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Dynamic mechanical properties of block copolymers over a wide temperature range have been previously correlated with the phase-separated microstructure of these systems. In the present work the morphology of the block copolymer is altered by large tensile deformation at various temperatures. Upon removal of the applied stress the morphological features of such stretched-and-released systems become functions of time, as the non-equilibrium microstructure reverts to a thermodynamically stable state. This reformation process is monitored by dynamic mechanical measurements with a modified torsion pendulum capable of applying both tensile and torsional deformation. Experimental results are analyzed using a modified Nielsen model to obtain information on the time-dependent structural state of the samples. These results are then compared with stress-strain curves to provide further insight into the structure breakdown-reformation mechanisms. Two competing mechanisms, domain fracture and block pull out, are proposed to explain these experimental observations. (Author)

We derive the mean-field theory of disordered block-copolymers composed of two monomeric species, combining Edwards' functional method with the replica technique of disordered systems. In the absence of disorder we recover the canonical self-consistent field theory of inhomogeneous polymers. In the presence of sequence disorder the theory can be regarded as a comprehensive, novel self-consistent treatment of copolymer melts, unifying the weak- and strong-inhomogeneous regimes. In particular, we study the stability of the microphase separation transition in a melt of diblock-copolymers, composed of $N$ monomers and equal $A$- $B$-volume fraction, against the disruptive effect of disorder. We obtain a phase diagram in terms of the relevant parameters, namely the rescaled Flory-Huggins parameter $\chi N$ and disorder strength $p$.

A soft particle model for diblock (AB) copolymer melts is proposed. Each molecule is mapped onto two soft spheres built by Gaussian A- and B-monomer distributions. An approximate analytical expression for the joint distribution function for the distance between both spheres and their radii of gyration is derived, which determines the entropic contribution to the intramolecular free energy. Adding a mean-field expression for the intermolecular interactions, we obtain the total free energy of the system. Based on this free energy, Monte Carlo simulations are carried out to study the kinetics of microphase ordering in the bulk and its effect on molecular diffusion. This is followed by an analysis of thin films with emphasis on pattern transfer from walls with a periodic structure. It is shown that the level of coarse graining in the soft particle model is suitable to describe structural and kinetic properties of copolymers on mesoscopic scales.

Deuterium NMR relaxation times of specifically deuterated block terpolymers of 2-vinyl pyridine (VP), styrene (S), and deuterostyrene (DS) were measured for the polymers in solution and on silica as a function of temperature and solvent. The block polymers were attached to the silica through the VP segments; the S and DS segments were extended into the solution. In a thermodynamically poor solvent, such as carbon tetrachloride, the relaxation times were consistent with the S segments on the surface-bound polymer being less mobile than their counterparts in solution. This is in contrast with their behavior in toluene (previously reported), where the styrene segments of the surface-bound polymer appeared to be more mobile than in solution. The results demonstrate that the solvent quality may have a dramatic effect on the dynamics of the chain segments of the surface-bound polymer. In a mixture of solvents, namely carbon tetrachloride and methanol there was evidence for more mobile S segments in the surface-bound polymer, however, the VP units also had additional mobility due to the presence of the methanol. The relaxation times were also used, along with the model of Hall and Helfand, to determine the motional parameters and spectral densities for the polymers in the different systems.

Calculations utilizing a scattering formalism due to deGennes are compared with previously-reported SANS data from two polystyrene-polybutadiene samples which have been blended with similar diblocks in which the B segment is deuterated. The present conclusion is that both the lower- and higher- molecular-weight samples exhibit scattering in excess of that predicted, presumably due to clustering of the labelled chains or some other chain-length dependent phenomenon. Keywords: small angle neutron scattering.

The physical aging process in styrene-butadiene and carbonate- siloxane block copolymers has been studied by monitoring the time dependent changes in mechanical and thermal properties. Specifically, stress-strain, stress relaxation and differential scanning calorimetry experiments were utilized. For the styrene-butadiene systems, it was found that the rate of physical aging increases with decreasing glassy content between 50 and 100% glass. However, the rate must decrease to zero when the percent glass reaches zero. The occurrence of physical aging was also noted in the polycarbonate siloxane block copolymer investigated. The data are discussed in light of the practical ramification of utilizing these block copolymers in material applications.

Diblock copolymers with well defined block length yield ordered phase separation. Morphology of the microphase separation is controllable by varying the weight ratio of the two blocks and the length of each block. If one of the blocks is a side chain liquid crystalline polymer (SCLCP), microphase separated systems with liquid crystalline microphases may be realized. Such systems are of fundamental as well as practical interest. The effect of size and type of the liquid crystalline microphase transition is one of the fundamental questions. This effect is recently investigated by the polymer system in which low molecular weight liquid crystals are dispersed. Different from the low molecular weight liquid crystals dispersed systems, the block copolymer can give several types of microdomains (lamellae, cylinders, or spheres).

