Gelatin has been used as a binder or dispersing agent for light-sensitive and non-light-sensitive photographic layers. The ability to keep the silver halide crystals finely dispersed and to protect the silver halide crystals and other additives from abrasion and other mechanical and chemical influences make gelatin desirable in photographic applications. However, gelatin is very sensitive to changes in humidity. Although this sensitivity to moisture is favorable when the film must be processed, it is also a drawback to the use of gelatin in an emulsion layer. The absorption of moisture can induce swelling stresses, causing dimensional instability commonly observed as bending or curling in the photographic films. This dissertation focuses on the effects of moisture on the state of stress and dimensional stability of gelatin coatings. The hygroscopic effects on the thermal, mechanical, and transport properties were also investigated. Two types of polymer latices, poly(ethyl acrylate) and poly(ethyl methacrylate), were studied as additives to gelatin. The effects of latex concentration, latex particle size, drying condition at vitrification, and gelatin concentration at set point were examined as a function of relative humidity. The goal is to develop an understanding of these properties and assist in controlling or selecting conditions which will minimize the dimensional instability of photographic films over a wide range of use conditions. A vibrational holographic interferometry method and a thermomechanical analyzer were adopted to measure the stresses and dimensional changes as a function of relative humidity. The incorporation of a polymer latex can reduce the moisture sensitivity, and hence increases the dimensional stability of the emulsion layer exposed to the moisture. Composite theories for an isotropic composite filled with spherical particles were applied to determine the humidity expansion coefficient and elastic moduli of the gelatin-latex films. The experimental data were in excellent agreement with the theories. The decrease in swelling stress with an addition of the polymer latex was explained by the incremental linear elasticity theory. Based on this theory, the best material (i.e., minimum swelling stress, lowest Eβ value) was found to be the gelatin film with 40 parts PEA and 15% gelatin concentration at set point, and was dried at the LMERH condition (130F/5.5% RH).

The effects of molecular architecture on block copolymer morphological behavior for two distinct types of architectures have been investigated. The first, AnBm-type stars, have a single, centrally located junction point from which blocks of two polymer species radiate, and are referred to as miktoarm stars. The extremes of a model proposed by Milner were investigated using three miktoarm systems, A2B2 stars, A8B 8 “Vergina” stars, and A5B stars. Samples having a low molecular asymmetry agreed in general with the predictions of this model, although bicontinuous morphologies were not observed. The A5B miktoarm samples, which have a high level of molecular asymmetry, exhibited behavior not predicted by the model, but which was consistent with a trend of discrepancies observed in prior studies. The effect of the junction point on chain stretching behavior in miktoarm stars was noted by comparing the lamellar period of several A2B2 and A8B8 stars to comparable AB diblocks. These materials were found to have significantly increased lamellar periods, thought to result from the increased chain stretching at and near the junction point. The second type of molecular architecture investigated was the multiple-graft architecture. Three series of multigrafts, were characterized: regular multigrafts with tetrafunctional branch points, random multigrafts with trifunctional branch points, and random multigrafts; with tetrafunctional branch points. Using the constituting block copolymer hypothesis, the behavior of these molecules was predicted using existing theories for block copolymers with simpler architectures. Use of this hypothesis is justified herein, and illustrates that the behavior of block copolymers with complex architectures is dictated by the preferred behavior of smaller architectural subunits from which the multigraft is comprised. The morphological behavior of multiple-graft block copolymers was shown to be influenced by branch point functionality, branch point location, and the number of branch points per molecule. Architectural heterogeneity was found to impair self-assembly behavior of the multigrafts. Small-angle scattering data indicating the formation of microphase separated domains of specific shapes were observed for non-lamellar morphologies, which are able to form and fill space without ordering on a lattice. Finally, lamellar grain size and shape a the series of regular multigrafts was investigated. Grain size was seen to be influenced by the total molecular weight of the multigraft. Grain anisotropy was found to increase as the lamellar grains increase in size, indicating that the growth of lamellar grains is anisotropic, occurring more readily in the direction normal to the plane of the lamellae.

