Showing papers on "Polymerization published in 1982"

Purification of muscle actin.

Abstract: Publisher Summary This chapter explores some of the pitfalls associated with actin purification and to clarify in some detail the correct use and expected result from each step of the widely used muscle actin purification procedure. Typical preparations use about 10 g of acetone powder. The steps include in the purification are following: extraction of acetone powder; filtration using sterile cheesecloth; centrifugation; polymerization; high salt wash: tropomyosin removal; sedimentation of filamentous actin; depolymerization. It is found that extensive dialysis results in eventual dissociation of actin-myosin complexes and appearance of myosin in the final product. Prolonged dialysis can also lead to observable actin proteolysis and should therefore be avoided. Final steps are Clarification of G-actinadn Polymerization. Depending upon individual technique, buffer purity, dialysis times employed, and so forth, the actin preparation can contain small amounts of contaminating protein, including proteolysed actin. Thus, the chapter presents several techniques for further purification of the actin.

Principles of Polymer Systems

Abstract: 1. Introduction 2. Basic Structures of Polymers 3. Physical States and Transitions 4. Polymer Formation 5. Polymerization Processes 6. The Molecular Weight of Polymers 7. Viscous Flow 8. Mechanical Properties at Small Deformations 9. Ultimate Properties 10. Some General Properties of Polymer Systems 11. Degradation and Stabilization of Polymer Systems 12. Fabrication Processes 13. Extrusion and Molding 14. Recycling and Resource Recovery 15. Carbon Chain Polymers 16. Heterochain Polymers 17. Analysis and Identification of Polymers Appendix 1. List of symbols Appendix 2. Harmonic motion of a Maxwell model Appendix 3. Selected properties of polymer systems Appendix 4. Major Markets for selected plastics and rubber

Fundamental Principles of Polymeric Materials

Abstract: Partial table of contents: POLYMER FUNDAMENTALS Types of Polymers Bonding in Polymers Stereoisomerism Characterization of Molecular Weight Polymer Solubility and Solutions Transitions in Polymers POLYMER SYNTHESIS Step-Growth (Condensation) Polymerization Free-Radical Addition (Chain-Growth) Polymerization Nonradical Addition Polymerization Copolymerization POLYMER PROPERTIES Rubber Elasticity Purely Viscous Flow Viscometry and Tube Flow Linear Viscoelasticity POLYMER TECHNOLOGY Processing Plastics Rubber Synthetic Fibers Surface Finishes Adhesives Index.

Structural Determination of the Symmetry-Breaking Parameter in trans-(CH) x

Abstract: The magnitude of the symmetry-breaking dimerization distortion has been determined by analysis of x-ray scattering data from trans-${(\mathrm{CH})}_{x}$ ${u}_{0}\ensuremath{\simeq}0.03$ \AA{}.This distortion can account for the magnitude of the energy gap, implying that electron-electron interactions do not dominate the physics of long-chain polyenes.

Poly(Vinylidene Fluoride)

Abstract: This chapter presents an extensive review of the important ferroelectric polymer, poly(vinylidene fluoride). Covered topics include: polymerization, molecular structure, and defects; dilute-solution properties; crystalline structure of the various polymorphic phases, crystallization, and morphology; polymorphic transitions induced through a variety of means (e.g. thermal, mechanical, electrical); relaxational characteristics; melting behaviour and thermal degradation; ferroelectric properties, with emphasis on piezoelectricity and pyroelectricity; copolymers and compatible blends with other polymers and general engineering properties and uses.

The elements of polymer science and engineering

Abstract: Preface. Introductory Concepts and Definitions. Basic Principles of Polymer Molecular Weights. Practical Aspects of Molecular Weight Measurements. Effects of Polymers Isomerism and Conformational Change. Step-Growth Polymerization. Free Radical Polymerization. Copolymerization. Dispersion and Emulsion Polymerizations. Ionic and Coordinated Polymerizations .Polymer Reaction Engineering. Mechanical Properties of Polymer Solids and Liquids. Polymer Mixtures. Subject Index.

Factors affecting the quantity of remaining double bonds in restorative resin polymers

Abstract: The quantity of remaining unreacted double bonds may be a significant factor pertaining to the mechanical, physical and chemical properties of restorative resins. The said quantity was determined from the transmission IR-spectrum of the materials before and after polymerization. For proprietary resins the quantity of remaining double bonds was found to vary between 23 and 43%. For experimental, chemically cured resins the quantity in question was found to decrease with increasing resin content of amine and peroxide, and to increase with the content of inhibitor. The content of peroxide was the more influential of the three factors. For constant content of amine, peroxide, and inhibitor the number of remaining double bonds decreased with increasing content of diluting monomer in BISGMA-based monomer mixtures. The use of a trifunctional monomer as diluting monomer did not give rise to a higher degree of conversion of the double bonds in comparison to a bifunctional diluting monomer. The quantity of remaining double bonds of a light curing material was relatively small when compared to the quantity present in chemically cured materials of adequate setting time.

