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Related Concept Videos

Polymers: Defining Molecular Weight01:01

Polymers: Defining Molecular Weight

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Unlike small molecules with definite molecular weights, polymers are a mixture of individual polymer chains of varying lengths, each with a unique molecular weight.  So, the molecular weight of a polymer is expressed as an average value based on the average size of the polymer chains. The two most common forms of averages used for polymers are the number average molecular weight and weight average molecular weight.
The number average molecular weight (Mn) is the summation of the number...
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Polymers: Molecular Weight Distribution01:10

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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.
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Matrix-Assisted Laser Desorption Ionization (MALDI)01:08

Matrix-Assisted Laser Desorption Ionization (MALDI)

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Matrix-assisted laser desorption ionization (MALDI) is a powerful analytical technique used in mass spectrometry. It enables the identification and characterization of various biomolecules, including proteins, peptides, nucleic acids, and carbohydrates. MALDI spectrometry is widely employed in biological and medical research, as well as in fields like pharmacology and biochemistry.
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Molecular Weight of Step-Growth Polymers01:08

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Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
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High-Resolution Mass Spectrometry (HRMS)01:15

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The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For...
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MALDI-TOF Mass Spectrometry01:19

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Mass spectrometry is a powerful characterization technique that can identify and separate a wide variety of compounds ranging from chemical to biological entities, based on their mass-to-charge ratio (m/z). The instruments that allow this detection, known as mass spectrometers, have three components: an ion source, a mass analyzer, and a detector. These spectrometers differ based on the nature of their ion source and analyzers.
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Atomic-Scale Imaging of Polymers and Precision Molecular Weight Analysis.

Arkadios Marathianos1, Alexandros Magiakos2, Yisong Han3

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Researchers developed a new method for near-atomic level polymer imaging using annular dark field-scanning transmission electron microscopy (ADF-STEM). This technique precisely determines polymer molecular weight by counting metal atoms, even for commodity polymers.

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Area of Science:

  • Polymer Chemistry
  • Materials Science
  • Nanotechnology

Background:

  • Precise polymer characterization is crucial for advanced material design.
  • Determining molecular weight is a key challenge in polymer science.
  • Existing imaging techniques often lack the resolution for subnanoscale polymer analysis.

Purpose of the Study:

  • To achieve near-atomic level imaging of polymers.
  • To enable precise molecular weight determination of polymers.
  • To expand atomic-level visualization to commodity polymers.

Main Methods:

  • Synthesis of linear metal(loid)-rich homopolymers.
  • Subnanoscale imaging using annular dark field-scanning transmission electron microscopy (ADF-STEM).
  • Derivatization of commodity polymers for enhanced imaging.

Main Results:

  • Achieved near-atomic level imaging of polymers.
  • Precisely determined polymer molecular weight by counting metal(loid) atoms.
  • Demonstrated imaging of derivatized poly(methyl acrylate) at the subnanoscale.

Conclusions:

  • Developed a novel ADF-STEM approach for high-resolution polymer imaging.
  • Enabled accurate molecular weight determination through metal atom counting.
  • Expanded the applicability of atomic-level polymer visualization to common polymers.