Showing papers by "Marc A. Hillmyer published in 2009"
TL;DR: The first successful application of an ordered bicontinuous gyroid semiconducting network in a hybrid bulk heterojunction solar cell is reported, a major step toward realizing the full potential of self-assembly in the next generation of device technologies.
Abstract: We report the first successful application of an ordered bicontinuous gyroid semiconducting network in a hybrid bulk heterojunction solar cell. The freestanding gyroid network is fabricated by electrochemical deposition into the 10 nm wide voided channels of a self-assembled, selectively degradable block copolymer film. The highly ordered pore structure is ideal for uniform infiltration of an organic hole transporting material, and solid-state dye-sensitized solar cells only 400 nm thick exhibit up to 1.7% power conversion efficiency. This patterning technique can be readily extended to other promising heterojunction systems and is a major step toward realizing the full potential of self-assembly in the next generation of device technologies.
442 citations
TL;DR: In this article, a review summarizes experimental and theoretical investigations of the structures and properties of network morphologies in AB block copolymer and ABC block terpolymer systems and includes a discussion of some proposed technological appli
Abstract: Block polymers are formed by the covalent union of two or more chemically distinct homopolymers These composite macromolecules self-assemble into a variety of ordered morphologies with features on the nanometer length scale, a phenomenon that has interested researchers for roughly four decades The known ordered morphologies include numerous multiply continuous network mesostructures, the focus of this review Multiply continuous network morphologies contain two or more chemically distinct domains that continuously percolate through the specimen in all three dimensions They have captivated researchers because of their superior mechanical properties and could potentially find utility in technologies such as catalysis, photonic materials, solar cells, and separations This review summarizes experimental and theoretical investigations of the structures and properties of network morphologies in AB block copolymer and ABC block terpolymer systems and includes a discussion of some proposed technological appli
252 citations
175 citations
TL;DR: This work integrates mesostructured titania arrays into dye-sensitized solar cells by replicating ordered, oriented one-dimensional columnar and three-dimensional bicontinuous gyroid block copolymer phases and observes faster charge transport in 1D "wires" than through 3D gyroid arrays.
Abstract: We integrate mesostructured titania arrays into dye-sensitized solar cells by replicating ordered, oriented one-dimensional (1D) columnar and three-dimensional (3D) bicontinuous gyroid block copolymer phases. The solar cell performance, charge transport, and recombination are investigated. We observe faster charge transport in 1D "wires" than through 3D gyroid arrays. However, owing to their structural instability, the surface area of the wire arrays is low, inhibiting the solar cell performance. The gyroid morphology, on the other hand, outperforms the current state-of-the-art mesoporous nanoparticle films.
163 citations
152 citations
TL;DR: Indium trichloride, benzyl alcohol, and triethylamine generate a catalyst in situ for the room temperature polymerization of D,L- lactide affording highly heterotactic polylactide of controlled molecular weight and narrow molecular weight distribution.
111 citations
TL;DR: The results demonstrate that the properties of these new biorenewable thermoplastic elastomers can be systematically modulated by changing the stereochemistry of the polylactide end blocks.
98 citations
TL;DR: The influence of crystal size on polymorph formation and stability is largely unexplored as mentioned in this paper, and the ability of a compound to adopt more than one solid-state structure, often relies on empirical manipulations of conditions such as solvent, temperature, and mode of crystallization.
Abstract: Controlling polymorphism, the ability of a compound to adopt more than one solid-state structure, often relies on empirical manipulations of conditions such as solvent, temperature, and mode of crystallization. Despite a growing interest in nanocrystalline formulations, however, the influence of crystal size on polymorph formation and stability is largely unexplored. Nanocrystals of pimelic acid, HO2C(CH2)n-2CO2H (n = 7), glutaric acid (n = 5), suberic acid (n = 8), and coumarin (1,2-benzopyrone) in nanometer-scale pores of controlled pore glass (CPG) beads and hexagonally ordered cylindrical pores of poly(cyclohexylethylene) (p-PCHE) monoliths exhibit size-dependent polymorphism and thermotropic behavior because of the physical constraints imposed by the dimensions of the pores. Pimelic acid, suberic acid, and coumarin also exhibit heretofore unknown polymorphs, denoted δ-pimelic acid, β-suberic acid, and β-coumarin, in CPG with pore sizes <23 nm and p-PCHE with pore diameters <40 nm. The melting points ...
