Monomer oxidation

Cyclic voltammetry is most commonly used to investigate the polymerization of a new monomer. Polymerization and film deposition are characterized by increasing peak currents for oxidation of the monomer on successive cycles, and the development of redox waves for the polymer at potentials below the onset of monomer oxidation. A nucleation loop, in which the current on the reverse scan is higher than on the corresponding forward scan, is commonly observed during the first cycle.56,57 These features are all illustrated in Fig. 3 for the polymerization of a substituted pyrrole.58... 

When cells are grown on non-aliphatic substrates, such as glucose, fructose, acetate, or glycerol, these are converted to appropriate precursors that can be incorporated into poly(3HAMCL)s via fatty acid synthesis. The resulting PHAs have a monomer composition that is similar to that seen after growth on alkanes, often with 3-hydroxydecanoic acid as the major monomer. ( -Oxidation does not seem to play a role in the conversion of these substrates into poly(3HAMCL) since the addition of a -oxidation inhibitor did not affect the monomer composition [47]. 

Epoxide is formed side by side with oligomeric peroxide during monomer oxidation. Miller and Mayo [54] assumed the following mechanism of decomposition of formed radicals ... 

Over 40 different chemical classes (i.e., acids, bases, monomers, oxidizers, etc.), with no single dominating class. 

The step 1 product and 2,2, 5,2"-terthiophene were reacted to form the copolymer using cyclic voltammetry and electro-copolymerizalion. Cyclic voltammetry in CH2CI2 containing 0.1 M tetrabutylammonium perchlorate supporting electrolyte indicated that the co-monomer oxidation began at approximately 0.70 V vs. Ag/Ag+. 

Oxidation of mixtures of 2,6-disubstituted phenols leads to linear poly(arylene oxides). Random copolymers are obtained by oxidizing mixtures of phenols. Block copolymers can be obtained only when redistribution of the first polymer by the second monomer is slower than polymerization of the second monomer. Oxidation of a mixture of 2,6-di-methylphenol (DM ) and 2fi-diphenylphenol (DPP) yields a random copolymer. Oxidation of DPP in the presence of preformed blocks of polymer from DMP produces either a random copolymer or a mixture of DMP homopolymer and extensively randomized copolymer. Oxidation of DMP in the presence of polymer from DPP yields the block copolymer. Polymer structure is determined by a combination of differential scanning calorimetry, selective precipitation from methylene chloride, and NMR spectroscopy. 

Hexafluoropropylene does not polymerize into a homopolymer easily therefore, it can be stored as a liquid. Flowever, it forms industrially useful copolymers and terpolymers with other fluorinated monomers. Oxidation of F1FP yields an intermediate for a number of perfluoroalkyl perfluorovinyl ethers.30... 

Pickup and Osteryoung investigated the polymerization of pyrrole in both the AlCl3/[C4py][Cl] molten salt [48] and the more conductive AlCl3/[C2mim][Cl] [49]. Synthesis of poly(pyrrole) is only possible in neutral melts. In basic melts oxidation of Cr to CI2 occurs before the monomer oxidation and in acidic melts no films are produced due to the formation of a 1 1 AlC -pyrrole adduct, as determined by NMR spectroscopy [50]. 

According to Eq. (25), a cyclic phosphite monomer (MN) 38 is oxidized to a phosphate unit yielding copolymer 40 whereas the a-keto acid monomer (ME) 39 is reduced to the corresponding a-hydroxy acid ester. Thus, the term redox copolymerization has been proposed to designate this type of copolymerization in which one monomer is reduced and the other monomer oxidized. The redox copolymerization clearly differs from the so-called redox polymerization in classical polymer chemistry where the redox reaction between the two catalyst components (oxidant and reductant) is responsible for the production of free radicals. 

The anionic polymerization of optically active (+)-or (—)-m-tolyl vinyl sulfoxide ([a]o +486°, —486°) using BuLi or BuLi—(—)-Sp leads to an optically active polymer, 37 [[cx]d +274° to +311° (from (+)-monomer) [cx]d -272° to -310° (from (-)-monomer)]. Oxidation of 37 afforded polymer 38 with an achiral... 

The counterion should also be stable both chemically and electrochemically otherwise, breakdown products may interfere in the polymerization process. If it is electroactive at potentials lower than the monomer oxidation potential, it can be incorporated using potentiostatic methods but not with constant-current techniques because the counterion will be preferentially oxidized. 

Electrochemical polymerization is routinely carried out in an acidic aqueous solution of aniline. This low pH is required to solubilize the monomer and to generate the PAn/HA (HA = acid) emeraldine salt as the only conducting form of PAn. Constant potential (potentiostatic) or potentiodynamic techniques are generally employed because the overoxidation potential for PAn is very close to that required for monomer oxidation. 

Electrode Adsorption Behavior of Monomers. In order to understand the pure adsorption behavior of the monomers at the Pt electrode, we carried out the EQCM experiments presented in Figs. 9 and 10. In Fig. 9, monomers in the absence of an apphed potential and at pH 6.5 were allowed to interact with the Pt electrode surface on the quartz crystal [70]. The results clearly indicated that even at the high concentration of 3 mM, Httle, if any, L-tyrosine adsorbs to the Pt surface. On the other hand, DEDT at the low concentration of 0.032 mM, well below the cmc, adsorbs to the Pt surface readily from solution. These results are in agreement with the Fig. 8 cycHc voltage sweep results where the electropolymerized DEDT rapidly formed a film that almost completely prevented monomer oxidation. In contrast, L-tyrosine had less restricted access to the electrode, since a significant level of monomer... 

From X-ray diffraction, it is known that semicrystalline polythiophene powder consists of completely co-planar molecules [64], in contrast to the oligomers with chain length of and above three. The crystallinity of powders of chemically coupled polythiophene prepared by monomer oxidation with iodine, increases from 35% as synthesized up to 56% after annealing at 753 K for 30 minutes [65]. At the same time the residual iodine content decreased from 3.17% as synthesized to 0.13% after the heat treatment. Whereas annealing at 753 K leads to a first degradation of the polymer, heat treatment at 673 K results in polythiophene with chains of approximately 1200 thiophene units. Electrochemically polymerized polythiophene gives a completely different X-ray diffraction pattern [66],... 

Procedure 5-6 is an example of a redox-initiated system involving the use of three separate streams to add monomer, oxidizer, and reducer. 

The thermo-oxidative degradation products of PMMA are those from monomer oxidation, as well as from oxidation of carbon monoxide and methane. 

One-pot synthesis approaches have also been developed, involving sonication [23,26], and UV- [15,28] or y-irradiation [27,32,41]. It was found that sonication and y-irradiation resulted in acceleration of the nanocomposite formation by inducing radical formation (i.e. H2O H + OH"). The hydrogen and hydroxyl radicals drive both metal-ion reduction and monomer oxidation. The role of H2O2, either available in the solution or generated through radical recombination, for the enhancement of the rate of polymerization was extensively discussed [23,26]. 

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