Polymerisation, condensation

Sonopolymerisation is not only restricted to the polymerisation of vinyl monomers. The use of ultrasound in ring opening polymerisation, condensation polymerisation and polymerisation by coupling reactions have all been reported. 

Experiment Treat 1 c.c. bf aldehyde with one drop of concentrated sulphuric acid. The aldehyde boils, and polymerisation (condensation) takes place. 

Preparation of synthetic polymers. The polymerisation process (chemical joining of monomers) generally occurs by means of one of the three major mechanisms, namely, addition polymerisation, condensation polymerisation and rearrangement polymerisation. 

The analysed data on carbon content and also on content of organic N and P in dissolved and particulate state at the end of all the experiments illustrate the stability of OM. The experiments simulate accumulation of resistant insoluble and soluble organic compounds in reservoirs and soils. These compounds appear as the result of decomposition of dead living matter and its living excretions. The processes are not only responsible for transformation of initial OM (oxidation, polymerisation, condensation), but also for synthetic processes, caused by bacterial activity (Kononova, 1963), and this is the water humus of planktonic origin. 

The analysis of the results of the experiments on decomposition of OM in dead plankton presents a view of the time-related changes of particulate and dissolved organic C, N and P, and some components of OM. The processes occurring are responsible not only for oxidation of the initial OM, but also in soils (Kononova, 1963) for the polymerisation (condensation of the more biochemically resistant dissolved and particulate fractions of OM. 

Polysilicic Acid Gel. Term for the (more or less) soft or plastic gel, saturated with liquid (e. g., water) that is, for a reaction product that can be derived from silicic acids of low molecular weight through processes of polymerisation, condensation and aggregation. 

The biggest portion of grape pomace polyphenols has been reported to be highly polymerised condensed tannin, and some polyphenols form complexes with fibers and are non-extractable unless strong acidic treatments are applied [13]. Thermal processing may... 

Kondensationspolymerisation/ kondensative Polymerisation/ kondensierende Polymerisation condensation polymerization, condensed polymerization... 

Place 25 g. of methyl methacrylate polymer (G.B. Diakon (powder). Perspex (sheet) U.S.A. Lucite, Plexiglass) in a 100 ml. Claisen flask, attach an efficient condenser e.g., of the double smface type) and distil with a small luminous flame move the flame to and fro around the sides of the flask. At about 300° the polymer softens and undergoes rapid depolymerisation to the monomer, methyl methacrylate, which distils over into the receiver. Continue the distillation until only a small black residue (3-4 g.) remains. Redistil the hquid it passes over at 100-110°, mainly at 100-102°. The yield of methyl methacrylate (monomer) is 20 g. If the monomer is to be kept for any period, add 0 -1 g. of hydro quinone to act as a stabiUser or inhibitor of polymerisation. 

Acetaldehyde is a highly reactive compound exhibiting the general reactivity of aldehydes (qv). Acetaldehyde undergoes numerous condensation, addition, and polymerisation reactions under suitable conditions, the oxygen or any of the hydrogens can be replaced. 

Polyesters were initially discovered and evaluated ia 1929 by W. H. Carothers, who used linear aliphatic polyester materials to develop the fundamental understanding of condensation polymerisation, study the reaction kinetics, and demonstrate that high molecular weight materials were obtainable and could be melt-spun iato fibers (1 5). 

G. D. Cooper and A. YjCiXPSmi2cn.,A.ddition and Condensation Polymerisation Processes, Pidvances in Chemistry Series No. 91, American Chemical Society, Washiagton, D.C., 1969, p. 660. 

Chain transfer also occurs to the emulsifying agents, leading to their permanent iacorporation iato the product. Chain transfer to aldehydes, which may be formed as a result of the hydrolysis of the vinyl acetate monomer, tends to lower the molecular weight and slow the polymerisation rate because of the lower activity of the radical that is formed. Thus, the presence of acetaldehyde condensates as a poly(vinyl alcohol) impurity strongly retards polymerisation (91). Some of the initiators such as lauryl peroxide are also chain-transfer agents and lower the molecular weight of the product. 

Step-Growth Gopolymerization. A sample of a block copolymer prepared by condensation polymerisation is shown in equation 30 (37). In this process, a prepolymer diol (HO—Z—OH) is capped with isocyanate end groups and chain extended with a low molecular-weight diol (HO—E—OH) to give a so-called segmented block copolymer, containing polyurethane hard blocks and O—Z—O soft blocks. 

These processes have supplanted the condensation reaction of ethanol, carbon monoxide, and acetylene as the principal method of generating ethyl acrylate [140-88-5] (333). Acidic catalysts, particularly sulfuric acid (334—338), are generally effective in increasing the rates of the esterification reactions. Care is taken to avoid excessive polymerisation losses of both acryflc acid and the esters, which are accentuated by the presence of strong acid catalysts. A synthesis for acryflc esters from vinyl chloride (339) has also been examined. 

An alternative technique is that of condensation polymerisation. A simple example of this is seen in the manufacture of linear polyesters. Here a dibasic acid is reacted with a dihydroxy compound, e.g. a glycol (Figure 2.5). 

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