Blends of lightly sulfonated polystyrene and poly(N,N'-dimethylethylene sebacamide) (Li-SPS/mPA) are miscible as a result of strong ion-amide complexation. The blends exhibit LCST phase behavior and an increase of the sulfonation level from 4 to 9.5 mol% raises the critical temperature by 150°C. Phase separation may be thermally induced and isthermodynamically reversible. The phase separation kinetics that occur following a temperature-jump deep into the spinodal region of the phase diagram deviate from conventional Cahn-Hilliard theory and the phase separation process stalls after a couple of hours, essentially pinning the structure at that point. The extent of phase-separation that occurs before pinning is temperature-dependent.

The phase behavior of blends of zinc sulfonated polystyrene (ZnSPS) and bisphenol-A polycarbonate (PC) was studied as a function of the sulfonation level and the molecular weight of the ZnSPS ionomer. The system exhibits upper critical solution temperature (UCST) behavior. The cloud point temperatures increased with increasing ZnSPS molecular weight and decreased with increasing sulfonation level. No strong interactions between ZnSPS and PC were detected by FTIR. The composition dependence of the glass transition temperatures of the miscible blends exhibited negative deviation from linear additi vity, which is consistent with no or weak interactions between ZnSPS and PC. Miscibility is believed to arise from strong repulsive interactions between the charged and uncharged species on the ionomer chain.

Rigid-rigid blends made of an ionomer and an ionomer precursor polymer, based on either polystyrene (PS) or poly(methyl methacrylate)(PMMA), were studied. A positive deviation from the rule of mixtures in both strength and toughness was observed over the entire composition range; and an especially significant enhancement was observed at low ionomer composition (e.g., 10 wt.%). This is attributed to a fine dispersion of the rigid ionomer phase in the matrix polymer together with good interfacial adhesion between the phases. The adhesion arises from entanglements due to athermal interactions between the same monomeric units of both the ionomer and the ionomer precursor. In addition, all the blend samples are found to be transparent due to similar refractive indices of the two components.

A polymer blend of an ionomer based on zinc neutralized sulfonated poly(phenylene oxide) or polystyrene with a silicone copolymer containing 6.45% propylamine groups in place of one of the methyl groups on a backbone silicon was prepared. Carbon-13 magic angle spinning spectra show coordination of the amine by the zinc ions. Morphological characterization was made by NMR spectroscopy based on proton spin diffusion, by small angle x-ray scattering and by energy filtered transmission electron microscopy. All experiments show domains in the range of 1 to 1000 nm and domain size can be controlled by the extent of coordination of the amine groups by the zinc ions and by thermal history. The different morphological experiments lead to an apparent hierarchy of domain sizes. The NMR experiment yields the smallest domains, 2 to 10 nm, where contrast is produced by differences in chain mobility. Small angle x-ray scattering indicates domains of 16 nm while electron microscopy indicates domains in the range of 100 to 1000 nm. The variation of the domain size between experiments may reflect the different sources of contrast in each case.

Microstructures of PEEK|PEKK blends at both structural and lamellar levels were studied using simultaneously time-resolved small-angle and wide-angle x-ray scattering (SAXS and WAXS) with synchrotron radiations. Lamellar dimensions and unit cell parameters were determined, and phase separation within the blends were observed. A suitable two-phase growth model is proposed. It is concluded that when crystallized from the melt, PEEK and PEKK lamellae formed in separate lamellar bundles within a common spherulite.

Mechanical alloying represents a potential method for producing finely dispersed alloys of normally incompatible polymers. In this paper, PET and blends of PET with a Vectra thermotropic copolyester have been processed via high energy ball milling at room temperature (ambimilled) and at liquid nitrogen temperatures (cryomilled). Milled powders and compacted disks have been characterized using molecular weight, density and hardness measurements, aswell as DSC, WAXS, TEM and FTIR.

We present here our probing research with segmented block copolyimdes derived on the basis of certain design principles to optimize performance and processability. We have shown that incorporation of relatively short blocks of rigid mesogenic segments along the backbone of flexible polyimide chains produce thermoprocessable polymeric systems which exhibit self-reinforcing characteristics.

Atomic Force Microscopy with Phase Detection Imaging is used to study the surface microdomain morphology of thick (i.e., ca. 2 mm) films of triblock copolymers, such as polymethylmethacrylate - block - polybutadiene - block - polymethylmethacrylate copolymers prepared by a well-taylored two-step sequential copolymerization promoted by a 1,3-diisopropenylbenzene based difunctional anionie initiator. By means of this new scanning probe microscopy technique, it is shown that the surface exhibits a segregated microphase structure, corresponding to the different types of components predicted theoretically by thermodynamic processes. We investigate the relationships between the size and characteristics of the microdomain structure as a function of the molecular parameters of the constituent polymers. Our data illustrate the interest of Phase Detection Imaging in the elucidation of surface phase separation in block copolymers.

