Chapter 2

Research Opportunities for NRL

The panel has attempted to discuss briefly the potential directions and opportunities for NRL research and development related to polymers. The six major categories are (1) polymer surfaces and interfaces, (2) synthesis and characterization, (3) theory, modeling, and simulations, (4) biomimetics, biocomposites, and biomedical applications, (5) electronic properties, and (6) polymers with other special properties. In regard to the programmatic emphasis placed on these areas, the panel recognized that priorities are to be established by the NRL. In any case, regardless of choice, it is necessary that NRL maintain basic research competence in the core areas of theory, synthesis, and characterization. This approach would continue to provide an important Navy communication bridge with the advanced materials industry, government laboratories, and academia, where a number of innovative opportunities may develop.

POLYMER SURFACES AND INTERFACES

Polymer surfaces and interfaces are of great importance to the Navy. Such interfaces include the interface between polymer coatings and seawater, the interface between polymer matrices and inorganic fibers in composites, and polymer-polymer interfaces in rubber-modified polymer blends. The processes occurring at such interfaces control corrosion and biofouling of ship hulls, affect the reflection and scattering of electromagnetic and sound waves, and determine the mechanical properties (e.g., toughness) of structural materials.

Polymers for coatings in contact with seawater are of obvious importance. Prospects exist for the synthesis of new polymers for such coatings which allow bulk and water interface properties to be separately tailored and optimized. Polymers with controlled molecular architecture, e.g., specific end groups or blocks, can promote molecular self-assembly at such an interface. A fundamental understanding of interface reconstruction and the molecular rearrangement of polymer interfaces over time is particularly desirable. Surfaces that are hydrophobic in air can become hydrophilic in water; interfaces that initially have low adhesion with marine organisms can reconstruct when they come into contact with such organisms to produce much stronger adhesion. The thermodynamics and kinetics of such reconstruction deserve special emphasis.

Polymer-inorganic and polymer-polymer interfaces can also have a great impact on naval materials. Controlling adhesion at these interfaces often involves other polymer additives, e.g., block copolymers or end-functional polymers, which organize themselves or react to strengthen the interface. Synthesis of new, more effective polymeric “coupling agents” is a worthwhile objective, as is the development of new theoretical and simulation methods for describing the segregation or reaction of these additives at such interfaces.

Another area where it appears that rapid progress will be possible in the future is the friction and wear of polymer surfaces. This area is important in a number of practical applications ranging from the behavior of thin layers of polymers as lubricants for magnetic disk heads to the lifetime of polymer protective coatings for ship hulls affected by wear due to waterborne debris. In the related area of drag reduction, a currently dormant field, precise control of polymer surface structure or the use of slowly released soluble polymers, which might affect hydrodynamics, may offer new approaches.

Much of the opportunity for advances in the above areas derives from the emergence of new



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Polymers Chapter 2 Research Opportunities for NRL The panel has attempted to discuss briefly the potential directions and opportunities for NRL research and development related to polymers. The six major categories are (1) polymer surfaces and interfaces, (2) synthesis and characterization, (3) theory, modeling, and simulations, (4) biomimetics, biocomposites, and biomedical applications, (5) electronic properties, and (6) polymers with other special properties. In regard to the programmatic emphasis placed on these areas, the panel recognized that priorities are to be established by the NRL. In any case, regardless of choice, it is necessary that NRL maintain basic research competence in the core areas of theory, synthesis, and characterization. This approach would continue to provide an important Navy communication bridge with the advanced materials industry, government laboratories, and academia, where a number of innovative opportunities may develop. POLYMER SURFACES AND INTERFACES Polymer surfaces and interfaces are of great importance to the Navy. Such interfaces include the interface between polymer coatings and seawater, the interface between polymer matrices and inorganic fibers in composites, and polymer-polymer interfaces in rubber-modified polymer blends. The processes occurring at such interfaces control corrosion and biofouling of ship hulls, affect the reflection and scattering of electromagnetic and sound waves, and determine the mechanical properties (e.g., toughness) of structural materials. Polymers for coatings in contact with seawater are of obvious importance. Prospects exist for the synthesis of new polymers for such coatings which allow bulk and water interface properties to be separately tailored and optimized. Polymers with controlled molecular architecture, e.g., specific end groups or blocks, can promote molecular self-assembly at such an interface. A fundamental understanding of interface reconstruction and the molecular rearrangement of polymer interfaces over time is particularly desirable. Surfaces that are hydrophobic in air can become hydrophilic in water; interfaces that initially have low adhesion with marine organisms can reconstruct when they come into contact with such organisms to produce much stronger adhesion. The thermodynamics and kinetics of such reconstruction deserve special emphasis. Polymer-inorganic and polymer-polymer interfaces can also have a great impact on naval materials. Controlling adhesion at these interfaces often involves other polymer additives, e.g., block copolymers or end-functional polymers, which organize themselves or react to strengthen the interface. Synthesis of new, more effective polymeric “coupling agents” is a worthwhile objective, as is the development of new theoretical and simulation methods for describing the segregation or reaction of these additives at such interfaces. Another area where it appears that rapid progress will be possible in the future is the friction and wear of polymer surfaces. This area is important in a number of practical applications ranging from the behavior of thin layers of polymers as lubricants for magnetic disk heads to the lifetime of polymer protective coatings for ship hulls affected by wear due to waterborne debris. In the related area of drag reduction, a currently dormant field, precise control of polymer surface structure or the use of slowly released soluble polymers, which might affect hydrodynamics, may offer new approaches. Much of the opportunity for advances in the above areas derives from the emergence of new

