Polymer surface, modification, degradation

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. 

K. Allmer, A. Hult, and B. Ranby, Surface modification of polymer films. IV. U V initiated degradation of... 

Albertsson and coworkers [240-244] carried out extensive research to develop polymers in which the polymer properties are altered for different applications. The predominant procedure is ring-opening polymerization which provides a way to achieve pure and well defined structures. They have utilized cyclic monomers such as lactones, anhydrides, carbonates, ether-lactones. The work involved the synthesis of monomers not commercially available, studies of polymerization to form homopolymers, random and block copolymers, development of cross-linked polymers and polymer blends, surface modification in some cases, and characterization of the materials formed. The characterization is carried out with respect to the chemical composition and both chemical and physical structures, the degradation behavior in vitro and in vivo, and in some cases the ability to release drug components from microspheres prepared from the polymers. 

Being essentially a surface technique, XPS valence band spectra also allows to monitor modifications occurring at the polymer surface during adsorption, reactions, of degradation... Very few contributions are, up to now, dealing with such studies ( ). The most direct use of the technique is actually a comparison of the core and valence photoelectron line intensities to deduce informations about the surface and the in-depth composition of the polymer, as well as about the orientation of the macromolecular chain at the surface boundary. 

The Modification, Degradation, and Synthesis of Polymer Surfaces Studied hy ESCA... 

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. 

Preparation of the samples included the following steps, surface modification of the substrate, polymer film deposition, thermal annealing, and selective degradation of the PLA phase, as illustrated in Fig. 4.1. The PLA removal does not alter the copolymers morphology and is comparatively easy, whereas the substrate choice, the surface modification, and thermal annealing protocol decisively influence the copolymer self-assembly behavior as will be discussed in the context of polymer phase separation [2,3]. The vast possible parameter space of the latter two preparation steps, combined with the numerous copolymers, presented a real challenge. 

Fig. 4.1 Preparation of mesoporous thin film polymer templates on suitable substrates, a Substrate surface modification tailoring a neutral surface, b Copolymer film deposition and phase transition to the double-gyroid morphology during thermal annealing, c Selective degradation of PLA yields the mesoporous template...

Composites utilizing cellulose fibers have been prepared with many different materials, especially polymers. It has been well demonstrated that these fibers help to alter and in general enhance the physical properties of polymeric composites [140, 149-157]. Additionally, their bio-degradability and biocompatibility enables cellulose-reinforced materials to be suitable for bio-scaffolding in medical applications, if the polymeric component is also biocompatible [140, 158]. Some surface modifications have been performed on cellulose to add selected characteristics, such as antimicrobial properties to polymeric matrixes [140,159]. 

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