Surface modification polymer materials

Hirotsugu Yasuda is Professor Emeritus of Chemical Engineering and Director of the Center for Surface Science and Plasma Technology, University of Missouri-Columbia. He has over. 300 publications in refereed journals and books and was a pioneer in the exploration of low-pressure plasma for surface modification of materials and deposition of nanofilms as barrier and permselective membranes in the late 1960s. He received the Ph.D. degree in physical and polymer chemistry from the State University of New York, College of Environmental Science and Forestry, Syracuse. 

Microwave irradiation has been successfully applied in polymer chemistry (Ref [10] and Chapter 14 of this book) - for the synthesis and processing of polymers, e.g. for modification of the surface and cross-linking, and also in the degradation of polymers. Microwave plasmas also have been used in the polymerization and surface modification of materials. The enhanced reaction rates have been attributed to thermal effects - although for some reactions it seems the advantages arise from the selective excitation of one of the educts involved. Shifts in selectivity have also been observed. 

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. 

Biomaterials with Low Thrombogenicity. Poly(ethylene oxide) exhibits extraordinary inertness toward most proteins and biological macromolecules. The polymer is therefore used in bulk and surface modification of biomaterials to develop antithrombogenic surfaces for blood contacting materials. Such modified surfaces result in reduced concentrations of ceU adhesion and protein adsorption when compared to the nonmodifted surfaces. 

Mirzadeh H, Khorasani MT, and Sammez P. Laser surface modification of polymers A novel technique for the preparation of blood compatible materials-II In vitro assay. Iranian Polym, 1998, 7, 5. 

Surface modification of any material including polymers is concerned with a change of the surface properties. The surface properties can be controlled by adjusting the concentration of one... 

The reason for surface modification of a polymer is in most cases a wish to improve wettability and adhesion towards more hydrophilic materials. Both adhesion and wettability are interfacial phenomena. 

Apart from modifications in the bulk, also surface modification of PHAs has been reported. Poly(3HB-co-3HV) film surfaces have been subjected to plasma treatments, using various (mixtures of) gases, water or allyl alcohol [112-114]. Compared to the non-treated polymer samples, the wettability of the surface modified poly(3HB-co-3HV) was increased significantly [112-114]. This yielded a material with improved biocompatibility, which is imperative in the development of biomedical devices. 

In dentistry, silicones are primarily used as dental-impression materials where chemical- and bioinertness are critical, and, thus, thoroughly evaluated.546 The development of a method for the detection of antibodies to silicones has been reviewed,547 as the search for novel silicone biomaterials continues. Thus, aromatic polyamide-silicone resins have been reviewed as a new class of biomaterials.548 In a short review, the comparison of silicones with their major competitor in biomaterials, polyurethanes, has been conducted.549 But silicones are also used in the modification of polyurethanes and other polymers via co-polymerization, formation of IPNs, blending, or functionalization by grafting, affecting both bulk and surface characteristics of the materials, as discussed in the recent reviews.550-552 A number of papers deal specifically with surface modification of silicones for medical applications, as described in a recent reference.555 The role of silicones in biodegradable polyurethane co-polymers,554 and in other hydrolytically degradable co-polymers,555 was recently studied. 

In a previous section, the effect of plasma on PVA surface for pervaporation processes was also mentioned. In fact, plasma treatment is a surface-modification method to control the hydrophilicity-hydrophobicity balance of polymer materials in order to optimize their properties in various domains, such as adhesion, biocompatibility and membrane-separation techniques. Non-porous PVA membranes were prepared by the cast-evaporating method and covered with an allyl alcohol or acrylic acid plasma-polymerized layer the effect of plasma treatment on the increase of PVA membrane surface hydrophobicity was checked [37].The allyl alcohol plasma layer was weakly crosslinked, in contrast to the acrylic acid layer. The best results for the dehydration of ethanol were obtained using allyl alcohol treatment. The selectivity of treated membrane (H20 wt% in the pervaporate in the range 83-92 and a water selectivity, aH2o, of 250 at 25 °C) is higher than that of the non-treated one (aH2o = 19) as well as that of the acrylic acid treated membrane (aH2o = 22). 

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