Segmental immobilization

Segmental immobilization of chains in the presence of solid surfaces... 

On the nano-scale, the discrete moleculai structure of the polymer has to be considered. Segmental immobilization seems to be the primary reinforcing mechanism in true polymer nanocomposites at temperatures near and above the Tg. Reptation model and simple percolation model were used to describe immobilization of chains near solid nanopaiticles and to explain the peculiarities in the viscoelastic response of polymers near solid surfaces of lar ge polymer-inclusion contact areas. The inteiphase in the continuum sense does not exist at the nano-scale when relaxation processes in individual discrete chains are taken into account and the chains with retarded reptation catr be considered forming the iirterphase analogue irr the discrete matter. For a common polymer, all the chains in the composite are immobilized when the internal filler-matrix interface area reached about 42 m per 1 g of the nanocomposite. 

Block copolymers with stmctures such as A—B or B—A—B ate not thermoplastic elastomers, because for a continuous network to exist both ends of the elastomer segment must be immobilized in the hard domains. Instead, they are much weaker materials resembling conventional unvulcanized synthetic mbbers (4). 

Well-dispersed silica and polymer/Co(salen) segments at a molecular level were obtained. Nondestructive immobilization of Co(salen) complexes within silica aero- and xerogels was also achieved with the sol-gel method using silylether-appended salen.1227... 

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