Surface modification, definition

The already mentioned definition of seeded polymerization is in the broad sense of the word. Seeded polymerization in the narrow sense is polymerization after swelling the seed particle with monomer. Figure 12.2.4 shows what the seeded polymerization can form. Making larger particles is one of popular uses of seeded polymerization, but it does not belong to surface modification. Therefore, making larger particles is not discussed here. 

Hardness has been generally defined by Martens in about 1900 as the resistance of a material able to counter the penetration of another harder material. Sometimes, also in polymer testing, the older definition of hardness as a scratch resistance first introduced by Mohs in 1820 is used. The scratch resistance to be determined in the form of the scratch hardness applying depth-sensing approaches or the Buchholz hardness, for example, is used for characterising (1) elastic and plastic deformations, (2) adhesive failure and crack formation, (3) abrasion and (4) recovery of strains and residual stresses of paintings, coatings or surface modification etc. 

Surface Cleaning. The first step in surface modification is generally cleaning. Prior to cleaning, every surface is dirty, i.e. at the very least it is covered by adsorptive layers. But sometimes native adsorption layers are usefiil or can fulfil a receptor function, as with the oxide film on a platinum surface. In the majority of cases, adsorbed layers must be removed to establish a definite initial state for further modification. 

This chapter will focus on fundamental concepts related to surface modification of materials utilized within polymeric biocomposites for orthopedic applications. For this chapter, orthopedic applications are defined as medical indications or procedures that benefit from utilization of polymeric biocomposites and/or additional implanted therapeutic material to aid in bone regeneration at a localized site. The term surface modification refers to the physical attachment of molecules, predominantly silanes and/or polymers, to the surface of a solid-phase material. Polymeric biocomposites are a class of biomaterials that comprises a biocompatible bulk polymer and a particulated solid phase, often referred to as a binder and a filler, respectively. As there are vast combinations of polymers and solid materials that fit this definition, this chapter highlights solely those combinations that have been utilized for orthopedic applications, in either the acadenuc or the medical industry settings. 

Figure 7.1. Definition of absolute electron potential in aqueous electrochemistry according to Trasatti16 in a classical (a) and liquid covered (b) electrode geometry. Point C corresponds to the zero energy level. O0 is the work function of the bare electrode surface and AC>(=eA P) is the work function modification induced by the presence of the electrolyte layer (b). Reprinted with permission from Elsevier Science.

---