Kinds Of Monomers Research Articles

Piezoelectric Sensors Using Rubber Sensing Film

Piezoelectric sensors, consisting of multiple-crystal oscillators or surface acoustic wave (SAW) devices, are effectively used as highly functional and highly sensitive chemical sensors which identify unknown or target materials in gasses and liquids. We present the results of a basic study on applying rubber materials as the sensing films of the piezoelectric sensors and a simple method of preparing crystals with sensing films of various characteristics. We verified the feasibility of the materials used as sensing films of the piezoelectric sensors. We made several films with different adhesive natures by bonding reactive materials on the surface of the rubber films instead of preparing various kinds of monomers. We also present the results of the basic characteristics of SAW sensors with rubber films.

Microphase Separation in Correlated Random Copolymers

In the Leibler description of copolymer systems containing only two kinds of monomers, the state of the system is described by one order parameter, ψ(r), representing the deviation of the local composition from the space-averaged value. The Landau free energy is expanded up to fourth order in powers of ψ(r) and subsequently minimized with respect to the symmetry, the amplitude, and the period of the microstructure. However, if the system contains some kind of polydispersity, so that the copolymers are no longer all identical, the description in terms of only one order parameter is an oversimplification. Recently, Erukhimovich and Dobrynin refined the theory by introducing separate order parameters for each type of molecule (Erukhimovich, I.; Dobrynin, A. V. Macromol. Symp. 1994, 81, 253). Their procedure eventually leads to a Leibler-like free energy, with various additional terms. One of these terms, called the nonlocal term, is of great importance for the system under consideration, since it is responsible for microphase separation instead of the macrophase separation predicted by previous theories. In our article, the results of the application of this theory to a random copolymer, containing two types of monomers A and B, are presented. The resulting microstructure will be given for various values of the χ-parameter and the A-monomer fraction.

Production of polyclonal antisera that recognize and distinguish between the extracellular domains of neuronal nicotinic acetylcholine receptor subunits.

Ligand-gated ion channels are oligomeric transmembrane proteins that usually contain more than one kind of monomer. The variety of monomers available to participate in oligomer formation and the apparent latitude in acceptable monomer combinations allows considerable diversity. Mechanisms for identifying the monomers comprising specific receptors are needed. We have generated affinity-purified polyclonal antisera that recognize the extracellular domain of nine neuronal nicotinic acetylcholine receptor (nAChR) subunits and distinguish between them. We prepared these antisera by immunizing rabbits with bacterially expressed recombinant protein representing the N-terminal extracellular domain of each neuronal nAChR subunit followed by affinity purification of antibodies against synthetic peptides corresponding to residues 68-81 of the alpha 1 subunit. We demonstrate subunit specificity of each affinity-purified antisera by western blots of the bacterially expressed protein and immunoblot against peptide. We further used these antibodies to demonstrate expression of neuronal nAChR subunits on the surface of transiently transfected simian kidney (COS-7) cells.

Fluctuation effects on microphase separation in random copolymers

We study random copolymers consisted of two kinds of monomers with attraction between similar kinds. The mean field analysis of this system indicates a continuous phase transition into a phase with periodic microdomain structure. It is shown that the inverse of the renormalized propagator has a minimum at non-zero wave-numbers. Consequently, there is an anomalously large contribution of fluctuations that make the disordered phase locally stable at every finite temperature. However, below a certain temperature, the ordered phase is shown to be locally stable and a weak first order transition is possible, similar to the weak crystallization theory developed by Brazovskii.

Fluctuation effects on microphase separation in random copolymers

We study random copolymers consisting of two kinds of monomers with attraction between similar kinds. The mean-field analysis of this system indicates a continuous phase transition into a phase with periodic microdomain structure. It is shown that the inverse of the renormalized propagator has a minimum at non-zero wave numbers. Consequently, there is an anomalously large contribution of fluctuations that make the disordered phase locally stable. However, below a certain temperature, the ordered phase is shown to be locally stable and a weak first-order transition is possible, with qualitative differences from the weak crystallization theory developed by Brazovskii. These differences are due to the peculiar form of the fourth-order vertex of the effective Hamiltonian for the system. We calculated the temperature region for the validity of the mean-field estimates of the amplitude and the scale of microphase separation.

Purification of Two Forms of Bovine Liver Glycogen Phosphorylase b with Distinct Subunit Composition

The procedures for the purification of two forms of bovine liver glycogen phosphorylase b are described. Both forms showed a single band in nondenaturing gel electrophoresis. Gel electrophoresis in the presence of sodium dodecyl sulfate produced a single-band pattern for one of the enzyme forms (phosphorylase b1) and a triple-band pattern for the other (phosphorylase b3). Molecular weights associated with these bands were 97 kDa in the first case and 97, 55, and 40 kDa in the second. The yield from 1 kg of liver was approximately 10 mg for phosphorylase b1 and 140 mg for phosphorylase b3. The specific activity was 40-44 U/mg in both cases. As phosphorylase b1 is composed of just one kind of monomer, it is a novel bovine liver phosphorylase b structure.

