Solvent Content in Thin Spin-Coated Polystyrene Homopolymer Films

Abstract

The solvent content of thin polystyrene (PS) films, spin-coated from protonated and deuterated toluene onto silicon substrates, is investigated. Neutron reflectometry (NR) is used to probe the total remaining solvent inside the PS films in a nondestructive and noninvasive way. In freshly prepared films, the investigated parameters are the molecular weight of PS and the total film thickness. Moreover, the effect of postproduction treatment by annealing at temperatures below and above the glass transition of PS as well as long-term storage over 2 years are examined to deduce the reduction of the remaining solvent. The remaining solvent content increases with increasing molecular weight and with increasing film thickness. An enrichment of toluene at the Si/polymer interface is found. Under the different annealing and storage conditions tested, the remaining solvent is not totally removed. The observed behavior is discussed in the framework of polymer thin films and compared with results obtained by alternative experimental approaches.

Influence of drying procedure on glass transition temperature of PMMA based nanocomposites

“…Moreover, they found that the solvent molecules are mainly located at the interface between polymer and substrate. Their findings were supported by the observations of Perlich et al 47 who used neutron reflectometry to assess the amount of retained toluene in spin cast PS films annealed at different temperatures, both above and below the glass transition temperature. They found that solvent retention was molecular weight dependent and increased with increasing molecular weight.…”

“…44,45 The amount of retained solvent in different cast films was studied by several groups. 44,45,[47][48][49] García-Turiel and Jé rô me 47 used gas chromatography to study solvent retention in PS films spin cast from toluene. They concluded that while in thick films, there are only a few percent of solvents left after annealing at a temperature above the glass transition temperature, the amount of retained solvent can be much higher in thin films.…”

Distributions of glass-transition temperature and thermal expansivity in multilayered polystyrene thin films studied by neutron reflectivity

“…First we prepared a d-PS layer directly onto a 3-in.-diam Si substrate by spin-coating toluene solutions at 2000 rpm and dried in a vacuum oven at 343 K for 24 h after drying in a vacuum oven at room temperature for 2 days to remove a residual solvent. The residual solvent in polymer thin films is a matter of discussion and some researchers studied this problem using chromatography, neutron reflectivity, and Fourier transform infrared spectroscopy [14][15][16]. Recently, Zhang et al studied the residual solvent in PS and polymethyl methacrylate (PMMA) thin films [16] and found that no trace of solvent was observed even for as-deposited PS thin films, indicating that our drying condition was enough to remove the residual solvent in thin films.…”

Cooling Rate Dependent Glass Transition in Thin Polymer Films and in Bulk

“…As-deposited PS films were annealed in vacuum at 433 K for several days to remove traces of residual solvents. This has been shown to be a concern in the study of thin polymer films [14,53,86,98,111].…”