The influence of polymer molecular weight, molecular weight distribution, and polymer‐solvent interactions on the thickness and topography of spin‐coated polymer films was examined. For films prepared from dilute solutions, highly volatile solvents or fair or “poor” solvents for the polymer adversely affect film surfaces causing nonuniformities (waves) to appear. However, if the concentration of these solutions is increased to approximately the concentration at which entanglements are formed, nearly uniform films are produced even if the solvent employed is highly volatile, such as dichloromethane. When toluene is employed as the solvent, which has a relatively low volatility and therefore forms nearly flat film surfaces, films prepared from dilute solution were found to have thicknesses, h, proportional to η o0.34 Ω−0.49 for polystyrene and η o−0.39 Ω−0.49 for poly(methylmethacrylate) where ηo is the zero‐shear rate solution viscosity and Ω is the rotational speed at which the films were prepared. These results suggest that the exponents associated with ηo and Ω may be nearly independent of the type of polymer used as long as flat films are produced. Finally, the molecular weight parameter most important in controlling final film thickness for films made from dilute solutions is Mv, the viscosity‐average molecular weight.

The fluorescence response of a mobilityor free volume-sensitive molecule, julolidenemalononitrile (JMN), is shown to be affected by the relaxations that occur on the molecular scale during physical aging in various glassy polymers including polystyrene, polycarbonate, poly(methyl methacrylate), and poly-(isobutyl methacrylate). In general, the change in fluorescence intensity is approximately linear with logarithmic aging time as has been found in bulk volume and enthalpy relaxations. Near the glass transition temperature, JMN monitors the relaxations until equilibrium is reached where the fluorescence response maintains a constant value. Additionally, the physical aging rate was found to depend on temperature in all polymers as has been observed in bulk specific volume behavior. The temperature trends found in polystyrene, poly-(methyl methacrylate), and polycarbonate with the molecular fluorescence technique agree well with those from specific volume relaxation. These results provide experimental evidence of how the molecular environments contribute to the traditionally observed bulk properties.

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Multiple photochromic probes requiring different volumes to isomerize were used to monitor the effects of physical aging on Bisphenol-A polycarbonate (PC) glass. PC was found to possess a local free volume distribution that is more broad than those of polystyrene (PS) and poly(methyl methacrylate) (PMMA). Contrary to aging results in PS and PMMA, physical aging of PC affected the isomerization abilities of the smaller probes as well as the larger probes, and all probes are affected nearly equally. Physical aging in dry and wet poly (vinyl acetate) (PVAc) showed that absorbed water increases the fraction of local free volume sampled by azobenzene as would be expected in a plasticized system. Additionally, it was found that a local free volume distribution is difficult to determine with the photochromic technique in polymers such as PVAc that have glass transition temperatures near the experimental temperature. At temperatures near Te, the polymer has enough mobility to allow structural reorganization on the time scales required to reach the photostationary state, generally, 10-30 min. Therefore, the environments surrounding the probes change before the photostationary state is established, thereby making interpretation of the data difficult.

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