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Author ORCID Identifier
Open Access Dissertation
Doctor of Philosophy (PhD)
Polymer Science and Engineering
Year Degree Awarded
Month Degree Awarded
Alfred J. Crosby
Applied Mechanics | Engineering Physics | Materials Chemistry | Polymer and Organic Materials | Polymer Chemistry
Mesoscale materials, with feature sizes in the range of one hundred nanometers to tens of micrometers, are ubiquitous in Nature. In organisms, mesoscale building blocks connect the properties of underlying molecular and nanoscructures to those of macroscale, organism-scale materials through hierarchical assemblies of recurring structural motifs. The collective action of large numbers of mesoscale features can afford stunning features like the structural color of the morpho butterfly wing, calcium ion-mediated movement in muscle, and wood structures like xylem that can support enormous external compressive loads and negative internal pressure to transport nutrients throughout an organism. In synthetic systems, the design, fabrication, and assembly of mesoscale building blocks has advanced remarkably in recent years. Abundant examples of simple, rigid structures like tiles, polyhedra, spheres, and rods have been driven to assemble through a variety of clever strategies, including site-specific functionalization, capillary forces, and depletion-attraction. Yet, despite these striking reports, considerable opportunity remains for a specific geometry: flexible filaments with mesoscale cross-sectional dimensions. The key opportunities in this case are twofold. First, few fabrication strategies have shown local control of chemical composition in flexible 1-dimensional mesomaterials despite the reported utility of this approach when applied to rigid, 2-to-3D mesoscale objects. Second, assembly of flexible fibrils is uniquely challenging in that the building blocks can adopt a range of shapes, precluding simple aggregation behaviors accessible to rigid, homogeneous bodies like monodisperse tiles and spheres. Thus, a research plan designing routes to fibrous mesoscale assemblies will be well served by developing strategies that embed local compositional control in synthetic fibrils and form robust, anisotropic assemblies of multiple filaments. This thesis details three research projects that realize 1) compositional control by photopatterning arrays of filaments—termed mesoscale polymers—and demonstrating independent mechanical response in domains of differing compositions, 2) solution pH- and light-mediated assemblies of mesoscale polymers with foreign bodies, exemplified by oil-in-water droplets, and 3) self-spinning mesoscale polymer yarns that form topologically linked bundles.
First, a fluorescent and patternable copolymer is prepared and printed from solution by advective assembly to afford structures of submicron thickness, microscale width, and macroscale length. When irradiated through a photomask, these polymer ribbons undergo compositional changes to afford a dramatic increase in polarity in irradiated regions. Alternating segments along the ribbon length display orthogonal solubility in solvent environments such as alcohols to realize selective coiling in irradiated domains while the masked sections act as rigid rods.
Then, the interfacial activity of mesoscale polymers is studied. A new polymer is synthesized with pendent tertiary amines to offer pH-mediated surface charge. Upon contact with an oil-in-water-droplet, amine-functionalized polymer ribbons display dramatically different modes of interaction spanning weak adhesion to spontaneous wrapping. Properties of the system, including the work of adhesion for a droplet-wrapped ribbon, are quantified. Then, a novel photoresist copolymer is synthesized with a pendent photoacid generator and used to prepare mesoscale block copolymers with alternating domains of dramatically different adhesive strength at the oil-water interface. These demonstrate site-selective wrapping behavior and are used to build unprecedented assemblies such as droplets with appendages extended into solution.
Finally, the mesoscale block copolymer concept is adapted to prepare “photocreased” polymer ribbons that adopt locally programmed curvature and twist upon release from the substrate surface. The photocrease platform is shown in the case of constant curvature and twist (i.e., helices) to control helical pitch, radius, and handedness. Then, arrays of helically programmed ribbons are released from the substrate surface, whereupon their spontaneous coiling affords collectively twisted and highly linked bundles. Key features of these striking assemblies are characterized, including number of links and the specific paths traced by each constituent ribbon.
Barber, Dylan M., "SYNTHESIS, FABRICATION, AND ASSEMBLY OF MESOSCALE POLYMER FILAMENTS" (2022). Doctoral Dissertations. 2419.
Creative Commons License
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Representative matlab code used to convert HELFIT outputs into a useful, tabulated form and calculate uncertainty.
Nikon_analysis_file.ga3 (337 kB)
General analysis 3 code used to estimate segment centroids in z-stacks of coiled PMSP helices.
reorganize_raw_centroids.m (2 kB)
Matlab code used to reorganize the xyz centroid location data output by Nikon’s general analysis software into a format that can be input into HELFIT.
Video_S1.mp4 (14457 kB)
A helical MSP (copolymer 2, helix radius r = 38 micrometers) in pH 1 buffer solution with one end fixed to the substrate surface in contact with a PFD droplet (R = 132 micrometers). As the substrate with adhered MSP end is translated to the left, the coiled helical MSP stretches until it detaches from the droplet surface and recoils through the solution. Scale bar 200 micrometers. 1x playback speed.
