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Covalent Bonds

Covalent Bonds

Covalent Bonds

Covalent Bonds

Overview
When two atoms share electrons to complete their valence shells, they create a covalent bond. An atom's electronegativity—the force with which shared electrons are pulled towards an atom—determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally,...

Covalent Bonding and Lewis Structures

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual attraction of atoms for a “shared” pair of electrons.

Polar Covalent Bonds

Polar Covalent Bonds

Covalent bonds are formed between two atoms when both have similar tendencies to attract electrons to themselves (i.e., when both atoms have identical or fairly similar ionization energies and electron affinities). Nonmetal atoms frequently form covalent bonds with other nonmetal atoms. For example, the hydrogen molecule, H2, contains a covalent bond between its two hydrogen atoms. When two separate hydrogen atoms with a particular potential energy approach each other, their valence orbitals...

MO Theory and Covalent Bonding

MO Theory and Covalent Bonding

The molecular orbital theory describes the distribution of electrons in molecules in a manner similar to the distribution of electrons in atomic orbitals. The region of space in which a valence electron in a molecule is likely to be found is called a molecular orbital. Mathematically, the linear combination of atomic orbitals (LCAO) generates molecular orbitals. Combinations of in-phase atomic orbital wave functions result in regions with a high probability of electron density, while...

Network Covalent Solids

Network Covalent Solids

Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...

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Related Experiment Video

Updated: Feb 13, 2026

Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly

Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly

Published on: February 6, 2020

Sweet Switch: Sugar-Responsive Bioactive Surfaces Based on Dynamic Covalent Bonding.

Wenjun Zhan¹, Yangcui Qu¹, Ting Wei¹

¹State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science , Soochow University , 199 Ren'ai Road , Suzhou 215123 , P. R. China.

ACS Applied Materials & Interfaces

|March 14, 2018

Summary

Researchers developed a smart surface with switchable bioactivity using dynamic covalent bonds. This on-off switch, triggered by sugars, offers a mild, noninvasive method for dynamic bioactive surfaces in biomedical applications.

Keywords:

bioactive surface dynamic covalent bond phenylboronic acid sugar-responsive β-cyclodextrin

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Area of Science:

Materials Science
Biotechnology
Surface Chemistry

Background:

Smart bioactive surfaces are crucial for modulating biological interactions.
Developing surfaces with tunable bioactivity is a key challenge in biomedical engineering.

Purpose of the Study:

To create a novel surface with switchable bioactivity responsive to sugar molecules.
To demonstrate an on-off mechanism for controlling surface-bound biological functions.

Main Methods:

Utilized dynamic covalent chemistry between phenylboronic acid (PBA) and beta-cyclodextrin (β-CD).
Functionalized gold surfaces with PBA-polymer brushes and beta-cyclodextrin-ligand conjugates (CD-X).
Triggered bioactivity release using cis-diol containing biomolecules like fructose.

Main Results:

Successfully demonstrated a switchable surface where bioactivity (e.g., protein capture, bacterial killing) can be turned on and off.
Achieved mild and noninvasive control over surface bioactivity via sugar-induced release.
Showcased the release of CD-X, captured proteins, and bacteria upon sugar treatment.

Conclusions:

Developed a dynamic bioactive surface with an on-off switchable mechanism.
The system shows significant potential for advanced biomedical applications requiring tunable surface interactions.
This approach offers a versatile platform for designing responsive biomaterials.