Chemical and Biomolecular Engineering

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3D Covalent Organic Frameworks with Interpenetrated pcb Topology Based on 8-Connected Cubic Nodes
(American Chemical Society, 2022) Shan, Zhen; Wu, Miaomiao; Zhu, Dongyang; Wu, Xiaowei; Zhang, Kan; Verduzco, Rafael; Zhang, Gen
The connectivity of building units for 3D covalent organic frameworks (COFs) has long been primarily 4 and 6, which have severely curtailed the structural diversity of 3D COFs. Here we demonstrate the successful design and synthesis of a porphyrin based, 8-connected building block with cubic configuration, which could be further reticulated into an unprecedented interpenetrated pcb topology by imine condensation with linear amine monomers. This study presents the first case of high-connectivity building units bearing 8-connected cubic nodes, thus greatly enriching the topological possibilities of 3D COFs.
A 2-D simulation study on CO2ﾠsoluble surfactant for foam enhanced oil recovery
(Elsevier, 2019) Zeng, Yongchao; Farajzadeh, Rouhi; Biswal, Sibani L.; Hirasaki, George J.
This paper probes the transport of CO2ﾠsoluble surfactant for foaming in porous media. We numerically investigate the effect of surfactant partitioning between the aqueous phase and the gaseous phase on foam transport for subsurface applications when the surfactant is injected in the CO2ﾠphase. A 2-D reservoir simulation is developed to quantify the effect of surfactant partition coefficient on the displacement conformance and CO2ﾠsweep efficiency. A texture-implicit local-equilibrium foam model is embedded to describe how the partitioning of surfactant between water and CO2ﾠaffects the CO2ﾠfoam mobility control when surfactant is injected in the CO2ﾠphase. We conclude that when surfactant has approximately equal affinity to both the CO2ﾠand the water, the transport of surfactant is in line with the gas propagation and therefore the sweep efficiency is maximized. Too high affinity to water (small partition coefficient) results in surfactant retardation whereas too high affinity to CO2ﾠ(large partition coefficient) leads to weak foam and insufficient mobility reduction. This work sheds light upon the design of water-alternating-gas-plus-surfactant-in-gas (WAGﾠ+ﾠS) process to improve the conventional foam process with surfactant-alternating-gas (SAG) injection mode during which significant amount of surfactant could possibly drain down by gravity before CO2ﾠslugs catch up to generate foam in situ the reservoir.
A Decarbonization Roadmap for Taiwan and Its Energy Policy Implications
(MDPI, 2022) Lau, Hon Chung; Tsai, Steve C.
The objective of this paper is to propose a decarbonization roadmap for Taiwan to achieve net-zero emissions by 2050 by analyzing the status of fossil and non-fossil energies, screening applicable decarbonization technologies for their effectiveness, and then proposing an energy mix for the future. The novelty of this work lies in the screening process, which considers six, instead of one or two, categories: sustainability, security, affordability, reliability, technology readiness, and technology impact. Based on this screening, a decarbonization roadmap is proposed and compared with the announced net-zero emissions (NZE) plan. The proposed roadmap requires renewable electricity to grow at an average annual growth rate of 7% between now and 2050, instead of the 10.1% required by the NZE plan, which is more achievable based on issues identified with renewable energies during our screening exercise. The proposed roadmap improves on the NZE plan in the following aspects: (1) using clean coal technologies to decarbonize existing coal-fired power plants, (2) relying more on gas than wind and solar energies to replace coal and nuclear energy for power generation, (3) accelerating carbon capture and storage (CCS) implementation, (4) delaying the phaseout of nuclear energy until 2050, and (5) using blue instead of green hydrogen to decarbonize the transport and industry sectors. Implications of this roadmap for future research and development and energy policies are also discussed.
A density functional theory for patchy colloids based on Wertheim's association theory: Beyond the single bonding condition
(American Institute of Physics, 2013) Marshall, Bennett D.; Chapman, Walter G.