96 citations
TL;DR: Using a combination of dynamic light scattering and cryogenic transmission electron microscopy, it is demonstrated that mu-SODA micelles formed in water evolve from mixed corona (PEO + PDMAEA corona; PS core) and predominantly spherical micelle to multicompartment micells with increasing pH.
Abstract: We describe the synthesis of pH-responsive miktoarm star block terpolymers μ-[polystyrene][poly(ethylene oxide)][poly(2-(dimethylamino)ethyl acrylate)] (μ-SODA) using a combination of two successive living anionic polymerizations and one reversible addition−fragmentation chain-transfer polymerization. Poly[2-(dimethylamino)ethyl acrylate] (PDMAEA) is a weak polybase that is hydrophilic at low pH and hydrophobic at high pH because of the protonation of the dimethylamino functional group with decreasing pH. In addition, our results suggest that PDMAEA is immiscible with polystyrene (PS), a feature that is desirable for the formation of multicompartment micelles. Using a combination of dynamic light scattering and cryogenic transmission electron microscopy, we demonstrate that μ-SODA micelles formed in water evolve from mixed corona (PEO + PDMAEA corona; PS core) and predominantly spherical micelles to multicompartment (PEO corona; PS + PDMAEA core) micelles with increasing pH.
90 citations
TL;DR: These membranes are effective for ultrafiltration, with molecular weight cutoffs consistent with theoretical predictions with no adjustable parameters, and can be tuned by changing the size of the constituent blocks in the templating copolymer.
Abstract: We report gas and liquid transport measurements through membranes that have 40% voids made of 14 nm pores. A reactive polylactide−polynorbornenylethylstyrene block polymer is used as a structural template in the polymerization of dicyclopentadiene during the membrane formation process. After the membrane is cast, the pore structure is formed by etching the polylactide component using dilute aqueous base. The pore structure is isotropic; therefore, there is no need for special alignment techniques. Knudsen diffusion experiments and water flow experiments show pores with a tortuosity of 1.81 and a size of 14 nm, a diameter consistent with nitrogen adsorption and small-angle X-ray scattering measurements. These membranes are effective for ultrafiltration, with molecular weight cutoffs (MWCO) consistent with theoretical predictions with no adjustable parameters. These MWCO’s can be tuned by changing the size of the constituent blocks in the templating copolymer.
87 citations
TL;DR: A series of reactive liquid perfluoropolyether (PFPE) precursors were synthesized which can be photochemically cross-linked (UV-cured) into high-performance PFPE elastomers in one step as discussed by the authors.
Abstract: A series of reactive liquid perfluoropolyether (PFPE) precursors were synthesized which can be photochemically cross-linked (UV-cured) into high-performance PFPE elastomers in one step. To investigate how fundamental changes in the PFPE molecular structure correlate to bulk and surface properties, the variable functional end group, molecular weight, and the copolymer content were systematically explored in relation to thermal stability, contact angle/surface tension, modulus, and biofouling behavior. The morphologies of these PFPE materials were studied using differential scanning calorimetry, dynamic mechanical thermal analysis, and small-angle X-ray scattering. From these studies, it was determined that clusters of polymerized functional end groups were found to be nanophase separated within the PFPE matrix. By varying the cross-link density, the Young’s modulus of the fully cross-linked PFPE elastomeric film could be tuned from 1.5 to 90 MPa with a critical surface tension of 8.6−16 mN/m. The marine an...
TL;DR: It is demonstrated that crystal growth occurs such that the fast-growing direction, which can be altered by adding chiral auxiliaries, is parallel to the pore direction.
