Search results for "quantitative"

One- and two-component bottle-brush polymers: simulations compared to theoretical predictions

2007

Scaling predictions and results from self-consistent field calculations for bottle-brush polymers with a rigid backbone and flexible side chains under good solvent conditions are summarized and their validity and applicability is assessed by a comparison with Monte Carlo simulations of a simple lattice model. It is shown that under typical conditions, as they are also present in experiments, only a rather weak stretching of the side chains is realized, and then the scaling predictions based on the extension of the Daoud-Cotton blob picture are not applicable. Also two-component bottle brush polymers are considered, where two types (A,B) of side chains are grafted, assuming that monomers of …

Parity violation energy of biomolecules - III: RNA

2006

The energy of parity-violation associated with a typical DNA double helix is estimated with ab initio techniques. It is shown that weak-nuclear interactions do not favor the formation of the double helices found in nature. Possible implications regarding the potential effect of parity-violation interactions on the evolution of biological homochirality are discussed.

Structure and dynamics of amorphous polymers: computer simulations compared to experiment and theory

2004

This contribution considers recent developments in the computer modelling of amorphous polymeric materials. Progress in our capabilities to build models for the computer simulation of polymers from the detailed atomistic scale up to coarse-grained mesoscopic models, together with the ever-improving performance of computers, have led to important insights from computer simulations into the structural and dynamic properties of amorphous polymers. Structurally, chain connectivity introduces a range of length scales from that of the chemical bond to the radius of gyration of the polymer chain covering 2–4 orders of magnitude. Dynamically, this range of length scales translates into an even larg…

KINETICS OF POLYMER EJECTION FROM CAPSID CONFINEMENT: SCALING CONSIDERATIONS AND COMPUTER EXPERIMENT

2012

We investigate the ejection dynamics of a flexible polymer chain out of confined environment by means of scaling considerations and Monte Carlo simulations. Situations of this kind arise in different physical contexts, including a flexible synthetic polymer partially confined in a nanopore and a viral genome partially ejected from its capsid. In the case of cylindric confinement the entropic driving force which pulls the chain out of the pore is argued to be constant once a few persistent lengths are out of the pore. We demonstrate that in this case the ejection dynamics follows a [Formula: see text]-law with elapsed time t. The mean ejection time τ depends nonmonotonically on chain length…

Polymer-induced shape changes and capping in giant liposomes

1995

We studied the coupling of a polymeric amphiphile undergoing a transition from an expanded to a collapsed state of the hydrophilic polymer chain upon heating above 29°C with free and solid supported lipid bilayers. Lateral diffusion measurements and studies of vesicle shape-changes confirmed previous calorimetric studies, suggesting that the amphiphile remains incorporated in the giant vesicles and the supported bilayer during the transition. The two-dimensional hydrodynamic radii of the amphiphile in the expanded and collapsed state was measured by making use of the strong quadratic dependence of the diffusion coefficient on the radius of the diffusant (D ∞ r−2) due to the frictional coupl…

Counterion-Mediated Crossing of the Cyanine Limit in Crystals and Fluid Solution: Bond Length Alternation and Spectral Broadening Unveiled by Quantum…

2020

Absorption spectra of cyanine⊕·Br⊖ salts show a remarkable solvent dependence in non/polar solvents, exhibiting narrow, sharp band shapes in dichloromethane but broad features in toluene; this chan...

Halogen bonding enhances nonlinear optical response in poled supramolecular polymers

2015

We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems. acceptedVersion Peer reviewed

Pulling Single Adsorbed Bottle-Brush Polymers off a Flat Surface: A Monte Carlo Simulation

2013

Force versus extension behavior of flexible chains and semiflexible bottle-brush polymers adsorbed from a good solvent on a planar substrate is studied by Monte Carlo simulation of the bond fluctua...

Modification of Polymers in Supercritical Carbon Dioxide

2003

The interaction of scFluids and polymers are governed by the intermolecular forces between solvent-solvent, solvent-polymer segment, and polymer segment-segment pairs. Because of its symmetry, within reasonable pressure values, CO2 does not have a dipole moment, but it does have a quadrupole moment significant over a much shorter distance than dipolar interactions. The quadrupole moment and the Lewis acidity of CO2 imparts to the carbon dioxide the peculiarity to be a solvent for selected classes of polymers like perfluorinated polyacrylates, polysiloxanes and polyether-polycarbonate diblock copolymers [1–3].

1988

The unperturbed dimensions parameter KΘ is one of the most important characteristics of a polymer chain. For binary systems (polymer/solvent) and mostly for ternary systems (polymer/solvent(1)/solvent(2)) the KΘ values show large discrepancies with respect to those under thetaconditions in a single solvent. These discrepancies can be explained by considering that the interaction parameter χ (and consequently the coil dimensions or the number of intramolecular contacts between polymer segments) changes with molecular weight M. Assuming this dependency, a modified Stockmayer-Fixman equation is proposed from which a unique value of KΘ for a given polymer, independent of M, is obtained. The use…