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Polymers characterization methods over the past decade. New depth profiling methods can give concentration versus depth information about polymeric additives labelled with deuterium with resolutions ranging from 1 to 100 nm. These methods include neutron and x-ray reflectivity, ion beam analysis (e.g., forward recoil spectrometry), and secondary ion mass spectrometry. When combined with older surface analytical methods, such as x-ray photoelectron spectroscopy and attenuated total reflection infrared spectroscopy and ellipsometry, these methods provide a powerful array of tools for polymer surface and interface characterization. A number of new surface analysis techniques have also become available with the advent of high-brightness synchrotron x-ray sources. Grazing incidence x-ray diffraction methods now allow one to elucidate the state of order in the 5 nanometers just below polymer surfaces, while near-edge absorption of polarized soft x-rays can interrogate the orientation of molecular segments of polymers at surfaces. New methods based on the contact mechanics technique promise to make it possible to measure simultaneously the work of adhesion, area of contact, and normal and lateral forces between two elastomer surfaces and thus offer the possibility of providing new insights on microscopic mechanisms of friction, adhesion, and wear. Finally, new scanning probe microscopies will make a substantial impact on our knowledge of polymer surfaces by revealing the lateral structure of these interfaces with unprecedented resolution. Scanning force microscopy (SFM) (also called atomic force microscopy) is now in common use to reveal surface topology. Lateral force microscopy, a variant of SFM, has been shown to be capable of imaging polymer surfaces with chemical, rather than just topological, resolution. Another variant, tapping-mode SFM, is capable of revealing local differences in near-surface elastic properties. Near-field scanning optical microscopy promises eventually to allow various optical spectroscopies to be done on polymer surfaces with lateral resolutions as small as 10 nm. Perhaps the most intriguing possible development is a scanning probe NMR spectrometer, an instrument that would make it possible to determine directly the lateral chemical structure of polymer surfaces. Since most of these scanning probe microscopies do not require vacuum, or even air, environments, they can be adapted to examine the structure of water-polymer interfaces as well. SYNTHESIS AND CHARACTERIZATION Novel Syntheses Polymer synthesis has seen major advances in regard to the preparation and controlled design of structure to obtain specific properties or improvements in properties. Structural detail and the tailoring of properties depend on factors such as the control of chain length, molecular weight distribution, sequencing of copolymer units, microstructure isomer control, and end groups. The past 10 years have seen developments such as group transfer polymerization, ring-opening metathesis for cyclic hydrocarbons, improved cationic and anionic techniques for molecular weight control, and new biosynthetic routes. Much remains to be done to more exactly control stereochemistry. The understanding and use of new catalysts for architectural control, and for coupled integrated syntheses from monomer through polymer and product, are significant opportunities for further research. The creation of new techniques for the synthesis of block, telechelic, and functional polymers will be essential for the study and development of new methods to control the interface of polymers with incompatible environments. Although there are now some techniques for the synthesis of block systems, new high-efficiency systems that allow the incorporation of blocks of standard polymers are required. Methods that produce polymers with controlled levels of functionality, as in telechelic polymers, are also needed.