The morphology of multiphase polymeric materials is often a strong function of temperature as well as thermal history. For example, the temperatures at which apparent multiple melting endotherms are observed in some materials are found to be sensitive to the thermal annealing conditions. The availability of synchrotron radiation sources makes possible the collection of small and wide angle x-ray scattering data during a differential scanning calorimetry experiment. The technique is applied to examine the possible origins of multiple endotherms and annealing induced morphological changes in segmented polyurethane - poly(ether-ester) copolymers. The results of the polyurethane experiments are compared to thermal-mechanical measurements of softening behavior, from which a number of structure-property relations may be inferred.

We consider a pattern-forming system in two space dimensions defined by an energy G_e. The functional G_e models strong phase separation in AB diblock copolymer melts, and patterns are represented by {0,1}-valued functions; the values 0 and 1 correspond to the A and B phases. The parameter e is the ratio between the intrinsic, material length scale and the scale of the domain. We show that in the limit (as e goes to 0) any sequence u_e of patterns with uniformly bounded energy G_e(u_e) becomes stripe-like: the pattern becomes locally one-dimensional and resembles a periodic stripe pattern of periodicity O(e). In the limit the stripes become uniform in width and increasingly straight. Our results are formulated as a convergence theorem, which states that the functional G_e Gamma-converges to a limit functional G_0. This limit functional is defined on fields of rank-one projections, which represent the local direction of the stripe pattern. The functional G_0 is only finite if the projection field solves a version of the Eikonal equation, and in that case it is the L^2-norm of the divergence of the projection field, or equivalently the L^2-norm of the curvature of the field. At the level of patterns the converging objects are the jump measures |grad(u_e)| combined with the projection fields corresponding to the tangents to the jump set. The central inequality from Peletier & Roeger, (Archive for Rational Mechanics and Analysis, to appear), provides the initial estimate and leads to weak measure-function-pair convergence. We obtain strong convergence by exploiting the non-intersection property of the jump set.

Ten years of ONR sponsored research in this laboratory has led to a clear and unified view of the emulsifying or homogenizing role of diblock copolymers in blends of amorphous rubbery polymers. Recent work emphasized that a similar, but more complex set of phenomena may be useful in the manipulation of semicrystalline polymer blend morphologies and properties. The research focused on model polymers comprised of nonpolar hydrocarbon repeat units. The work built on strong capabilities for in-house synthesis of the required homopolymers and diblock copolymers and for molecular, morphological, and mechanical characterization of the selected polymers. Keywords: Block copolymers, Emulsions.

AFOSR sponsored research on multifunctional polymers which has been conducted in our laboratories over the past three years covers three main areas. Each of the three areas is summarized below and described more completely in some depth in the three sections of this report. The first area includes the synthesis of siloxane modified silicate ceramics produced by sol-gel chemistry followed by ultrastructure processing. Using techniques such as acid free hydrolysis condensation reaction systems, it has been possible to incorporate at least 30% of siloxane oligomers via cohydrolysis of suitably terminated materials in the presence of TMOS. In different but somewhat related work based upon polyimides, extensive studies have been conducted with linear thermoplastic polyimide siloxane copolymers. The polyimide siloxane copolymers prepared to date have been based largely upon aliphatic terminated polydimethyl-siloxanes which have adequate thermal stability for most purposes. The third area of investigation on multifunctional polymers was the synthesis and characterization of isotropic polyarylene sulfone, anisotropic aromatic polyester liquid crystal copolymers. We have demonstrated that with as little as 10 or 15 weight % of the liquid crystal segment, organic solvents which would easily dissolve or stress crack the amorphous engineering homopolymers like polysulfones, are no longer able to do so. Multifunctional polymers; Sol-gel; Polysiloxane modified silicates; Polyimide-siloxane copolymers; Isotropic-anisotropic copolymers; Electronic materials; Ceramic materials.

We show that it is possible to incorporate polymerizable diacetylene groups within both the hard and soft segments of polyurethane/polyester-based segmented copolymers. The resultant microphase separated polymers are comprised of soft and hard segment domains that are both capable of supporting the solid-state polymerization of the diacetylene groups. Cross-polymerization of the diacetylene groups therefore creates polydiacetylene chains within two distinctly different microenvironments, each with its own thermal and mechanical behavior. As a result of this, these new multiple environment polydiacetylene containing block copolymers exhibit complex chromic behavior that is directly associated with the phase transitions of both the soft and hard segment domains.