Polymerization of olefin

Abstract: PURPOSE:To polymerize an olefin in excellent polymerization activity even in a decreased amount of an aluminoxane used, by using a catalyst comprising a specified supported solid catalyst component, an aluminoxane and a specified organoaluminum compound. CONSTITUTION:An olefin is (co)polymerized in the presence of a catalyst formed from a solid catalyst component (A) formed by allowing an inorganic carrier (e.g., SiO2 or Al2O3) to support a Group IV B transition metal compound [e.g., bis(cyclopentadienyl)zirconium dichloride], an aluminoxane (B) [e.g., a compound of formula I or II (wherein R is methyl or the like and m is an integer >=2)] and an organoaluminum compound (c) having a hydrocarbon group other than an n-alkyl group (e.g., triisopropylaluminum). When olefin polymerization, especially, ethylene polymerization or copolymerization of ethylene with an alpha-olefin according to the above process is performed by a slurry polymerization or vapor-phase polymerization process, the catalytic activity is high even in a decreased amount of the aluminoxane used and no adhesion of polymer to the reactor occurs. When this process is applied to the copolymerization of at least two olefins, a copolymer of a narrow MW distribution and a narrow composition distribution can be obtained.

Diluent and inert gas recovery from a polymerization process

Abstract: A polymerization process wherein a slurry of polymer and diluent is passed from the polymerization zone to a flash zone, then polymer solids having residual diluent carried thereon are passed to a purge zone wherein a heated noncombustible gas is used to remove additional amounts of diluent, and then the vapor purge zone is condensed and cooled to produce a vapor stream comprising said noncombustible gas and a liquid stream comprising diluent.

Synthesis of poly-ϵ-caprolactone via a free radical mechanism. Free radical ring-opening polymerization of 2-methylene-1,3-dioxepane

Abstract: 2-Methylene-1,3-dioxepane 6 polymerized with a quantitative ring opening to form poly-ϵ-caprolactone via a free radical mechanism. On the other hand, 2-methylene-1,3-dioxolane (ethylene ketene acetal) 4 and 2-methylene-1,3-dioxane 5, under the same conditions, generated polymers with mixed ring-opened and nonring-opened structures. In copolymerization monomer 6 also showed a high tendency toward ring opening by which the ester functionality could be conveniently introduced into the backbone of the addition polymers.

Aliphatic Polyesters. III. Molecular Weight and Molecular Weight Distribution in Alcohol- Initiated Polymerizations of e-Caprolactone

Abstract: The effect of initiation of ϵ-caprolactone polymerization with mono- and polyfunctional alcohols was investigated. The resulting linear and starshaped polymers were characterized by measurement of the molecular weight and molecular weight distribution. The polymerizations were characterized by (1) rapid initiation, (2) invariance of the number of growing chains corresponding to the amount of initiator, and (3) a dominant role played by ester interchange reactions.

Unreacted Methacrylate Groups on the Surfaces of Composite Resins

Abstract: The unreacted methacrylate groups on the surface of conventional composites and microfilled composites were studied by means of multiple internal reflection infrared spectroscopy. The influences of polymerization time, temperature, and the effect of polishing were studied. We also attempted to relate the results of some mechanical tests to the degree of chemical unsaturation measured in the different resins. All surface treatment and manipulative variables caused a decrease in double bond content and interfacial bond strength.

Process and apparatus for preparing uniform size polymer beads

Abstract: Spheroidal polymer beads having a uniform size are prepared by polymerizing uniformly sized monomer droplets formed by the vibratory excitation of a laminar jet of monomeric material flowing in a continuous liquid medium containing a suitable suspending agent. For example, a laminar jet of a monomer mixture comprising a monovinylidene aromatic such as styrene, a polyvinylidene aromatic such as divinylbenzene and a polymerization initiator can be subjected to vibratory excitation and the resulting monomer droplets polymerized to yield copolymer beads having a narrow particle size range distribution. The resulting copolymer beads can be employed to prepare high yields of ion exchange resins exhibiting superior properties, particularly in continuous ion exchange operations.