電子線橋かけ型ポリ塩化ビニル被覆鋼板の塗膜特性に及ぼすモノマー種の影響

電子線橋かけ型ポリ塩化ビニル被覆鋼板の塗膜特性に及ぼすモノマー種の影響

Surface-modified hydrophilic membranes in membrane distillation

The porosity and the hydrophobicity of membranes are two essential requirements for membrane distillation (MD) of aqueous solutions. So far, the hydrophobic porous membranes used in MD studies have been prepared from hydrophobic materials. In this work, hydrophilic cellulose acetate and cellulose nitrate membranes were modified into hydrophobic membranes by radiation grafting polymerization and plasma polymerization, and used in MD studies successfully. The results indicated that modified membranes with good performance in MD can be obtained if the modifying conditions are controlled appropriately. Especially plasma polymerization, in which many particular kinds of monomer could be polymerized onto the surface of porous materials, has become an efficient method to prepare hydrophobic porous membrane with high performance from hydrophilic membranes. It will stimulate the development and practical application of MD.

Conversion in Visible Light-cured Resins III : Kinds of Monomers and Photoinitiator Compositions

Conversion in Visible Light-cured Resins III : Kinds of Monomers and Photoinitiator Compositions

Electro-polymerization of phenols

Electro-polymerization of phenols has been investigataed. Conditions of polymerization, such as kind of monomer, concentrations of monomer and supporting electrolyte, electricity and current density were studied. The mechanism of polymerization is discussed on the basis of results from measurements by gel permeation chromatography, i.r. absorption and nuclear magnetic resonance for polymerized products. It was found that the polymerization proceeded by a stepwise mechanism. Structure and some properties of the polymers are also discussed.

可視光線重合型レジンに関する基礎的研究 : FT-IR法による表層低重合層中の残存二重結合量の経時的変化について

The quantity of the remaining double bonds (RDB) in polymerized visible light cured resins has been determined. Five trial unfilled resins, eight commercial composite resins and three commercial crown and bridge resins were investigated by Fourier transform infrared spectrophotometer with the liquid-film method. Infrared absorbance was measured before irradiation and at various times after irradiation. The quantity of RDB was determined and the data expressed as percentage of the total amount of double bonds in the unpolymerized resins. The quantity of RDB of five trial unfilled resins decreased linearly corresponding to the logarithmic time after the start of irradiation. The difference in the quantity of RDB at 5 min and decreasing rate of RDB could be seen in accordance with the kind of monomer. Among five trial unfilled resins, one with BMPEPP (BPE-200) used as monomer gave the smallest RDB, and one with 4 PN-(TF)2-(EMA)6 used as monomer gave the largest value. The quantity of RDB in the unfilled resin with Tri-EDMA at 5 min decreased in accordance with the irradiation time, but after 1 month, it showed almost the same value irrespective of the irradiation time. The quantity of RDB of commercial composite resins and crown and bridge resins decreased linearly corresponding to logarithmic time. In all commercial resins, the quantity of RDB became small when the base monomer was Bis-GMA but large when it was UDMA.

Externally induced phase transition for random inhomogeneous polymers

The author considers an ensemble of frozen linear sequences with intrachain long-range interactions in the good solvent region. The sequences are made up of two kinds of monomers and they are subject to the influence of an external attractive field. He studies the phase transition caused by adsorption of the coil below a critical temperature. Making use of the replica method to average over macroscopic samples, he gets the temperature dependence for the dispersion of polymer sizes.

Scattering from concentration fluctuations in polymer blends: A monte carlo investigation

The collective scattering function Scoll( $$\vec q$$ ), which describes light (neutron-, x-ray) scattering under wavevector $$\vec q$$ , is obtained from Monte Carlo simulations for a symmetrical polymer mixture. The polymers are modelled by self-avoiding walks ofN A=NB=N steps on a simple cubic lattice, where a fractionφ V of sites is left vacant, and an attractive energye occurs if two neighboring sites are taken by the same kind of monomer. Spinodal curves are estimated from linear extrapolation of S coll −1 (0) vs.e/k B T, whereT is the temperature. Also the single chain structure factor is obtained and the de Gennes random phase approximation (RPA) can thus be tested. Unexpectedly, strong deviations are found if one species is very dilute. The estimation of an effective Flory-Hugginsχ-parameter from scattering data is also discussed.

Characterization of linear copolymers by methods sensitive to the refractive index increment

AbstractFor linear copolymer molecules, the refractive index increment depends on the chemical composition of the molecules. However, the polydispersity in chemical composition of the sample introduces a great complexity in the data analysis in order to obtain a true molecular weight distribution. Even when the mean chemical composition does not depend on the molecular weight, a correction has to be applied when the output of an instrument depends quadratically on the refractive index Increment of the sample, such as in a light‐scattering measurement. For that purpose, the light‐scattering expressions are written in terms of polydispersity in chemical composition, which in turn is modeled using linear copolymerization equations. The microstructure effects, which are related to the order in which two different kinds of monomers appear along the chain, are not as yet taken into account in this approach.