Abstract: Glycine nanocrystals, grown in aligned nanometer-scale cylindrical pores of nanoporous polystyrene-poly(dimethyl acrylamide) monoliths by evaporation of imbibed aqueous solutions, adopt preferred orientations with their fast-growth axes aligned parallel with the pore direction. X-ray diffraction analysis revealed the exclusive formation of the metastable β-polymorph, with crystal size comparable with the 22 nm pore diameter, in contrast to the formation of α-glycine in the absence of nanoscale confinement. When grown from aqueous solutions alone, the nanocrystals were oriented with their [010] and [010] axes, the native fast growth directions of the (+) and (−) enantiomorphs of β-glycine, respectively, aligned parallel with the pore direction. In contrast, crystallization in the presence of racemic mixtures of chiral auxiliaries known to inhibit growth along the [010] and [010] directions of the enantiomorphs produced β-glycine nanocrystals with their [001] axes nearly parallel to the pore direction. En...
TL;DR: The diene 3-methylenecyclopentene was synthesized from the naturally occurring monoterpene myrcene by ring-closing metathesis using Grubbs second generation catalyst to afford regiopure 1,4-poly-2.
Abstract: The diene 3-methylenecyclopentene (2) was synthesized from the naturally occurring monoterpene myrcene (1) by ring-closing metathesis using Grubbs second generation catalyst. Radical, anionic, and cationic polymerizations of 2 were investigated. The anionic polymerization of 2 with sec-butyllithium (s-BuLi) in cyclohexane gave poly-2 in quantitative yield, with a narrow molecular weight distribution and predictable molecular weight based on the molar ratio of 2 and s-BuLi. Radical polymerization of 2 was also successful using AIBN as the initiator. Samples of poly-2 obtained from the anionic and radical polymerization of 2 possessed mixed regiochemistry (i.e., 4,3 and 1,4 addition). The cationic polymerization of 2 proceeded smoothly to afford regiopure 1,4-poly-2. For example, the i-BuOCH(Cl)Me/ZnCl2/Et2O initiating system afforded 1,4-poly-2 with controlled molecular weight and narrow molecular weight distribution. Samples of 1,4-poly-2 were semicrystalline as determined by differential scanning calorim...
TL;DR: In this article, a series of reactive poly(norbornenylethylstyrene-s-styrene)-poly(n-propyl-p-styrenesulfonate) (PNS−PSSP) block polymers were prepared by atom transfer radical polymerization.
Abstract: A series of reactive poly(norbornenylethylstyrene-s-styrene)-poly(n-propyl-p-styrenesulfonate) (PNS−PSSP) block polymers were prepared by atom transfer radical polymerization. Solutions containing PNS−PSSP, the cyclic olefins dicyclopentadiene and/or cyclooctene, and the second-generation Grubbs metathesis catalyst were prepared, cast as thin films, and allowed to cure at room temperature by a ring-opening metathesis polymerization mechanism. Small-angle X-ray scattering (SAXS) data on cured films were consistent with the formation of nanostructured materials containing PSSP domains confined in a cross-linked matrix of the metathesis-reactive PNS block and the poly(cyclic olefins). The PSSP phase in these films was converted into the sulfonic acid form by hydrolysis of the propyl sulfonate ester. The resulting cross-linked polymer electrolyte membranes (PEMs) were characterized by SAXS and transmission electron microscopy. A bicontinuous morphology with continuous domains of the sulfonic acid phase suppor...
TL;DR: ABA triblock copolymers were synthesized by combining ring-opening metathesis polymerization (ROMP) of 1,5-cyclooctadiene (COD) with ringopening polymerization of d,l-lactide.
