| Abstract
| - We have investigated ultrasonic degradations of poly(ethylene oxide) (PEG) and poly(methyl methacrylate)(PMMA) in aqueous media by means of matrix-assistedlaser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The ultrasonic degradation ofpolymers was monitored as a function of ultrasonicationduration to examine the structural details of ultrasonicdegradation polymers. PEG solution ultrasonication produced five types of oligomers (M̄ ∼1000 Da) with differentend groups, irrespective of the initial average molecularmasses (M̄ = 2, 6, 20, and 2000 kDa). Several degradation pathways with free radical reactions have beensuggested to explain these degradation products: theultrasonic degradation of PEG is initiated by breaking ofthe C−O bond in the PEG chain, generating polymericradicals with two terminal groups, i.e., X•(∼CH2CH2•) andY•(∼CH2CH2O•), followed by termination with extractionor release of a hydrogen atom. However, PMMA (M̄ =1630 Da) ultrasonication generated only one type ofdegradation oligomer, which has a hydrogen group at bothends, the same as that of the original oligomer. It has beensuggested that the presence of the radical terminal groupsX•(∼CH2•) and Y•(∼(CH3)CCOO(CH3)C•) is due to selective C−C bond breaking in the chain during the ultrasonicdegradation of PMMA. The MALDI-TOFMS combinedwith the ultrasonic degradation technique (UD/MALDI-TOFMS) developed in this study could be extended to theanalysis of synthetic polymer structures with high molecular weights.
|
