Gel
permeation chromatography (GPC) is a generally applied
method
for the mass analysis of various polymers and copolymers, but it inherently
fails to provide additional important information such as the composition
of copolymers. However, we will show that GPC measurements using different
solvents can yield not just the correct molecular weight but the composition
of the copolymer. Accordingly, artificial neural networks (ANNs) have
been developed to process the data of GPC measurements and determine
the molecular weight and the chemical composition of the copolymers.
The target values of the ANNs were obtained by matrix-assisted laser
desorption/ionization time-of-flight mass spectrometry (MALDI-TOF
MS) and nuclear magnetic resonance (NMR) spectroscopy. Our GPC–ANN
method is demonstrated by the analysis of various poloxamers, i.e.,
poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO) block
copolymers. Two ANNs were constructed. The first one (ANN_1) works in a wider mass range (from 900 to 12,500 dalton), while
the second one (ANN_2) produces more output values. ANN_2 can thus predict seven characteristic copolymer parameters,
namely, two average molecular weights, the average weight fraction
of the EO unit, and four average numbers of the repeat units. The
correlation between the experimentally obtained outputs and the predicted
ones is high (r > 0.98). The accuracy of the ANNs
is very convincing, and both ANNs predict the number-average molecular
weight (M
n) with an accuracy below 5%.
Furthermore, this work is the first step for creating an open database
and applications extending the use of the GPC–ANN method for
the analysis of copolymers.