Abstract: ABA triblock copolymers were synthesized by combining ring-opening metathesis polymerization (ROMP) of 1,5-cyclooctadiene (COD) with ring-opening polymerization of d,l-lactide. Hydroxyl-functionalized telechelic polyCOD was prepared by taking advantage of chain transfer during ROMP of COD using the acyclic chain transfer agent cis-1,4-diacetoxy-2-butene. These hydroxy-terminated macroinitiators were used as initiators for the polymerization of lactide to form a series of triblock copolymers with compositions in the range 0.24 ≤ fPLA ≤ 0.89 and molecular weights ranging from 22 to 196 kg mol−1. The ordered-state morphologies of the triblocks were determined using small-angle X-ray scattering; well-ordered microstructures were observed for several samples, in accordance with the predicted dependence of morphology on composition. The mechanical properties of these materials were also investigated by performing tensile measurements; the triblocks were considerably tougher than poly(d,l-lactide), most markedly...
TL;DR: The natural product dihydrocarvone, found in caraway oil, was oxidized to an epoxylactone on a multigram scale, used as a multifunctional monomer and cross-linker in ring-opening polymerizations and showed near perfect shape memory properties even after repeated bending.
TL;DR: In this article, the influence of thermal annealing on the performance of polymer bilayer solar cell devices of regioregular poly(3-hexylthiophene), regiorandom poly( 3hexyl-2...
Abstract: We describe the influence of thermal annealing on the performance of polymer bilayer solar cell devices of regioregular poly(3-hexylthiophene), regiorandom poly(3-hexylthiophene), or poly(3-hexyl-2...
TL;DR: After initial water uptake in which the mechanical properties were compromised to an extent, the Young's modulus and elongation at break of the biorenewable copolymers remained relatively unperturbed for up to 16 weeks, with significant retention of thermoplastic elastomeric properties for up- 21 weeks.
TL;DR: In this article, the acyclic diene metathesis (ADMET) was used for the synthesis of poly(3-hexyl-2,5-thienylene vinylene) (P3HTV).
Abstract: We report the acyclic diene metathesis (ADMET) polymerization of 2,5-dipropenyl-3-hexylthiophene using ruthenium metathesis catalysts as a facile method for the production of poly(3-hexyl-2,5-thienylene vinylene) (P3HTV). Using a high-temperature polymerization under dynamic vacuum to remove the 2-butene byproduct, we were able to prepare polymers with apparent weight-average molecular weights as high as 19 kg/mol. P3HTV samples were characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, UV−vis spectroscopy, cyclic voltammetry (CV), differential scanning calorimetry (DSC), and elemental analysis.
TL;DR: In this article, an end-functionalized regioregular poly(3-hexylthiophene) (P3HT) was synthesized by a combination of a controlled polymerization technique and postpolymerization functionalization.
Abstract: End-functionalized, regioregular poly(3-hexylthiophene) (P3HT) was synthesized by a combination of a controlled polymerization technique and postpolymerization functionalization. Both ends of the polymer chains were terminated with fullerene units to create an internal electron accepting−donating−accepting molecule, methylfulleropyrrolidine−poly(3-hexylthiophene)−methylfulleropyrrolidine (C60-P3HT-C60). The molecular properties of the polymer were characterized using 1H NMR spectroscopy, size exclusion chromatography (SEC), ultraviolet−visible (UV−vis) absorption spectroscopy, and fluorescence spectroscopy. These results show that the fullerene units are covalently bound to the polymer chain ends. Differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and small-angle X-ray scattering (SAXS) were used to determine the bulk microstructure of the polymers. In addition, atomic force microscopy (AFM) was used to examine spun-cast thin films. These experiments revealed that microphase sepa...
TL;DR: The ability to block large molecules without hindering smaller ones, coupled with the potential for surface modification of the polymer and the microelectromechanical system style of support, makes this composite membrane an attractive candidate for interfacing implantable sensing and drug-delivery devices with biological hosts.
Abstract: Block polymers offer an attractive route to densely packed, monodisperse nanoscale pores. However, their fragility as thin films complicates their use as membranes. By integrating a block polymer film with a thin (100 μm) silicon substrate, we have developed a composite membrane providing both nanoscale size exclusion and fast transport of small molecules. Here we describe the fabrication of this membrane, evaluate its mechanical integrity, and demonstrate its transport properties for model solutes of large and small molecular weight. The ability to block large molecules without hindering smaller ones, coupled with the potential for surface modification of the polymer and the microelectromechanical system style of support, makes this composite membrane an attractive candidate for interfacing implantable sensing and drug-delivery devices with biological hosts.
