lymphatics by combination of β-cyclodextrin polymer complexation and absorption promoter in the rat

The β-cyclodextrin polymer (polyβCD) was used as a candidate for a macromolecular carrier of a bifunctional delivery system, and the applicability of this new biodegradable polymer was studied using 1-hexylcarbamoyl-5-fluorouracil (HCFU) by administering into the lumen of the large intestine, and into the abdominal cavity. Bifunctional delivery system (mixed micelles + HCFU-polyβCD complex) increased the selective transfer of HCFU into the lymphatics after the large intestinal administration. On the other hand, after the intraperitoneal administration, we found that the administration of HCFU-polyβCD complex without mixed micelles increased the selective transfer of HCFU into the lymphatics. The selective transfer into the lymphatics was found by administration of drug into the abdomen rather than into the large intestine. These results suggest that such a new bifunctional delivery system will be a powerful tool in the field of antitumor chemotherapy.

Photochemical probes of the active site of myosin. Irradiation of trapped 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate labels the 50-kilodalton heavy chain tryptic peptide.

3'-O-(4-Benzoyl)benzoyl-ATP (Bz2ATP), an analog of ATP containing a photoreactive benzophenone moiety, was used as a probe of the ATP binding site of myosin subfragment 1 (SF1). The inactivation of SF1 NH+4-EDTA ATPase by the bifunctional thiol crosslinking system cobalt(II)/cobalt(III) phenanthroline complexes was enhanced by Bz2ATP to the same degree as by ATP. This treatment resulted in the stable trapping of Bz2ATP at the active site in nearly stoichiometric amounts in a manner exactly analogous to ATP (Wells, J.A., and Yount, R.G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970). Irradiation of SF1 containing trapped [3H]Bz2ATP gave approximately 50% covalent incorporation of the trapped nucleotide into the enzyme. Analysis of photolabeled SF1 by gel electrophoresis showed that all of the [3H]Bz2ATP was attached to the 95-kDa heavy chain fragment. No label was found in the light chains. Similar analysis of the same protein after limited trypsin treatment demonstrated that approximately 75% of the [3H]Bz2ATP was bound to the central 50-kDa peptide and its 75-kDa precursor from the heavy chain. The N-terminal 25-kDa tryptic peptide, shown to be photolabeled by other ATP analogs (Szilagyi, L., Balint, M., Sreter, F.A., and Gergely, J. (1979) Biochem. Biophys. Res. Commun. 87, 936-945; Okamoto, Y., and Yount, R.G. (1983) Biophys. J. 41, 298a), was not labeled (less than 1%) by Bz2ATP. These results demonstrate that portions of the 50 kDa-peptide of the heavy chain are within 6-7 A of the ATP binding site on SF1 and possibly contribute to nucleotide binding.

Mechanism for selective transfer of bleomycin into lymphatics by a bifunctional delivery system via the lumen of the large intestine

The mechanism for the selective lymphatic transfer of bleomycin from the lumen of the large intestine of rat by the administration of a bifunctional delivery system was investigated. This system is a combination of a macromolecular bleomycin-dextran sulfate complex as a lymphotropic carrier, and a lipid-surfactant mixed micelles as an absorption promoter. The administration of the bifunctional delivery system into the lumen of the large intestine showed that the macromolecular complex was stable in the lumen, but half of the complex dissociated in the tissue and 95% of the absorbed bleomycin was detected as free drug in the lymph and the blood. The absorption percentages of bleomycin and dextran sulfate from the lumen were approximately identical but the lymphatic transfer of dextran sulfate was greater than for bleomycin. Intravenous pretreatment with dextran sulfate indicated no effect on the lymphatic transfer of bleomycin from the lumen of the large intestine. The necessity for a specific binding was tested with 5-fluorouracil; the dextran sulfate showed no effect on the transfer of this drug into the lymphatics when administered concomitantly into the lumen. The formation of a stable macromolecular complex which exists intact in the intestinal lumen was found to be necessary in order to obtain enhanced selective transfer of bleomycin into the lymph in the presence of mixed micelles. A basis for understanding the selective lymphotropic mechanism is presented, and the implication of a bifunctional delivery system in the enhancement of absorption is discussed.

Mechanism of transfer of bleomycin into lymphatics by bifunctional delivery system via lumen of small intestine.

