Generally,organic materials require stabilizer against uncontrolled oxidation which causes undesirable changes in the polymer, including chain scission,crossing, discoloration, as well as changes in mechanical and physical properties. The addition of stabilizers is the most convenient and effective way to block the degradation. Among stabilizers, sterically hindered phenolic (SHP) antioxidant and hinder amine light stabilizer (HALS) are known for scavenging radicals to prevent materials from degradation. However, low molecular weight stabilizers easily give off bad smell and depart from the polymers by the physical loss such as migration, evaporation, and extraction. To achieve long term stabilizing efficiency and avoid potential toxicity,polymeric stabilizers have gained much interest to overcome the physical loss and to enhance compatibility and durability. Our interest in the development of polymeric stabilizers based on SHP, HALS functionalized norbornene derivatives and ring-opening metathesis polymerization (ROMP) strategies had led us to recently communicate a series of polymers bearing SHP (Scheme 1) or HALS (Scheme 2) groups in side chain and their performance for scavenging radical. Therein, they were called radical scavenging polymers sometimes.Recently, it was proved that o-allylphenol could scavenge both alkyl and peroxy radical. As shown in scheme 3, (N, N-dimesityl-4, 5-dihydroimidazoi-2-ylidene)(PCy3)(Cl)2Ru=CHPh catalyst and o-allylphenol derivatives (CTA1 and CTA2) were employed in an attempt to prepare high molecular weight o-allylphenol stabilizers. The results were partly shown in Table 1. Compared Run 2 with Run 1 in Mn, it can be found that the high molecular weight PNB suffered depolymerization after the addition of allylphenol. Therefore, allylphenol derivatives appeared to be a chain transfer agent (CTA), leading to incorporation of the end allylphenol functional groups as well as causing the molecular weight to be reduced. As shown in scheme 3.1, an alternative approach used low catalyst loadings and gave the end allylphenol functionalized PNBs with tunable molecular weighs. Herein, the polymerization behavior and the properties of the resulting polymers will be reported.
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