Liquid state polymerization

All polymers are formed in a condensed phase. In the liquid state polymerizations start (a) in bulk, (b) in solution, (c) in suspension and (d) in emulsion. 

One final, though extremely important, method of generating reactive cations is by the use of ionizing radiation. Though irradiation with 7-rays from a °Co source was known to initiate free radical, liquid state, polymerizations [36], it was not until 1957 that the polymerization of isobutene at —78°C was shown unequivocally to be a cationic process [37]. Presumably on irradiation an electron is ejected from a suitable liquid monomer with the generation of a radical cation [38] which can then propagate. 

Tabata et al. [63] reported the polymerization of acetylene in the liquid and solid state by irradiation with y-rays from a Co source over the dose rate range of 3 X 10 tol X 10 R/h. The product obtained in the liquid-state polymerization was a relatively bulky orange-yellow powder that was soluble in aniline, isopropylamine, and DMF, and the polymer obtained by the solid-state polymerization was a rigid deep brown material and was insoluble in almost all solvents. Infrared spectra of the product were quite different from those of polyacetylene prepared with Ziegler-Natta catalysts. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials In presence of moisture may severely corrode some metals. In liquid state this chemical will attack some plastics Stability During Transport Stable Neutralizing Agents for Acids and Caustics Flush with water Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Foamed polyurethane. The basic chemicals are mixed in the liquid state with foaming agents, and swell into a low-density foam which sets by polymerization into a rigid mass. As the swelling material will expand into any shape required, it is ideal for the core of sandwich panels, and the sheet material skins may be flat or profiled. When the panels are manufactured the mixture is injected between the inner and outer skins and expands to the thickness required, adhering to the lining materials. 

One of the most important areas of application of the solid-state NMR technique is the investigation of the structures of cross-linked amorphous materials in cases where X-ray diffraction technqiues are not applicable. Polymeric resins are one such important class of materials. A lot of work has been done in this area by several investigators 36,37 38 since the beginning of the 80. Some solid-state NMR data of phenolic resins are presented in Fig. 10. Comparison with liquid state data for... 

The activities of the various components 1,2,3. .. of an ideal solution are, according to the definition of an ideal solution, equal to their mole fractions Ni, N2,. . . . The activity, for present purposes, may be taken as the ratio of the partial pressure Pi of the constituent in the solution to the vapor pressure P of the pure constituent i in the liquid state at the same temperature. Although few solutions conform even approximately to ideal behavior at all concentrations, it may be shown that the activity of the solvent must converge to its mole fraction Ni as the concentration of the solute(s) is made sufficiently small. According to the most elementary considerations, at sufficiently high dilutions the activity 2 of the solute must become proportional to its mole fraction, provided merely that it does not dissociate in solution. In other words, the escaping tendency of the solute must be proportional to the number of solute particles present in the solution, if the solution is sufficiently dilute. This assertion is equally plausible for monomeric and polymeric solutes, although the... 

The DEP ends with a filament wire onto which a drop of sample is deposited. After evaporation to dryness, the probe is introduced into the source of the mass spectrometer and is rapidly heated to a temperature that can reach 1000°C. This probe is ideal for the study of high molecular weight or polymeric components. It is mostly dedicated to the analysis of samples in the liquid state. Although a small solid fragment of matter may be placed on the filament, this critical operation may lead to the loss of the sample, especially if it is particularly small. To avoid such a difficult handling, the sample may be ground and homogenised in a mini-mortar and then made into suspension with a few drops of appropriate solvent (Scalarone et al., 2003). 

Enzymes that contain carbohydrate, such as HRP or GO, may be oxidized with periodate to create reactive derivatives that subsequently can be used to label antibodies or other targeting molecules at their amine groups. The aldehyde-HRP intermediate may be stored for extended periods in a frozen or lyophilized state without loss of activity (either enzymatic or coupling potential). Avoid, however, storage in a liquid state, since polymerization may occur—resulting in precipitation and loss of activity. 

Container molecules are of great interest because their encapsulated guests often exhibit novel and unusual properties, which are not observed in the free or solvated state (8,9). They are used today as probes of isolated molecules and of the intrinsic characteristics of the liquid state, and are capable of enantiose-lective recognition (10), reversible polymerization (11), isolation of reactive species (12-14), and promoting reactions within their interiors (15-18). For a valuable introduction to this area the reader is directed to some excellent review articles (15,19-21). 

