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Related Concept Videos

Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
Intermolecular Forces03:13

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
Intermolecular Forces03:13

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
Noncovalent Attractions in Biomolecules02:35

Noncovalent Attractions in Biomolecules

Noncovalent attractions are associations within and between molecules that influence the shape and structural stability of complexes. These interactions differ from covalent bonding in that they do not involve sharing of electrons.
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...
Noncovalent Attractions in Biomolecules02:35

Noncovalent Attractions in Biomolecules

Noncovalent attractions are associations within and between molecules that influence the shape and structural stability of complexes. These interactions differ from covalent bonding in that they do not involve sharing of electrons.
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...
Van der Waals Interactions01:24

Van der Waals Interactions

Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions between particles with permanent, partial, or temporary charges. The intermolecular forces between neutral atoms and molecules are ion–dipole, dipole–dipole, and dispersion forces, collectively known as van der Waals forces.

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Updated: May 14, 2026

Forming Giant-sized Polymersomes Using Gel-assisted Rehydration
08:45

Forming Giant-sized Polymersomes Using Gel-assisted Rehydration

Published on: May 26, 2016

Polymer-mediated entropic forces between scale-free objects.

Mohammad F Maghrebi1, Yacov Kantor, Mehran Kardar

  • 1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. magrebi@mit.edu

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|February 2, 2013
PubMed
Summary
This summary is machine-generated.

Confining polymers near scale-invariant obstacles like cones generates repulsive entropic forces. The force magnitude depends universally on the polymer

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Area of Science:

  • Polymer Physics
  • Soft Matter Physics
  • Statistical Mechanics

Background:

  • Polymers confined by obstacles experience reduced configurations and entropy loss.
  • This entropy loss contributes a repulsive entropic force.
  • Scale-invariant obstacles (cones, wedges) simplify the analysis of these forces.

Purpose of the Study:

  • To investigate entropic forces on polymers near scale-invariant obstacles.
  • To determine the universal amplitude (A) and anomalous scaling exponents (η) of these forces.
  • To analyze ideal and self-avoiding polymers attached to cone tips.

Main Methods:

  • Analytical calculations
  • Numerical simulations
  • Epsilon-expansion techniques

Main Results:

  • Derived the universal form of entropic force F = Ak(B)T/h at close proximity (h << R(0)).
  • Computed the anomalous scaling exponent η for polymers near cones and plates.
  • Quantified entropic forces, finding ~0.1 pN at 0.1 μm for single polymers, higher for star polymers.

Conclusions:

  • Entropic forces near scale-invariant obstacles are universal and depend on geometry.
  • The computed exponent η characterizes polymer behavior in confined geometries.
  • Results provide insights into polymer interactions in nanoscale confinement.