Possible New Materials

Fullerene cages (C ) and carbon nanotubes (C are currently of interest as possible biomaterials, biosensors and drug dehvery agents. Analogous cage and tube structures based on phosphorus, if they can be made, may well be of greater use in these and other fields of bioscience activity (Chapter 4.1). 

Recent reports [14,72] describe the preparation of various calcium phosphate nanoparticles. It is believed that such products might prove to be of great value in biomedicine, for drug delivery, gene silencing, and so on. Phosphoras-based dendrimers have recently been investigated with a view to medical applications, or as potentially useful nanoparticle or nanotube materials [73,74,75], 

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Lechna-Marczynska M., Ulatowska A., Podbielska H., Grzegorzewski B., Light scattering measurements in ormosil and PHEMA - possible new materials for contact lenses, EOS 23, 33-34, (1999). 

As carriers, oils enter the picture where low-volume airplane applications are made. The cheap oils are used in higher volumes in grass killers. Possibly new materials will displace the present wasteful high-volume spraying of grasses. 

After an extensive review of possible new materials, the team found a material that had a surface-to-volume ratio closer to 1000 M /M and a void volume up to 98%. A hydrophilic coating could be grafted to its surface to provide a reservoir capacity to release nutrients in a controlled manner. Lastly, the hydrophilic coating could be copolymerized with certain bioactive polymers and ligands that improve cell adhesion dramatically. 

There is still much interest in the chemical industry in developing new grouts, particularly if these can be made from otherwise wasted byproducts. At a recent seminar to discuss possible new materials, participants were seriously talking about the need for products with 1000 year permanence, for applications near radioactive wastes. Hopefully, technological progress will evolve much better solutions to both ends of the problem long before 1000 years. 

This chapter will be devoted to the consideration of nascent research undertakings, possible new materials, and as yet unanswered research questions. First, an effort will be made to codify and classify composite materials and polyblends with respect to topological considerations. We will examine what other ways may possibly exist to make new combinations of two types of polymeric molecules. How many ways exist to mix two kinds of polymer molecules What relationships can be developed among such diverse materials as particulate and fiber-reinforced plastics, polymer-impregnated concrete, and foams, paint films, etc. ... 

Exfoliated clay nanocomposites formed between organocation exchanged montmorillonites and thermoplastic Nylon-6 have recently been described by Toyota researchers (9-11). Clay exfoliation in the Nylon-6 matrix gave rise to greatly improved mechanical, thermal and rheological properties, mal g possible new materials applications of this polymer. However, it is relatively difficult to achieve complete exfoliation of smectite clays into a continuous polymer matrix, because of the strong electrostatic attraction between the silicate layers and the intergallery cations. 

Transient, or time-resolved, techniques measure tire response of a substance after a rapid perturbation. A swift kick can be provided by any means tliat suddenly moves tire system away from equilibrium—a change in reactant concentration, for instance, or tire photodissociation of a chemical bond. Kinetic properties such as rate constants and amplitudes of chemical reactions or transfonnations of physical state taking place in a material are tlien detennined by measuring tire time course of relaxation to some, possibly new, equilibrium state. Detennining how tire kinetic rate constants vary witli temperature can further yield infonnation about tire tliennodynamic properties (activation entlialpies and entropies) of transition states, tire exceedingly ephemeral species tliat he between reactants, intennediates and products in a chemical reaction. 

Surface Modification. Plasma surface modification can include surface cleaning, surface activation, heat treatments, and plasma polymerization. Surface cleaning and surface activation are usually performed for enhanced joining of materials (see Metal SURFACE TREATMENTS). Plasma heat treatments are not, however, limited to high temperature equiUbrium plasmas on metals. Heat treatments of organic materials are also possible. Plasma polymerization crosses the boundaries between surface modification and materials production by producing materials often not available by any other method. In many cases these new materials can be appHed directly to a substrate, thus modifying the substrate in a novel way. 

During the last century and a half, two new closely related classes of material have been introduced which have not only challenged the older materials for their well-established uses but have also made possible new products which have helped to extend the range of activities of mankind. Without these two groups of materials, rubbers and plastics, it is difficult to conceive how such everyday features of modern life such as the motor car, the telephone and the television set could ever have been developed. 

Such new materials should reveal various possibilities for application. Molecular hybrids between organic polymers and silica gel may become a novel type of composite material. 

The twenty-first century demands novel materials of the scientist. New instruments have made possible the field of nanotechnology, in which chemists study particles between 1 and 100 nm in diameter, intermediate between the atomic and the bulk levels of matter. Nanotechnology has the promise to provide new materials such as biosensors that monitor and even repair bodily processes, microscopic computers, artificial bone, and lightweight, remarkably strong materials. To conceive and develop such materials, scientists need a thorough knowledge of the elements and their compounds. 

Since initiation with conventional Friedel-Crafts halides cannot be controlled, the fine-tuning of reactions becomes extremely cumbersome. In contrast, by the use of alkylaluminum compounds elementary events (initiation, termination, transfer) become controllable and thus molecular engineering becomes possible. Indeed, by elucidating the mechanism of initiation etc., a large variety of new materials, i.e., block3, graft4-6 bigraft7 copolymers, have been synthesized and some of their physical-chemical properties determined. 

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