Two block copolymers of isotactic polypropylene and 1,4 polybutadiene were synthesized using techniques involving a transformation from anionic to Ziegler-Natta polymerization mechanisms. The yield of block copolymer was about fifteen percent (weight basis) in both polymerizations, the remainder being unreacted polybutadiene from the first block synthesis. Molecular characterization experiments and model reactions were consistent with a block-like structure for the copolymers; definitive evidence for the proposed molecular structure was obtained through transmission electron microscopy which clearly revealed microphase-separated morphologies characteristic of block copolymers. (Author)

This article is from Beilstein Journal of Nanotechnology , volume 5 . Abstract In this work, we investigated the cytotoxicity, colloidal stability and optical property of gold nanorods before and after functionalizing them with thiolated PEG and Pluronic triblock copolymer (PEO–PPO–PEO) molecules. The morphology of functionalized gold nanorods was characterized by UV–visible absorption spectroscopy, transmission electron microscopy, and dynamic light scattering. Solution phase synthesis of gold nanorods has remained the method of choice for obtaining varying shapes and aspect ratios of rod nanoparticles. This method typically involves the use of cetyltrimethylammonium bromide (CTAB) surfactants as directing agents to grow gold nanorods in the solution phase. The as-synthesized gold nanorods surfaces are terminated with CTAB molecules and this formulation gives rise to adverse toxicity in vitro and in vivo. To employ the gold nanorods for biological studies, it is important to eliminate or minimize the exposure of CTAB molecules from the gold nanorods surface to the local environment such as cells or tissues. Complete removal of CTAB molecules from the gold nanorods surface is unfeasible as this will render the gold nanorods structurally unstable, causing the aggregation of particles. Here, we investigate the individual use of thiolated PEG and PEO–PPO–PEO as capping agents to reduce the cytotoxicity of gold nanorods formulation, while maintaining the optical, colloidal, and structural properties of gold nanorods. We found that encapsulating gold nanorods with the thiolated PEG or PEO–PPO–PEO molecules guarantees the stability and biocompatibility of the nanoformulation. However, excessive use of these molecules during the passivation process leads to a reduction in the overall cell viability. We also demonstrate the use of the functionalized gold nanorods as scattering probes for dark-field imaging of cancer cells thereby demonstrating their biocompatibility. Our results offer a unique solution for the future development of safe scattering color probes for clinical applications such as the long term imaging of cells and tissues.

Rod-coil diblock copolymers in a selective solvent for the coillike polymer self-organize into hollow spherical micelles having diameters of a few micrometers. Long-range, close-packed, self-ordering of the micelles produced highly iridescent periodic microporous materials. Solution cast micellar films consisted of multilayers of hexagonally ordered arrays of spherical holes whose diameter, periodicity, and wall thickness depended on copolymer molecular weight and composition. Addition of fullerenes into the copolymer solutions also regulated the microstructure and optical properties of the microporous films. These results demonstrate the potential of hierarchical self-assembly of macromolecular components for engineering complex two- and three-dimensional periodic and functional mesostructures.

The relationships between microdomain structure and properties in segmented polyurethane elastomers have been elucidated by application of a number of sophisticated characterization techniques. Solid state deuterium NMR spectroscopy was used to explore the degree of phase separation in elastomers based upon 4,4'-diphenylmethane diisocyanate (MDI), butane diol(deuterium labelled)(BDO), and oxyethylene end-capped polyoxypropylene; and to study molecular motions in model hard segments of MDI/BDO and 2,4-toluene diisocyanate/BDO. The influence of morphological transitions on hydrogen bonding in the elastomers was examined by performing Fourier transform infrared spectroscopy simultaneously with a Differential Scanning Calorimeter (DSC) experiment. The origins of multiple endotherms in crystallizable polyurethanes were probed by performing simultaneous Small-Angle X-Ray Scattering (SAXS)/DSC and Wide-Angle X-Ray Diffraction (WAXD)/DSC experiments. Real-time SAXS and WAXD experiments have also been accomplished in order to characterize the kinetics of crystallization and microphase separation.

Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

We investigate the folding transition of a single diblock copolymer consisting of a semiflexible and a flexible block. We obtain a {\it Saturn-shaped} core-shell conformation in the folded state, in which the flexible block forms a core and the semiflexible block wraps around it. We demonstrate two distinctive features of the core-shell structures: (i) The kinetics of the folding transition in the copolymer are significantly more efficient than those of a semiflexible homopolymer. (ii) The core-shell structure does not depend on the transition pathway.

The purpose of this review is to discuss the more recent advances in the investigation of the relation between the morphology of block copolymers and their properties. First we shall discuss the thermodynamic conditions under which homogeneous block copolymers can be formed. These homogeneous systems are interesting because their underlying chain dynamics can be treated by the accepted molecular models. Viscoelastic relaxation times computed from these theories are in good agreement with experimental data. Next we present some examples of block copolymer morphologies, taken from the electron micrographs now available in the literature. Statistical theories capable of satisfactorily explaining the observed morphologies are then briefly discussed. Finally the elastic, viscoelastic and rheological properties of these materials are described. In all instances the dominant influence of the microdomain structure on these properties is demonstrated.

