Alan Tonelli

To more fully understand and improve the properties of polymer materials we must develop structure-property relations, i.e., we need to understand how changing the chemical microstructures of polymers effects their behaviors. To establish these structure-property relations we must be able to measure the properties of polymers with different microstructures, and these microstructures need to be carefully characterized. Here we suggest that observation of the birefringence that is produced by application of a strong electric field to dilute solutions of polymers dissolved in non-polar solvents with low dielectric constants, ie., electrical birefringence or the Kerr-Effect, may provide a means to more fully characterize polymer microstructures than can be achieved with the currently most sensitive technique, NMR spectroscopy. Kerr-Effect studies of dilute polymer solutions (our own past and recent work) demonstrated their unique promise to more fully characterize polymer microstructures. In cases where at least one of their mono-mer repeat units is polar or at least reasonably and anisotropically polarizable, the molar Kerr constants, mK, of polymers, as obtained from the electrical birefringence measured from their dilute solutions, were found to be exquisitely sensitive to their microstructures, including the tacticities of homo- and copolymers and the comonomer sequences of copolymers. Because the mKs expected for polymers with given or known microstructures can be estimated if their conformational characteristics have been established, comparison of observed and calculated mKs can be used to confirm or derive their conformational preferences, such as those embodied in their Rotational Isomeric States (RIS) models. From such comparisons of observed and calculated mKs, we were able to conclude that among all characterization techniques, Kerr-Effect studies of dilute polymer solutions are clearly the most sensitive to both their microstructures and their conformations. This is largely a consequence of the fact that the mKs of small molecules, including monomers, range over more than four orders of magnitude, and, in addition, may be either positive or negative in sign. A polymer?s mK is a ?macroscopic? property characteristic of its entire chain. Any microstructural element that alters its overall polarizability tensor or changes the magnitude and/or orientation of its overall dipole moment vector with respect to the direction of its maximum polarizability will affect its molar Kerr constant. Thus, the positions/locations of microstructural elements along the polymer chain (middle vs. end) may also effect its mK. New potential applications of the Kerr-Effect are suggested for polymers that interact/complex with each other or with certain small molecules in solution and also for polymers at interfaces, eg., polymer brushes bathed/swollen in solvents. Prior to our recent Kerr-Effect studies of styrene/p-Br-styrene copolymers, more than a decade had elap-sed without any reported observations of the electrical birefringence of dilute polymer solutions. A state-of the-art Kerr-Effect instrument (ARO-DURIP, 2008) has just been constructed in our laboratory and therefore provides us with the unique capability for further evaluating the Kerr-Effect as a sensitive means to characterize both polymer microstructures and conformations, and potentially their interactions, as well. The NC-State Kerr-Effect instrument is the only experimental means in the world available for determining the long-range microstructures of polymers, thereby enabling the development of more realistic and effective structure-property relationships for materials made from them. The recent NSF Workshop report on Polymers concluded that ?recent advances in polymer syntheses leading to elaborate and precise architectures require accompanying advances in microstructural characterization beyond currently available techniques, which are collectively inadequate? (http://www.nsf.gov/mps/ dmr/reorts.jsp). We agree, and, furthermor

The goal of this work is to develop innovative new approaches to integrating flame retardants into polymeric substances as a means of optimizing its effectiveness while reducing their adverse health effects. This goal will be accomplished through the synergistic combination of an interdisciplinary team of scientists and engineers.

Cyclodextrin (CD) molecules tend to form inclusion compounds (ICs) with many small molecules and polymers. Our objective is to exploit this tendency to improve/enhance the properties of textile products by processing them with CDs in the following two ways: (1) Improved delivery of textile additives using CD-stars (CD-cores with polymer arms) to treat fiber/fabric surfaces . CD-star arms selected for compatibility with the textile surface should anchor the host CD cores facilitating their ability to complex and retain a wide variety of textile additives. (2) Use of non-stoiciometric (n-s)-polymer-CD-ICs with partially unincluded dangling chains as nucleants for the melt-crystallization of the same bulk polymer. When small amounts of (n-s)-polymer-CD-ICs are finely dispersed in the same bulk polymer, they produce a more homogeneous and finer scale semi-crystalline morphology leading to improved mechanical properties upon melt-processing. (3) In addition, physical coloration of textiles based on their underlying nanostructures rather than dyes or pigments will be attempted . In nature color is often produced by nanostructured mater-ials via diffraction, multilayer reflection, cholesteric analogues or photonic crystal-like structures. We hope to build such nanostructures into or on textile fibers. Figure

Cyclodextrin (CD) molecules tend to form inclusion compounds (ICs) with many small molecules and polymers. Our objective is to exploit this tendency to improve/enhance the properties of textile products by processing them with CDs in the following ways: (1) improved delivery of textile additives using soluble additives complexed with CDs and (2) covalent bonding of CDs to polymers, followed by introduction of other polymers or small molecules that normally complex with CDs to confer new functionalities and properties to textiles.

