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Reptation

    Reptation is a specific (snake-like) thermal motion of very long linear macromolecules in the melts and concentrated solutions of polymers These systems called also entangled polymers are characterized with effective internal scale commonly known as ‘the length of macromolecule between adjacent entanglements’ Me . The concept of reptation was introduced into polymer physics by Pierre-Gilles de Gennes De Gennes PG Reptation of a polymer chain in the presence offixed obstacles J. Chem Phys 55, 572 - 579 (1971) to explain the dependence of mobility of macromolecule on its length
    The linear macromolecules reptate if the length of macromolecule M is bigger than ten times ‘the length of macromolecule between adjacent entanglements’ Me . There is no reptation motion for polymers with M<10 Me so that the point 10 Me is a point of dynamic phase transition Due to the reptation motion the coefficient of self-diffusion and conformational relaxation times of macromolecules depend on the length of macromolecule as M-2 and M3 correspondingly Pokrovskii VN A justification of the reptation-tube dynamics of a linear macromolecule in the mesoscopic approach Physica A 366 88-106 (2006)Pokrovskii VN The reptation and diffusive modes of motion of linear macromolecules J. Exper Theor Phys 106 (3) 604-607 (2008)The conditions of existence of reptation in the thermal motion of macromolecules of complex architecture (macromolecules in the form of branch star comb and others) has not established yet

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