Entropically Influenced Reconstruction at the PBD-ox/Water Interface:  The Role of Physical Cross-Linking and Rubber Elasticity

Abstract

Oxidation of the surface of syndiotactic 1,2-polybutadiene (PBD) films with aqueous KMnO4/K2CO3 at room temperature produced PBD-ox, containing a range of oxidized functionality. When heated against water, the surface of PBD-ox became more hydrophobic, a result contrary to what would be expected if enthalpic forces dominated the reconstruction. Initially, the hydrophilicity of the surface varied reversibly as a function of temperature, reflecting reversible changes in the relative concentrations of hydrophilic and hydrophobic groups at the interface. Eventually, however, the surface remained hydrophilic against water, independent of temperature. The temperature dependence of this phenomenon suggests the importance of entropy in determining the state of minimum interfacial free energy in this system. This entropic effect is attributable to rubber elasticity arising from crystallinity in the polymer, and its loss is associated with a change in the amount and type of crystallinity.

Propriedades mecânicas e molhabilidade de filmes de zeínas extraídas de glúten de milho

“…Essa reorientação tem sido modelada como um mecanismo que ocorre para minimizar a energia livre interfacial e, portanto, estabelecer uma maior estabilidade no sistema [44,45] , o que parece ser facilitado com o aumento do teor de plastificante.…”

Formation and Properties of Responsive Siloxane‐Based Polymeric Surfaces with Tunable Surface Reconstruction Kinetics

“…Implementing the thiol-ene addition reaction on PVMS networks, a route others demonstrated with fluid polymers, [15,[22][23][24] we modified PVMS substrates with 11-dodecanethiol (HS(CH 2 ) 11 CH 3 ) and 3-mercaptopropionic acid (HS(CH 2 ) 2 COOH). The addition to the vinyl bond was confirmed via the elimination of the C --C peaks at 960, 1407, and 1587 cm À1 in Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR).…”

“…[12] By varying substrate elasticity and composition of oxidized butadienes to create a system with a controlled rate of surface reconstruction, Ferguson and coworkers argued that surface reconstruction was dictated by shifts in enthalpic and entropic driving forces on the surface free energy. [13][14][15] Surface reconstruction is also associated with surface segregation of polymers and their reorientation at the surface. These two modes often act in accord and contribute simultaHere, the formation of responsive polymeric materials with tunable response time is reported.…”

Synthesis and Surface Properties of Environmentally Responsive Segmented Polyurethanes

“…In achieving the above properties, what is required is a polymer, the surface properties of which would spontaneously adjust by interacting with the environment in order to achieve low interfacial tension in both air and water. Such types of materials with switchable surface properties have been observed with surface-modified polymers (40) and silicones containing segmented polyurethane (41)(42)(43)(44)(45)(46)(47)(48). Polymers containing multiblock functional copolymer additives (49,50), fluorinated coupling agents (51,52) and fluoro-organo modified polymeric amphilphiles (53-59) also exhibit switchable surface properties.…”