Antioxidants copolymerised

Oxidative attack at random along the chain leading to chain scission and subsequent depolymerisation. Initial chain scission is reduced by the use of antioxidants (see Chapter 7) and in recent formulations hindered phenols seemed to be preferred. It is reported that 2,2 -methylenebis-(4-methyl-6-t-butylphenol) is present in Celcon and 4,4 -butylidene bis-(3-methyl-6-t-butylphenol) in Derlin. The copolymerisation helps to reduce the rate of depolymerisation where initiation of depolymerisation is not completely prevented. 

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

CS-grafted copolymers Copolymerisation reactions Modifying the chemical and physical properties of chitin and CS to widen their practical use Tissue engineering, antibacterial and superoxide scavenging (antioxidant) activity... 

A more versatile method of achieving antioxidant substantivity in rubbers is to chemically attach the antioxidant to the polymer. A commercial nitrile-butadiene rubber contains a copolymerised antioxidant, N-methacrylamidodiphenylamine (MADPA) which is much more resistant to oil extraction. A similar result has been achieved by forming an adduct of the analogous mercaptoacryloyl-amidodiphenylamine, MADA [reaction (3.18)] by processing of MADA with nitrile-butadiene rubber. 

Copolymerisation of styrene with butadiene (SB). This generates an impact-resistant polystyrene. This modification however results in a loss of transparency and necessitates the addition of stabilizers such as antioxidants. 

To prevent losses of antioxidants through volatilisation or extraction, Kline and Miller have proposed the use of antioxidants which copolymerise with butadiene and styrene or butadiene and acrylonitrile. They draw particular attention to N-(4-anilinophenyl) methacrylic amide, which is used for a number of special grades. 

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