Polystyrene peroxide formation

In order to avoid chemical compounds at all, it is also possible to apply a high voltage to kill microbes on surfaces. It was found that a direct current kills E. coli cells, probably by heat or by hydrogen peroxide formation [84], Microbial cells can be effectively killed by using pulsed electric fields (PEF), probably by frequently disturbing the cell membrane potential [85], PEF that was found to lower microbial cell numbers in food and drinks was also shown to effectively kill E. coli and Listeria innocua cells attached to polystyrene beads [86], This demonstrates the potential of applying this purely physical method to surfaces as well. 

It is well known that several monomers,such as styrene, < ( methylstyrene,isoprene,vinyl acetate (jj) have shown formation of oharge-transfer complexes in the presence of oxygen. Polystyrene peroxide is formed by photoirradiation of charge-transfer complex in the initial stage of polymerisation and the further photoinduced decomposition of the polystyrene peroxide initiates the polymerisation of styrene. On the other way,the reaction between excited state of styrene and oxygen may induce the formation of an alternating copolymer with peroxide groups -0-0- in-backbone. 

The vector fluid concept was first suggested for a polyethylene (PE)/polyamide (PA) reactive blending system [12], as mentioned earlier in this chapter. This concept is interesting because it has the potential to provide a compatibilization method for polymers that have no chemical functionalities suitable for copolymer formation during melt blending (e.g. the case of polyolefin and polystyrene). It has been seen that the blends of polyolefin/polystyrene are difficult to compatibilize in situ by simply adding a free radical initiator into the blending process. Usually, flie pre-made block or reactive polymers or copolymers, which can be expensive, are needed for polyolefin/polystyrene compatibilization [15-17]. If a suitable vector fluid can be found for the polyolefin/ polystyrene/peroxide in situ compatibilization, the process could become more controllable and more cost efficient. 

Numerous polymers autooxidize to form peroxides. These compositionally, and thus calorimetrically, ill-defined products may be considered polymeric peroxides. However, one well-defined polymeric peroxide is that of polystyrene with the repeat unit —CHa-CH(CeH5)-0-0-. Through a combination of combustion and reaction calorimetry (chain degradation to benzaldehyde and formaldehyde), a solid phase enthalpy of formation of this species was found to be 27 21 kJ mol . Much the same procedure was used to determine the enthalpy of degradation for the polyperoxide polymers of 2-vinylnaphthalene and the isomeric 1- and 2-propenylnaphthalene to form the related acylnaphthalene and formaldehyde. Numerically, the reaction enthalpy values for these last three polyperoxides were —206+4, —222 + 8 and —222 + 10 kJmol, to be compared with the aforementioned polystyrene with a value of —209 + 8 kJ mol. However, in the absence of enthalpy of formation data for the decomposition products in the naphthalene case, we hesitate to derive enthalpies of formation for these three species. ... 

The graft copolymerization of acrylonitrile onto polystyrene was attempted using benzoyl peroxide, di-/-butylperoxide, and 2,5-dimethyl-2,5-di-(/-butylperoxy)hexane as initiators. In all cases no increase in mass of the polystyrene was observed. Attempts were also made to test whether the polystyryl radical was ever formed by combining the initiator and the polymer or the initiator, polymer and a nitroxide radical trap. In the first case the formation of a radical must lead to cross-linking of the polymer and in the second case the polystyryl radical will be trapped by the nitroxide. ... 

The [Ru(bpy)3]2+ photosensitized reduction of methyl viologen (MV2+) proceeds rapidly in water-swollen iminodiacetic acid type chelate resin beads which adsorb both [Ru(bpy)3]2+ and MV2+ (RM resin). The reduction takes place with the aid of polymer-bound iminodiacetate as a donor 102). Photosensitized formation of hydrogen peroxide occurs in an aqueous solution containing RM resin and oxygen molecules (Fig. 8)102 The some reaction also occurs using a polystyrene-coated filter paper, onto which both [Ru(bpy)3]2 + and MV2+ were adsorbed 103). 

Many researchers have attempted to make branched polystyrene in continuous bulk radical polymerization processes. Approaches involving the addition of additives to the polymerization process which lead to branching inside the polymerization reactor always lead to gel problems. Examples include addition of divinylmonomer [4], vinyl peroxides (e.g. I) [5,6], branched peroxides (e.g. II) [7], vinyl-functional chain transfer agents (III) [8], and the use of addition-fragmentation chain transfer agents that lead to the formation of polystyrene macromonomers (Figure 24.3) [9]. 

An example of an excellent latent functional group for this purpose is benzocyclobutene (BCB) [13]. Polystyrene made using a BCB functional peroxide leads to the formation of linear polystyrene because the BCB moieties are inert below 180°C. Once the polymer exits the polymerization reactor it is... 

The effect of ozone on saturated polymers, polyolefins (PO) and polystyrene (PS) in particular, is underrated. Ozone is involved in the initiation phase of their oxidation. Its attack results in formation of R, RO, ROO, ROOH and I CO species in PO, and free radicals and polymeric peroxides in PS. Moreover, ozone decomposes hydroperoxides into oxygen-centred radicals RO, ROO and HO. ... 

The bulk polymerization of DAP has been studied at 60°C with azobisisobutyronittile as initiator (39). Branching of the polymer chains is confirmed by enhanced broadening of the molecular weight distribution imtil gdation occurred at about 25% conversion. In copolymerizations with styrene at 80°C with benzoyl peroxide as initiator the gel time increases with fraction comonomer in the feed. Both the yidd of gd and the styrene units in the gel increase with copolymerization time. Heating DAP prepolymer with styrene in benzene solution at 60—100°C with the initiators gives no gelation, but slow formation of polystyrene and copolymer. 

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