Touching Objects : Objects as Force-Feedback Devices

This study proposes the use of actuated physical objects to investigate force-feedback sensations to explore a 3D environment. In this study, touch triggers and feedback methods, such as haptic icons, were incorporated to the physical objects to engage the person‟s attention and interest towards the virtual objects. Rhythmical patterns were produced to indicate that the user is in proximity to the virtual objects. Afterwards, these virtual objects inside the 3D environment were modeled and analyzed based from the story, The Necklace by Guy de Maupassant. The Necklace, as a story, encloses visual details about the story‟s environment. Also, the necklace, as a physical object, is a representation of the main character‟s mishaps. Observations from the study indicate that users perceive the sensations as unique to that specific virtual object. Further observations reveal that it takes time to build mental associations between the actuated object and the 3D environment

Molecular design of ordering transitions in block copolymers

Thesis (Ph.D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2000.Vita.Includes bibliographical references (p. 201-216).The tendency of block copolymers (BCP's) to microphase separate at the molecular level, producing a wide array of ordered nanostructures, is of particular interest from an engineering standpoint due to the unique mechanical, optical or electrical properties that ensue. Upon considering the potential applications of these materials, however, one limitation arises from the lack of control over bulk thermodynamics and the appearance of order/disorder (solid-like/liquid-like) transitions in these materials. To address this problem, this thesis aims to, firstly, develop a more quantifiable understanding of the molecular factors governing BCP phase behavior, and, secondly, use that knowledge to molecularly engineer new BCP's with enhanced processibility. While most BCP's microphase separate upon cooling through an upper disorder-to-order transition (UDOT), polystyrene-block-poly n-butyl methacrylate, PS-b-PBMA, undergoes ordering upon heating through a lower disorder-to-order transition (LDOT). Preliminary studies on this material revealed a unique pressure sensitivity of this ordering transition. By applying pressure, this material could be forced into the segmentally mixed liquid state, implying "baroplasticity", a highly attractive property from a processing standpoint. To better understand the molecular origin of this behavior, the bulk thermodynamics of a family of BCPs formed from styrene and a homologous series of n-alkyl methacrylates (PS-b-PnAMA, n ranging from 1 to 12) was investigated, both as a function of pressure and temperature. The results of this study reveal an unexpected, though systematic, dependence of the phase behavior of these BCP's on monomer architecture. In short, over a certain range of alkyl side chain length, PS-b-PnAMA block copolymers are marginally compatible and exhibit unexpectedly large pressure coefficients for the ordering transition, ranging from 60 to 150°C/kbar. In an attempt to identify molecular parameters responsible for these thermodynamic trends, as well as those displayed by other systems reported in the literature, combined group contribution/lattice fluid model calculations of the cohesive properties of the corresponding homopolymers are performed. Based on this analysis, the homopolymer mass density is proposed as a macroscopic parameter that appears to govern phase behavior in weakly interacting block copolymers or polymer blends. Using this new criterion, a simple tool for the molecular design of phase behavior into weakly interacting BCP's is identified, which is successfully used to engineer "baroplastic" behavior into several new systems of commercial relevance, including elastomers and adhesives based on styrene and low Tg acrylates. In light of the improved understanding of BCP phase behavior emerging from these studies, a simple phenomenological free energy expression is proposed for compressible polymer mixtures, that can be extended to block copolymers. Its ability to predict qualitative phase diagrams for the systems investigated in this thesis as well as many other polymer pairs is demonstrated. Using this expression, basic principles regarding polymer thermodynamics are outlined.by Anne-Valérie G. Ruzette.Ph.D

Self-Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra- to Nanofiltration

The self-assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra- to nanofiltration and decrease the pore size of self-assembled block copolymer membranes to below 5 nm without post-treatment. It is now reported that the self-assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol-1 in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux

Unique aqueous self-assembly behavior of a thermoresponsive diblock copolymer

It is well-recognized that block copolymer self-assembly in solution typically produces spheres, worms or vesicles, with the relative volume fraction of each block dictating the copolymer morphology. Stimulus-responsive diblock copolymers that can undergo either sphere/worm or vesicle/worm transitions are also well-documented. Herein we report a new amphiphilic diblock copolymer that can form spheres, worms, vesicles or lamellae in aqueous solution. Such self-assembly behavior is unprecedented for a single diblock copolymer of fixed composition yet is achieved simply by raising the solution temperature from 1 °C (spheres) to 25 °C (worms) to 50 °C (vesicles) to 70 °C (lamellae). Heating increases the degree of hydration (and hence the effective volume fraction) of the core-forming block, with this parameter being solely responsible for driving the sphere-to-worm, worm-to-vesicle and vesicle-to-lamellae transitions. The first two transitions exhibit excellent reversibility but the vesicle-to-lamellae transition exhibits hysteresis on cooling. This new thermoresponsive diblock copolymer provides a useful model for studying such morphological transitions and is likely to be of significant interest for theoretical studies

Protonation-Induced Microphase Separation in Thin Films of a Polyelectrolyte-Hydrophilic Diblock Copolymer

Block copolymers composed of poly(oligo ethylene glycol methyl ether methacrylate) and poly(2-vinylpyridine) are disordered in the neat state but can be induced to order by protonation of the P2VP block, demonstrating a tunable and responsive method for triggering assembly in thin films. Comparison of protonation with the addition of salts shows that microphase separation is due to selective protonation of the P2VP block. Increasing acid incorporation and increasing 2-vinylpyridine content for P2VP minority copolymers both promote increasingly phase-separated morphologies, consistent with protonation increasing the effective strength of segregation between the two blocks. The self-assembled nanostructures formed after casting from acidic solutions may be tuned based on the amount and type of acid incorporation as well as the annealing treatment applied after casting, where both aqueous and polar organic solvents are shown to be effective. Therefore, POEGMA-b-P2VP is a novel ion-containing block copolymer whose morphologies can be facilely tuned during casting and processing by controlling its exposure to acid.United States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-SC0001088)National Science Foundation (U.S.) (Award CMMI-1246740

Mesostructured Block Copolymer Nanoparticles: Versatile Templates for Hybrid Inorganic/Organic Nanostructures

We present a versatile strategy to prepare a range of nanostructured poly(styrene)-block-poly(2-vinyl pyridine) copolymer particles with tunable interior morphology and controlled size by a simple solvent exchange procedure. A key feature of this strategy is the use of functional block copolymers incorporating reactive pyridyl moieties which allow the absorption of metal salts and other inorganic precursors to be directed. Upon reduction of the metal salts, well-defined hybrid metal nanoparticle arrays could be prepared, whereas the use of oxide precursors followed by calcination permits the synthesis of silica and titania particles. In both cases, ordered morphologies templated by the original block copolymer domains were obtained