Three distinct heterogeneous polymer modification reactions are explored in this work. The first is a bulk reaction commonly conducted on polyolefins—the free radical addition of maleic anhydride. This reaction was run using supercritical carbon dioxide (SC CO2) as the solvent. The second was the chemical surface modification of an amorphous fluorocopolymer of tetrafluoroethylene and a perfluorodioxole monomer (Teflon AF). Several reactions were explored to reduce the surface of the fluorocopolymer for the enhancement of wettability. The last modification was also on Teflon AF and involved the physical modification of the surface through the transport polymerization of xylylene in order to synthesize a novel bilayer membrane. The bulk maleation of poly-4-methyl-1-pentene (PMP) was the focus of the first project. SC CO2 was utilized as both solvent and swelling agent to promote this heterogeneous reaction and led to successful grafting of anhydride groups on both PMP and linear low density polyethylene. Varying the reaction conditions and reagent concentrations allowed optimization of the reaction. The grafted anhydride units were found to exist as single maleic and succinic grafts, and the PMP became crosslinked upon maleation. The surface of a fluoropolymer can be difficult to alter. An examination of three reactions was made to determine the reactivity of Teflon AF: sodium naphthalenide treatment (Na-Nap), aluminum metal modification through deposition and dissolution, and mercury/ammonia photosensitization. The fluorocopolymer with the lower perfluorodioxole percentage was found to be more reactive towards modification with the Na-Nap treatment. The other modification reactions appeared to be nearly equally reactive toward both fluorocopolymers. The functionality of the Na-Nap-treated surface was examined in detail with the use of several derivatization reactions. In the final project, an asymmetric gas separation membrane was synthesized using Teflon AF as the highly permeable support layer and chemical vapor deposited poly(p-xylylene) (PPX) as the thin selective layer. This bilayer membrane has oxygen and nitrogen permeability values close to those predicted by the series resistance model. To enhance the weak adhesive bond between Teflon AF and PPX, Na-Nap reduction was used to modify the Teflon AF surface prior to the vapor deposition polymerization of di-p-xylylene monomer.

This dissertation describes the characterization of post-yield deformation processes in thin polyethylene films under biaxial stress states. In particular, research focused on the development of test methodologies and analyses associated with post-yield deformation is described. Considerable emphasis is placed on the initiation and evolution of a unique heterogeneous, post-yield deformation process observed in thin polyethylene films under biaxial stress states. This process closely resembles the necking phenomenon noted in uniaxial tests, and hence initial efforts have primarily involved characterizing the new phenomenon and comparing it to uniaxial necking. The effects of initial molecular orientation and stress state on the formation of either heterogeneous or homogeneous post-yield deformation are investigated and discussed. The evolution of the heterogeneous deformation zones, which are referred to as dilatational bands (DB), is modeled within a thermodynamic framework. The results from the phenomenological characterization are used to determine how the thermodynamic model is to be applied. A kinematic analysis of DB's on the local and global level is also presented. The global kinematics are obtained by measuring changes in the overall dimensions of the DB's as they evolve, while local kinematics are obtained by measuring the principal draw ratios. Results from these studies dictate how the thermodynamic model is to be applied. The thermodynamic model accounts for the energy associated with DB evolution. Based on conclusions derived from phenomenological and kinematic observations, the model is reduced to a single parameter model manifesting expansion of the DB. Correspondingly, the M-integral is the energy release rate describing DB evolution. A material property known as the specific enthalpy of transformation is obtained for several polyethylene films under various biaxial stress states. This property is a measure of the material's resistance to undergoing a post-yield drawing from an initial state to the final, drawn state. A practical outcome for the test methodology might be a scheme to optimize operating conditions for solid-state drawing in a film processing line. The final part of this dissertation presents the development and application of an in-situ birefringence technique able to monitor the molecular orientation direction. The technique is employed to determine the molecular orientation direction field in the process zone of a crack tip for a polyethylene film subjected to a Mode I loading condition. The orientation direction is determined from an analysis of digital images obtained in-situ, in which the tested sample is placed between a pair of constantly rotating crossed polarizing films.

The process of electrospinning and the physical properties of electrospun fibers are presented in this thesis. In electrospinning, polymeric fibers having diameters ranging from 50 nanometers to 1 micrometer are prepared by applying high static charge to a polymer solution. The mechanical properties and molecular morphology of some electrospun polymers are shown to be fundamentally different compared to their bulk analogs. Experimental results indicate that the mechanical behavior of electrospun polyurethane fiber mats is influenced by fiber mat morphology, molecular orientation, and surface flaws on electrospun fibers. This research characterizes the mechanical behavior of randomly oriented electrospun polyurethane mats and sheds light on general differences in behavior between electrospun and bulk materials. Further, the mechanical response of random fiber mats is modeled based on the mechanical characterization of aligned electrospun fibers. Also, empirical models are employed to relate the tensile properties of electrospun materials to their bulk analogs. The crystallinity and melting behavior of a family of electrospun polyesters is studied and provides insight to the rapid cooling and effects on solidification and crystallization of electrospun polymeric fibers. The results indicate a commonly accepted idea in electrospinning, that electrospun fibers result from rapid solvent evaporation and experience quench-like solidification from a jet of polymer solution. A qualitative study illustrates a color change phenomenon in a series of electrospun polymer/solvent systems. Color change is produced by electrospinning, and subsequent heating, and occurs at characteristic temperatures dependent on the polymer system used. These color change systems are also demonstrated as candidates for imageable media.