Preceramic block or graft copolymers may offer entree into nanocomposite ceramics provided the two homopolymers are immiscible and one can carefully control the size of the blocks or grafts. We are exploring the possibility of making copolymers from methlsilsesquioxane, -(MeS(O)1.5)(x-), (SiO), a precursor to black glass and the polysilazane, -(MeHSiNH)(x-), (SiMe), (SiMe), a precursor to silicon carbide nitride. Our initial efforts have been directed towards delineating the chemical transformations that SiO, prepared by room temperature catalytic redistribution of -(MeHSiO)(x-) using Cp2 TiMe2 as the catalyst (0.1 wt%), undergoes as it is heated to 900 C in N2. We find that although Cp2TiMe2 will not catalyze the redistribution of SiMe at room temperature; in the presence of even small amounts of -(MeHSiO) (x-), it is an active catalyst precursor and copolymer be formed. Spectral and chemical composition studies on the pyrolysis products of the copolymers and SiO are described.

The phase transition and phase separation behavior occurring in mixtures containing an A-B block copolymer and an A homopolymer is discussed. With a pure block copolymer an order-disorder transition can be induced by raising the temperature, whereby the ordered lattice of segregated microdomains becomes unstable and give way to a homogeneous liquid structure. Small amounts of a homopolymer added to a block copolymer can be accomodated in the microdomains consisting of the same type of monomeric units, up to a solubility limit that depends on the relative length of the homopolymer and the compolymer block and on the temperature. The order-disorder transition temperature of the block copolymer is also affected by the added homopolymer. At the other extreme of concentration, spherical micelles of block compolymer is formed when a small amount of the copolymer is formed when a small amount of the compolymer is added in the bulk homopolymer, and its critical micelle concentration again depends on the relative length of the molecules and block involved and on the temperature. Measurements were made with light scattering and small-angle X-ray scattering techniques to determine the phase behavior of mixtures containing a styrene-butadiene block copolymer and either a polystyrene or a polybutadiene.

Heat buildup and the effective lifespan of current chemical agent protection for military personnel are still concerns. A semipermeable membrane that allows sweat to escape a chemical protection garment, while rejecting chemical agents, would provide a potential solution for both of these issues. Few semipermeable membranes transport water vapor at a sufficient rate to cool a Soldier working at moderate levels of effort, and the mechanical properties of these materials are also of concern. Membranes fabricated from reactive block copolymers and a small molecule cross-linker using ring-opening metathesis chemistry were tested for their water transport properties. These materials were found to transport water faster than current commercially available membranes at lower humidity levels. The mechanical properties of the membrane still limit its use as a garment in chemical agent protection.

We propose a molecular setup for the physical implementation of a barrier global quantum computation scheme based on the electron-doped pi-conjugated copolymer architecture of nine blocks PPP-PDA-PPP-PA-(CCH-acene)-PA-PPP-PDA-PPP (where each block is an oligomer). The physical carriers of information are electrons coupled through the Coulomb interaction, and the building block of the computing architecture is composed by three adjacent qubit systems in a quasi-linear arrangement, each of them allowing qubit storage, but with the central qubit exhibiting a third accessible state of electronic energy far away from that of the qubits' transition energy. The third state is reached from one of the computational states by means of an on-resonance coherent laser field, and acts as a barrier mechanism for the direct control of qubit entanglement. Initial estimations of the spontaneous emission decay rates associated to the energy level structure allow us to compute a damping rate of order 10^{-7} s, which suggest a not so strong coupling to the environment. Our results offer an all-optical, scalable, proposal for global quantum computing based on semiconducting pi-conjugated polymers.

We apply self consistent field theory to twist grain boundaries of block copolymer melts. The distribution of monomers throughout the grain boundary is obtained as well as the grain boundary free energy per unit area as a function of twist angle. We define an intermaterial dividing surface in order to compare it with minimal surfaces which have been proposed. Our calculation shows that the dividing surface is not a minimal one, but the linear stack of dislocations seems to be a better representation of it for most angles than is Scherck's first surface.

