END-FUNCTIONALIZED POLYMERS .2. QUANTIFICATION OF FUNCTIONALIZATION BY TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY

The applicability of time-of-flight secondary ion mass spectrometry (T OF-SIMS) for quantification of functionalization is demonstrated using five 1.0 x 10(3) g/mol polystyrene samples which were synthesized by living anionic polymerization. The polymerizations were functionally t erminated to various extents (0, 25,50,75, and 100 %) by using sequent ial termination techniques with chlorodimethylphenylsilane and methano l. Two distinct molecular weight distributions of intact oligomer sign als are resolved in the TOF-SIMS spectra resulting from the functional ized and unfunctionalized (protonated) oligomer species in each sample . Through direct comparison of the signal intensities of the two types of oligomers, the extent of functionalization is determined at each d egree of polymerization and agrees well with expected values. The resu lts are substantiated using physical mixtures of dimethylphenylsilyl ( 100% functionalized) and proton (0% functionalized) terminated polymer s. The relative oligomer intensities for the physical mixture of polym ers corresponds well to the ratio in which they were initially combine d. Sputter yield, extent of fragmentation, and ionization and detectio n probabilities are determined to be very similar for the proton- and dimethylphenylsilyl-functionalized oligomers. Thus, quantification of end groups can be achieved without standards calibration. Analysis by gel permeation chromatography (GPC) shows a systematic shift to higher [M(n)] values as the extent of functionalization of the polystyrene s amples is increased from 0 to 100%. [M(n)] values calculated from TOF- SIMS analysis for the oligomers agree well with GPC results. The [M(n) ] values for the functionalized and unfunctionalized components in eac h sample can also be determined by TOF-SIMS and are distinct for each oligomer type.