Video_S2.mp4 (16696 kB)
A helical MSP (copolymer 2, helix radius r = 55 micrometers) in pH 4 buffer solution with one end fixed to the substrate surface in contact with a PFD droplet (R = 335 micrometers). As the substrate with adhered MSP end is translated to the left, the coiled helical MSP stretches until 4 coils detach from the droplet surface (time T ~ 2.3 s). Upon further stretching, the droplet is pulled from the microcapillary tip by the adhered MSP spring. Scale bar 200 micrometers. 1x playback speed.
Video_S3.mp4 (20427 kB)
A helical MSP (copolymer 2) in pH 6 buffer solution. The left end of the helix is attached to the substrate, while the right end became fixed to the substrate after release, affording a structure with 2 fixed ends. As a PFD droplet is brought into contact with the helical ribbon, the two bodies slide past each other without apparent adhesion. Scale bar 200 micrometers. 3x playback speed.
Video_S4.mp4 (20329 kB)
A short MSP segment (copolymer 1, length ~ 400 mircometers) in pH 8 buffer solution is adhered at one end to the surface of a droplet and at the far end to the substrate. Ribbon and droplet are manipulated through the solution via microcapillary tip and translating stage, revealing selective adhesion at the ribbon tip. Scale bar 200 micrometers. 1x playback speed.
Video_S5.mp4 (17616 kB)
MSPs (copolymer 2) in pH 10 buffer solution wrapped around a droplet. The droplet is anchored in place by the fixed end of a wrapped ribbon, while the microcapillary tube and translating stage are used to “unwrap” the droplet. Scale bar 200 micrometers. 2x playback speed.
Video_S6.mp4 (17189 kB)
An MSP (copolymer 2) is held in tension by the microcapillary tip to control wrapping in pH 10 buffer solution. As slack is added to the system by bringing the MSP end toward the wrapped droplet, the MSP continues to wrap until it overlaps an existing coil, arresting the wrapping event. Scale bar 200 micrometers. 10x playback speed.
Video_S7.mp4 (19324 kB)
A droplet is inflated next to an MSP (copolymer 2) in pH 10 buffer solution. To the left (out of frame), the MSP is fixed to the substrate surface; to the right it floats freely. When the droplet touches the MSP, spontaneous wrapping occurs until a defect in the ribbon causes self-overlap, stopping the wrapping event before the ribbon length is consumed and creating a droplet with a pendent arm. To the left, wrapping continues until the ribbon is pulled tight against the substrate-adhered end. Scale bar 200 micrometers. 1x playback speed.
Video_S8.mp4 (19919 kB)
A droplet is inflated until it comes into contact with an MSP (copolymer 2) in pH 10 buffer solution. The ribbon is fixed to the substrate to the left (out of frame) and floats freely to the right. Upon contact, the ribbon spontaneously wraps the droplet until the free end is consumed and the ribbon is pulled tight against the substrate-bound end to the left, final droplet radius R = 360 micrometers. Scale bar 200 micrometers. 3x playback speed.
Video_S9.mp4 (19661 kB)
An MSP (copolymer 2) in pH 10 buffer with one end adhered to the substrate surface (left, out of frame) is partially wrapped around a droplet (R = 88 micrometers) that is adhered to a superglue bead near the end of a carbon fiber cantilever. The ribbon-droplet and cantilever-droplet interfaces are loaded by translating the substrate to the left to pull on the ribbon. Cantilever deflection is used to quantify the applied loads as the system is loaded, unloaded, and then loaded until detachment of the ribbon from the droplet surface. Scale bar 200 micrometers. 5x playback speed.
Video_S10.mp4 (18982 kB)
Copolymer 3 MSBCP with 500 micrometer block length has selectively wrapped a droplet (R = 110 micrometers) in pH 10 buffer solution to afford a droplet with a single arm extended into solution. Scale bar 200 micrometers. 2x playback speed.
Video_S11.mp4 (19520 kB)
An MSBCP in pH 10 buffer solution attached to the same droplet as in Video S10 via selective wrapping to add a second arm. Scale bar 200 micrometers. 2x playback speed.
Video_S12.mp4 (17152 kB)
More MSBCPs in pH 10 buffer solution adhered to and selectively wrapped around the same droplet as in Videos S10 and S11. In this case, we observe mixed assembly modes, including end-on adhesion, adhesion of the hydrophilic segment without wrapping (R < Rc), and selective segmental wrapping of the hydrophobic block (R > Rc). Scale bar 200 micrometers. 1x playback speed.
