Performance and properties of materials may strongly depend on processing conditions. This is particularly so for polymers, which often have relaxation times much longer than the processing times and therefore may adopt preparation dependent nonequilibrated molecular conformations that potentially cause novel properties. However, so far it was not possible to predictably and quantitatively relate processing steps and resulting properties of polymer films. Here, we demonstrate that the behavior of polymer films, probed through dewetting, can be tuned by controlling preparation pathways, defined through a dimensionless parameter , which is the appropriate preparation time normalized with the characteristic relaxation time of the polymer. We revealed scaling relations between and the amount of preparation-induced residual stresses, the corresponding relaxation time, and the probability of film rupture. Intriguingly, films of the same thickness exhibited hole nucleation densities and subsequent dewetting kinetics differing by up to an order of magnitude, indicating possibilities to adjust the desired properties of polymer films by preparing them in appropriate ways.

Conditions of rapid processing often drive polymers to adopt nonequilibrium molecular conformations, which, in turn, can give rise to structural, dynamical, and mechanical properties that are significantly different from those in thermodynamic equilibrium. However, despite the possibility to control the desired nonequilibrium properties of polymers, a rigorous microscopic understanding of the processing–property relations is currently lacking. In an attempt to stimulate progress along this topical direction, we focus here on three prototypical and apparently different cases: spin-coated polymer films, rapidly drawn polymer fibers, and sheared polymer melts. Inspired by the presence of common observations in the chosen cases, we search for order parameters as, for example, topological correlations and heterogeneities, which may allow characterizing the processing-induced behavior of polymers. We highlight that such approaches, necessitating concerted efforts from theory, simulations, and experiments, can provide a profound understanding leading to predictable and tunable properties of polymers.

We compare the high velocity dewetting behavior, at elevated temperatures, of atactic polystyrene (aPS) and isotactic polystyrene (iPS) films, with the zero shear bulk viscosity (η_{bulk}) of aPS being approximately ten times larger than iPS. As expected, for aPS the apparent viscosity of the films (η_{f}) derived from high-shear dewetting is less than η_{bulk}, displaying a shear thinning behavior. Surprisingly, for iPS films, η_{f} is always larger than η_{bulk}, even at about 50 °C above the melting point, with η_{f}/η_{bulk} following an Arrhenius behavior. The corresponding activation energy of ∼160±10  kJ/mol for iPS films suggests a cooperative motion of segments which are aligned and agglomerated by fast dewetting.

Polymer nanocomposites constitute an important class of materials whose properties depend on the state of dispersion of the nanoparticles in the polymer matrix. Here we report the first observations of confinement-induced enhancement of dispersion in nanoparticle-polymer blend films. Systematic variation in the dispersion of nanoparticles with confinement for various compositions and matrix polymer chain dimensions has been observed. For fixed composition, strong reduction in glass transition temperature, T g , is observed with decreasing blend-film thickness. The enhanced dispersion occurs without altering the polymer-particle interactions and seems to be driven by enhanced matrix-chain orientation propensity and a tendency to minimize the density gradients within the matrix. This implies the existence of two different mechanisms in polymer nanocomposites, which determines their state of dispersion and glass transition.

We probed the relaxation of preparation-induced residual stresses in nonequilibrated polymer films through dewetting experiments. While we observed fast relaxations at temperatures close to or below the glass transition, at elevated temperatures these relaxation times were orders of magnitude longer than the reptation time. Intriguingly, applying appropriate scaling of preparation conditions allowed us to present all relaxation times, including published data, from various complementary experiments on a single master curve exhibiting an Arrhenius-type behavior. The corresponding activation energy (75 ± 10 kJ/mol) is similar to values obtained for the relaxation of segments in polystyrene. The observed long relaxation times suggest that residual stresses, a consequence of nonequilibrium conformations inherited from preparation, relax via concerted rearrangements of many segments.