PHYSICAL-CHEMISTRY OF TOPOLOGICAL DISORDER IN POLYMERS - RECONSTRUCTION OF SORPTION CENTERS AND ANTIOXIDANT EFFECTIVITY IN ISOTACTIC POLYPROPYLENE

Formation and transformation of additive sorption centers in isotactic polypropylene was studied. According to a two-component model of a po lymeric substance, these centers are formed around the elements or uni ts of disorder (UODs) which are knots, folds, and other interlacements of long polymer chains. These elements are formed at the precipitatio n of the polymer and are stable even in the polymer melt because of th e great lengths of the polymer chains. In some cases, the elements una ble to sorb the given compound may be transformed into the sorption ce nters for it. When present in the sorption center, antioxidant molecul es cannot move and react with macroradicals participating in the polym er oxidation, which results in the dependence of the so-called critica l antioxidant concentration on that of the sorption centers. The theor y of the formation and reconstruction of UOD-based sorption centers is discussed. Formation of a polymeric substance may be divided into two stages: polymerization or polycondensation of low-molecular compounds and self-assembling of macromolecules into polymeric material. Opposi te to numerous investigations of the first step of this process and of the properties of the end products, the stage of transition of the ma cromolecules into the polymeric material and possibilities of regulati ng its properties in this stage are usually neglected. (C) 1998 John W iley & Sons, Inc. J Appl Polym Sci 69: 1847-1854, 1998.