In the framework of Wertheimﾒs theory, we develop the first classical density functional theory for patchy colloids where the patch can bond more than once. To test the theory we perform new Monte Carlo simulations for the model system of patchy colloids in a planar slit pore. The theory is shown to be in excellent agreement with simulation for the density profiles and bonding fractions. It is also shown that the theory obeys the wall contact rule by accurately predicting bulk pressures from the wall contact density.
A general theoretical framework to design base editors with reduced bystander effects
(Springer Nature, 2021) Wang, Qian; Yang, Jie; Zhong, Zhicheng; Vanegas, Jeffrey A.; Gao, Xue; Kolomeisky, Anatoly B.; Center for Theoretical Biological Physics
Base editors (BEs) hold great potential for medical applications of gene therapy. However, high precision base editing requires BEs that can discriminate between the target base and multiple bystander bases within a narrow active window (4 – 10 nucleotides). Here, to assist in the design of these optimized editors, we propose a discrete-state stochastic approach to build an analytical model that explicitly evaluates the probabilities of editing the target base and bystanders. Combined with all-atom molecular dynamic simulations, our model reproduces the experimental data of A3A-BE3 and its variants for targeting the “TC” motif and bystander editing. Analyzing this approach, we propose several general principles that can guide the design of BEs with a reduced bystander effect. These principles are then applied to design a series of point mutations at T218 position of A3G-BEs to further reduce its bystander editing. We verify experimentally that the new mutations provide different levels of stringency on reducing the bystander editing at different genomic loci, which is consistent with our theoretical model. Thus, our study provides a computational-aided platform to assist in the scientifically-based design of BEs with reduced bystander effects.
A Monte Carlo density functional theory for the competition between inter and intramolecular association in inhomogeneous fluids
(AIP Publishing LLC, 2013) Marshall, Bennett D.; García-Cuéllar, Alejandro J.; Chapman, Walter G.
A Monte Carlo density functional theory is developed for chain molecules which both intra and intermolecularly associate. The approach can be applied over a range of chain lengths. The theory is validated for the case of an associating 4-mer fluid in a planar hard slit pore. Once validated, the new theory is used to study the effect of chain length and temperature on the competition between intra and intermolecular association near a hard wall. We show that this competition enhances intramolecular association near wall contact and inverts the chain length dependence of the fraction bonded intermolecularly in the inhomogeneous region.
A New Stabilization of Adaptive Step Trapezoid Rule Based on Finite Difference Interrupts
(Society for Industrial and Applied Mathematics, 2015) Lee, J. Alex; Nam, Jaewook; Pasquali, Matteo
The adaptive step trapezoid rule (TR) is a generally effective numerical integrator, but it is prone to ringing instability and solution stall. We introduce a new stabilization algorithm based on finite difference interrupts (FDI) that reduces ringing and prevents stall. Unlike previously reported stabilization schemes, our algorithm achieves stability and second order accuracy without incurring significant computational cost or spurious diffusion. TR with FDI is at least as stable and accurate as existing methods when solving the prototypical scalar problem. We demonstrate that it has better stability, accuracy, and cost when solving the tightly coupled system describing free surface flows of viscoelastic liquids. Though we demonstrate TR with FDI in the context of a finite element method-of-lines, it is applicable to any TR-based algorithm.
A perturbation density functional theory for the competition between inter and intramolecular association
(AIP Publishing LLC, 2012) Marshall, Bennett D.; García-Cuéllar, Alejandro J.; Chapman, Walter G.
Using the framework of Wertheim's thermodynamic perturbation theory we develop the first density functional theory which accounts for intramolecular association in chain molecules. To test the theory new Monte Carlo simulations are performed at a fluid solid interface for a 4 segment chain which can both intra and intermolecularly associate. The theory and simulation results are found to be in excellent agreement. It is shown that the inclusion of intramolecular association can have profound effects on interfacial properties such as interfacial tension and the partition coefficient.