It was indeed found necessary to have excess antimony pentafluoride present in order to obtain stable alkylcarbonium hexafluoroantimonate complexes. Antimony pentafluoride is a liquid Lewis acid fluoride (b.p. 148-150°) of low dielectric constant (e 3), which has been shown by fluorine N.M.R. studies in the pure liquid state and in solution to exist in both cyclic and acyclic polymeric forms involving fluorine bridges. The antimony is in approximately octahedral co-ordination with predominant bridging by coordinating fluorines (Gillespie and Rothenbury, 1963). As fluorine generally does not show bridging properties, the structure of antimony pentafluoride itself indicates the very... 

The monodisperse fragmentation process can be extended to produce monodis-perse solid particles [156], The general strategy consists of performing the emulsification in conditions such that the dispersed phase is in the liquid state, and to solidify the drops either by a temperature quench or through polymerization. The microscopic image in Fig. 1.29 illustrates this possibility. It corresponds to solid paraffin oil dispersed in water at room temperature. The emulsification was performed in the liquid state, at a temperature above the melting point of the... 

Sulfur nitride polymers [-(-S = N-)-], which have optical and electrical properties similar to those of metals, were first synthesized in 1910. These crystalline polymers, which are super-conducive at 0.25 K, may be produced at room temperature using the solid state polymerization of the dimer (S2N2). A dark blue-black amorphous paramagnetic form of poly(sulfur nitride) (structure 11.30) is produced by quenching the gaseous tetramer in liquid nitrogen. The polymer is produced on heating the tetramer to about 300°C. 

That the liquid phase polymerization of isobutylene in the presence of aluminum chloride or boron fluoride occurs even in the absence of a third component may be seen in the results of another worker (Houtman, 88). With solid aluminum chloride polymerization occurred at room temperature when isobutylene vapors were passed over the catalyst and at —80° when the isobutylene was in the liquid state. In both cases the reaction was incomplete probably because the catalyst was covered with a layer of polymer. The reaction at — 80° was not however as explosive in character as when moisture was present. When boron fluoride was added to isobutylene at about —80°, the polymerization started immediately in the gas phase above the liquid (owing to a somewhat higher temperature) and sometimes continued for a considerable time before reaction was noticeable in the liquid phase. There was no difference in behavior between the experiments in which the catalyst was led through or over the liquid. It was pointed out, however, that these results are not necessarily in contradiction with those of Polanyi and Evans and co-workers and that it is possible that the presence of moisture is neces-... 

Condensed monolayer films of pure 6 polymerized rapidly, as did mixed 6/DSPE films of up to 75% DSPE, provided the monolayers were in the condensed state [33], In the liquid-expanded state, polymerization did not occur. In the condensed state, lateral diffusion of individual lipids within the monolayer is severely restricted compared to the liquid-like state. This precludes initiation of polymerization by diffusive encounter between excited-state and ground-state diacetylene lipids. In order for polymerization to occur in the condensed state, the film must be separated into domains consisting of either pure 6 or pure DSPE. A demonstration that the rates of photopolymerization for pure 6 and mixed 6/DSPE monolayers are equal would be a more stringent test for separate domains of the lipids, but no kinetic data have been reported for this system. 

Sulfur Trioxide. Pure sulfur trioxide [7446-11-9] at room temperature and atmospheric pressure is a colorless liquid that fumes in air. This material can exist in both monomeric and polymeric forms. In the gaseous and liquid state pure S03 is an equilibrium mixture of monomeric S03 and... 

Nanosecond transient absorption measurements provided a further indication of efficient mediator transport within the nanopores of the gel, showing basically no difference in dye regeneration using the liquid iodide/iodine precursor and the quasi-solid-state polymeric electrolyte. 

In most carbon and graphite processes, the initial polymerization reactions occur in the liquid state. The subsequent stages of crystal growth, heteroatom elimination, and molecular ordering occur in the solid phase. The result is the development of a three-dimensional graphite structure. 

Radiation-induced polymerization of nitroethylene in the liquid state was studied by Yamaoka and one of the present authors (K. H.). They verified that nitroethylene polymerizes in the anionic mechanism by radiation too, from the following three observations (7). Tetrahydro-furan is the most favorable solvent for the polymerization, among nitro-ethane, ethylether and tetrahydrofuran. The addition of hydrogen chloride remarkably retards the polymerization. Finally, nitroethylene copolymerizes with acrylonitrile. 

Reacting gases may be in excess if they react with solids and do not condense in liquid phases, but supercritical media are clearly not the subject of solvent-free chemistry and deserve their own treatment. For practical reasons, this book does not deal with homogeneous or contact-catalyzed gas-phase reactions. Furthermore, very common polymerizations (except for solid-state polymerizations), protonations, solvations, complexations, racemizations, and other stereo-isomerizations are not covered, to concentrate on more complex chemical con-... 

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