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Polymers The ultimate control is that demonstrated by biological systems. Currently, only biological systems (in vivo or in vitro) can control monomer sequence efficiently. Professor Robert Bruce Merrifield was awarded the 1984 Nobel Prize in Chemistry for establishing a procedure that allows rather inefficient control of the monomer sequence in certain classes of materials. The ability to control sequence confers remarkable power. From only about 21 different amino acid monomers, nature is able to build the myriad proteins that make up functioning human organisms. Efficient and precise varying of the sequence of these monomers in biological systems leads to materials that function as structural materials, muscles, brains, or catalysts. The opportunity for the next great leap in polymer science is establishment of new synthetic methods that allow rational control of the sequence of monomers in complex copolymers. Advances in this area are being made by polymer synthetic chemists through enlistment of biological sequence control mechanisms. There is a very long way to go, but this frontier area clearly represents the great opportunity in polymer synthesis. Opportunities to develop high-performance materials will continue as new technologies become limited by the materials available and their costs. Economical preparation of new polymer structures capable of functioning in new and/or previously “hostile” environments will continue to be important. Major opportunities also exist for upgrading the less expensive commodity-type materials to compete more effectively with new engineered structures, and this will be done by stereochemical design and morphological control in homopolymer, copolymer, and blend systems. Cost and environmental issues related not only to syntheses but also to disposal or recycling are becoming increasingly important and will pose significant problems for the Navy and opportunities for NRL research. Opportunities in regard to supramolecular structures are discussed below. When new polymers are synthesized, their molecular characterization becomes imperative. NRL should continue to explore the newer methods of molecular characterization, including, for example, such methods as laser desorption mass spectrometry, which has been used to obtain molecular weight distributions for samples with molecules having molecular weights up to 105 grams per mole (g/mol). Supramolecular Chemistry The design and synthesis of polymeric materials as described above have traditionally focused on the covalent structure of the chain. With the development of new catalyst systems, living polymerization methods, and biosynthetic routes to new polymers, a high level of control of molecular architecture has been achieved. But because the materials properties of polymers depend on interactions among many contiguous chains in the solid state, it seems clear that a comprehensive view of the design process must include consideration of supramolecular phenomena, i.e., the exploitation of secondary interactions to control structure and properties on length scales greater than those of the single chain. At the same time, experimental and theoretical tools are emerging that enable a meaningful attack on problems of supramolecular chemistry. Particularly promising points of departure for studies of this kind are provided by ongoing investigations of hydrogen-bonded aggregates, liquid crystals, micellar and vesicular systems, and self-assembling membranes. For example, recent theoretical work has demonstrated the similarity of the thermodynamics that controls phase behavior and that which controls pattern selection in phospholipid bilayers and in multiphase block copolymers, and vesicular structures—known for many years in aqueous surfactant chemistry—have been identified in seemingly dissimilar styrene-diene-block copolymers in the absence of solvent. The size of supramolecular structures of concern is often of the order of the wavelength of light, and so