A platform for post-translational spatiotemporal control of cellular proteins
(Oxford University Press, 2021) Jayanthi, Brianna; Bachhav, Bhagyashree; Wan, Zengyi; Martinez Legaspi, Santiago; Segatori, Laura; Systems, Synthetic, and Physical Biology Program
Mammalian cells process information through coordinated spatiotemporal regulation of proteins. Engineering cellular networks thus relies on efficient tools for regulating protein levels in specific subcellular compartments. To address the need to manipulate the extent and dynamics of protein localization, we developed a platform technology for the target-specific control of protein destination. This platform is based on bifunctional molecules comprising a target-specific nanobody and universal sequences determining target subcellular localization or degradation rate. We demonstrate that nanobody-mediated localization depends on the expression level of the target and the nanobody, and the extent of target subcellular localization can be regulated by combining multiple target-specific nanobodies with distinct localization or degradation sequences. We also show that this platform for nanobody-mediated target localization and degradation can be regulated transcriptionally and integrated within orthogonal genetic circuits to achieve the desired temporal control over spatial regulation of target proteins. The platform reported in this study provides an innovative tool to control protein subcellular localization, which will be useful to investigate protein function and regulate large synthetic gene circuits.
A Polysulfone/Cobalt Metal–Organic Framework Nanocomposite Membrane with Enhanced Water Permeability and Fouling Resistance
(American Chemical Society, 2022) Gil, Eva; Huang, Xiaochuan; Zuo, Kuichang; Kim, Jun; Rincón, Susana; Rivera, José María; Ranjbari, Kiarash; Perreault, François; Alvarez, Pedro; Zepeda, Alejandro; Li, Qilin; Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment
Ultrafiltration membranes are widely used in water and wastewater applications. The two most important membrane characteristics that determine the cost-effectiveness of an ultrafiltration membrane process are membrane permeability and fouling resistance. Metal–organic frameworks (MOFs) have been intensively investigated as highly selective sorbents and superior (photo) catalysts. Their potential as membrane modifiers has also received attention recently. In this study, a non-functionalized, water-stable, nanocrystalline mixed ligand octahedral MOF containing carboxylate and amine groups with a cobalt metal center (MOF-Co) was incorporated into polysulfone (PSF) ultrafiltration (UF) membranes at a very low nominal concentration (2 and 4 wt %) using the conventional phase inversion method. The resultant PSF/MOF-Co_4% membrane exhibited water permeability up to 360% higher than of the control PSF membrane without sacrificing the selectivity of the membrane, which had not been previously achieved by an unmodified MOF. In addition, the PSF/MOF-Co_4% membrane showed strong resistance to fouling by natural organic matter (NOM), with 87 and 83% reduction in reversible and irreversible NOM fouling, respectively, compared to the control PSF membrane. This improvement was attributed to the increases in membrane porosity and surface hydrophilicity resulting from the high hydrophilicity of the MOF-Co. The capability of increasing membrane water permeability and fouling resistance without compromising membrane selectivity makes the MOF-Co and potentially other hydrophilic MOFs excellent candidates as membrane additives.
A Rapid and Sensitive Method for Measuring NAcetylglucosaminidase Activity in Cultured Cells
(Public Library of Science, 2013) Mauri, Victor; Lotfi, Parisa; Segatori, Laura; Sardiello, Marco
A rapid and sensitive method to quantitatively assess N-acetylglucosaminidase (NAG) activity in cultured cells is highly desirable for both basic research and clinical studies. NAG activity is deficient in cells from patients with Mucopolysaccharidosis type IIIB (MPS IIIB) due to mutations in NAGLU, the gene that encodes NAG. Currently available
A Simple and Rapid Method of Forming Double-Sided TiO2 Nanotube Arrays
(Wiley, 2022) Conrad, Christian L.; Elias, Welman C.; Garcia-Segura, Sergi; Reynolds, Michael A.; Wong, Michael S.; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
Highly ordered TiO2 nanostructures, known as nanotube arrays (NTAs), exhibit potential in various energy, chemical sensing, and biomedical applications. Owing to its simplicity and high degree of control, titanium anodization serves as the prevailing NTA synthesis method. However, the practicality of this approach is marred by sluggish and inconsistent growth rates, on the order of 10 nm min−1. Growth rates strongly depend on the electrolyte conductivity, yet most reports neglect to consider this property as a measured and controllable parameter. Here, we have systematically determined a broad set of conditions (at 60 V applied potential, elevated temperatures) that allow researchers to fabricate NTAs quickly and simply. By modulating conductivity through variation of bulk electrolyte temperature and the controlled addition of several hydroxy acid species, we achieve consistent accelerated growth up to 10 times faster than traditional methods. We find that regulating the solution conductivity within a desired region (e. g., ∼800–1000 μS cm−1) enabled the fabrication of double-sided NTA layers of around 10 μm and 90 μm NTA in 10 and 180 min, respectively.