Characterization of polyphenol oxidase from Chaetomium thermophile, a thermophilic fungus.

The polyphenol oxidase from Chaetomium thermophile Isolate O-453 was examined for its substrate specificity. The purified enzyme acted on polyphenols but not on monophenols. Among the polyphenols and phenol-like compounds tested, those oxidized were d-catechin (relative activity, 100%), l-epicatechin (95.3%), chlorogenic acid (80.0%), pyrocatechol (53.8%), DOPamine (47.8%), guaiacol (87.5%), and N, N-dimethyl-p-phenylenediamine (75.3%). Esculine (7.8%), resorcinol (0%), p-quinone (0%), o-phenylenediamine (1.3%), phenol (0%), and L-tyrosine (0%) werescarcely oxidized. The purified enzyme was inhibited by potassium xanthogenate, thiourea, cysteine, potassium cyanide, and sodium azide. Mercuric and ferrous ions inactivated the enzyme. Carbon monooxide did not inhibit the activity (residual activity, 92.0%). SDS-polyacrylamide gel electrophoresis showed that the purified enzyme (mw, 98, 000) is a trimer composed of three of the same kinds of monomers (mw, 36, 000). These data indicate that the polyphenol oxidase from C. thermophile Isolate O-453 is a copper-containing protein and is classified as laccase [benzenediol: oxygen oxidoreductase, EC 1.10.3.2].

GRAFT COPOLYMERIZATION OF VINYL MONOMERS ONTO JUTE FIBERS

Abstract Among the various types of copolymerization, graft copolym-erization has attracted considerable attention among applied polymer chemists. Graft copolymerization is a process of copolymerization of one kind of monomer in its polymeric state with another polymer which may be either synthetic or natural. So a graft copolymer is a high polymer whose molecule consists of two or more polymeric parts of different composition, chemically united together. Graft copolymerization onto textile fibers is a challenging field of research with unlimited future prospects [1-10]. This is attractive to chemists as a means of modifying macromolecules since, in general, degradation is minimized. The desirable properties of the polymer are retained, and copolymerization Drovides additional properties throuerh the added polymer.

Statistics of Disordered Polymers: An Effective Hamiltonian and its Associated Gibbs Measure

AbstractAn ensemble of random polymers made of two kinds of monomers is considered. The effect of quenched randomness on two and three body interactions is evaluated by comparing the Gibbs measure for an effective Hamiltonian with that for a homogeneous polymer with the same bare Flory interaction constants.

Effects of organometallic cocatalysts on the polymerization of disubstituted acetylenes by TaCl5 and NbCl5

AbstractThe effects of organometallic cocatalysts on the polymerization of disubstituted acetylenes were investigated. Diphenylacetylene did not polymerize with TaCl5 alone, while it produced a polymer quantitatively in the presence of appropriate cocatalysts (Me4Sn, Et3SiH, etc.). The poly(diphenylacetylene) formed was an insoluble yellow solid. 1‐Phenyl‐1‐alkynes (1‐Phenyl‐1‐butyne and ‐1‐octyne) polymerized with TaCl5 and NbCl5 alone to yield polymers whose weight‐average molecular weights (Mw's) were ca. 5 × 105. Use of cocatalysts (nBu4Sn etc.) to the polymerization of these monomers accelerated the reaction, and increased the polymer molecular weights up to ca. 1.5 × 106. The poly(1‐phenyl‐1‐alkynes) were soluble white solids. Internal octynes (2‐, 3‐, and 4‐octynes) gave mixtures of a polymer and cyclotrimers with TaCl5 alone. In contrast, cyclotrimers formed virtually selectively by addition of cocatalysts. Thus, various effects of organometallic cocatalysts were observed depending on the kind of monomer.

Statistical Weights for Primary Structures of Inhomogeneous Polymer Chains

AbstractWe analyze the distribution of configurational averages over an ensemble of primary structures. These primary structures are given by base sequences for linear polymers of fixed length N constructed randomly from two different kinds of monomers. The variance V(R2) of the thermally averaged square size of the random coil is calculated by defining a virtual ensemble of homogeneous polymers of length N. This ensemble is determined by effective short range two and three body interactions. We prove that V(R2) increases with the information content given by the length N. Specially, V(R2) ∼ N2.

Statistics of the ensemble of primary structures for inhomogeneous polymer chains

We consider linear polymer chains of fixed lengthN made up randomly of two different kinds of monomers X and Y near the tricritical theta point. Two kinds of short-range repulsive volume-excluded interactions, X-X and Y-Y are considered. In addition, short-range attractive two-body X-Y interactions and threebody interactions are included in the theoretical treatment. We derive the distribution of the average size of the random coil over the ensemble of primary structures or X-Y sequences. The variance of thermal or configurational averages for the different sequences is calculated making use of field-theoretic methods.