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Polymers the use of light-scattering techniques may be appropriate for NRL. NRL is well positioned to participate in the development of new materials based on supramolecular interactions. Current NRL investigations of ferroelectric liquid crystals and lipid tubules provide excellent examples of the kinds of novel structures and properties to be realized by taking proper account of both covalent and noncovalent bonds in controlling the architectural features of materials. These investigations have been unusually productive and merit high priority. Polymer–Ceramic Composites Ceramists have exploited the sol-gel chemical route to prepare high-performance ceramics. For example, the catalyzed hydrolysis of tetraethylorthosilicate coupled with an appropriate heat cycle can give useful silica-based ceramic materials. Various opportunities exist in exploiting this type of reaction system in the presence of organic-based polymers. For example, elastomers, particularly those that cannot undergo strain-induced crystallization, are compounded with a reinforcing filler such as silica to improve abrasion resistance, tear strength, and tensile strength. The processes and mechanisms for these improvements are still poorly understood. The NRL's elastomer research program might consider precipitating reinforcing fillers into polymers prior to and also after the formation of network structures. In addition to silicates, titanates, aluminates, and combinations of these are available for this approach. Reinforcing ability has been demonstrated by this approach, but much remains to be done in elucidation of properties, e.g., dynamic mechanical properties, as well as in processing. This approach would seem to have an advantage over the usual blending of separately prepared agglomerated filler into high-molecular-weight polymer, which is a difficult, time-consuming, and energy-intensive process, usually done with an elastomer that modifies a ceramic in which it is dispersed, leading to significant improved properties (e.g., impact strength). Also, the hydrolysis reaction can generate functional groups that form hydrogen bonds, leading to interesting inorganic-organic gels, which upon controlled pyrolysis can lead to foamed ceramics. Relatively little has been done in these areas, which suggests an opportunity for NRL involvement. In prepared composites, the adhesion between the phases is related to the distance between atoms and groups of atoms in the two phases, which are subject to specific interactions, as well as the effects of surface orientation, geometry, and roughness. Solidstate NMR can be used to determine these distances, and this kind of method could be explored further by NRL. Mechanical Properties and Failure Mechanisms The mechanical properties of polymers are of importance for most applications. For the Navy, polymer mechanical properties determine the acoustical impedance and damping of sound waves in sonar structures, on the one hand, and the fracture characteristics of polymer-based composite materials for aircraft structure, on the other. While the mechanical properties of elastomeric networks and polymer melts, especially those of miscible polymer blends, seem to be well represented in the present NRL research program, there is potential for extending this expertise to the mechanical properties of solid (glassy or semicrystalline) polymers and phase-separated polymer blends (both those in the melt and solid state). Understanding of the fracture properties of these materials has increased dramatically recently, but the understanding of the mechanism of shear deformation is incomplete even in single-phase polymers and is particularly poor for phase-separated rubber-modified polymers—yet these polymers include the toughest polymeric materials available. New experimental techniques have been developed for the study of the fracture properties of these materials, but

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Polymers good methods for testing small quantities of polymer for screening purposes are badly needed. Since many of the properties of phase-separated polymer blends depend on the mechanical behavior of polymer interfaces, the relationship between the interface structure and the fracture properties is particularly important. Proper understanding of the fracture mechanism requires real-time observation of the process using a variety of techniques such as computer-assisted microscopies and x-ray scattering synchotron measurements. THEORY, MODELING, AND SIMULATIONS Theoretical Modeling Computer simulations provide insight into the behavior of polymers under a variety of circumstances and make it possible to probe problems that are analytically intractable. Theoretical modeling has the distinct advantage that the effects of various parameters can be explored more exhaustively than through simulations. That is, through mathematical models, we can determine the limits of certain behavior or map out phase diagrams for a system—those kinds of explorations that are more cumbersome and more time consuming through simulations (if at all feasible). One area where mathematical models have played a significant role is in polymer blends. In fact, NRL is conducting considerable experimental research on this topic. Combining this experimental program with theoretical modeling would facilitate and enhance both efforts. In particular, equation-of-state models could be used to predict the phase diagrams of polymers mixtures. These predictions could guide experimental efforts in designing new, miscible blends. Self-consistent mean field (SCF) models are useful in predicting the behavior of polymers at both penetrable and impenetrable surfaces. These techniques are now fairly standard; the analytical equations are solved numerically and can be carried out on workstations. The model can be used to examine the adsorption of copolymers onto surfaces and establish guidelines for synthesizing protective coatings and films. The technique can also be used to examine the behavior of chains at fluid-fluid interfaces. Consequently, the findings yield insight regarding the behavior of polymeric surfactants or compatibilizers. These studies would also complement the ongoing work on composites. Finally, the SCF approach can also be used to model interactions within lipid bilayers. Such calculations could complement the NRL work on lipid tubules and biomembranes. Computer Simulations Computer simulations have become an important research tool for determining the properties of polymers. With the advent of fast workstations, many computationally intensive simulations can now be carried out on reasonable time scales. Furthermore, recent studies have demonstrated the power of simulations to predict polymer properties, especially at interfaces and in solution. Thus, simulation can provide a valuable tool to supplement the ongoing NRL research on the interface between phase-separated domains and would complement current NRL studies in the area of blends and composites. There also exists at NRL considerable expertise in molecular dynamics techniques and other simulation methods. Consequently, a collaboration between the two groups in this area would provide a rich research opportunity. A specific area of investigation could be using computer simulations to model failure at an interface. An important goal would be to use the simulations to isolate signatures for a specific failure mode. These studies would be particularly helpful in designing high-strength composites. Another area in which computer simulations are useful is in modeling polymer self-assembly in solution. Current NRL studies on lipid tubules could be complemented by computer simulations to determine how the architecture of the lipid chains affects self-assembly or to