Process for preparation of high water-absorbent polymer beads

Abstract: Water-insoluble, high water-absorbent polymer beads are prepared by dispersing and suspending an aqueous solution of a water-soluble, ethylenically unsaturated monomer containing a small amount of a crosslinking agent in a dispersion medium of a hydrocarbon or a halogenated aromatic hydrocarbon, carrying out the bead polymerization in the presence of a water-soluble radical polymerization initiator and a protecting colloid comprising a cellulose ester or cellulose ether which is oil-soluble at the polymerization temperature, and separating the resulting beads.

Formation of transmembrane tubules by spontaneous polymerization of the hydrophilic complement protein C9

Abstract: The ninth component of complement C9 can undergo circular polymerization in the fluid phase and on lipid membranes. The concomitant hydrophilic-amphiphilic transition is the result of a conformational reorganization of C9 and allows insertion of poly C9 into membranes in the form of a transmembrane protein channel. The ultrastructure of poly C9 resembles that of membrane lesions caused by complement.

Polymerization of the ninth component of complement (C9): formation of poly(C9) with a tubular ultrastructure resembling the membrane attack complex of complement

Abstract: The ninth component of complement (C9) has a marked propensity to polymerize. C9 polymers [poly(C9)] formed spontaneously in Veronal-buffered saline upon incubation of purified C9 for 64 hr at 37 degrees C or within 2 hr at 46--56 degrees C. Poly(C9) formed at 37 degrees C was visualized by electron microscopy as a tubular structure with an internal diameter of 110 A and a length of 160 A. Its ultrastructure suggested a dodecameric composition and resembled that of the membrane attack complex of complement. The wider end of the tubular structure was formed by an approximately 30-A-thick torus with inner and outer diameters of 110 A and 220 A, respectively. Because the dimensions of C9 within poly(C9) were 160 x 55 A (maximal) and 20 A (minimal) and because monomeric C9 has dimensions of approximately 80 x 55 A, it is proposed that monomeric C9 unfolds during polymerization into tubules. Polymerization also occurred upon treatment of C9 for 1 hr at 37 degrees C with 0.6 M guanidine . HCl, 0.1 M octyl glucoside, or 1.5% sodium deoxycholate. Guanidine . HCl-induced C9 polymers consisted of elongated highly curved strands 55--80 A wide, suggesting that these polymers were formed by globular C9 that had not unfolded.

Molecular organization of C9 within the membrane attack complex of complement. Induction of circular C9 polymerization by the C5b-8 assembly

Abstract: Evidence has been presented suggesting that during assembly of the membrane attack complex (MAC) of complement, the C5b-8 complex induces polymerization of C9. The C9 polymer was detected by sodium dodecyl sulfate (SDS) gel electrophoresis of MAC isolated from complement-lysed erythrocytes. It resembled the previously described polymerized C9 (poly C9) produced from isolated monomeric C9 by prolonged incubation at 37 degrees C in that it was resistant to dissociation by SDS and reducing agents and had an apparent molecular weight of approximately 1.1 million. The presence of poly C9 in the MAC was further supported by the expression of identical neoantigens by the MAC and poly C9 and by the high C9 content of the MAC relative to its other constituents. Isolated C8 in solution was found to have a single C9-binding site. In mixture, the two proteins formed a reversible equimolar complex that had a sedimentation coefficient of 10.5S. In contrast, a single, cell-bound C5b-8 complex was found to bind up to 12-15 C9 molecules and clusters of C5b- 8 bound 6-8 C9 molecules per C8 molecule. In either case, typical ultrastructural membrane lesions were observed, suggesting that the membrane lesion is identical with the tubular poly C9 consisting of 12-16 C9 molecules, and that the MAC can have either the composition (C5b-8)polyC9 or (CSb-8)(2)polyC9. When C9 input was restricted so that the molar C9/C8 ratio was less than or equal to 3, C9-induced aggregates of C5b-8 were observed but virtually no circular membrane lesions were found. We suggest, therefore, that C9, at low dosage, causes cross-linking of multiple C5b-8 complexes within the target membrane and that, at high dosage, C9 is polymerized by C5b-8 to form a transmembrane channel within the MAC assembly. It is primarily the C9 polymer that evokes the ultrastructural image of the MAC or of membrane lesions caused by complement.

Bulk polymerization process for preparing high solids and uniform copolymers

Abstract: A process to continuously bulk polymerize vinylic monomers to prepare low molecular weight, uniform, polymers employs minor amounts of initiator and, optionally solvents, at short residence times and moderate reaction temperatures to provide high yields of a product suitable for high solids applications.

