Polymer-bound stabilizers

This indicates that polymeric stabilizers having M > 800 have high resistance against extraction by components of foods, and, moreover, they do not enter into the metabolic cycle. Public concern over the contamination of the human environment can be thus satisfied. As a consequence, stabilizers like Poly AO-79 (97), Chimassorb 944 (161a) or Tinuvin 622 (146) may be legally used in stabilization of polymers in contact with food. Possibilities for application of other polymeric stabilizers for articles used in the home are open. Extractability problems may be thus overcome. Articles made from weather resistant butadiene based multiphase systems like ABS, MBS or MABS [84] stabilized in the most sensitive BR phase with polymer bound stabilizers may serve as an example. 

In the last few years, it has become fully appreciated that polymeric antioxidants are effective in retarding the thermal and autooxidation. Such polymer-bound stabilizers are similar in efficiency to the low molecular weight stabilizer incorporated into the polymer by blending. The polymer-bound stabilizer should have a flexible spacer between the point of attachment to the polymer and the functional group of the phenolic antioxidants. 

RL Gray, RE Lee. Polymer Bound Stabilizers-A Review Past and Present. Additives Conference, Orlando, FL, Feb. 16-18, 1998. 

Graham Boden Should we encourage the use of polymer-bound stabilizers to extend the life time of plastics and produce environmentally friendly materials, or is the expense not justified ... 

Lezsek Utracki That could be a good idea, but there are two difficulties the cost of polymer grafting, and the possibility of neutralization of the polymer-bound stabilizers by additives used in other plastics that are commingled with. 

The first reports on polymer-bound phenolic stabilizers for the preparation of poly[propene-co-4-(hept-6-enyl)-2,6-di-terf-butylphenol] show much higher stability of the resulting copolymer toward irradiation than commercial available poly(propene) containing non-polymer-bound stabilizers.In the copolymerization reactions of... 

For the last two decades, we have been studying the concept of polymerizable, polymeric or polymer-bound stabilizers. Vie have focused our efforts on non-leachable ultraviolet (UV) stabilizers with a major emphasis on 2(2-hydroxyphenyl)2H-benzotriazole derivatives and have reported extensively on this subject [1]. 

Trimethylsilyl ethers are quite susceptible to acid hydrolysis, but acid stability is quite dependent on the local steric environment. For example, the 17o -TMS ether of a steroid is quite difficult to hydrolyze. TMS ethers are readily cleaved with the numerous HF-based reagents. A polymer-bound ammonium fluoride is advantageous for isolation of small polar molecules. ... 

A polymer-bound hindered amine light stabilizer [P-HALS] has been synthesized by terminating the living anionic polymerization of isoprene with 4(2,3-epoxy pro-poxy)-1,2,2,6,6-pentamethylpiperidine followed by hydrogenation of the resulting polymer to E-P copolymer using Zeigler type catalyst [40] ... 

Modes of attachment of functional groups to crosslinked polystyrene are discussed ( 1). Attention is drawn to improved stability and activity of polymer-bound reagents and catalysts incorporating dimethylene spacer between polystyrene aryl and functional group heteroatom, and the simplicity and versatility of their synthesis through high-conversion functional group modifications. 

It seemed reasonable to anticipate that the synergism of these two features (high heparin content and stability of the resultant materials) would result in long-term thromboresistant polymers. The in vivo tests revealed, however, their extremely low thromboresistance as compared to the ionically bound heparin-containing polymers, in particular. The effect is assumed to be caused by a lack of sufficient mobility of the polymer-bound heparin molecules, which prevents the performance of the intrinsic anticoagulant properties of heparin. 

Arasabenzene, with chromium, 5, 339 Arcyriacyanin A, via Heck couplings, 11, 320 Arduengo-type carbenes with titanium(IV), 4, 366 with vanadium, 5, 10 (Arene(chromium carbonyls analytical applications, 5, 261 benzyl cation stabilization, 5, 245 biomedical applications, 5, 260 chiral, as asymmetric catalysis ligands, 5, 241 chromatographic separation, 5, 239 cine and tele nucleophilic substitutions, 5, 236 kinetic and mechanistic studies, 5, 257 liquid crystalline behaviour, 5, 262 lithiations and electrophile reactions, 5, 236 as main polymer chain unit, 5, 251 mass spectroscopic studies, 5, 256 miscellaneous compounds, 5, 258 NMR studies, 5, 255 palladium coupling, 5, 239 polymer-bound complexes, 5, 250 spectroscopic studies, 5, 256 X-ray data analysis, 5, 257... 

A material with nitrogen-coordinated Ru was obtained from a silica-linked 2-(phenylazo)pyridine ligand. Results for cyclobutanol oxidation with 02 and the sacrificial oxidant isobutyraldehyde indicate that one- and two-electron oxidations occur simultaneously. The stability of the catalyst is not always guaranteed, probably because acids may be formed in oxidations of alcohols (284). Leaching problems are also encountered with a polymer-bound Ru Schiff base complex, used in oxidation of benzyl alcohol (285). 

These results lead to the following scheme for the cooperative disordering of these polynucleotides by Cu(II). Initial increments of Cu(II) bind to phosphate and stabilize the helical structure, as the initial increase in rotation in Figure 4 demonstrates. As the concentration of polymer-bound Cu(II) increases, crosslinking to bases takes place. Such crosslinks may be within the same polymer strand or between different strands. Once such crosslinking has begun, additional cooperative cross-... 

Compared to other carriers and particularly functionalized polymers the stability of the rhodium catalyst in the zeolite medium is far superior presumably due to the stronger Rh-0 bond compared to P-Rh bond in phosphine bound rhodiumCI)dicarbonyl. Also the cage structure of the zeolite almost precluded inner interaction of the active species and therefore their association into inactive compounds. 

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