Compression polymer-bearing surfaces

Whether a polymer is grafted on the surface or simply adsorbed on the surface has a bearing on the force between two polymer-coated surfaces. Adsorption is a reversible process and can be affected by temperature, compression of the polymer layer, and the like. 

Over the last 10 years there have been a large number of experimental, theoretical and numerical simulations on the properties of polymer brushes. The static properties of polymer brushes are now very well understood and have been reviewed extensively elsewhere [26-29]. In this article I will concentrate on more recent results for polymer brushes in a shear flow. Accordingly, the next section on the static properties will be brief. In Section III, the hydrodynamic penetration depth for the solvent into the brush will be discussed for shear flow past the brush and for two surfaces approaching each other. In Section IV, the normal and shear forces between two surfaces bearing end-grafted chains will be discussed. Two processes, interpenetration and compression, are found to occur concurrently. The origin of the reduced friction observed in recent SFA ex-... 

The surface force trend resembles that of the interaction energy as a function of the distance between two mica surfaces bearing polymer brushes as obtained with the surface forces apparatus (SFA) (e.g. [242]). Such a similarity between polymer brushes symmetrically compressed by different phases is not unexpected. 

We need to understand the force-bearing characteristics of the asperity-rich pad surface. The scale of this perspective shrinks another order of magnitude from that used to examine the pad s pore structures. As seen in Figure 6.16, the wafer compression action on the polymer material is likely to show a viscoelastic response (the compression span of the traveling wafer is sufficiently long for the polymer material to respond viscoelastically). The asperities in contact with the wafer surface will then suffer a viscoelastic modification. The nature of this modification will be defined by the forces at work on the asperity profiles. 

In our laboratory, we have studied the effects of various surface-modified alumoxane nanoparticles on the mechanical properties of a biodegradable polymer for load-bearing bone tissue applications [4j. Alumoxane nanoparticles with three different surface modifications were tested — activated alumoxanes possessing two reactive double bonds available for interaction with the cross-link network of the polymer surfactant alumoxanes modified with long fatty acid chains to aid in dispersion within the hydrophobic polymer and hybrid alumoxanes modified with a surfactant chain and a reactive double bond within the same substituent (Figure 40.2). These nanoparticles were incorporated into a biodegradable poly(propylene fumarate)-based (PPF) system and the nanocomposites were tested for flexural and compressive mechanical properties. 

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