A symmetrical method to obtain shear moduli from microrheology
(Royal Society of Chemistry, 2018) Nishi, Kengo; Kilfoil, Maria L.; Schmidt, Christoph F.; MacKintosh, F.C.
Passive microrheology typically deduces shear elastic loss and storage moduli from displacement time series or mean-squared displacements (MSD) of thermally fluctuating probe particles in equilibrium materials. Common data analysis methods use either Kramers–Kronig (KK) transformation or functional fitting to calculate frequency-dependent loss and storage moduli. We propose a new analysis method for passive microrheology that avoids the limitations of both of these approaches. In this method, we determine both real and imaginary components of the complex, frequency-dependent response function χ(ω) = χ′(ω) + iχ′′(ω) as direct integral transforms of the MSD of thermal particle motion. This procedure significantly improves the high-frequency fidelity of χ(ω) relative to the use of KK transformation, which has been shown to lead to artifacts in χ′(ω). We test our method on both model and experimental data. Experiments were performed on solutions of worm-like micelles and dilute collagen solutions. While the present method agrees well with established KK-based methods at low frequencies, we demonstrate significant improvement at high frequencies using our symmetric analysis method, up to almost the fundamental Nyquist limit.
A systematic approach to alkaline-surfactant-foam flooding of heavy oil: microfluidic assessment with a novel phase-behavior viscosity map
(Springer Nature, 2020) Vavra, Eric; Puerto, Maura; Biswal, Sibani L.; Hirasaki, George J.
The apparent viscosity of viscous heavy oil emulsions in water can be less than that of the bulk oil. Microfluidic flooding experiments were conducted to evaluate how alkali-surfactant-foam enhanced oil recovery (ASF EOR) of heavy oil is affected by emulsion formation. A novel phase-behavior viscosity map—a plot of added salinity vs. soap fraction combining phase behavior and bulk apparent viscosity information—is proposed as a rapid and convenient method for identifying suitable injection compositions. The characteristic soap fraction, XSorsoap, is shown to be an effective benchmark for relating information from the phase-viscosity map to expected ASF flood test performance in micromodels. Characteristically more hydrophilic cases were found to be favorable for recovering oil, despite greater interfacial tensions, due to wettability alteration towards water-wet conditions and the formation of low apparent-viscosity oil-in-water (O/W) macroemulsions. Wettability alteration and bubble-oil pinch-off were identified as contributing mechanisms to the formation of these macroemulsions. Conversely, characteristically less hydrophilic cases were accompanied by a large increase in apparent viscosity due to the formation of water-in-oil (W/O) macroemulsions.
A unique biomimetic modification endows polyetherketoneketone scaffold with osteoinductivity by activating cAMP/PKA signaling pathway
(AAAS, 2022) Yuan, Bo; Zhang, Yuxiang; Zhao, Rui; Lin, Hai; Yang, Xiao; Zhu, Xiangdong; Zhang, Kai; Mikos, Antonios G.; Zhang, Xingdong
Osteoinductivity of a biomaterial scaffold can notably enhance the bone healing performance. In this study, we developed a biomimetic and hierarchically porous polyetherketoneketone (PEKK) scaffold with unique osteoinductivity using a combined surface treatment strategy of a sulfonated process and a nano bone-like apatite deposition. In a beagle intramuscular model, the scaffold induced bone formation ectopically after 12-week implantation. The better bone healing ability of the scaffold than the original PEKK was also confirmed in orthotopic sites. After culturing with bone marrow–derived mesenchymal stem cells (BMSCs), the scaffold induced osteogenic differentiation of BMSCs, and the new bone formation could be mainly depending on cell signaling through adenylate cyclase 9, which activates the cyclic adenosine monophosphate/protein kinase A signaling cascade pathways. The current work reports a new osteoinductive synthetic polymeric scaffold with its detailed molecular mechanism of action for bone repair and regeneration.