The texture and microstructural order present in mesomorphic polymers and their relation to their macroscopic behavior has been investigated using rheological, optical and dynamic scattering (WAXS and SALS) experiments. Shear orientation is observed under constant rate-of-deformation conditions where this orientation is always parallel to the flow direction. However, the high degree of orientation suggested by optical and SALS measurements is not reflected in the degree of molecular order observed in WAXS experiments. After cessation of flow, a rapid relaxation of stress is observed, while only little microstructural relaxation is found; i.e., the state of orientation is very stable

Addition of a block-selective homopolymer to a microphase-ordered block copolymer is known to result in preferential swelling of the chemically compatible microdomain. In this work, we examine the miscibility between a triblock copolymer and a relatively low-molecular-weight, chemically dissimilar, midblock-associating homopolymer and demonstrate that the homopolymer molecules residing in the swollen midblock matrix self-assemble to avoid repulsive interactions with neighboring microdomains. We extend this investigation to include systems composed of a very low-molecular-weight, midblock-associating additive (an oil). At high oil concentrations, the glassy copolymer endblocks micellize, resulting in the formation of a thermoplastic elastomer gel.

While numerous studies have addressed the morphological characteristics of diblock copolymer blends either with a second copolymer or a parent homopolymer, relatively few have examined comparable blends containing a triblock copolymer. In this study, we investigate the role of mid-block bridging on the morphological and physical characteristics of blends composed of a poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer with either an unconstrained homo-polyisoprene (hI) or an end-grafted SI diblock copolymer. Blend compositions and molecular weights of the hi, as well as the I-block of the copolymer, have all been systematically varied to elucidate the effect of additive constraint on the extent of nonideal intramicrodomain mixing. Blend morphologies are characterized using transmission electron microscopy, while blend properties have been measured by dynamic mechanical analysis.

The adhesion of crosslinked PDMS surfaces to self-assembled monolayers with different chemical functionality was investigated using the JKR method, the contact mechanics of solids spreading their interfacial area under load. Interfacial H-bonding was shown to be an important chemical interaction causing significant adhesion hysteresis. The number of H-bonds between PDMS and silanol groups on SiO2/Si surfaces increased with time of the contact under a constant load, indicating pressure-induced reorganization of the PDMS network near the interface. The interaction between PDMS and carboxylic acid groups showed somewhat smaller hysteresis which suggests weaker H-bonding strength. The interaction between PDMS and functionalized biphenyl groups exhibited small hysteresis which is believed to be caused by dipolar interaction. whereas that between PDMS and nonpolar perfluorocarbon groups showed negligible hysteresis. The distinction in the behavior of the unloading data between H-bonding related interaction and dipolar interaction seems to indicate the difference in the nature between non-specific (van der Waals, dipolar) and specific (donor-acceptor, H-bond, acid-base) interactions.

The highly electroactive thiokol rubber (TR)/ conjugated polymer (eg. polyaniline (PAn) or polypyrrole (PPy)) composite films were prepared by electropolymenzation deposition via one-step process in the electrolytic solutions containing aniline or pyrrole and TR oligomer. The electrocatalysis of PAn or PPy for the electrodepolymerization (reduction)- electropolymenzation (oxidation) reaction of TR in the interface between PAn or PPy and TR is determined by cyclic voltammograms. The differeme between the oxidation potential and the reduction potential is 0.05V and 0.36V or less for TR/PAn and TR/PPy composite films, respectively The chemical bands between the nitrogen atoms of PAn or PPy and the mercaptan groups of TR (oligomer) are formed in the electropolymenzation process that is indicated by XPS. The conductivities of TR/PAn and TR/PPy composite films and the stability of the cells consisting of those films are remarkably improved after electrochemical reduction with addition of a suitable conducting carbon black.

Kinetics of phase separation at air/polymer interface in a binary polymer mixture on evaporation of common solvent is studied. The lateral dimension of the highly anisotropie, pancake-like, minority phase increases with a growth exponent of 2/3 identical to ‘late-stage’ growth under (classical) thermal-quench at interface. In contrast to the thermal-quench, during drying the kinetics depends on the initial condition (i.e., initial concentration, Co) that is rescaled to obtain a master-curve.

