Frequency (cm⁻¹)

Origin/Type of Vibration

Functional Group Assignment

2692/2546

-OH stretching of a phosphonic acid; O=P-O-H

Assumed to have come from the O=P-O-H bond created in Crosslinked-PPTE and Substituted-PPTE during modification. The intensity of the absorption band in Substituted-PPTE was twice that in Crosslinked-PPTE.

1350/1250

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

P-containing organic compounds are characterized by IR absorption in this region. These absorptions bands are not present in the IR spectra of the starting materials, thus lending credence to the formation of new chemical bonds and successful modification of PTE polyphenol swith POCl₃.

1198/1087

-P=O stretch

Supposedly from the new-PTE--P=O bond, presumably formed between O-H of PTE catechins and P of POCl₃ in the crosslinking or substitution processes.

997/993

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

Most likely from the R-O-P- bond created in the crosslinking or substitution processes.