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Polymers investigate how these tubules interact with polymers in solution or other tubules. BIOMIMETICS, BIOCOMPOSITES, AND BIOMEDICAL APPLICATIONS Biomimetics Biomimetics involves studying structure-property-function relationships in biological materials and then utilizing this information to guide in the design of synthetic materials that mimic these properties or functions. Polymer scientists already know, for example, that the cross-linking of polymer chains is essential for rubber elasticity. Nature, however, is more sophisticated in designing such structures, so that bioelastomers have higher efficiencies than synthetic rubbers in storing elastic energy. Understanding and control of such structures could be used to design more efficient synthetic rubbers with reduced degradation from the heat buildup due to inefficient energy storage. Biocomposites Various types of naturally occurring biocomposites differ from most synthetic composites in one or more important respects. For example, while the hard reinforcing phase in synthetic composites may be either amorphous or crystalline, it is generally crystalline in biocomposites. Furthermore, this crystalline hard phase is carefully controlled with regard to amount, morphology, crystallite size, and crystallite size distribution. Moreover, the crystalline region orientation is fixed by the use of templates or epitaxial growth. Sometimes, an advantageous gradation of properties is built into the biomaterial as a result of changes in either chemical composition or physical structure. Large-scale ordering is often also present, and these complex laminated structures have specific interactions within the layers, resulting in excellent overall properties of the biocomposites. An understanding of the complexities of structure and morphology leading to these biocomposites should eventually be coupled with improved methods of synthesizing controlled polymer structures, thus translating the knowledge obtained from biosystems into the sphere of synthetic polymers. Although it may not be feasible for NRL to study biomaterials, researchers at NRL should be aware of the relevant research elsewhere and should probably be ready to use this information to design new materials. Biomedical Applications Polymeric materials are playing an increasing role in biomedical applications. These range from the polymers substituted in applications where glass and metal were traditionally used, to completely new technologies such as controlled release of drugs, drug delivery systems, dressings, and prostheses. Essential in most of these applications is the biocompatibility of the material and the useful lifetime of the device in the harsh environment of the body. Many of the same techniques and approaches that have been and are being developed by the Navy to study the interface of materials with nonbiological environments will be valuable in these studies. Many of the present NRL programs will provide materials that could have direct application in biomedical applications. ELECTRONIC PROPERTIES Organic polymers are widely employed in applications based on their excellent electrical insulating properties, coupled with mechanical toughness and flexibility. They also play a key role in the manufacture of integrated circuits as photoresists that define the microscopic patterns required. Polymers can be made to be photoconductive, piezoelectric, and pyroelectric, which makes them well adapted to xerography and sensor applications. In recent years, polymers have been discovered that have an array of electronic and optical properties that are promising for information processing, memory, displays, switching, and transmission. These rapidly evolving applications take polymeric materials into realms in which polymers have not been important in the past.

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Polymers NRL is well positioned to contribute in these emerging areas with selective choices of research topics and close coupling with other materials scientists and communications and information-processing engineers. The following research topics match NRL's existing expertise, equipment, and facilities and could offer special opportunities for NRL contributions that have clear-cut relevance to the Navy. fabrication of integrated circuits. Photoresist materials are essential to the Advanced materials have an enormous impact on device function, cost, and reliability. For various reasons, U.S. industrial research in this field has diminished, and there is a danger that foreign interests could come to control lithographic materials, a critical requirement for progess in electronics. NRL polymer chemists, working with other divisions at NRL, could make important contributions in research on these enabling materials. Close collaboration with industrial and academic groups is essential. Nonlinear optical materials are employed to construct optical circuits, and polymeric materials are prime candidates in this field. The nonlinear optical behavior is based on the dipolar nature of the polymers, and many promising structures have been synthesized. Key issues are the creation and the stability of dipolar order. Flat panel display devices will have increasing importance to the Navy. Displays based on ferroelectric (chiral smectic) liquid crystals have the potential for providing a major reduction in the cost of such devices together with an improvement in performance. The NRL has the resources and the expertise to solve the critical problem in this technology—the stability of mesophase alignment. Display devices have also been demonstrated based on polymeric lightemitting diodes (LEDs). These devices are mechanically flexible and have color potential. Polymers are favorable materials for applications in holography. Holographic devices offer applications in optical computing pattern recognition and very high density memory. A wide range of sensor types are based on polymeric media. The sensor response may be based on the electrical or optical properties of the polymer, or may be controlled by a secondary factor such as permeability by a chemical entity to be detected. Electronically conducting polymers offer many possible applications. To date, only novel batteries have been commercialized, but transistors have been demonstrated, and many possible opportunities for NRL could emerge. POLYMERS WITH OTHER SPECIAL PROPERTIES Reduced Flammability Flammability is a major problem associated with extended use of polymers in the Navy for structurally related components. The design of materials with greatly improved resistance to flammability would enhance their use by the Navy. At present, some work has been done by NRL in this regard based on phthalonitrile-based systems. Recent studies by others have indicated opportunities for reducing flammability by incorporation of new phosphorus-containing monomers and also of monomers incorporating structures capable of crosslinking at high temperatures. These operate primarily by the formation of barriers to heat, air, and pyrolysis products. This area is worthy of systematic investigation, and tools not previously applied are available now for investigating the chemical and physical nature of the chemistry involved and that of the barriers formed. The condensed phase reactions that occur at the elevated temperatures usually

