Related Experiment Video
Updated: Sep 21, 2025
09:22
Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
7.9K
Synthesis and Characterization of Segmented Polyurethanes Containing Trisaminocyclopropenium Carbocations
Robert H Lambeth1, MyVan H Baranoski1, Alice M Savage1
1U.S. Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005, United States.
ACS Macro Letters
|June 2, 2022
Summary
Trisaminocyclopropenium (TACP) carbocations, novel chain extenders, enhanced polyurethane properties like thermal stability and elasticity. These ionic aggregates offer superior performance compared to traditional butane diol extenders.
Area of Science:
- Polymer Chemistry
- Materials Science
Background:
- Segmented polyurethanes are versatile materials with tunable properties.
- Traditional chain extenders like butane diol limit the thermal and mechanical performance.
- Novel chain extenders are needed to overcome these limitations.
Purpose of the Study:
- To synthesize novel segmented polyurethanes using diol-functionalized trisaminocyclopropenium (TACP) carbocations as chain extenders.
- To investigate the effect of TACP structure on polymer crystallization and hydrogen bonding.
- To evaluate the thermomechanical properties and morphology of TACP-modified polyurethanes.
Main Methods:
- Two-step polyurethane synthesis.
- Differential scanning calorimetry (DSC) for crystallization analysis.
- Fourier transform infrared spectroscopy (FTIR) for hydrogen bonding characterization.
- Dynamic mechanical analysis (DMA) for thermomechanical behavior.
- Small-angle X-ray scattering (SAXS) for morphology.
- Tensile testing for mechanical properties.
Main Results:
- TACP chain extenders significantly altered the crystallization behavior of the poly(tetramethylene oxide) soft segment.
- TACP incorporation limited hydrogen bonding compared to butane diol controls.
- TACP-containing polyurethanes exhibited enhanced resistance to high-temperature flow.
- SAXS confirmed phase-separated morphology, suggesting ionic aggregates over physical cross-links.
- Tensile tests revealed excellent elasticity and strain hardening.
Conclusions:
- Diol-functionalized TACP carbocations serve as effective chain extenders for segmented polyurethanes.
- TACP-based polyurethanes demonstrate improved thermal stability and mechanical properties.
- The observed properties are attributed to ionic aggregates formed by TACP, rather than traditional hard segment physical cross-links.
Related Concept Videos
00:57Cationic Chain-Growth Polymerization: Mechanism
2.4K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
2.4K
01:26Polymer Classification: Stereospecificity
2.7K
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
2.7K
01:03Step-Growth Polymerization: Overview
3.7K
Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
Many natural and synthetic polymers are produced by...
3.7K
01:17Ziegler–Natta Chain-Growth Polymerization: Overview
3.5K
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta...
3.5K
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
01:20Anionic Chain-Growth Polymerization: Overview
2.2K
The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
2.2K