The mechanism of lymphatic transfer of bleomycin from the lumen of the small intestine of rats following the administration of a bifunctional delivery system was investigated. This system is a combination of macromolecular bleomycin·dextran sulfate complex as a lymphotropic carrier and lipid-surfactant mixed micelles as an absorption promoter. After administration of this bifunctional delivery system into the lumen of the small intestine, 56% of the complex was left intact in the lumen after 2 h, but 85, 95 and 97% of the absorbed bleomycin were detected as the free drug in the tissue of the small intestine, the lymph and the blood, respectively. The absorption percentage of bleomycin from the lumen of the small intestine at 3 h after the administration of the bifunctional delivery system was significantly different from that of dextran sulfate, and the total lymphatic transfer of dextran sulfate was greater than that of bleomycin. These findings suggest that the extent of the selective lymphatic transfer of bleomycin was smaller than that of dextran sulfate because of the dissociation of the bleomycin·dextran sulfate complex in the lumen and the tissue of the small intestine.

Requirement of macromolecular complex formation for selective lymphatic transfer of bleomycin from large intestine by bifunctional delivery system.

The requirement of complex formation for the selective transfer of bleomycin from the large intestine of rat by a bifunctional delivery system was investigated. The delivery system developed by us is a combination of macromolecular dextran sulfate, mean molecular weight (MW), 500000, as a lymphotropic carrier forming an ionic complex with bleomycin, and lipid-surfactant mixed micelles as an absorption promoter. Co-existence of the bifunctional delivery system (bleomycin dextran sulfate complex+mixed micelles) with saline resulted in the dissociation of the complex. Administration of this system with saline into the lumen of the large intestine showed no selective rise of lymph level of bleomycin compared with the blood level, and pretreatment with dextran sulfate into the lumen did not increase the lymphatic transfer of bleomycin. Lower molecular weight dextran sulfate (MW, 5000) formed a complex with bleomycin, like macromolecular dextran sulfate (MW, 500000). However, administration of this complex with mixed micelles failed to selectively enhance the lymphatic transfer of bleomycin. Co-administration of bleomycin with other macromolecules (dextran or diethylaminoethyl dextran, MW, 500000) that do not form a complex with bleomycin also failed to selectively increase the lymphatic transfer of bleomycin. These findings suggest that the complex formation of bleomycin with a macromolecule over a certain molecular weight is required for the selective transfer of bleomycin into the lymphatics from the large intestine by a bifunctional delivery system.

Development of novel reactive dyes with a mixed bifunctional reactive system

The advantages of the mixed bifunctional reactive system—vinylsulphone and monochlorotriazine—with respect to dyeing and fastness properties are discussed in detail.

Bifunctional delivery system for selective transfer of bleomycin into lymphatics via enteral route

Development of lymphotropic delivery system for poorly absorbed drug administered via enteral route was attempted. Lymphotropic property of dextran sulfate (DS) combined with the absorption-inducement property of lipid—surfactant mixed micelles was studied for the delivery of bleomycin (BLM). Monoolein-sodium taurocholate mixed micelles induced a remarkable absorption of BLM from the small and the large intestine of rat, but its concentration in the blood and the lymph was almost identical. However, administration of BLM-DS complex together with the mixed micelles induced a very high concentration rise only in the lymph. This lymphotropic selectivity, observed by complexation of BLM with DS, was much more effective in the large intestinal rather than in the small intestinal administration. Lower lymphotropic selectivity of BLM from the small intestine was due to the dissociation of the complex since instability of BLM-DS complex in the small intestinal lumen was demonstrated by gel filtration studies. Development of this bifunctional delivery system, as an advantageous device for a selective delivery of poorly absorbed anticancer drug into the lymph by way of rectal administration, holds considerable promise.

Optimal contaminant removal in fermentation and waste treatment processes

A bifunctional enzymatic catalyst system may be optimally distributed along a plug flow tubular reactor to reduce trace contamination. For the system considered in this study, there are nine possible optimal catalyst distribution policies, depending on the magnitude of the initial concentrations, the relative oxidizing power of the contaminants, and the residence time in the reactor. The effects of these system parameters on the optimal distribution policies are discussed, as is the possibility of replacing the optimal policies with suboptimal decisions. The relative errors caused by the suboptimal policies are found to be insignificant in many cases, but the approximations may not do as well if the oxidizing contaminants have relatively very different effects.