Stabilizers, polymers containing

The generally low chemical, mechanical and thennal stability of LB films hinders their use in a wide range of applications. Two approaches have been studied to solve this problem. One is to spread a polymerizable monomer on the subphase and to polymerize it either before or following transfer to the substrate. The second is to employ prefonned polymers containing hydrophilic and hydrophobic groups. 

Metal carboxyiates have been considered as nucleophilic agents capable of removing aHyUc chlorine and thereby affording stabilization (143). Typical PVC stabilizers, eg, tin, lead, or cadmium esters, actually promote the degradation of VDC polymers. The metal cations in these compounds are much too acidic to be used with VDC polymers. An effective carboxylate stabilizer must contain a metal cation sufftcientiy acidic to interact with aHyUc chlorine and to facihtate its displacement by the carboxylate anion, but at the same time not acidic enough to strip chlorine from the polymer main chain (144). 

Vinyhdene chloride polymers containing stabilizing features have been prepared. In general, these have been polymers containing comonomer units with functionahty that can consume evolved hydrogen chloride and do so in such a manner that good radical scavenging sites are exposed (145,146). 

It has been observed that all the phenoxaphosphine ring-containing polymers have excellent thermal stability and show better heat resistance than open-chain phosphorus containing polymers. The phenoxaphosphine polymers containing aromatic rings in the backbone show little degradation below 400°C in air. 

It is well known that the trimeric phosphonitri-lic chloride can be polymerized, at 200-300°C, to poly(dichlorophosphazene) (1), hereafter this polymer will be referred to as chloropolymer. Since this polymer contains hydrolytically-unstable chlorine groups, these groups are usually replaced with various alcohols, phenols, or amines to import the polymer stability. In our laboratories, the substitution is generally with alcohols or phenols. The reaction scheme is shown in Figure 1. 

A. G. Sommese and R. Nagarajan. Settling stabilization of polymer containing particle dispersions in oil. Patent US 5438088, 1995. 

Andrianov and Zhdanov have developed a method for the synthesis of polymers containing heterochain and carbon-chain units by free-radical copolymerization of metal-containing polyorganosiloxanes bearing a pendant vinyl group with vinyl monomers. The copolymers thus obtained display increased thermal stability and can be used for the production of laminated plastics, adhesives and other valuable materials 53),... 

Organotin polymers containing one carboxyalkyl group bound to the tin atom in each recurring monomer unit are obtained by polymerization of an organotin acid of the type Sn[(CH2)mCOOH]4. in aqueous medium at 60 °C. The powdery products are used as biocides and stabilizers for synthetic polymers 81). 

Another recent innovation to improve the efficiency of polymer addition to water and derive the maximum yield from hydrophylic polymers was introduced by Briscoe(165,166). The method involved the preparation of a stabilized polymer slurry (SPS) to be added to water. Briscoe used water as the suspension liquid, usually also containing dissolved KC1 as a clay stabilizer, and formulated a package of inhibitors (borate and caustic) to prevent the polymer from hydrating until the pH was lowered. These concentrates remain in routine use today. 

The third class of polymers contains one or more nitrogen atoms on a pendant sidechain in the polymer repeat unit (13,14). The nitrogen may or may not be quaternary. In addition to being swelling clay stabilizers, these polymers also stabilize nonswelling mineral fine particles. Limited molecular weight data ig available but molecular weight values from 50,000 to 1 X 10 daltons have been cited for various polymers. 

Average treatment volume was 600 gallons. All fluids contained 1% (by volume) of water wetting non-emulsifier. The treatments utilizing a cationic organic polymer included the polymer in all aqueous based fluids. The reported polymer concentration of one percent by volume of the aqueous polymer solution as supplied. Active polymer concentration is actually less than this. When the clay stabilization polymer was part of the well treatment, a non-ionic water wetting nonemulsifier was used. 

Ando and co-workers have reported the synthesis of a silyl-carborane hybrid diethynylbenzene-silylene polymer (108) (Fig. 66) possessing high thermal stability.136 The polymer contained Si and —C=C— group in the main chain and m-carborane and vinyl groups in the side chain. The 5% weight-loss temperature of the cured polymer in air was over 1000°C as determined by thermogravimetric analysis. 

The final class of polymers containing carboranyl units to be mentioned here is the polyphosphazenes. These polymers comprise a backbone of alternating phosphorous and nitrogen atoms with a high degree of torsional mobility that accounts for their low glass-transition temperatures (-60°C to -80°C). The introduction of phenyl-carboranyl units into a polyphosphazene polymer results in a substantial improvement in their overall thermal stability. This is believed to be due to the steric hindrance offered by the phenyl-carborane functionality that inhibits coil formation, thereby retarding the preferred thermodynamic pathway of cyclic compound formation (see scheme 12). 

Polymers have served roles in PEM fuel cell cathodes such as modifiers to macrocycle-based electrodes to improve conductivity and stability,165 composite materials with heteropolyacids,166 and as precursors to pyrolyzed catalysts.38,112,132,133 However, as discussed in the previous section, the activity of nitrogen-containing carbon raises the possibility of non-metal electrodes functioning in a cathode environment. Likewise, researchers have noted ORR activity for various conducting polymers containing nitrogen, and recently studies on their potential use in PEM fuel cell cathodes have been reported. 

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