The binary polymer system of polystyrene and poly(n-pentyl methacrylate) was recently found to exhibit closed-loop type phase behavior. This is the first known example of a weakly interacting system exhibiting such a phase diagram. At atmospheric pressure the block copolymer displays both a lower disorder-to-order and upper-order-to-disorder transition, representing the lower and upper bounds of the closed-loop phase diagram. The application of hydrostatic pressure served to shrink the closed-loop, yielding pressure coefficients of the lower disorder-to-order and upper order-to-disorder transitions of 725°C/kbar and -725°C/kbar respectively. These pressure coefficients were consistent with those calculated from the Clausius-Clapeyron equation, using the experimentally determined ΔHdisorder and ΔV disorder for each transition. The χeff determined from small angle neutron scattering (SANS) was found to decrease, pass through a minimum, increase to a maximum, and then decrease with increasing temperature. Swelling the system with carbon dioxide served to promote an expansion of the closed-loop. This was due to the entropic nature of both transitions, with differential dilation of the copolymer domains resulting in dissimilar compressibilities of the blocks. In addition to influencing block copolymer phase behavior, carbon dioxide can have a profound impact on resulting morphological structure. A 42/58 PS-b-PnPMA diblock copolymer was found to exhibit lamellar morphology at ambient pressures. With the application of 2500 psi carbon dioxide the morphology shifted to hexagonally-packed cylinders due to preferential absorption into the PnPMA block. Furthermore, the influence of carbon dioxide sorption on the morphology of the PS/poly(n-alkyl methacrylate) block copolymer series was studied both in thin films and in the bulk.

The adsorption of negatively charged polymer, negative/neutral block copolymer and a polyampholyte to patterned surfaces is investigated using off-lattice Monte Carlo simulations. The surface is decorated by stripe and checkerboard patterns of mixed charges. The polymer has periodic charge segments, which potentially match the periodicity of the surface pattern. Results show that the chain entropy of a flexible polymer disrupts and prevents full pattern recognition. Quantities such as average adsorption energy and the radii of gyration of the adsorbed polymer are calculated and found to be dictated by the size of the surface pattern and its correlation to the polymer charge density. We performed small angle light scattering on dilute-solution-grown polyethylene crystals grown from quenches in para-xylene. The quench depths ranged from 60 to 85°C for 0.05 wt.% and 0.1 wt.% linear-low-polydispersity polyethylenes. We found asymmetric scattering patterns for the lower temperature quenches to 65°C, and symmetric scattering patterns for the higher temperature quenches to 80°C. There is a smooth transition from asymmetric to symmetric scattering as we change the quench depth. The correlation lengths d=2π/qmax corresponding to the peaks of intensity versus q ranged from 15 to 30 μm. We find evidence that these length scales correspond to assemblies of single polyethylene crystals. Also, we have performed dynamic light scattering on solutions of sodium-poly(styrene-sulfonate) (NaPSS) and poly(ethylene-oxide) (PEO) in water with BaCl2. The fast mode ( Dfast) and slow mode (Dslow) diffusion coefficients were measured as a function of polymer concentration for both polymers in dilute solution. We found that the diffusion coefficients remained relatively constant in the concentration regimes investigated and Dfast and Dslow for both polymers differed by about 1½ orders of magnitude: 1.1 × 10-6 cm2/s versus 7.8 × 10-8 cm2/s for NaPSS and 6.7 × 10-7 cm2/s versus 4.2 × 10-8 cm2/s for PEO. Also, we studied more concentrated solutions of PEO without salt and used Dfast and Dslow to calculate hydrodynamic radii of single and aggregated PEO chains. Using a concentration-dependent viscosity for PEO in water, we found single chain radii from 1 to 5 nm and aggregate radii from 45 to 60 nm.

