Surface phase separation, dewetting feature size, and crystal morphology in thin films of polystyrene/poly(ε-caprolactone) blend

Ultrathin film crystallization of poly(ε-caprolactone) in blends containing styrene-isoprene block copolymers: The nano-rose morphology

“…These branches form an incomplete layer at low thicknesses (6 -9 nm) but gradually cover the substrate as film thickness increases ( Figure 3d); however, no evidence of curling crystalline features was observed. The PCL/PS blend exhibited a thick bi-continuous phase separated morphology with PS at the free surface and PCL at the substrate, consistent with previous reports [2,3]. Thus, the nano-rose morphology could not be attributed to the polymer architecture (star, diblock, linear triblock) or molecular weight of the amorphous component, but blending with a block copolymer rather than another homopolymer was necessary for its formation.…”

“…Much work has been done on the theoretical and experimental aspects of miscibility and phase separation in polymer blends and the synergistic benefits of polymer blending for a wide variety of consumer applications. In thin films, research has focused on specialty coatings and the effect of substrate and free surface interfaces and film thickness on polymer blend and block copolymer phase behavior [1][2][3][4][5][6]. These variables may lead to thin film phase behavior that differs significantly from the bulk.…”

Suppression of Melt-Induced Dewetting in Cyclic Poly(ε-caprolactone) Thin Films

“…Dewetting is a complex and important phenomenon that can be attributed largely to a few important factors, namely, film thickness, polymer−substrate/polymer−polymer interactions, temperature, and molecular weight. [21][22][23][24][25]28,[31][32][33][34][35]46 In sufficiently thick films (micrometers and above), molecular forces that drive film instability are overcome by gravity, which allows the polymer film to resist dewetting. 22,46 Below a critical thickness, molecular forces become dominant, and the film may break up into droplets on the substrate through homogeneous or heterogeneous nucleation and propagation of dewetting holes.…”

“…Progress in the synthesis of cyclic polymers has taken place alongside significantly increased interest in studying polymers confined to thin and ultrathin films, which are relevant to applications in photolithography , and nanoscale membranes. − However, thin film confinement often produces dramatic and sometimes deleterious effects on physical properties, such as the depression or elevation of thermal transitions. − Additionally, poor substrate adhesion can lead to film dewetting. − By contrast, several groups have shown that the cyclic architecture exhibits unique and useful phenomena, such as a decrease in domain size in cyclic block copolymer thin films, , and a lack of T g depression in cyclic polystyrene thin films . In this Note, we describe our observation that low molecular weight cyclic poly­(ε-caprolactone) (PCL) resists thin film dewetting in the melt state better than its linear analogue, regardless of linear PCL end-group chemistry.…”

Impact of Molecular Weight on the Thermal Stability and the Miscibility of Poly(ε-caprolactone)/Polystyrene Binary Blends

“…It is also important to employ different molecular weight of PS to evaluate the miscibility due to the fact that molecular chain length might have a significant effect on the miscibility and possibly a miscible PCL/PS blend can be found for the low molecular weight PS. In addition, thin films can be fabricated with unique phase separation and crystal morphologies from PCL/PS blend in solution, which has great potential for application in the biomaterials field [19].…”