Stabilization of polystyrene thin films by introduction of a functional end group

Abstract

The thin film stabilities of ω-N-(3-(dimethylamino)propyl)propylamide-terminated polystyrene (PS-N) and its blends with conventional polystyrene (PS-H) supported on silicon wafers with a native oxide layer were examined. Whereas a 20-nm-thick film of PS-H with a number-average molecular weight of ∼ 50k decomposed at 423 K, a comparable PS-N film and blended films containing a PS-N fraction of 440 wt% were stable. Although the local conformation of chains at the substrate interface was not the same for PS with and without the functional end group, the glass transition temperature at the interface was identical for both PS-H and PS-N. The residual adsorbed layer on the substrate after washing the films with a good solvent was thicker for PS-N than for PS-H. This implies that end functionalization, rather than segmental dynamics, affects chain movement on a large scale.

Unswollen layer of cross-linked polyisoprene at the solid interface

“…[24][25][26][27][28] This is mainly because the dynamics of the chains is faster in the surface region than in bulk. [29][30][31][32][33][34][35] At the same time, it is also accepted that chains form an adsorbed layer on the silicon surface [36][37][38][39][40][41][42][43][44][45][46][47] and exhibit slower dynamics. [48][49][50] These properties are similar to those of bound rubber, meaning that we should be able to explain how rubber and glassy polymers attach to solid surfaces in the same way.…”

Effect of Molecular Architecture on Conformational Relaxation of Polymer Chains at Interfaces

“…However, since no vibration mode contributed from phenyl rings was observed in this wavenumber region, [ 43 ] it seems that the slight increase in signal at 3010 cm −1 was within the experimental accuracy. Taking into account our previous results, [ 5,16,44,45 ] the local chain conformation at the interface remained in a nonequilibrium state after annealing at 423 K for 1 h, regardless of the molecular architecture.…”

“…[ 42,43 ] This is consistent with previously reported results. [ 5,16,44,45 ] After 1 h annealing, SFG spectra were basically similar in shape to one another. In the case of 8sPS, signals at a wavenumber region centered 3010 cm −1 appeared to be slightly stronger than the baseline ones.…”

“…This means that phenyl rings were reoriented toward the direction parallel to the interfacial plane, possibly on the way to the randomization of interfacial chains. [ 14,44,45 ] Such a spectral change was not clearly discerned for sPS chains under the same annealing condition. Although the ν 2 peak intensity for 3sPS and 8sPS chains slightly decreased with annealing up to 168 h, this peak remained the strongest in the region employed.…”

Thermal Stability and Interfacial Segregation for Polymer Thin Films Blended with a Homologue Having Different Tacticity

“…Generally, a polymer thin film is affected by interfacial interaction with air and/or a substrate when it is getting thinner down to an order of nm, and often is thermally unstable leading to de-wetting from a substrate. So far various attempts have been made to prevent or retard de-wetting of a polymer thin film [1]: surface modification of a substrate with an end-functionalized polymer [2,3], addition of a surface active component [4,5] or inorganic nanofiller [6,7], formation of cross-linking [8,9], etc.…”