Video_S13.mp4 (17647 kB)
MSBCPs are picked up from the substrate using a PFD droplet (R = 150 micrometers) adhered to the microcapillary tip in 500 mM NaOH solution. Scale bar 200 micrometers. 4x playback speed.
Video_S14.mp4 (17822 kB)
Cantilever deflection of an MSBCP (patterned segment length 50 micrometers) with one end adhered to the substrate surface, and a far segment adhered to a cantilever-bound droplet (R = 60 micrometers). The system is twice subjected to a full cycle of loading until peel initiation and unloading until re-wrap. On the third cycle, peel is initiated, then propagated until complete detachment of the adhered segment. Scale bar 200 micrometers. 3x playback speed.
VIdeo_S15.mp4 (4707 kB)
Scanning the length of the helix in Figure 4.8a,d; counterclockwise rotation confirms left-handed chirality.
Video_S16.mp4 (4513 kB)
Scanning the length of the helix in Figure 4.8b,e; clockwise rotation confirms right-handed chirality.
Video_S17.mp4 (24968 kB)
Release of fully deprotected copolymer 4 film strips with h0 ~ 1080 nanometers into pH 8 buffer solution to confirm bottom-face-in bending in the absence of cross-sectional asymmetry, supporting the hypothesis of swelling-mediated curvature. Scale bar 1 millimeter. 5x playback speed.
Video_S18.mp4 (21746 kB)
A coiling array of copolymer 4 MSPs in pH 8 buffer solution with photocrease dose of 25 joules per square centimeter (lambda max = 365 nanometers). Scale bar 500 micrometers. 1x playback speed.
Video_S19.mp4 (20754 kB)
A coiling array of copolymer 4 MSPs in pH 8 buffer solution with photocrease dose of 50 joules per square centimeter (lambda max = 365 nanometers). Scale bar 500 micrometers. 1x playback speed.
Video_S20.mp4 (21183 kB)
A coiling array of copolymer 4 MSPs in pH 8 buffer solution with photocrease dose of 75 joules per square centimeter (lambda max = 365 nanometers). Scale bar 500 micrometers. 1x playback speed.
Video_S21.mp4 (8407 kB)
Deflection of copolymer 4 MSPs of h0 ~ 1 micrometers without photopatterning and after release into aqueous solution; MSPs do not spontaneously coil and are elastically bent in flow. Scale bar 500 micrometers. 1x playback speed.
Video_S22.mp4 (7249 kB)
Deflection of copolymer 5 MSPs of h0 ~ 1 micrometers after patterning with photocrease tilt angle ~ 45° and release into pH 8 buffer solution; MSPs do not spontaneously coil and are elastically bent in flow. Scale bar 200 micrometers. 1x playback speed.
Video_S23.mp4 (19929 kB)
Release and coiling of a photocreased MSP array in pH 8 buffer with d = 60 micrometers and photocrease tilt angle = 26°. Scale bar 500 micrometers. 1x playback speed.
Video_S24.mp4 (22032 kB)
Release and coiling of a photocreased MSP array in pH 8 buffer with d = 60 micrometers and photocrase tilt angle = 44°. Scale bar 500 micrometers. 1x playback speed.
Video_S25.mp4 (13641 kB)
Detaching a representative 12-MSP bundle from the substrate by cutting the fixed ends. Scale bar 500 micrometers. 10x playback speed.
Video_S26.mp4 (22066 kB)
Moving the detached MSP bundle of Video S25 through solution by injecting flow through a capillary tube. Scale bar 500 micrometers. 4x playback speed.
Video_S27.mp4 (11898 kB)
Bending a 5-MSP bundle (Photocrease tilt angle = 18° and average h0 = 0.84 micrometers) in pH 8 buffer with 3 mM sodium dodecyl sulfate via suction at 500 microliters/minute through a capillary tube. Scale bar 1 millimeter. 5x playback speed.
Video_S28.mp4 (7253 kB)
Bending a single MSP helix (Photocrease tilt angle = 18° and average h0 = 0.98 micrometers) in pH 8 buffer with 3 mM sodium dodecyl sulfate via suction at 300 microliters/minute through a capillary tube. Scale bar 1 millimeter. 5x playback speed.
Video_S29.mp4 (12945 kB)
Bending a 5-MSP bundle (Photocrease tilt angle = 60° and average h0 = 1.04 micrometers) in pH 8 buffer with 3 mM sodium dodecyl sulfate via suction at 200 microliters/minute through a capillary tube. Scale bar 1 millimeter. 5x playback speed.
Video_S30.mp4 (23253 kB)
Bending a single MSP helix (Photocrease tilt angle = 60° and average h0 = 1.10 micrometers) in pH 8 buffer with 3 mM sodium dodecyl sulfate via suction at 30-50 microliters/minute through a capillary tube. Scale bar 1 millimeter. 1x playback speed.
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