Thin film polymer nanofoams are produced from triblock copolymers of a fluorinated polyimide, 3F/PMDA (derived from pyromelletic dianhydride (PMDA) and 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3F)) as the center block and polypropylene oxide (PO) as the end blocks. The nanofoam is produced using a three step process: 1.) spin casting the triblock copolymer onto a silicon substrate, 2.) thermal treatment in an Argon atmosphere to imidize the center block and 3.) thermal treatment in air to degrade the PO domains and form nanoscale voids. This process was characterized using both transmission electron microscopy (TEM) and small angle neutron scattering (SANS). For the TEM studies, Ruthenium tetroxide staining was used to enhance the contrast between the polyimide (PI) matrix and the PO microdomains or voids, which permitted a more detailed view of the microstructure of both the foamed and unfoamed materials. From the two dimensional Fourier transform of the micrographs the spatial correlation between the PO microdomains in the unfoamed material and between the voids in the foam were found. An interdomain separation distance of -37 nm was observed. SANS was performed to follow the imidization and foaming processes both in-situ and on a Si substrate. The SANS results indicated that the films are homogeneous when spun from solution and that the microphase separation of the PO domains occurs during the imidization step. The subsequent foaming step leaves the morphology generally intact with the PO domains converting to voids. A peak was found in the SANS curve with a spacing of about 26 nm, which is qualitative agreement with the TEM data.

Local control of domain orientation in diblock copolymer thin films is demonstrated through the use of external electric fields. Thin films of a polystyrene-polymethylmethacrylate diblock copolymers, denoted P(S-b-MMA), were spin coated onto silicon nitride membrane substrates with prefabricated in-plane electrodes, forming cylindrical PMMA microdomains. Films annealed under an applied electric field (E ≤ 37V/μm) at 250°C for 24h under an argon atmosphere showed an alignment of the cylindrical microdomains parallel to the electric field lines. A quantitative measure of the degree of alignment was obtained by correlating the local field strength, E, and direction with the observed cylinder orientation. The alignment was found to saturate above E≈30V/μm, and to decrease rapidly as E falls below this value.

Using a two dimensional self-consistent field theory, we investigate the interactions between two planar surfaces that are coated with terminally-anchored homopolymers. One surface is coated with A chains and the other is covered with B homopolymers. The chains are grafted at low densities and the B polymers are chosen to be solvophobic, while the A chains are relatively solvophilic. We determine the morphology of the layers and the energy of interaction asthe surfaces are compressed. Our results provide guidelines for controlling the interaction between polymer-coated colloidal particles.

The role of copolymer sequence distribution on the interfacial characteristics of a ternary polymer blend containing 2 homopoiymers and a copolymer in the phase separated state are examined using Monte Carlo Simulation. The copolymer does migrate to the biphasic interface in the phase separated regime while the configuration and expansion of the copolymer at the interface is a function of sequence distribution within the copolymer. This effect is interpreted in terms of the efficiency of the copolymer to strengthen the biphasic interface. These results suggest that block, alternating, and block-ran structures show promise as interfacial modifiers, while the purely random and alt-ran copolymers will be less efficient as an interfacial strengthener. It is also found that a variation of the sequence distribution away from a purely random structure can dramatically effect the ability of the copolymer to modify the interface. As most polymers which are not block nor alternating are termed ‘random’, this differentiation may have an effect on experimental studies of ‘random’ copolymers as compatibilizers in polymer blends.

An efficient continuum-space model for simulating polymer blends and copolymers is presented. In this model, the interactions are short-range and purely repulsive, thus allowing for excellent computational performances. The driving force for phase separation is a difference in the repulsive interaction strength between like and unlike mers. To demonstrate the effectiveness of the model, we study the phase behavior of a symmetric binary blend of polymers as well as the interface between the two immiscible phases. As predicted by theory, we find the critical interaction parameter to scaie with the inverse of the chain length of the polymers. The structure of the interface between two immiscible phases is investigated as a function of chain length and immiscibility. Capillary waves are observed and their measurementallows us to determine the surface tension accurately. Finally, the surface tension is related to the interface width.

The fracture toughness Gc of epoxy/high impact polystyrene (HIPS) interfaces was measured as a function of grafting chain density Σ of dPS-COOH chains of various degrees of polymerization N. For short chains, no effective entanglements can be formed between the dPS chains and the PS matrix of the HIPS, thus no enhancement in Gc over that of a bare interface. For very long chains, even though each chain is well entangled with the HIPS, the maximum grafting density achievable is very low and such an interface fails by scission of the grafting chains so that the interface fracture toughness is also low. Large values of Gc are observed at intermediate chain lengths where both effective entanglements can be formed and a large Σ can be achieved. Under these conditions the interface fails initially due to the formation of crazes and the subsequent break down of one of these crazes at the interface. The transition areal chain density from chain scission to crazing, Σc,is independent of N.