The Departments of Chemical & Biomolecular Engineering (CMBE), Chemistry (CHEM), and Textile Eng. Chem. & Sci. (TEX) at North Carolina State University (NCSU) request funding that will be used to build an experimental instrument for carrying out Kerr effect measurements of polymers in solutions. The team of investigators whose research provides the immediate impetus for the acquisition of this instrument comprises: Jan Genzer (JG, PI), Bruce M. Novak (BMN, coPI), and Alan Tonelli (AT, coPI). In addition, the availability of this unique instrument should provide major benefits to other research groups within NCSU and similar polymer research programs at various military laboratories and other universities. The construction of the Kerr effect apparatus will provide important new capabilities for investigating the comonomer sequence distributions in random copolymers prepared by i) ?coloring? homopolymers under different solvent conditions ii) selective catalytic hydrogenation of polymers, and iii) the structural characterization of newly synthesized copolymers vis-??A -vis their sequence distribution, regiochemical insertion selectivity, and kinetically controlled conformations. The new apparatus will also facilitate determination of tacticities of polymers grown by templated polymerization in cyclodextrins. Because of the exquisite sensitivity of the Kerr effect evidenced by dissolved polymers to both their solution conformations and their detailed long-range microstructures, we and others will be able to not only more fully characterize the structural differences between polymers produced during their syntheses, but also those produced by post-polymerization reactions, such as functionalization, grafting, cross-linking, etc. and how these affect their conformations. The construction of the proposed instrumentation will provide needed capabilities for solving a range of scientific problems that have direct impact on society and on the military. The new equipment will play a major role in training both undergraduate and graduate students. In particular, new hands-on laboratory experiments will be created to enhance the technical training of undergraduates and stimulate their interest in graduate research.

We seek to obtain ultra-high modulus and high strength fibers using aliphatic polyamides to replace the current generation of high strength fibers made from polyethylene (Spectra??A?) and aromatic polyamides (Kevlar??A?), which suffer, respectively, from a relatively low melting temperature and elaborate production requirements. By comp-lexing high molecular weight (~200,000 g/mol) nylon 6,6 obtained by solid state polymerization and ultra-high molecular weight (~400,000 g/mol) nylon 6, obtained by anionic polymerization of ??AY-caprolactam, with the Lewis acids GaCl3, LiCl to disrupt the amide group hydrogen-bonds between chains, we are able to spin the complexed nylon 6,6 fibers and draw them well beyond the DR ~ 5 typically obtained for melt-spun nylon 6,6 fibers. We will form complexes with other salts such as CaCl2, LiBr and SnCl4 and fibers will be spun using the same spinning method as used earlier. Following decomplexation/regeneration the drawn nylon 6,6 fibers obtained by soaking them in water yielded dramatically high initial moduli (20-30 GPa) and tenacities (1-1.5 GPa), which are in fact the highest values ever reported. We plan to obtain mechanical properties of fibers obtained from other complexes and will be compared to those from GaCl3 and LiCl. We also plan to produce fibers via gel spinning using benzyl alcohol or dimethyl sulfoxide (DMSO) and melt spinning of nylon complexes. As a consequence, we seek to optimize our highly encouraging preliminary results and to understand further the role played by the amide group hydrogen-bonds between nylon 6,6 chains during their spinning/drawing into high strength fibers. We believe that the spinning/drawing/decomplexation of nylon 6,6 fibers from spin dopes complexed with Lewis acids, will aid in achieving this objective. In addition, we are investigating both the coagulation step in the wet/dry spinning of the complexed nylon fibers and the production of ultra-high molecular weight aliphatic nylons, which appear to play significant roles in the ultimate production of high strength fibers.

Cyclodextrin (CD) molecules tend to form inclusion compounds (ICs) with many small molecules and polymers. Our objective is to exploit this tendency to improve/enhance the properties of textile products by processing them with CDs in the following 3 ways: (1) improved delivery of textile additives using melt-processable additive-CD-ICs or additives that are permanently complexed (rotaxanated) with CDs, (2) covalent bonding of CDs to linear polymer chains, followed by formation of a CD-IC with other polymers or small molecules to confer new functionalities and properties to textiles and (3) creation of electro-spun webs of nano-fibers containing CD-modified polymers, CDs, or additive-CD-ICs.

Cyclodextrin (CD) molecules tend to form inclusion compounds (ICs) with many small molecules and polymers. Our objective is to exploit this tendency to improve/enhance the properties of textile products by processing them with CDs in the following 3 ways: (1) improved delivery of textile additives using melt-processable additive-CD-ICs or additives that are permanently complexed (rotaxanated) with CDs, (2) covalent bonding of CDs to linear polymer chains, followed by formation of CD-IC with other polymers or small molecules to confer new functionalities and properties to textiles and (3) creation of electro-spun webs of nano-fibers containing CD-modified polymers, CDs, or additive-CD-ICs.

We seek to obtain ultra-high modulus and high strength fibers using aliphatic polyamides to replace the current generation of high strength fibers made from polyethylene (Spectra) and aromatic polyamides (Kevlar), which suffer, respectively, from a relatively low melting temperature and elaborate production requirements. By complexing high molecular weight (-200,000 g/mol) nylon 6,6, obtained by solid state polymerization, with the Lewis acid GaCl3 to disrupt the amide group hydrogen-bonds between chains, we are able to wet/dry spin GaCl3complexed nylon 6,6 fibers and draw them well beyond the DR - 5 typically obtained for melt-spun nylon 6,6 fibers. Following decomplexation/regeneration of the drawn nylon 6,6 fibers by soaking them in water, we observe them to exhibit dramatically high initial moduli (20-30 GPa) and tenacities (1-1.5 GPa), which are in fact the highest values ever reported. As a consequence, we seek to optimize our highly encouraging preliminary results and to understand further the role played by the amide group hydrogen-bonds between nylon 6,6 chains during their spinning/drawing into high strength fibers. We believe that the spinning/drawing/decomplexation of nylon 6,6 fibers that are only partially complexed with GaCI3 will aid in achieving this objective.

This proposal is a request for supplemental funds to accelerate the pace of research associated with a new National Textile Center sponsored project (M05-NS05) pertaining to the development of ultra high modulus/high strength fibers based on aliphatic nylons.