10 research outputs found
Dynamics of a three-dimensional inextensible chain
In the first part of this work the classical and statistical aspects of the
dynamics of an inextensible chain in three dimensions are investigated. In the
second part the special case of a chain admitting only fixed angles with
respect to the axis is studied using a path integral approach. It is shown
that it is possible to reduce this problem to a two-dimensional case, in a way
which is similar to the reduction of the statistical mechanics of a directed
polymer to the random walk of a two-dimensional particle.Comment: 15 pages, 3 figures, LaTeX, version accepted for publicatio
The size and shape of snowflake star polymers in dilute solutions: analytical and numerical approaches
We investigate the conformational properties of a multi-branched polymer
structure with a dendrimer-like topology, known as a snowflake polymer. This
polymer is characterized by two parameters: , which represents the
functionality of the central star-like core, and , which represents the
functionality of the side branching points. To analyze the conformational
properties, we have employed various approaches, including analytical methods
based on direct polymer renormalization and the Wei's approach as well as
numerical molecular dynamics simulations. These methods have allowed us to
estimate a size and shape characteristics of the snowflake polymer as functions
of and . Our findings consistently demonstrate the effective
compactification of the typical polymer conformation as the number of branching
points increases. Overall, our study provides valuable insights into the
conformational behavior of the snowflake polymer and highlights the impact of
branching parameters on its overall compactness
Description of the dynamics of a random chain with rigid constraints in the path integral framework
In this work we discuss the dynamics of a three dimensional chain which is
described by generalized nonlinear sigma model The formula of the probability
distribution of two topologically entangled chain is provided. The interesting
case of a chain which can form only discrete angles with respect to the
axis is also presented.Comment: 4 pages. To appear in the proceedings of `Path Integrals - New Trends
and Perspectives`, 23-28 September 2007, Dresden, German
Super-soft and super-elastic dry gels
Molecular combs and bottlebrushes are a new class of polymer architecture allowing for anomalously low density of entanglements in polymer melts. The conformations and rheological properties of melts of these branched macromolecule composed of a flexible backbone and side chains densely tethered to it are investigated theoretically, experimentally and by computer simulations.1,2 We develop the rule for dialing in the desired value of the melt plateau modulus of these molecules as low as 1000 times below the conventional values for linear polymer melts and experimentally verify the validity of our theory. The theory also predicts that elastomers made from these melts should be super-elastic and reversibly stretch up to ten times more than elastomers made from linear polymers. Hybrid networks with both permanent and reversible bonds made with this novel architecture are predicted to be super-tough and self-healing.
References W.F.M. Daniel, J. Burdynska, M. Vatankhah-Varnoosfaderani, K. Matyjaszewski, J. Paturej, M. Rubinstein, A.V. Dobrynin and S.S. Sheiko, Nature Materials, 2016, 15, 183-190. L.H Cai, T.E. Kodger, R.E. Guerra, A.F. Pegoraro, M. Rubinstein, and D.A. Weitz, Advanced Materials 2015, 27, 5132–5140
Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: Molecular Dynamics Simulation
The scission kinetics of bottle-brush molecules in solution and on an
adhesive substrate is modeled by means of Molecular Dynamics simulation with
Langevin thermostat. Our macromolecules comprise a long flexible polymer
backbone with segments, consisting of breakable bonds, along with two side
chains of length , tethered to each segment of the backbone. In agreement
with recent experiments and theoretical predictions, we find that bond cleavage
is significantly enhanced on a strongly attractive substrate even though the
chemical nature of the bonds remains thereby unchanged.
We find that the mean bond life time decreases upon adsorption by
more than an order of magnitude even for brush molecules with comparatively
short side chains $N=1 \div 4$. The distribution of scission probability along
the bonds of the backbone is found to be rather sensitive regarding the
interplay between length and grafting density of side chains. The life time
declines with growing contour length as ,
and with side chain length as . The probability
distribution of fragment lengths at different times agrees well with
experimental observations. The variation of the mean length of the
fragments with elapsed time confirms the notion of the thermal degradation
process as a first order reaction.Comment: 15 pages, 7 figure