Related Experiment Video
Updated: Sep 22, 2025
07:28
Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
13.3K
Precision Long-Chain Branched Polyethylene via Acyclic Diene Metathesis Polymerization
Hong Li1, Giovanni Rojas1,2, Kenneth B Wagener1
1The George and Josephine Butler Polymer Research Laboratory, Department of Chemistry, University of Florida, Gainesville, Florida 326011-7200, United States.
ACS Macro Letters
|May 26, 2022
Summary
Synthesized polyethylenes with precisely placed 21-carbon branches show that longer side chains are excluded from crystal units. Branch frequency impacts melting temperature, offering insights into polymer crystallization behavior.
Area of Science:
- Polymer Chemistry
- Materials Science
Background:
- Polyethylene's properties are significantly influenced by branching.
- Understanding the impact of long alkyl branches on polyethylene crystallization is crucial for designing advanced materials.
Purpose of the Study:
- To synthesize polyethylenes with precisely controlled long alkyl branches using acyclic diene metathesis (ADMET) polymerization.
- To investigate the effect of branch frequency and length on the thermal properties and crystalline behavior of polyethylene.
Main Methods:
- Acyclic diene metathesis (ADMET) polymerization was employed to create polyethylenes with 21-carbon alkyl branches.
- Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and ¹³C) was used to verify the precise placement and structure of the branches.
- Differential Scanning Calorimetry (DSC) was utilized to analyze melting profiles and determine melting temperatures.
Main Results:
- Polyethylenes with precisely placed 21-carbon branches were successfully synthesized.
- All synthesized polymers exhibited well-defined melting profiles, even with high branch incorporation (up to 13.3% mol).
- Melting temperature increased with decreasing branch frequency, indicating side chain exclusion from crystal structures.
Conclusions:
- The precise placement of long 21-carbon alkyl branches influences polyethylene's thermal properties.
- The observed relationship between branch frequency and melting temperature supports the exclusion of these long side chains from polyethylene crystal units.
- Findings provide valuable insights into structure-property relationships for branched polyethylenes.
Related Concept Videos
00:53Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
2.0K
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
2.0K
01:17Radical Chain-Growth Polymerization: Chain Branching
2.0K
The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
2.0K
02:35Free-Radical Chain Reaction and Polymerization of Alkenes
8.2K
The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
8.2K
01:14Polymer Classification: Architecture
3.1K
Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
3.1K
01:13Olefin Metathesis Polymerization: Overview
2.3K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
2.3K
01:16Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
2.7K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
2.7K