Polyester Molecular Weight Measurement via NMR Solvent Shift

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current 1H NMR measurement methods fail to accurately determine the number average molecular weight of polyesters due to overlapping peaks of terephthalic acid terminals and monomers, leading to inaccurate calculations.

Innovation Solution

A method involving a solvent mixture of chloroform, 2,2,2-trifluoroethanol, and an organic base, with specific mixing ratios, is used to separate and quantify the terephthalic acid and hydroxy group terminals in polyesters via 1H NMR spectroscopy, allowing for precise calculation of the number average molecular weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If 1H NMR measurement is used to measure number average molecular weight, then measurement time and running cost are reduced, but measurement precision deteriorates due to peak overlapping

Engineering Contradiction:

Improvemeasurement speedVSAvoidnumber average molecular weight accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent changes the chemical environment parameters by introducing a basic substance (triethylamine, pyridine, or diisopropylamine) into the measurement system. This causes a chemical shift in the NMR signals, separating the terephthalic acid terminal peak from the monomer peak that previously overlapped. The basic substance modifies the electronic environment around the protons, allowing resolution of previously overlapping signals and enabling accurate quantification of terminal groups for molecular weight calculation.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If HFIP is used as solvent in SEC measurement, then measurement precision is improved, but running cost increases

Engineering Contradiction:

Improvenumber average molecular weight accuracyVSAvoidsolvent cost

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent replaces the expensive HFIP solvent with a cheaper solvent system consisting of common organic solvents (CDCl3, DMSO-d6, or acetone-d6) combined with a small amount of basic substance. This substitution maintains the ability to dissolve polyester samples while significantly reducing solvent cost. The basic substance serves as a key additive that enables peak separation without requiring the expensive HFIP.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If SEC measurement is used to obtain number average molecular weight, then measurement reliability is improved, but measurement time increases

Engineering Contradiction:

Improvenumber average molecular weight reliabilityVSAvoidmeasurement time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the mechanical SEC measurement system with a chemical NMR analysis approach. Instead of using size exclusion chromatography columns and flow systems, the method uses nuclear magnetic resonance spectroscopy with a chemically modified solvent system. This substitution maintains reliability through accurate terminal group quantification while dramatically reducing measurement time from hours to minutes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach enables more accurate determination of the number average molecular weight of polyesters, improving the accuracy and efficiency of molecular weight analysis compared to conventional methods.

Implementation Method 1

measuring the amount of the terephthalic acid terminal and the amount of the hydroxy group terminal in the sample liquid through a nuclear magnetic resonance spectroscopy aiming at hydrogen atoms

Methodology Applied

Scientific EffectNuclear magnetic resonance spectroscopy:

Implementation Method 2

the exact peak of the terephthalic acid terminal cannot be observed... the amount of the terephthalic acid terminal and the amount of the hydroxy group terminal in the sample liquid are measured through a nuclear magnetic resonance spectroscopy

Methodology Applied

Scientific EffectChemical shift:

Implementation Method 3

the solvent comprises chloroform and 2,2,2-trifluoroethanol and has an organic base added thereto... the exact peak of the terephthalic acid terminal cannot be observed... enabling more accurate determination of the number average molecular weight

Methodology Applied

Scientific EffectChemical shift modification by base addition:

Data Source

PatentUS11921068B2Molecular weight measurement method and solvent for use in measurement

Publication Date: 2024.03.05 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

In a first step, a sample liquid is fabricated by mixing a sample formed of a polyester or decomposition products of a polyester into a solvent. The solvent used here contains chloroform and 2,2,2-trifluoroethanol and has an organic base added thereto. The organic base is at least one of a primary amine, a secondary amine, a tertiary amine and a heterocyclic amine. Next, in a second step, each of the amount of the terephthalic acid terminal and the amount of the hydroxy group terminal in the sample liquid is measured through a nuclear magnetic resonance spectroscopy aiming at hydrogen atoms. Subsequently, in a third step, the number average molecular weight of the sample is calculated from the amount of the terephthalic acid terminal and the amount of the hydroxy group terminal measured in the second step.