The molecular theory of Rouse-Bueche-Zimm has been modified to predict the viscoelastic behavior of homogeneous block copolymers. The model consists of beads and springs whose magnitudes correspond to the types of blocks in the polymer. Maximum relaxation times can be computed by this model. Viscoelastic data for poly(styrene-b-alpha-methylstyrene-b-styrene), poly(alpha-methylstyrene-b-styrene-b-alpha-methylstyrene) and poly(styrene-b-alpha-methylstryrene) were determined by stress relaxation methods. The results compare favorably with those predicted by the theory. (Author)

The phosphorylation reaction of Yamazaki and Higashi was used to prepare wholly aromatic block copolymers containing the rigid units poly(p-benzamide) (PBA) or poly(p-phenylene terephtalamide) (PPD-T) and the flexible units poly(m-phenylene isophthalamide) (MPD-I) or the polyterephthalamide of p-aminobenzhydrazide (PPD-T). Three synthetic procedures were investigated: A) monomers of the flexible block were added to the rigid prepolymer, B) monomers of the flexible block were added to the carboxy terminated rigid prepolymer, and C) the reaction of the carboxy terminated prepolymer of the rigid block with amine terminated prepolymer of the flexible block. Extraction of the copolymer with a non-solvent for the rigid homopolymer indicates that method B) gives the smallest amount of the flexible homopolymer. The extract from the PBA/MPD-I block copolymer was shown to be the flexible MPD-I homopolymer by NMR. The extract from the PBA/PABH-T copolymer could not be characterized by NMR due to overlapping of the spectra, but differential scanning calorimetry was used to identify the extract as PABH-T.

http://uf.catalog.fcla.edu/uf.jsp?st=UF001129795&ix=nu&I=0&V=D

Our work has led to 1) the identification of several new and facile routes to preparing polyphenylene and poly(arylene vinylene)-type polymers and copolymers, 2) the development of highly-efficient organolanthanide complexes and dendrimers for both photon and excited-state energy harvesting. 3) the demonstration of triplet excited-state harvesting and electrophosphorescence in polymers used for light-emitting diodes, and 4) the development of two-photon active dyes for chemical sensing and photonic applications. It is expected that these four accomplishments will lead to more robust and efficient polymers for solar energy harvesting and light-emitting devices, as well as optical sensors for the detection of chemicals and biological agents.

The major purpose of this proposal was to design, synthesize, and characterize new nanostructured polymer electrolytes for rechargeable lithium battery membranes using tapered block copolymers. Tapered block copolymers possess the ability to tune nanostructure, processing temperatures, and mechanical properties independent from chemical constituents and copolymer block segregation strength by manipulating the interfacial profile in the self-assembled nanostructures. The key outcomes of the completed proposal included: 1) generating nanoscale networks [such as the gyroid network] in tapered block copolymer selfassemblies to improve conductivity by 500x over non-cocontinuous nanostructures; 2) improving room-temperature conductivity by 150x through the incorporation of non-crystallizing PEO-like conducting domains; 3) improving all-temperature conductivity by 5x through the use of tapers to lower the glass transitions temperatures in the conducting polymer domains, thereby increasing chain mobility; 4) demonstrating the ability of tapering to tune network formation in various lithium salt counterion systems through adjustments in the taper profile in order to maximize conductivity; 5) improving mechanical properties through the formation of nanoscale network domains; 6) preliminary testing of battery cyclability at various currents to demonstrate ability to achieve neartheoretical capacities at well over 100 cycles of performance lifetime.

Some changes have been incorporated into a proposed method of manufacturing regular arrays of precisely sized, shaped, positioned, and oriented carbon nanotubes. Such arrays could be useful as mechanical resonators for signal filters and oscillators, and as electrophoretic filters for use in biochemical assays. A prior version of the method was described in Block Copolymers as Templates for Arrays of Carbon Nanotubes, (NPO-30240), NASA Tech Briefs, Vol. 27, No. 4 (April 2003), page 56. To recapitulate from that article: As in other previously reported methods, carbon nanotubes would be formed by decomposition of carbon-containing gases over nanometer-sized catalytic metal particles that had been deposited on suitable substrates. Unlike in other previously reported methods, the catalytic metal particles would not be so randomly and densely distributed as to give rise to thick, irregular mats of nanotubes with a variety of lengths, diameters, and orientations. Instead, in order to obtain regular arrays of spaced-apart carbon nanotubes as nearly identical as possible, the catalytic metal particles would be formed in predetermined regular patterns with precise spacings. The regularity of the arrays would be ensured by the use of nanostructured templates made of block copolymers.

Graft and block charge transfer copolymers of vinyl aromatic hydrocarbons

Dielectric relaxation spectra of block polymers containing sequential type-A dipoles are considered. Spectra of a specific set of block copolymers can be combined to isolate the dynamic cross-correlation between the motions of two distinct parts of the same polymer chain. Unlike past treatments of this problem, no model is assumed for the underlying polymer dynamics.

Dielectric relaxation spectra of block polymers containing sequential type-A dipoles are considered. Spectra of a specific set of block copolymers can be combined to isolate the dynamic cross-correlation between the motions of two distinct parts of the same polymer chain. Unlike past treatments of this problem, no model is assumed for the underlying polymer dynamics.

