What Happens When Threading is Suppressed in Blends of Ring and Linear Polymers?

Self-diffusivity of a large tracer ring polymer, D r , immersed in a matrix of linear polymers with N l monomers each shows unusual length dependence. D r initially increases, and then decreases with increasing N l . To understand the relationship between the nonmonotonic variation in D r and threading by matrix chains, we perform equilibrium Monte Carlo simulations of ring-linear blends in which the uncrossability of ring and linear polymer contours is switched on (non-crossing), or artificially turned off (crossing). The D r ≈ 6 . 2 × 10 - 7 N l 2 / 3 obtained from the crossing simulations, provides an upper bound for the D r obtained for the regular, non-crossing simulations. The center-of-mass mean-squared displacement ( g 3 ( t ) ) curves for the crossing simulations are consistent with the Rouse model; we find g 3 ( t ) = 6 D r t . Analysis of the polymer structure indicates that the smaller matrix chains are able to infiltrate the space occupied by the ring probe more effectively, which is dynamically manifested as a larger frictional drag per ring monomer.

The influence of small amounts of linear polycaprolactone chains on the crystallization of cyclic analogue molecules

C-PCL/L-PCL blends show a synergistic decrease in their isothermal crystallization rates as compared to the expectation of a simple mixing law due to the threading effect of the linear on the cyclic chains.

Understanding the dynamics of rings in the melt in terms of the annealed tree model

The dynamical properties of a long polymer ring in a melt of unknotted and unconcatenated rings are calculated. We re-examine and generalize the well known model of a ring confined to a lattice of topological obstacles in light of the recently developed Flory theory of untangled rings which maps every ring on an annealed branched polymer and establishes that the backbone associated with each ring follows self-avoiding rather than Gaussian random walk statistics. We find the scaling of the ring relaxation time and diffusion coefficient with ring length, as well as the time dependence of stress relaxation modulus, zero shear viscosity and the mean square averaged displacements of both individual monomers and the ring's mass centre. Our results agree within error bars with all available experimental and simulation data of the ring melt, although the quality of the data so far is insufficient to make a definitive judgement for or against the annealed tree theory. At the end we review briefly the relation between our findings and experimental data on chromatin dynamics.

Viscosity of ring polymer melts

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as function of the number of entanglements Z. In the unentangled regime η0,linear/η0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/η0,ring=2. In the entanglement regime, the Z-dependence of rings viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 Collapse

Key Words

• entanglements
• molecular weight
• purification
• ring polymers
• viscosity

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Grants

• P01 HL108808 NHLBI NIH HHS
• P50 HL107168 NHLBI NIH HHS

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Affiliation(s)

Rossana Pasquino FORTH, Institute for Electronic Structure and Laser, Heraklion 71110, Greece
Thodoris C Vasilakopoulos University of Athens, Department of Chemistry, Athens 15771, Greece
Youn Cheol Jeong Pohang University of Science and Technology, Division of Advanced Materials Science and Department of Chemistry, Pohang 790-784, Korea
Hyojoon Lee Pohang University of Science and Technology, Division of Advanced Materials Science and Department of Chemistry, Pohang 790-784, Korea
Simon Rogers FORTH, Institute for Electronic Structure and Laser, Heraklion 71110, Greece
George Sakellariou University of Athens, Department of Chemistry, Athens 15771, Greece
Jürgen Allgaier Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Atsushi Takano Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
Ana R Brás Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Taihyun Chang Pohang University of Science and Technology, Division of Advanced Materials Science and Department of Chemistry, Pohang 790-784, Korea
Sebastian Gooßen Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Wim Pyckhout-Hintzen Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Andreas Wischnewski Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Nikos Hadjichristidis University of Athens, Department of Chemistry, Athens 15771, Greece ; King Abdullah University of Science and Technology, Division of Physical Sciences & Engineering, KAUST Catalysis Center, Polymer Synthesis Laboratory, Thuwal, Kingdom of Saudi Arabia
Dieter Richter Forschungszentrum Jülich GmbH, Jülich 52428, Germany
Michael Rubinstein Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
Dimitris Vlassopoulos FORTH, Institute for Electronic Structure and Laser, Heraklion 71110, Greece ; University of Crete, Department of Materials Science & Technology, Heraklion 71003, Greece

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