Enhanced Thermal Stability of Polystyrene by Interfacial Noncovalent Interactions

Abstract

The local conformation of polystyrene (PS) and deuterated PS at the interface with quartz substrates, which were covered with phenyl groups using phenyltrimethoxysilane (PTS) under various conditions, was examined by sum frequency generation spectroscopy. As evidenced by the red-shift of the wavenumber of the v 2 vibration mode for phenyl groups, it was claimed that PTS phenyl groups standing vertically from the quartz surface induced the perpendicular orientation of PS phenyl rings by energetically favorable parallel-displaced π−π interactions at the interface. The local conformation of PS chains strongly anchored onto the substrate by the π−π interactions remained almost unchanged for 48 h even at a temperature 60 K higher than the bulk glass transition temperature. That is, the interfacial π−π interactions facilitated the adsorption of PS chains on the substrate to attain a large enthalpic gain, resulting in significantly slower dynamics of PS chains at the interface. Our results illustrate the importance of the interfacial noncovalent interactions in controlling the structure and dynamics of macromolecular chains at the interface as well as in the thin film geometry.

Interphase in Polymer Nanocomposites

“… 3 , 4 This dramatic increase in the interface area amplifies the interaction between nanofillers and polymer chains, and polymers located near the interface make a profound contribution to the macroscopic material properties of the nanocomposites. 5 Here, we broadly define the polymer components near the nanofiller surface that possess properties different from those of the bulk polymer as the interphase.…”

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.…”

Influence of the Filler Particles’ Surface Morphology on the Polyurethane Matrix’s Structure Formation in the Composite

“…The formation of covalent or non-covalent bonds between the polymer and the filler leads to the fact that the filler surface has a limiting effect on the polymer chain segment's molecular mobility, due to their conformational set's depletion. In this case, there is an increase in the glass transition temperature (Tg) and an improvement in physical and mechanical properties [20]. In order to enhance interactions at the polymer/filler interface, various covalent and non-covalent functionalization methods are used to promote the formation of active functional groups on the filler surface [21].…”