Journal Article•
TL;DR: There has been a general feeling that this high degree of order requires the block copolymers to have well-defined molecularweights with small polydispersities as mentioned in this paper.
Abstract: Block copolymers are renowned for self-assembling intoperiodic morphologies with long-range order, and for their richselection of interesting behaviors and potential applications.There has been a general feeling that this high degree of orderrequires the block copolymers to have well-defined molecularweights with small polydispersities.
TL;DR: In this article, a semicrystalline poly(3-hexyl-2,5-thienylene vinylene) (P3HTV) with a low band gap of 1.65 eV has been synthesized by acyclic diene metathesis polymerization and incorporated into bulk heterojunction (BHJ) organic solar cells.
Abstract: Semicrystalline poly(3-hexyl-2,5-thienylene vinylene) (P3HTV) with a low band gap of 1.65 eV has been synthesized by acyclic diene metathesis polymerization and incorporated into bulk heterojunction (BHJ) organic solar cells. The polymer was thermally characterized by differential scanning calorimetry and thermogravimetric analysis and was blended with the electron acceptor methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) to make a light-harvesting charge-transfer thin film. The properties of P3HTV/PCBM blends were studied as a function of PCBM composition by wide-angle X-ray scattering, atomic force microscopy, transmission electron microscopy, UV−vis absorption spectroscopy, and charge-transport and photovoltaic measurements. The PCBM solubility limit, that is, the phase separation point, was estimated to be 50 wt % PCBM. The phase behavior of the blend was directly correlated with electrical transport behavior in a field-effect transistor testbed. At the phase separation point, charge...
TL;DR: Renewable composites were prepared by melt blending of polylactide and soybean oil by tuning the addition of poly(isoprene-b-lactides) block copolymers to induce a phase inversion point at which the minor soybeanOil phase became the matrix surrounding polylACTide particles.
Abstract: Renewable composites were prepared by melt blending of polylactide and soybean oil. The blend morphology was tuned by the addition of poly(isoprene-b-lactide) block copolymers. Due to the extreme difference in the viscosities of soybean oil and polylactide, a critical block copolymer composition was found to induce a phase inversion point at which the minor soybean oil phase became the matrix surrounding polylactide particles. This transition was due to the thermodynamic interactions between the block copolymer and the two phases and shear forces acting on the mixture during blending. The size of the soybean oil droplets in the polylactide matrix was also highly dependent on the block copolymer composition. In binary polylactide/soybean oil blends, there was a limiting concentration of soybean oil that could be incorporated into the polylactide matrix (6% of the total blend weight), which could be increased up to 20% by the addition of block copolymers.
TL;DR: The morphological behavior was attributed to interactions between peptide moieties conjugated to the termini of coronal chains and has implications in the design of targeting micelles for drug delivery applications.
TL;DR: In this article, a norbornene functional styrene was synthesized and copolymerized with styrene, and monomer reactivity ratios were calculated in controlled radical copolymers.
Abstract: A norbornene-functional styrene was synthesized and copolymerized with styrene, and monomer reactivity ratios were calculated in a controlled radical copolymerization. Polylactide-b-poly(norbornenylethylstyrene-s-styrene) (PLA-b-P(N-S)) block polymers were produced by a reversible addition−fragmentation chain transfer polymerization technique using a PLA-based macro chain transfer agent and fully characterized using conventional techniques. Blends composed of this block copolymer, dicyclopentadiene (DCPD), and a metathesis catalyst were waxy materials that formed ordered structures containing cylindrical PLA nanodomains in a composite DCPD/P(N-S) matrix. These composite materials were pressed in a channel die to align the cylindrical domains and were cured by a ring-opening metathesis mechanism at elevated temperatures. Removal of the PLA from the resulting monoliths by mild basic etching resulted in nanoporous monoliths with cylindrical channels. The nanoporous materials were characterized by small-angle...
