Chemical polymerisation

An alternative to chemical polymerisation for coating is electropolymerisation of monomers at electrodes performed either in aqueous, or in organic solutions. However, electro-polymerisation is strongly restricted by the use of conducting materials because an activation potential needs to be applied, and an electrical current should be able to flow in the electrodes. This implies that the initial fibre to be coated should already have conductive properties which limits the use of this method52. Frequently, electropolymerisation is used as a finishing touch after fibres have been treated with a chemical deposition, the latter providing the conductive properties to the fibre necessary to perform electro-polymerisation. 

It should be mentioned that the defined interaction of dextran sulfate with amino functions is not only applied for the design of structures on the su-permolecular level but also on the molecular level. Thus, a preferred handed helical structure was induced into the polyaniline main chains by chemical polymerisation of achiral aniline in the presence of dextran sulfate as a molecular template. This affords a novel chemical route for the synthesis of chiral conducting polymers [158]. 

Both electrochemical and chemical oxidation have been used to produce 3-substituted alkylsulfonated pyrroles [106]. Electrochemical polymerisation was achieved using acetonitrile as solvent to form a solid deposit on the electrode. Alternatively, FeCl3 was used as oxidant. Conductivities in the range 0.001-0.500 S cm were obtained, with lower conductivity products obtained from chemical polymerisation. Others [107,108] have prepared homopolymers and copolymers of polypyrroles with alkyl sulfonate groups attached via the N-group. This N-group substitution decreases the polymers inherent conductivity. 

PAOs are synthetic lubricant bases, sometimes referred to as synthetic hydrocarbons, produced by a chemical polymerisation process, typically of 1-decene, Chapter 2. The resulting polymer chain lengths can be tailored to provide the fluid with the physical characteristics required ... 

Many modem composite materials are prepared by microemulsion methods. Polyaniline was prepared by one-step micellar chemical polymerisation of aniline with dodecyl benzene sulfonic acid via complex formation [297]. A transparent polyaniline suspension was made by dispersing polyaniline in m-cresol. Polyaniline composites blended with polymethyl methacrylate (PMMA) exhibits relatively high conductivity at low polyaniline volume fractions and keeps good mechanical properties equivalent to those of PMMA. It should be noted that most methods proposed for the preparation of new materials are at a laboratory level, however, a widespread commercial use can be predicted for the next decade. 

Chemical polymerisation of the monomers (3a) and (3b) were conducted by addition of 4 mol-equiv. of anhydrous FeCl3 in chloroform to a stirred solution of the respective monomers under dry nitrogen atmosphere. The reaction was allowed to continue for 2 hours at 25 °C and polymer products isolated by filtration, rinsed with deionised water and dried in vacuo. The undoped polymers were obtained by stirring the respective doped polymers in THF/water mixture for 4 hours and filtered. 

Chemical polymerisation of (2a) and ( 3b ) with iron (III) chloride enabled a facile multigram scale synthesis of the polymers pBr2BT and PCI2BT. The obtainment of these polymers were corroborated by elemental analysis and surface stoichiometric studies by ESCA (Table 2). 

A summary of the properties of polymers prepared chemically and electrochemically is shown in Table 3. The sizable differences in the ultraviolet absorption maxima is only apparent as the electrochemically polymerised samples were recorded as thin films on ITO glass whilst the chemically polymerised samples were recorded as solutions in NMP. Such hypsochromic changes in nre expected in going from the solid to solution phases and were borne out in model studies Although the conductivities of the polymers were of the order of 10 2 S cm-, these polymers were found to be soluble in a number of solvents (Table 4) in contrast to the total lack of solubility of polythiophene. 

In this section, the preparation of electrically conductive polyvinyl acetate (PVA) nanofibres, using vapour phase chemical polymerisation of pyrrole onto the surface of the nanofibres, is investigated. PVA is highly biocompatible and nontoxic and was selected for this study because of its excellent chemical resistance and physical properties. 

Core-shell latexes with a poly(butyl methacrylate) (PBM A) core and a polypyrrole (PPy) shell were prepared by chemically polymerising pyrrole in the presence of a PBMA latex, different shell thicknesses being obtained by varying the concentration of the PBMA latex in the polymerisation reactor. At low PPy concentrations, the shell was smooth and the conductivity correlated with the PPy content, with a percolation threshold of 0.25 wt% PPy, giving a theoretical shell thickness of 0.6 nm. At higher PPy concentrations, different morphologies were formed and the conductivity was almost independent of the PPy content. 4 refs. Presented at the International Conference on Science and Technology of Synthetic Metals (ICSM 98), Montpellier, France, 12-18 July 1998. 

The term hydrogel is derived from the Latin prefix hydro- referring to water and gel, gelu-or gelatus- to describe a frozen or immobilised structure. Hydrogels are super absorbent materials, which consist of over 90-99 % water and are prepared by chemical polymerisation or physical assembly of man made or namral resources. 

Syndiotactic PP is available from, e.g., Fina Oils and Chemicals, and Mitsui Toatsu Chemicals, polymerised using metallocene catalysts. It is claimed that the syndiotactic structure provides better impact strength, greater flexibility, lower haze, lower heat deflection temperature and lower residual monomer content. However, the full properties of these pol5miers are still to be evaluated and it remains to be seen whether S5mdiotactic PP can offer properties which are unique enough to market it as superior to isotactic PP and which can provide justification for the higher cost of material [8, 11, 12]. 

Bleda-Martinez, M. et al. 2007. Polyaniline/porous carbon electrodes by chemical polymerisation Effect of carbon surface chemistry. Electrochimica Acta 52 4962-4968. 

A soluble polyaniline derivative was prepared by the chemical polymerisation of 2-octadecylaniline. The monolayer of this compound on an aqueous HCl subphase was fabricated into LB film by the horizontal lifting method. Highly anisotropic conductivity was obtained after iodine doping (<7 il0 S/cm,... 

Next, it is briefly described the accepted polymerisation mechanism of poly-pyrrole, probably the most used conducting polymers, in the electrochemical synthesis, although this mechanism can be extended to the chemical polymerisation. 

Mineral polymers (MIP) are materials that have similar properties as ceramics, porcelain, pottery or glasses. They are however not obtained by fusion or firing at high temperature. MIP are inorganic materials that are obtained by chemical polymerisation or polycondensation of different oxydes from H, Li, Na, K, Al, Si, P,—... 

Chemical synthesis of a soluble polymer in the presence of nano-objects and subsequent deposition by means of drop casting or spin coating Chemical polymerisation of pyrrole in the presence of CNTs in acidic aqueous solution containing an oxidising species, namely persulphate ions 111... 

Costello, B.P.J., P. Evans, B.P.J. de Lacy et al. 2000. The synthesis of a number of 3-akyl and 3-carboxy substituted pyrroles their chemical polymerisation onto polyfvinylidene fluoride) membranes, and their use as gas sensitive resistors. Synth Met 114 (2) 181-188. 

Polylactic (and polyglycoUc) acids are mainly produced by chemical polymerisation of lactic acid (and glycoUc) acid obtained by Lactobacillus fermentation. Commercial applications of polylactic acid materials are growing up very rapidly under the trade marks of Ecopla ifom CargilFDow Chemical or Lacea Ifom Mitsui. Synthetic biodegradable polyesters are produced by the major chemical companies such as Basf (Ecoflex ), Eastman (Ecostar ), Showa Denco (Bionolle ) and Solvay. Thermoplastic biodegradable materials are sometimes formulated with paper, fibres or fibrous materials to form composites with optimised properties. 

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