Acid Anhydride Measurement in Degraded Polyesters via NMR
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Solution Overview
Problem
Conventional methods fail to accurately measure the acid anhydride content in degraded thermoplastic polyesters due to overlapping peaks with solvent components in NMR measurements, making it difficult to quantify using existing IR and NMR spectroscopy techniques.
Innovation Solution
A method involving dissolving a polyester sample in a pretreatment liquid containing 1,1,1,3,3,3-hexafluoro-2-propanol and an organic base, followed by mixing with deuterated chloroform and 1,1,1,3,3,3-hexafluoro-2-propanol to create a sample liquid for NMR measurement, allowing for the detection and quantification of acid anhydride structures by NMR spectroscopy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If 1H NMR measurement is performed using conventional solvents (CDCl3/HFIP-2d or CDCl3/TFA-d), then the sample can be dissolved and measured, but the acid anhydride peak overlaps with solvent peaks making quantification impossible
Solution Approach 1:
The patent changes the solvent composition parameters by introducing a carboxylic acid component to the measurement solvent system. Specifically, it uses a mixed solvent containing deuterated chloroform, deuterated 1,1,1,3,3,3-hexafluoro-2-propanol, and deuterated carboxylic acid (such as deuterated trifluoroacetic acid or deuterated acetic acid). This parameter change in solvent composition shifts the solvent peaks away from the acid anhydride region, enabling clear detection and quantification of acid anhydride structures in degraded polyesters.
2Measurement precision
If IR measurement is performed to detect acid anhydride structure, then the structure can be detected, but standard samples at arbitrary concentrations are difficult to acquire for quantitative measurement
Solution Approach 1:
The patent replaces the IR spectroscopy method with 1H NMR spectroscopy for measuring acid anhydride content. This substitution eliminates the need for standard samples and calibration curves required by IR measurement. The 1H NMR method allows direct quantification by comparing the integrated value of the acid anhydride peak with that of the solvent peak, providing a more convenient and accurate measurement approach without requiring manually prepared standard samples.
3Measurement precision
If amine is added and heating is performed to measure aromatic carboxylic acid terminal, then quantitative measurement is possible, but the acid anhydride structure is decomposed and peaks cannot be detected separately
Solution Approach 1:
The patent performs preliminary action by directly measuring the acid anhydride structure in situ using 1H NMR spectroscopy before any decomposition reactions occur. By using a specially designed measurement solvent system that prevents peak overlap, the method enables direct detection and quantification of the acid anhydride content without requiring prior decomposition or chemical modification steps, thus preserving the structural integrity during measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate measurement of acid anhydride content in degraded polyesters by chemically converting the acid anhydride structure into detectable compounds, avoiding peak overlap with solvent peaks, thus determining the extent of degradation effectively.
Implementation Method 1
a first step of dissolving a sample formed of a polyester or decomposition products of a polyester in a pretreatment liquid containing 1,1,1,3,3,3-hexafluoro-2-propanol and an organic base to obtain a reaction product of the sample
Implementation Method 2
a third step of measuring the amount of the reaction product in the sample liquid through a nuclear magnetic resonance spectroscopy aiming at hydrogen atoms
Data Source
AI summary
In a first step, a sample formed of a polyester or decomposition products of a polyester is dissolved in a pretreatment liquid containing 1,1,1,3,3,3-hexafluoro-2-propanol and an organic base to produce a reaction product of the sample, and in a second step, the obtained reaction product is mixed into a solvent (measurement solvent) containing deuterated chloroform and deuterated 1,1,1,3,3,3-hexafluoro-2-propanol to fabricate a sample liquid. Next, in a third step, the amount of the reaction product in the sample liquid is measured through NMR aiming at hydrogen atoms to determine the amount of an acid anhydride structure in the sample.