TL;DR: The changes in phase behavior that are associated with variations in the polydispersity of the middle bridged polystyrene block, however, are not analogous to those reported in AB diblock copolymers, as increases in this middle block poly Dispersity are not always accompanied by increased domain periodicities and a tendency for domain interfaces to curve toward thepolydisperse domain.
Abstract: Four hydroxyl-terminated polyisoprene-b-styrene diblock copolymers with comparable molecular weights and compositions equivalent volume fractions of polyisoprene and polystyrene but different polystyrene block polydispersity indices M w /M n =1.06,1.16,1.31,1.44 were synthesized by anionic polymerization using either sec-butyllithium or the functional organolithium 3-triisopropylsilyloxy-1-propyllithium. Polyethylene oxidePEO blocks were grown from the end of each of these parent diblocks to yield four series of polyisoprene-b-styrene-b-ethylene oxideISO triblock terpolymers that were used to interrogate the effects of varying the polydispersity of the middle bridged polystyrene block. In addition to the neat triblock samples, 13 multicomponent blends were prepared at four different compositions from the ISO materials containing a polystyrene segment with Mw /Mn=1.06; these blends were used to probe the effects of increasing the polydispersity of the terminal PEO block. The melt-phase behavior of all samples was characterized using small-angle X-ray scattering and dynamic mechanical spectroscopy. Numerous polydispersity-driven morphological transitions are reported, including transitions from lamellae to core-shell gyroid, from core-shell gyroid to hexagonally packed cylinders, and from network morphologies either O 70 the orthorhombic Fddd network or core-shell gyroid to lamellae. Domain periodicities and order-disorder transition temperatures also vary with block polydispersities. Self-consistent field theory calculations were performed to supplement the experimental investigations and help elucidate the molecular factors underlying the polydispersity effects. The consequences of varying the polydispersity of the terminal PEO block are comparable to the polydispersity effects previously reported in AB diblock copolymers. Namely, domain periodicities increase with increasing polydispersity and domain interfaces tend to curve toward polydisperse blocks. The changes in phase behavior that are associated with variations in the polydispersity of the middle bridged polystyrene block, however, are not analogous to those reported in AB diblock copolymers, as increases in this middle block polydispersity are not always accompanied by i increased domain periodicities and ii a tendency for domain interfaces to curve toward the polydisperse domain. These results highlight the utility of polydispersity as a tool to tune the phase behavior of ABC block terpolymers. © 2009 American Institute of Physics. DOI: 10.1063/1.3140205
TL;DR: In this paper, a polystyrene sulfonate domain was used to evaluate the selectivity of a mixed gas feed containing ammonia and nitrogen for separation of ammonia produced by the Haber-Bosch process, and the results showed that the sulfonated phase domain size and the degree of crosslinking in the membrane give permeabilities which increase with the average ammonia pressure and retain their selectivity at higher pressure.
TL;DR: A conjugated copolymer (PITN-co-ThBTD) composed of alternating isothianaphthene, thiophene, and benzothiadiazole units was synthesized and characterized in this paper.
Abstract: A novel conjugated copolymer (PITN-co-ThBTD) composed of alternating isothianaphthene, thiophene, and benzothiadiazole units was synthesized and characterized. The polymer has a low bandgap of 1.55 eV as a result of the intrachain coupling between electron-donating/withdrawing units. Thermal analysis and wide-angle X-ray scattering (WAXS) reveal that the polymer has a largely amorphous structure. Blends of PITN-co-ThBTD with the electron acceptor methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were studied as a function of increasing PCBM content by WAXS, atomic force microscopy, charge transport, and photovoltaic measurements. The PCBM solubility limit, i.e., the phase-separation point, was estimated to be 30 wt % PCBM, beyond which charge carrier transport switches from hole only to ambipolar (both electron and hole) in a field-effect transistor testbed. Bulk heterojunction solar cells were constructed from PITN-co-ThBTD films blended with varying weight fractions of PCBM. The best pe...