Because of the complexities involved in polyurethane reaction chemistry and the difficulties encountered in making experimental measurements, relatively little attention has been paid to determining the precise molecular weight, composition, and hard segment length distributions of polyurethane block copolymers. The available evidence suggests that variations in these distributions can markedly influence structure-property relationships in these materials. Computer models have been developed using Monte Carlo methods that allow for simulation of the polymerization process under various conditions and subsequent calculation of the various distributions. The model developed in this contribution is based on a sinking pool of monomers and is thus termed the simple sinking pool model. This model offers several advantages over previous models; in particular it can simulate effects ude to differing reactivity of the chain extender and the polyol, and effects due to phase separation occurring at varying points in the reaction. The model and rationale behind in the inclusion of lthe various parameters are described, and the effects of varying the model parameters on the simulated composition, molecular weight, and hard segment length distributions are determined and discussed.

Because of the complexities involved in polyurethane reaction chemistry and the difficulties encountered in making experimental measurements, relatively little attention has been paid to determining the precise molecular weight, composition, and hard segment length distributions of polyurethane block copolymers. The available evidence suggests that variations in these distributions can markedly influence structure-property relationships in these materials. Computer models have been developed using Monte Carlo methods that allow for simulation of the polymerization process under various conditions and subsequent calculation of the various distributions. The model developed in this contribution is based on a sinking pool of monomers and is thus termed the simple sinking pool model. This model offers several advantages over previous models; in particular it can simulate effects ude to differing reactivity of the chain extender and the polyol, and effects due to phase separation occurring at varying points in the reaction. The model and rationale behind in the inclusion of lthe various parameters are described, and the effects of varying the model parameters on the simulated composition, molecular weight, and hard segment length distributions are determined and discussed.

The thermal and thermomechanical properties of a series of compression molded MDI/BDO/PPO-PEO segmented polyurethane block copolymers are reported as a function of hard segment content. Correlations between these properties show that the hard microdomain morphology is continuous for hard segment contents exceeding ca. 40%. At high program temperature rates, DSC thermograms exhibit a single high temperature endotherm corresponding to the melting of an extended form of MDI/BDO crystal. Multiple endotherms are observed at low DSC scan rates. For high hard segment content specimens, catastrophic softening is coincident with the onset of the first high temperature endotherm. The primary softening point for materials with discrete hard microdomains occurs at the soft microphase Tg. The soft microphase Tg is a minimum for a hard segment content of 50%. The apparent hard microdomain Tg decreases monotonically with increasing hard content and is consistent with heat capacity data for the soft microphase Tg which indicates increased incorporation of soft segment material into the hard microdomain for higher hard segment content materials.

During this project more than one-hundred block copolymers, spanning seven different chemical combinations and numerous molecular weights and compositions, were synthesized using anionic polymerization and chemical modification techniques. Phase behavior was characterized with small-angle neutron scattering (SANS) and transmission electron microscopy, guided by dynamic mechanical spectroscopy measurements. A comprehensive picture of the phase behavior of diblock copolymers near the order-disorder transition has been established. Three new morphologies, bicontinuous with Ia3(bar)d space group symmetry, hexagonally perforated layers (HPL) and hexagonally modulated layers (HML) have been identified along with the classical lamellar, cylindrical and spherical structures. Application of a new in-situ shear-SANS experiment has aided in elucidating the susceptibility of these phases to deformation and flow. Reciprocating shear has been shown to produce macroscopic orientation, and to shift the phase boundaries. Similar static and dynamic phenomena were found for binary mixtures of diblock copolymers, thereby demonstrating a versatile method for controlling structure and properties without the need to produce new materials at each desired composition. p1

In an extension of previous work on polyurethane block copolymers for transparent armor applications, several additional variations of the basic 2,4- toluene diisocyanate/polytetramethylene oxide/1,4-butanediol formulation have been investigated. It has been found that excess diisocyanate in a given formulation improves ballistic resistance and that decreasing the amount of polyether (soft segment) has the same effect. More generally, it has been found that increased sample hardness (Shore D) parallels improved ballistic performance. High-speed photographic data have shown that these materials continue to absorb large amounts of ballistic energy, with relatively little of this energy manifested as fragment kinetic energy. A technique for the preparation of void-free ballistic test specimens involving the use of a polytetrafluoroethylene mold is also described.

We have studied structure formation in a confined block copolymer melt by means of dynamic density functional theory (DDFT). The confinement is two-dimensional, and the confined geometry is that of a cylindrical nanopore. Although the results of this study are general, our coarse-grained molecular model is inspired by an experimental lamellae-forming PS-PBD diblock copolymer system (Shin et al, Science, 306, 76 (2004)), in which an exotic toroidal structure was observed upon confinement in alumina nanopores. Our computational study shows that a zoo of exotic structures can be formed, although the majority, including the catenoid, helix and double helix that were also found in Monte Carlo (MC) nanopore studies, are metastable states. We introduce a general classification scheme and consider the role of kinetics and elongational pressure on stability and formation pathway of both equilibrium and metastable structures in detail. We find that helicity and three-fold connections mediate structural transitions on a larger scale. Moreover, by matching the remaining parameter in our mesoscopic method, the Flory-Huggins parameter, to the experimental system, we obtain a structure that resembles the experimental toroidal structure in great detail. Here, the most important factor seems to be the roughness of the pore, i.e. small variations of the pore radius on a scale that is larger than the characteristic size in the system.