Low density porous cross-linked polymeric materials and their preparation and use as carriers for included liquids

Abstract: Cross-linked homogenous porous polymeric materials are prepared by polymerization of monomers as the continuous phase in a high internal phase emulsion having above a critical limit of surfactant to ensure adequate absorbtivity. The porous materials may be dried and refilled with selected liquids and act as a high capacity reservoir.

Fragmentation of actin filaments

Abstract: The kinetics of actin polymerization were analyzed by taking into account nucleation, elongation, and spontaneous fragmentation of filaments. Polymerization curves measured in the presence of potassium (40 mM) were found to be in good agreement with curves calculated for the assumption that nucleation and elongation but no fragmentation reactions occur. Polymerization curves measured in the presence of calcium (1.8 mM) or magnesium (0.6 mM MgCl2 and 0.5 mM EGTA) could only be stimulated by calculated curves when spontaneous fragmentation was assumed to occur in addition to nucleation and elongation. The experiments reported in this study that even in the absence of ultrasonication or shear forces actin filaments may break spontaneously and that the extent of fragmentation depends strongly on the experimental conditions. Spontaneous fragmentation changes the shape of the polymerization curves significantly. When fragmentation of filaments takes place, a relatively long lag phase of polymerization is observed that is followed by a strongly increasing polymerization rate to reach the final constant value quickly. On the other hand, when filaments are formed exclusively by nucleation, the polymerization curves approach the final constant value slowly after a relatively short initial lag phase.

Inverse microemulsion polymerization

Abstract: Inverse lattices of small size (< 500 A in diam) have been prepared via photopolymerization of acrylamide in a microemulsion. The final lattices have been characterized by photon correlation spectroscopy. This polymerization process provides polyacrylamide of high molecular weight (ca. 3 X 10/sup 6/) confined in small micellar particles. 14 references.

Graft polymers with macromonomers. I. Synthesis from methacrylate‐terminated polystyrene

Abstract: Pure graft polymers having uniform molecular weight polystyrene side chains were prepared by free radical copolymerization of methacrylate-terminated polystyrene macromonomers (MA-CROMER) with ethyl acrylate, butyl acrylate, or other suitable monomers. The MACROMER monomer was synthesized by living anionic polymerization under conditions that led to very narrow molecular weight distributions. Very effective end capping produced a material that was highly monofunctional. The graft copolymers were prepared by several techniques such as free radical solution polymerization, by aqueous suspension polymerization which produced beads, or by emulsion reactions which yielded stable latices. Polymerizations were reproducible. High conversion of the MACROMER monomer into pure graft polymers was achieved, and the product was contaminated with only a little homopolymer. The milled and molded phase-separated graft polymers had optical clarity and physical properties characteristic of polystyrene-reinforced triblock polymers. Compositions of 20-30% polystyrene were thermoplastic elastomers with good recovery. When polystyrene contents were increased, the graft products were strong, flexible thermoplastics with well defined yield strengths and increased permanent set. Copolymers of polystyrene macromers with acrylonitrile or vinyl chloride produced transparent polystyrene homopolymer-free graft polymer products having improved processing over polyacrylonitrile or poly(vinyl chloride) homopolymers.

Synthesis and characterization of a new surface derivatizing reagent to promote the adhesion of polypyrrole films to N-type silicon photoanodes: N-(3-(trimethoxysilyl)propyl)pyrrole

Abstract: The synthesis, characterization, and application of N-(3-(trimethoxysilyl-propyl)pyrrole (I) as a photoanode derivatizing reagent that can be covalently anchored to the electrode via reaction of surface OH groups are described. The pendant group of I can then be used as the initiation site for polymerization of polypyrrole. The treatment of both Pt and n-type Si electrodes with I and films of polypyrrole to protect the semiconductor from photoanodic decomposition is described. Improved durability noted for the treated n-type Si electrodes is attributed to less H/sub 2/O/electrolyte undermining of the polymer when it is covalently anchored to the surface. (BLM)

Batch polymerization process

Abstract: In the batch process for copolymerizing tetrafluoroethylene and selected comonomers to prepare a copolymer thereof, the improvement which comprises employing a perfluoroalkylethane sulfonic acid or its salts as the dispersing agent.

High‐conversion diffusion‐controlled polymerization of styrene. I

Abstract: A kinetic model based on the free volume theory has been proposed for the polymerization of styrene. The model, which is capable of describing the course of polymerization in both bulk and solution, accounts for diffusion-controlled termination and propagation and gives a limiting conversion.