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Polymers associated with polymer pyrolysis can be followed and studied. Intumescence is also an important factor in barrier efficiency as well as in the ability to achieve coherent and oxidation-resistant barriers. Such barriers include glass, fluorocarbon, and metallic surface coatings, in addition to char formation. Areas that could also be considered for exploration include the new catalytic modes of flame retardation—for example, oxidative dehydrogenation of polyolefins to form water and char. Recent studies have also indicated that blends including high-char-forming polymers have reduced flammability. Many commodity polymers could be made less flammable by this blending route and could thus be more acceptable for naval and civilian use, since lower amounts of additives would be needed, and also improved mechanical properties could be obtained. Possibilities exist for control of smoke and toxic vapor by-products by these approaches, which were not available in previous char-forming systems, e.g., the antimony oxide plus halogen systems. For many reasons—environmental, corrosion, and so on—it has become increasingly important to avoid use of halogens. The Navy Technology Center for Safety and Survivability at NRL can provide a unique and efficient way to test these materials under realistic conditions. Controlled Transport Controlled Release Controlled-release systems have been developed to deliver one or more drugs, insecticides, and fungicides at specific sites and at specific times. Controlled-release delivery is done by means of such mechanisms as osmosis, diffusion through the carrier material, and erosion of the carrier material. Until recently, areas related to medicine and agriculture have received major emphasis. There are some specific areas related to possible naval use where this technology is not only applicable but also requires further exploration. As one example, marine fouling by various organisms remains a significant problem with regard to ship speed loss and the cleaning and renewal of the fouled surfaces. A number of the marine antifoulant approaches based on controlled release principles are environmentally unsuitable since they release antifoulants that are considered pollutants. Several new approaches include (1) release of a nonpolluting agent specific to particular fouling organisms; (2) release of an agent that attacks the chemistry of the fouling organism's natural adhesive rather than the organism per se; and (3) release of an agent that keeps renewing a non-adhesive surface, e.g., silicone, which may slough off continuously. Another area of controlled release that could also be of interest involves flame retardants, which normally create deleterious effects in regard to the aging of materials. Tailored release systems in which the polymer structure is protected from deterioration by the flame retardant package might be useful for designing systems with improved properties. Release systems for patching or repair of structures would also be useful. Curing agents could be released under specific environmental situations, either in situ or in vitro. Membranes and Microfilters The Navy's current interest in membranes and microfilters is related to attempts to develop zero-discharge systems. The Navy is now equipping its new ships with reverse osmosis units for potable and cooling water. A major area of concern for reverse osmosis systems generally has been related to fouling, which seriously affects the efficiency in regard to conversion of waste water content to potable water and allows for the disposal of the dewatered residues. For example, industrially manufactured ultrafilters in reverse osmosis systems foul and must be cleaned frequently. As a result, such systems are treated by high-pressure and high-flow-rate procedures and with chemicals such as hypochlorite to decrease fouling and increase efficiency. In the process, the membrane and its properties are degraded, and systems must be replaced frequently. Understanding the

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Polymers chemical and physical processes associated with fouling, and the hydrophilic-hydrophobic interactions with various polymers and their surfaces, allows opportunities for exploring new materials, surfaces, and membrane design to prevent and/or decrease the fouling problems.