This work describes the phase behavior and morphology of otherwise immiscible polymer blends that contain small numbers of specific interactions. The experimental results are explained in terms of a new model for phase separation, termed the "ionic crosslink model". Sulfonated polystyrene in both the acid and zinc-neutralized forms was blended with either ethyl acrylate/4-vinylpyridine copolymers or styrene/4-vinylpyridine copolymers. The blends were investigated using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and optical microscopy. At substitution levels of 2%, 5%, and 8% the blends are macrophase separated, microphase separated, and phase mixed, respectively. Microscopy shows that the macrophase separated blends exhibit smaller, more uniform sized domains compared to the unfunctionalized blend. The experimental results are qualitatively consistent with the proposed "ionic crosslink model" for phase separation, in which the chains between ionic groups phase-separate due to an unfavorable free energy of mixing, but the presence of ionic interactions restricts the size of the domains. Aggregation of the ionic groups within the blends was examined using DMTA and small angle x-ray scattering (SAXS). Viscoelastic measurements show the existence of a high temperature loss peak, similar to the peak observed in ionomers. However, the temperature of the transition is depressed relative to the parent ionomers due to internal plasticization. The presence of ionic aggregates was confirmed by calculating the average network functionalities. Activation energies for the high temperature transition are related to the relative strengths of the interactions, which is consistent with the transition being due to motion of the ionic groups. SAXS measurements show that the "ionic peak" present in ionomers is destroyed upon blending. The combined DMTA and SAXS results are consistent with intraparticle scattering models for ionomer morphology and are inconsistent with interparticle scattering models. Tensile properties show enhanced toughness and strength due to the presence of specific interactions. The improved properties are attributed to two factors: the presence of interactions which enhance the interfacial adhesion between phase separated domains and the presence of ionic aggregates which act as filler particles. Examination of freeze-fractured surfaces shows evidence for improved interfacial adhesion and enhanced formation of crazes.

The synthesis and adsorption characteristics of specifically functionalized block copolymers have been investigated. Specifically functionalized polymers are block copolymers of controlled MW, MWD, block size and block placement, and meet the requirement that one of the blocks interact strongly with a given surface whereas the other one does not. Synthetic procedures involved living anionic polymerization of various monomers, allowing preparation of narrow-dispersity block copolymers of specific molecular weight, overall composition, block lengths and (in one system used) block placement. The location (along the chain) of the surface attachment could be controlled through appropriate block sequences. The grafting of polystyrene chains to the surface of poly(chlorotrifluoroethylene) film was accomplished by reaction of the surface with three living polymer anions: polystyryl lithium, butadiene endcapped polystyryl lithium and ethylenesulfide endcapped polystyryl lithium. The effects of solvent, reaction temperature, reaction time and anion concentration of the grafted layer were studied by XPS, ATR-IR, gravimetrics and contact angle. The synthesis of styrene/propylenesulfide block copolymers was studied in some detail and was found to result in polymeric dimers caused by disulfide formation. These disulfide linkages were cleaved by reaction with dithiothreitol (DTT). Endcapping with ethyl bromide stabilized the polymers against disulfide formation and degradation of the polypropylenesulfide block. These polymers were adsorbed onto gold surfaces (from THF and cyclohexane) and analyzed by XPS, contact angle, and photomodulated external reflectance IR spectroscopy. The amount adsorbed was found to decrease with increasing size of the polypropylenesulfide (sticky) block. The largest body of work presented discusses the synthesis of SF polymers with controlled placement of SF blocks at desired locations along the chain. This work focussed on the specific functionalization of the styrene blocks in styrene/tert-butyl styrene block copolymers. The various sulfonation reactions investigated gave poor results. Reaction with DEOM/SnCl$\sb4$ was found to be very selective, controllable and allowed introduction of hydroxydiethyl malonate SF at various positions along the chain. The adsorption of these (diblock and triblock) polymers to various silica surfaces was investigated. The data are qualitatively compared with theoretical predictions by both Marques and Evers.

The stress relaxation behavior of critical gels originating from six highly entangled polybutadienes of low polydispersity with molecular weights from 18,100 to 97,000 g/mole were investigated. The polymers were vulcanized by a hydrosilation reaction which takes place nearly exclusively at the pendant 1,2-vinyl sites which are distributed randomly along the polybutadiene chain. The empirical BSW-spectrum was found to describe the relaxation behavior of the uncrosslinked precursor state. A characteristic parameter of the BSW-spectrum is the longest relaxation time of the precursor. Crosslinking increases this longest relaxation time even further but had little effect on the relaxation behavior in the entanglement and transition zones. The relaxation time spectrum of the material at the gel point (critical gel) was found to be well represented by the superposition of the BSW-spectrum and CW-spectrum with minor modifications to the intermediate time regime. The long time behavior follows a power law as described by the Chambon-Winter equation, G(t) = St$\sp{\rm -n}.$ n was found to be constant with a value close to 0.5 over a stoichiometric ratio range of 0.25 $<$ r $<$ 3.0. The gel strength (S) was found to scale with the precursor molecular weight as $\rm S \sim M\sbsp{w}{zn}$ where z is the exponent from the zero shear viscosity molecular weight relationship $\rm\eta\sb0\sim M\sbsp{w}{z},$ is commonly found to be z = 3.3-3.6. A simple empirical model combining first order kinetic analysis with the Flory-Stockmayer branching theory was developed to predict the gel time as a function of stoichiometric ratio and precursor functionality. In-situ rheological measuring techniques of gelation allow for accurate determination of the gel point. The kinetic model was found to agree well with experimental data.

Model networks of polytetrahydrofuran (PTHF) were prepared by end-linking reaction with the known functionality of cross-links, and the specific number of network chains of known molecular weight distribution. Bimodal networks are composed of stoichiometric amounts of short and long chain prepolymers. By selectively labeling either short or long chains with deuterium, one can simultaneously evaluate the local structure of each species by such methods as infrared (IR) and small-angle neutron scattering (SANS). The micro-structure of the bimodal networks were studied by these methods with an emphasis on the effect of spatial distribution of chain lengths between cross-links. IR results have revealed that the segmental orientation function for the long chains is almost equal to the one for the short species during the uniaxial deformation. There are two possible interpretations for the deformation mechanism from this equality according to the rubber elasticity theory of Kuhn and Grun. One is that the extension ratios of the two species are not equal as expected, therefore individual chain segments deform non-affinely. Another is that the bimodal network follows an affine deformation if it is treated as an "averaged unimodal" system consisting of the chain segments with the weight-averaged length between the long and short chains. SANS results have indicated spatial inhomogeneity in the bimodal network with a high mole fraction of short chains. The inhomogeneity is attributed to the formation of clusters of highly cross-linked domain of short chains in the media of sparsely cross-linked long chains. Size of a cluster increases in proportion to the increasing amount of short chains, while the average distance between clusters seems to be less dependent upon. The deformation ratios of the distance between clusters and that of the gyration radius of long chains were quantified. In all cases, it has observed that the bimodal network deforms locally in a non-affine manner, however, at the larger scale the effective functionality from the short chain clusters dominates and deforms close to affinely. These results suggest that theoretical developments incorporating the structural information are necessary to have a better understanding of the local behavior and to relate to macroscopic properties in real polymer networks.

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