Subject surface modification

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. 

Surface Modification of Cellulose and PVA Films. Cellulose, as well as PVA,is known to be a typical non-ionic, hydrophilic polymer possessing hydroxyl groups. As this group has a high reactivity,chemical modification of these polymers is relatively easy and, in fact, has been the subject of extensive research. However, so far as we know, no work has been reported concerned with reactions occurring only at the surface of films or fibers from these polymers. 

Additional surface modifications on vapor deposited SiC fibers, including WC. TaC, TiN, B4C, Al, Ni and Fe, have been applied with varying degree of success (Wawner and Nutt, 1980 DeBolt, 1982 Wawner, 1988). After exhaustive trial and error, TiB is selected as an additional coating material to further prevent the diffusion-induced reactions between the SCS-6 fibers and matrix materials, including Ti alloys and Ti Al intermetallic alloys (e.g. Ti Al, TiAl and TiAl ) (Donncllan and Frazier, 1991 James et al., 1991). When the coated fiber is subjected to tensile... 

In general, in the field of materials or condensed matter, the preparation of polymer brushes on solid surfaces is of great interest for surface modification and composite material preparation [4-6]. A number of model surface grafting techniques have been used on planar surfaces and particles and have been the subject of previous reviews. While a munber of polymer brush preparation methods have been reported using physisorption or chemisorption or so-called grafting onto methods, the emphasis of this review is on surface-initiated polymerization (SIP) methods or grafting from methods. 

It should be emphasized that these results are preliminary and subject to modification as further checks and measurements are made. They are included here to illustrate how a surface attached molecule can be treated quantitatively as a surface state. 

As mentioned, polymer hybrids based on POs are effective as a compati-bilizer between the olefinic materials and polar ones. Furthermore, some polymer hybrids, such as PP-g-PMMA, etc., show good mechanical strength as polymer materials. On the other hand, surface modification of the molded polymer is one of the most attractive methods to let polyolefin materials functionalize. In this sense, surface polymerization of functional monomers on polyolefins is an important subject for polyolefin hybrids. As previously referred to, the growth of PS on PP via the RAFT process has been reported [92]. 

Solar radiation is a form of thermal radiation having a particular wavelength distribution. Its intensity is strongly dependent on atmospheric conditions, time of year, and the angle of incidence for the sun s rays on the surface of the earth. At the outer limit of the atmosphere the total solar irradiation when the earth is at its mean distance from the sun is 1395 W/m2. This number is called the solar constant and is subject to modification upon collection of more precise experimental data. 

Surface-relief grating (SRG, regular topological surface modification) formed via irradiation with an interference pattern of coherent light has been demonstrated only recently/ " and is perhaps the most attractive target in the current research of azo polymers (Chapters 13 and 14 of this book focus on this subject). It is still unclear whether there are any common mechanisms involved between SRG formation and the photomechanical response observed in monolayers described in Section 15.4.1. Nevertheless, with regard to photoinduced motions in Az polymers, it is quite important to proceed with SRG experiments. 

The four kinds of active carbons used in our laboratory were obtained from different commercial sources and in accordance with supplier information were produced from various precursors. Ash was removed from the raw carbon using concentrated hydrofluoric and hydrochloric acids by Korver s method [166]. Carbon samples were subjected to surface modification by oxidation in air or with concentrated HNO, annealing in a vacuum or an ammonia atmosphere. Afterwards, all carbon samples were desorbed under vacuum (10" Pa) at 150°C (423 K) for 3 h. The procedure used for carhon purification ensured the removal of nitric acid and nitrogen oxides (after nitric acid oxidative modification) or physically sorbed NHi (after heat treatment in ammonia). The samples thus prepared... 

The surface modification was a two-step process including introduction of -SiCH=CH2 functions and their transformation to -SiCH2CH2SiCl. In the first step, the silica surface was subjected to silylation using a silicone coupling agent vinyltrichlorosilane, vinyltriethoxysilane, or... 

In conclusion future efforts in structural bulk and surface modifications are needed urgently unless ceria will stay an academic subject for research. This is illustrated by the following figure (Fig. 13.6) showing percentage of conversion (hydrocarbon combustion) versus temperature using a catalyst containing ceria as support or ceria-other oxide solid solution. Two dashed temperature zones are clearly evidenced ... 

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