  Communication Faster access than browser!

# Molar mass distribution

In linear polymers the individual polymer chains rarely have exactly the same degree of polymerization and molar mass, and there is always a distribution around an average value. 

## Arithmetic mean

In mathematics and statistics, the arithmetic mean (stress on third syllable of "arithmetic"), or simply the mean or average when the context is clear, is the sum of a collection of numbers divided by the number of numbers in the collection.

## Bar (unit)

The bar is a metric unit of pressure, but is not approved as part of the International System of Units (SI).

## Carothers equation

In step-growth polymerization, the Carothers equation (or Carothers' equation) gives the degree of polymerization, Xn, for a given fractional monomer conversion, p. There are several versions of this equation, proposed by Wallace Carothers who invented nylon in 1935.

## Chemical kinetics

Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes.

## Colligative properties

In chemistry, colligative properties are properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the nature of the chemical species present.

A cross-link is a bond that links one polymer chain to another.

## Degree of polymerization

The degree of polymerization, or DP, is the number of monomeric units in a macromolecule or polymer or oligomer molecule.

## Dispersity

A monodisperse, or uniform, polymer is composed of molecules of the same mass.

## Distribution function

In molecular kinetic theory in physics, a particle's distribution function is a function of seven variables, f(x,y,z,t;v_x,v_y,v_z), which gives the number of particles per unit volume in single-particle phase space.

## End-group

End groups are an important aspect of polymer synthesis and characterization.

## Gel permeation chromatography

Gel permeation chromatography (GPC) is a type of size exclusion chromatography (SEC), that separates analytes on the basis of size.

## Intrinsic viscosity

Intrinsic viscosity \left is a measure of a solute's contribution to the viscosity \eta of a solution.

## Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

## Living polymerization

In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to terminate has been removed.

## Mark–Houwink equation

The Mark–Houwink equation, also known as the Mark–Houwink–Sakurada equation or the Kuhn–Mark–Houwink–Sakurada equation or the Landau-Kuhn-Mark-Houwink-Sakurada equation gives a relation between intrinsic viscosity and molecular weight M: From this equation the molecular weight of a polymer can be determined from data on the intrinsic viscosity and vice versa.

## Mass distribution

In physics and mechanics, mass distribution is the spatial distribution of mass within a solid body.

## Molar mass

In chemistry, the molar mass M is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance.

## Molecular mass

Relative Molecular mass or molecular weight is the mass of a molecule.

## Osmometer

An osmometer is a device for measuring the osmotic strength of a solution, colloid, or compound.

## Polymer

A polymer (Greek poly-, "many" + -mer, "part") is a large molecule, or macromolecule, composed of many repeated subunits.

## Polymer fractionation

Polymers are chainlike molecules that are made of the same repetition unit.

## Proton nuclear magnetic resonance

Proton nuclear magnetic resonance (proton NMR, hydrogen-1 NMR, or 1H NMR) is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the structure of its molecules.

## Sedimentation

Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained and come to rest against a barrier.

## Size-exclusion chromatography

Size-exclusion chromatography (SEC), also known as molecular sieve chromatography, is a chromatographic method in which molecules in solution are separated by their size, and in some cases molecular weight.

## Small-angle neutron scattering

Small-angle neutron scattering (SANS) is an experimental technique that uses elastic neutron scattering at small scattering angles to investigate the structure of various substances at a mesoscopic scale of about 1–100 nm.

## Static light scattering

Static light scattering is a technique in physical chemistry that measures the intensity of the scattered light to obtain the average molecular weight Mw of a macromolecule like a polymer or a protein in solution.

## Step-growth polymerization

Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers.

## Ultracentrifuge

The ultracentrifuge is a centrifuge optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as (approx.). There are two kinds of ultracentrifuges, the preparative and the analytical ultracentrifuge.

## Vapor pressure osmometry

Vapor phase osmometry (VPO), also known as vapor-pressure osmometry, is an experimental technique for the determination of a polymer's number average molecular weight, Mn.

## Viscometer

A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid.

## Weighted arithmetic mean

The weighted arithmetic mean is similar to an ordinary arithmetic mean (the most common type of average), except that instead of each of the data points contributing equally to the final average, some data points contribute more than others.

## X-ray scattering techniques

X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystal structure, chemical composition, and physical properties of materials and thin films.

## References

Hey! We are on Facebook now! »