Low molecular weight monomer

The natural tendency of polypeptide chains to grow homochirally may suggest an alternative mechanism for the breaking of symmetry, based on macromolecules instead of monomers. The argument is that it should be easier to separate enantiomeric homochiral chains, rather than racemic low-molecular-weight monomers, from each other. It has been shown for example that when the NCA-polycondensation is performed on mineral support, the oligomeric product remained absorbed on the surface. The lower oligomers are, however, easily... 

In a plasma polymerization process, the growth of low molecular weight monomer species to a high molecular weight plasma polymer network takes place. In a chemical sense, plasma polymerization is different from conventional polymerizations, such as radical or ionic. The term radical polymerization means that propagating reactions of monomers are initiated by radical species. Ionic polymerization means that chemical reactions are propagated by ionic species in the polymerization step. Plasma polymerization involves an energy source to... 

The mechanical admixture of low molecular weight monomers into polymers normally in the glassy state at room temperature in order to increase the flexibility and softness of the polymer has great technical importance. Thus, such plasticizers as di-2 ethyl n-hexyl phthalate are frequently incorporated into polyvinyl chloride, homopolymer or copolymer, to increase the flexibility and commercial value of this resin. Cast (1953) as well as Hellwege, Knappe and Semjonow (1959) have... 

The nucleation mechanism of dispersion polymerization of low molecular weight monomers in the presence of classical stabilizers was investigated in detail by several groups [2,6,7]. It was, for example, reported that the particle size increased with increasing amount of water in the continuous phase (water/eth-anol), the final latex radius in their dispersion system being inversely proportional to the solubility parameter of the medium [8]. In contrast, Paine et al.[7] reported that the final particle diameter showed a maximum when Hansen polarity and the hydrogen-bonding term in the solubility parameter were close to those of steric stabilizer. 

The rate of the dispersion copolymerization of PEO-MA with styrene increased with increasing temperature [72], which was attributed to the increased rate of initiation and particle formation. The overall observed activation energy (E0) for the dispersion copolymerization of PEO-MA or PEO-VB macromonomer and styrene was found to be 48 or 53 kj mol-1. These values are much lower than those (ca. 90-100 kj mol-1 [73]) obtained in the solution polymerization of low molecular weight monomers. 

The values of relative reactivity of macromonomers (l/r2) in both solution and emulsion were found to decrease slightly with conversion. The r2 values in solution are lower than those for the copolymerization of low-molecular-weight monomers and macromonomers in emulsion. These results support the previous conclusion [95] about the incompatibility of macromonomer with a polymer trunk (polystyrene radical) which suppresses the mutual cross-propagation reactions of comonomers. 

Solvents, like contaminants, may be polar or nonpolar. As a general rule, polar solvents dissolve polar residues while nonpolar solvents dissolve nonpolar residues. Thus, ionic residues such as chlorides, salts, acids, acid fluxes, and alkalis are best dissolved and removed with polar solvents such as water, isopropyl alcohol, ethanol, or methylethyl ketone. Greases, oils, silicones, rosin flux, and low-molecular-weight monomers are best dissolved and removed with solvents such as hydrocarbons, Freons , hydrochloro-fluorocarbons, xylene, terpenes, and naphtha. To remove both polar and nonpolar residues, a two-step process using both types of solvents may be used or, more conveniently, an azeotrope mixture of the two solvents can be used in a one-step process. Most of the chlorofluorocarbon solvents (Freons ) and their azeotropes with alcohols, methylene chloride, or ketones are being phased out due to their high ozone-depletion potentials. Solvent blends and azeotropes of hydro-fluoroethers and hydrochlorofluorocarbons (HCFC) are now replacing these solvents. 

P23/25 (with a fourth generation of dendrons) from a low-molecular-weight monomer 23 and macromonomer 26, following a Suzuki polycondensation protocol. 

When polymers canying pendant double bonds are copolymerized with low molecular weight monomers, grafting may result. However, due to the fact that dirting such a copotymer-ization process, irreversible finks can be formed between two... 

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