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Tg Confinement Effect of Random Copolymers of 4-tert-Butylstyrene and 4‑Acetoxystyrene with Different Compositions
journal contribution
posted on 2019-09-18, 18:36 authored by Tong Wang, Jinsong Yan, Hailin Yuan, Jianquan Xu, Ho Yi Lam, Xuanji Yu, Chao Lv, Binyang Du, Ophelia K. C. TsuiWe
observe that the Tg confinement
effect of polymer films can saturate with polymer–substrate
interaction. Thickness dependences of the glass transition temperature, Tg(h0), of random
copolymer films of 4-tert-butylstyrene (TBS) and
4-acetoxystyrene (AS) supported by silica (SiOx) were measured for
different TBS concentrations, XTBS. For
0 ≤ XTBS ≤ 0.47, Tg(h0) displays identical
enhancements, independent of XTBS. For XTBS > ∼0.66; however, Tg(h0) decreases steadily with XTBS. The XTBS >
0.66 result is in keeping with expectations that TBS interacts less
strongly with SiOx than AS does, and weaker polymer–substrate
interaction renders greater dominance of the air surface over substrate
surface on Tg, and thereby Tg reduction. We propose that saturation in Tg(h0) found for XTBS ≤ 0.47 is caused by the maximization in polymer–substrate-specific
bond formation. Further experiments and a calculation support this
proposition.