We study the effect of a random Flory-Huggins parameter in a symmetric diblock copolymer melt which is expected to occur in a copolymer where one block is near its structural glass transition. In the clean limit the microphase segregation between the two blocks causes a weak, fluctuation induced first order transition to a lamellar state. Using a renormalization group approach combined with the replica trick to treat the quenched disorder, we show that beyond a critical disorder strength, that depends on the length of the polymer chain, the character of the transition is changed. The system becomes dominated by strong randomness and a glassy rather than an ordered lamellar state occurs. A renormalization of the effective disorder distribution leads to nonlocal disorder correlations that reflect strong compositional fluctuation on the scale of the radius of gyration of the polymer chains. The reason for this behavior is shown to be the chain length dependent role of critical fluctuations, which are less important for shorter chains and become increasingly more relevant as the polymer length increases and the clean first order transition becomes weaker.

This paper describes our research on the synthesis and properties of ABA block copolymers composed of a rigid-rod (B) block for reinforcement and a flexible coil (A) block as the matrix. In addition to better processability (Ccr), it was anticipated that the block copolymer would have better mechanical strength than those from physical blends of the rigid-rod/flexible coil composition. In the block copolymer, the rigid-rod constituent would be chemically bonded to the flexible coil matrix, while in the physically blended molecular composite the reinforcing rigid-rod polymer is only physically entangled in the matrix. Hence, the translation of stress or strain from the reinforcing rigid-rod molecule in the matrix should be more efficient in the block copolymer than in the physical blend. This would not only provide higher tensile strength, but also fracture toughness and dimensional stability.

Solubilization and encapsulation of fullerenes C60 and C70 by ultralarge hollow micelles formed by rod-coil diblock copolymers and characterization of the resulting self-organized fullerene-block copolymer assemblies are reported. The solubilization capacity of each fullerene in poly(phenylquinoline)-block-polystyrene (PPQ-PS) micelles in binary solvents, trifluoroacetic acid/dichloromethane and trifluoroacetic acid/toluene, was determined to be 200 mg fullerene per gram of PPQ-PS and found to be independent of block copolymer composition and concentration. This represents fullerene solubility enhancement by factors of 1040 and 63 compared to the solubilities in pure dichloromethane and toluene, respectively. Fullerenes C60 and C70 were found to change the micellization and self-assembly of PPQ-PS block copolymers in solution from polymorphic aggregates to only hollow spheres with encapsulated fullerenes. The solubilization and encapsulation of up to 1 - 10 billion fullerene molecules in PPQ-PS block copolymer micelles increased the aggregation number to over 10 to the 9th power while the aggregate diameter increased from 1-5 microns to over 30 microns. Photoluminescence emission and excitation spectra of the fullerene-PPQ-PS block copolymer assemblies evidenced fullerene-induced J-aggregation of the conjugated PPQ blocks. In addition to providing the first detailed knowledge of the effects of solubilizates on the molecular packing of block copolymer micelles, the self-organized fullerene-block copolymer assemblies constitute novel mesoscopic supramolecular materials for electronic, optoelectronic, photonic and other applications. The present results also provide evidence of micellization and micellar solubilization phenomena at the 1 to 30 micrometer size scale.

Diffusion of symmetric diblock copolymer chains in macroscopically oriented lamellar block copolymers are studied in a molecular dynamics simulation. Results for diffusion constant both parallel $D_\parallel$ and perpendicular $D_\perp$ to the lamellar planes are compared to results in the disordered one phase region. For diblocks of length N=40 (1.1 N_e) and $100 (3N_e)$, where $N_e$ is the entanglement length of a homopolymer melt at the same density, $D_\parallel$ is nearly independent of $\chi$, while $D_\perp$ is strongly suppressed as $\chi$ is increased. These results are in agreement with theoretical predictions based on the Rouse model. The isotropic diffusion constant of quenched disordered systems is approximated fairly well by $(2D_\parallel+D_\perp)/3$ of the corresponding lamellar system.

