Surface Studies of Polymers with a Well-Defined Segmental Length by ToF-SIMS and XPS. Relationship between the Surface Chemical Composition and Segmental Length

Abstract

Two series of sequential polymers were synthesized by polymerization of 1,n-dibromoalkane (n = 4, 6, 8, 10, 12, 14, and 18) with 4,4‘-(hexafluoroisopropylidene)diphenol (6FBA) and bisphenol A (BA). The flexible aliphatic segment length changes from 4 to 21 Å corresponding to 4−18 CH2 groups. The influence of the flexible aliphatic segment length on the surface composition of BA and 6FBA sequential polymers was investigated by XPS and ToF-SIMS. The O 1s/C 1s peak ratios of the BA polymers indicated that the flexible segment was enriched on the BA polymer surface when the number of the CH2 groups was larger than 14 (the length of the flexible segment ∼17 Å). The F 1s/C 1s peak ratios of the 6FBA polymers showed that the length of the flexible segment on the surface was the same as the bulk. The ratios between the intensities of the characteristic peaks of the flexible and rigid segments displayed a linear dependence on the surface flexible segment length determined by XPS.

Onset of surface segregation controlled by the segment length of the low-energy component of polymers

“…In 6FBA polymers, the surface energies of CH 2 groups and the rigid 6FBA component are similar; and no surface excess of the flexible segment was observed even when the number of CH 2 groups reached 18. From our previous 12,13 and current results, we can conclude that the length of the low-surface-energy segment and the surface energy difference between the low-and high-surface-energy segments are two important parameters that determine the surface composition of these polymers.…”

“…Recently, we studied two sequential polymers synthesized by polymerization of 1, n-dibromoalkane (n D 4, 6, 8, 10, 12, 14 and 18) with 4,4 0 -(hexafluoroisopropylidene)bisphenol (6FBA) and bisphenol A (BA) by XPS and ToF-SIMS. 13 Our results indicated that the surface of the BA polymers was enriched with the aliphatic segments as the number of CH 2 units reached 14 (with a segment length greater than 17Å). If BA was replaced with the lower-energy 6FBA (having two CF 3 groups instead of two CH 3 groups in BA), the surface composition was similar to the bulk even when the number of CH 2 units reached 18.…”

“…5, which displays n s determined using Eqn (3) as a function of n. The data clearly show that for small n and at large sampling depths n s D n. These results agree with those of our previous work. 12,13 The CH 2 segment has a lower surface energy than the rigid BA segment, but no surface segregation of the CH 2 segment occurred Figure 5. The number of CF 2 groups on the surface, n s , determined by the F-to-O atomic ratio versus the number of CF 2 group in the bulk, n, at different take-off angles.…”

“…In our previous study of the BA and 6FBA polymers, 13 if matrix effects can be neglected, the absolute intensity ratios, I F j /I R k , of the flexible fragment to the rigid fragment are related to the number of CF 2 groups at the surface, n, as shown by Eqn (4):…”

Quantitative analysis of styrene-pentafluorostyrene random copolymers by ToF-SIMS and XPS

“…Given the fact that the secondary ion intensities of 5FPS are higher than those of PS, these results suggest that the St characteristic peaks are enhanced, while the 5FSt characteristic peaks are prohibited. It is also interesting to note that a new peak at m/z D 283 (C 15 the copolymers, a number of fragments are found in the same nominal masses, but their exact masses are different. The high mass resolution capability of the ToF-SIMS instrument allows these ions to be identified.…”