Electrohydrodynamic instabilities in thin liquid polymer films are generated when electrostatic pressure overcomes surface tension, leading to amplification of fluctuations at the polymer surface. The growth kinetics of these fluctuations are, in principle, similar to the growth in size of domains during phase separation of polymer mixtures. Consequently, an exponential dependence of fluctuation height on time, characterized by a time constant, can be predicted from the strength of the electric field and the characteristics of the polymer. Results for in situ measurements of fluctuation growth in polydimethylsiloxane show good agreement with theory at early stages and divergence from theory at later stages. At the early stages, the measured time constants shoe quantitative agreement with theory, using no adjustable parameters. Furthermore, a significant reduction in the rate of amplification was observed when a low-viscosity thiolene mixture was used. To preserve the fluctuations and patterned structures, the low molecular weight liquid could be polymerized using ultraviolet light. In situ observation of the growth and decay of electrohydrodynamic instabilities in varying electric fields showed that, since the time scales are predictable, they can be manipulated by varying the electric field. When the electric field was cycled between low and high, growth and decay of fluctuations in the varying electric fields was observed. Electric fields were also used to generate patterns in polymer/polymer/air trilayers with a PS film sandwiched between a silicon substrate and a layer of PMMA. The degree to which the viscosity of the polymer film at the substrate is smaller than that of the upper layer has a strong effect on the morphology of structure formation. Several unique three-dimensional microstructures are made possible by tuning electric-field induced fluctuations in concert with dewetting. The kinetics of structure formation were enhanced by this configuration resulting in much faster patterning than achieved in prior studies. External electric fields were also used to amplify fluctuations in bilayers with block copolymers added to reduce interfacial tension. A significant reduction in characteristic length scale for the instabilities was observed. This process shows promise for application to nanometer-scale lithography.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows MediaPlayer or RealPlayer.

A novel manufacturing process called high-temperature high-pressure sintering was studied and explored. Solid fiber reinforced composites are produced by consolidating and compacting layers of polymeric fabrics near their melting temperature under high pressure. There is no need to use an additional matrix as a bonding material. Partial melting and recrystallization of the fibers effectively fuse the material together. The product is called a “matrix free” fiber reinforced composite and essentially a one-polymer composite in which the fiber and the matrix have the same chemical composition. Since the matrix is eliminated in the process, it is possible to achieve a high fiber volume fraction and light weight composite. Interfacial adhesion between fibers and matrix is very good due to the molecular continuity throughout the system and the material is thermally shapeable. Plain woven Spectra ® cloth made of Spectra® fiber was used to comprehensively study the process. The intrinsic properties of the material demonstrate that matrix free Spectra® fiber reinforced composites have the potential to make ballistic shields such as body armor and helmets. The properties and structure of the original fiber and the cloth were carefully examined. Optimization of the processing conditions started with the probing of sintering temperatures by Differential Scanning Calorimetry. Coupled with the information from structural, morphological and mechanical investigations on the samples sintered at different processing conditions, the optimal processing windows were determined to ensure that the outstanding original properties of the fibers translate into high ballistic performance of the composites. Matrix free Spectra® composites exhibit excellent ballistic resistance in the V50 tests conducted by the US Army. In the research, process-structure-property relationship is established and correlations between various properties and structures are understood. Thorough knowledge is obtained for this creative process regarding the procedures, outcomes, advantages and capabilities. Two other ultra high molecular weight polyethylene fiber containing materials, Dyneema Fraglight® nonwoven felt and Spectra Shield® Plus PCR prepreg, were also carefully studied using the process of high-temperature high-pressure sintering. Their structures, morphologies and thermo-mechanical properties were compared with consolidated Spectra® cloth. The results clearly demonstrate that Spectra® cloth is the best candidate for making ballistic protective shields.

Thermosetting materials have long been considered impossible to reuse since they do not melt or dissolve. Few technologies have been developed to recycle waste thermosets compared to those available for the recycling of metals, glasses, and thermoplastics (meltable polymers). As rubbers are a sub-category of thermosetting materials, they also suffer from these limitations to recycling. Currently, scrap rubber tires and waste polyurethanes represent two of the largest recycling dilemmas facing our society. The work herein offers two potential solutions to this problem of recycling thermosets. The first technique, High-Pressure High-Temperature Sintering (HPHTS), allows parts to be produced from 100% recycled material (current techniques typically use less than 10% recycled content). Several thermosetting systems were investigated in efforts to understand why certain thermosets are more recyclable via HPHTS than others. The goal of this work was to understand the mechanism of HPHTS and design and/or synthesize thermosets that are more easily recycled when they reach the waste stream. During this study, it was realized that Chemical Stress Relaxation (CSR) techniques offered excellent insight into the HPHTS process. As such, a section of the thesis is focused on Chemical Stress Relaxation and its correlation with HPHTS. The last sections devoted to HPHTS involve the utilization of additives in the HPHTS process as a means of increasing mechanical properties and engineering the backbone of thermosets in efforts to enhance recyclability. These chapters target the end uses of these materials; their purpose being to increase properties so that the materials can be utilized for real world products. The second technique, degradation/devulcanization of thermosets (specifically rubber), is carried out at high temperatures (>280°C) under a variety of conditions (in a melt press while under pressure, in a Parr-reactor, etc.) The resulting viscous liquid-like material has numerous uses that include revulcanization, asphalt modification, and oil replacement in the compounding and molding of virgin rubber. Many of these uses not only increased the amount of rubber recycled, but also offered potential improvements over prior art. Materials incorporating over 35% recycled content were produced and maintained all of the original mechanical properties of the control (oil compounded) specimen.