Frequency (cm⁻¹)

Origin/Type of Vibration

Functional Group Assignment

2700 - 2550

-OH stretch of phosphonic acid; H-O-P=O

Suspected to come from H-O-P=O bonds created during the formation of Crosslinked-PPTE.

1260/1230

-C-O-P=O stretch of organic ( ${\text{PO}}_4^{3-}$ ) phosphates

As for Crosslinked-PPTE.

1200/1100

-P=O stretch

Ditto.

1050/970

-P-O-C- stretch of ( ${\text{PO}}_4^{3-}$ ) phosphate esters.

Ditto.

1420 - 1100

Aryl sulphones, organic sulphates and sulphonates demonstrate IR absorption in this region.

SO₂, -SO₄, etc.

1450 - 1345

Asymmetric stretch of the -S=O group of ${\text{-SO}}_{\text{3}}{\text{H}}^{-}$ and ${\text{-SO}}_4^{2-}$

Sulphonic acid ( ${\text{-SO}}_{\text{3}}{\text{H}}^{-}$ ) group introduced to substitute for and replace the hydroxyl hydrogens(H) of PTE-catechin in the sulphonationprocess.

1323 - 1300

Asymmetric stretching of O=S- of (O=S=O) sulphones

Sulphone O=S=O bond created in the sulphonation process.

1160 - 1125

Symmetric stretching of O=S- of O=S=O

1062 - 1034

-S=O stretch of a -S-O-H

PTE-O-S-O-H created during sulphonation.