For this project a number of new polymer materials were synthesized including trifunctional, tetrafunctional and hexafunctional regular graft copolymers. Additionally, a range of poly(cyclohexadiene) (PCHD) homopolymers and block copolymers containing PCHD blocks were prepared. The morphologies of the regular graft copolymers, and PCHD containing block copolymers were determined by TEM and SAXS. Additionally, the morphologies of cyclic block copolymers were studied and compared to their linear analogs. The tensile mechanical properties of the regular multigraft materials were studied and related to molecular architecture. It was found that increasing junction point functionality and increasing number of junction points per molecule increased strength and toughness, and decreased hysterysis. A series of block double graft (BDG) copolymers of unique molecular architecture were studied to relate molecular architecture to morphology and mechanical properties. The mechanical properties of some BDG materials compared favorably to commercial thermoplastic elastomers.

The future U.S. Army soldier will require lightweight, flexible, durable, and selectively protective clothing for the battlefield. Current chemical protective clothing is worn as an overgarment and is impermeable to moisture vapor, imposing unbearable amounts of heat stress on the soldier. A new material, an ionic block copolymer, developed by researchers at the U.S. Army Research Laboratory, is both flexible and a breathable protective barrier. This study focuses on thermally processing and laminating this new material onto the standard baffle dress uniform (BDU). Polymer films were produced by cryogenically grinding the polymer to a powder and then thermally pressing it into a film. Films were pressed at 1.15 x 107 Pa (1668 psi) and 100 deg C and were uniform in thickness, with thicknesses ranging from 254 to 300 micrometers (10-13 mils) from film to film. Films were then laminated onto a standard cotton/nylon BDU fabric using a similar pressure, but lower temperature (50 deg C). The polymer/fabric composite nearly doubled the thickness of the fabric and increased the weight threefold. Additionally, infrared spectroscopy revealed no chemical change occurred in the pressed polymer films due to thermal processing.

In this study, sulfonated poly(styrene-isobutylene-styrene) (S-SIBS) block copolymers were characterized by thermogravimetry as a function of four different processing conditions: sulfonation level, annealing temperature, film formation, and casting solvent. Sulfonated samples showed an increase in degradation temperature from 432 to 450 degrees C compared to the unsulfonated polymer, regardless of sulfonation level or other processing condition. Sulfonated samples also showed an additional minor loss of mass at -290 degrees C, which was not observed in the unsulfonated polymer. At this temperature, desulfonation or a cleavage reaction of the aromatic carbon-sulfur bond occurs. In addition, annealing the sulfonated block copolymer at a higher temperature (180 degrees C) for an extended period of time also results in desulfonation. These results were confirmed by a reduction in water sorption and intensity of the infrared bands associated with sulfonic acid. There was no change in thermal stability in S-SIBS block copolymers as a function of film formation (solvent cast vs. heat pressed) and casting solvent (six different solvents).

This report includes the following papers: Anionic Copolymerization of Butadiene and Isoprene with Organolithium Initiators in Hexane; The Reactivity of Polydiene Anions with Divinyl Benzene; Hydrogenated Linear Block Copolymers of Butadiene and Isoprene; Effects of Variation of Composition and Sequence Architecture on Properties; and Chemorheology. (Author)

Addition of 50-200 eq of norbornene to Mo(CH Superscript t Bu) (NAr) (O Superscript t Bu)2 yields living polymers, Mo?CH(C5H8)CHxCH Superscript t Bu (NAr)(O Superscript t Bu)2 (55% trans), that are stable for days in the absence of water and oxygen with essentially no isomerization of the double bonds in the chain. Addition of benzaldehyde cleaves off the polymer in a Wittig-like reaction to yield polynorbornenens with polydispersities in the range 1.04-1.11. Analogous reactions involving 50-200 eq of endo, endo-5,6-dicarbomethoxynorbornene yields homopolymers with polydispersities in the range 1.11-1.22. Block copolymers containing 50 eq of endo,endo-5,6-dicarbomethoxynorbornene and 200 eq of norbornene prepared by adding one or the other monomer first are virtually identical (polydispersities 1.06 and 1.09 with M sub n 57200 and 59900, respectively). These results suggest that the molybdenum catalyst will not react significantly with up to 100 eq of ester functionality during the time of a typical polymerization reaction (approx. 15 m at 25 degs.).

An ABA triblock conjugated copolymer, poly(2,5-benzoxazole)-block-poly(benzobisthiazole-1,4-phenylene)-block-poly(2,5-benzoxazole), 1, was synthesized, characterized, and used to demonstrate spatial confinement effects on the electronic structure and the optical and optoelectronic properties of block copolymers. Optical absorption, photoluminescence, and photoluminescence excitation spectra of thin films of the triblock copolymer evidence spatial confinement of excitons as well as microphase separation. Efficient energy transfer via interchain and intrachain mechanisms were observed in the triblock conjugated copolymer. The results suggest that microphase separation in bulk block conjugated copolymers can significantly modify the spatial modulation and confinement dimensionalities expected in isolated block copolymer chains.