Reptation (Chemie)
Vorlage:Orphan Reptation is a specific (snake-like) thermal motion of very long linear macromolecules (polymer chains) 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 [1] 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. [2][3] 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) have not been established yet.
References
- ↑ De Gennes P.G. Reptation of a polymer chain in the presence of fixed obstacles. J. Chem. Phys. 55, 572 - 579 (1971).
- ↑ Pokrovskii V.N. A justification of the reptation-tube dynamics of a linear macromolecule in the mesoscopic approach. Physica A 366, 88-106 (2006).
- ↑ Pokrovskii V.N. The reptation and diffusive modes of motion of linear macromolecules. J. Exper. Theor. Phys. 106 (3), 604-607 (2008).