A zero-dimensional view of atmospheric degradation of levoglucosan (LEVCHEM_v1) using numerical chamber simulations
(Copernicus Publications, 2021) Suciu, Loredana G.; Griffin, Robert J.; Masiello, Caroline A.
Here, we developed a zero-dimensional (0-D) modeling framework (LEVCHEM_v1) to provide insights into the atmospheric degradation of a key tracer emitted during biomass burning – levoglucosan (LEV), while additionally exploring its effects on the dynamics of secondary organic aerosols (SOA) and other gases. For this, we updated existing chemical mechanisms (homogeneous gas-phase chemistry and heterogeneous chemistry) in the BOXMOXv1.7 model to include the chemical degradation of LEV and its intermediary degradation products in both phases (gas and aerosol). In addition, we added a gas-particle partitioning mechanism to the model to account for the effect of evaporation and condensation on the phase-specific concentrations of LEV and its degradation products. Comparison of simulation results with measurements from various chamber experiments (spanning summer and winter conditions) show that the degradation timescale of LEV varied by phase, with gas-phase degradation occurring over ∼1.5–5 d and aerosol-phase degradation occurring over ∼8–36 h. These relatively short timescales suggest that most of the initial LEV concentration can be lost chemically or deposited locally before being transported regionally. We varied the heterogeneous reaction rate constant in a sensitivity analysis (for summer conditions only) and found that longer degradation timescales of LEV are possible, particularly in the aerosol phase (7 d), implying that some LEV may be transported regionally. The multiphase chemical degradation of LEV has effects on SOA and other gases. Several first- or second-generation products resulted from its degradation; most of the products include one or two carbonyl groups, one product contains a nitrate group, and a few products show the cleavage of C−C bonds. The relative importance of the products varies depending on the phase and the timing of the maximum concentration achieved during the simulation. Our estimated secondary organic aerosol SOA yields (4 %–32 %) reveal that conversion of LEV to secondary products is significant and occurs rapidly in the studied scenarios. LEV degradation affected other gases by increasing the concentrations of radicals and decreasing those of reactive nitrogen species. Decreases of the mixing ratios of nitrogen oxides appear to drive a more rapid increase in ozone compared with changes in volatile organic compounds levels. An important next step to confirm longer degradation timescales will be to extend the evaluation of the modeled LEV degradation beyond 3–6 h by using more extensive data from chambers and, possibly, from fire plumes. The mechanism developed here can be used in chemical transport models applied to fire plumes to trace LEV and its degradation products from source to deposition, to assess their atmospheric implications and to answer questions relevant to fire tracing, carbon and nitrogen cycling, and climate.
Adverse Effect of PTFE Stir Bars on the Covalent Functionalization of Carbon and Boron Nitride Nanotubes Using Billups–Birch Reduction Conditions
(American Chemical Society, 2019) de los Reyes, Carlos A.; Smith McWilliams, Ashleigh D.; Hernández, Katharyn; Walz-Mitra, Kendahl L.; Ergülen, Selin; Pasquali, Matteo; Martí, Angel A.
The functionalization of nanomaterials has long been studied as a way to manipulate and tailor their properties to a desired application. Of the various methods available, the Billups–Birch reduction has become an important and widely used reaction for the functionalization of carbon nanotubes (CNTs) and, more recently, boron nitride nanotubes. However, an easily overlooked source of error when using highly reductive conditions is the utilization of poly(tetrafluoroethylene) (PTFE) stir bars. In this work, we studied the effects of using this kind of stir bar versus using a glass stir bar by measuring the resulting degree of functionalization with 1-bromododecane. Thermogravimetric analysis studies alone could deceive one into thinking that reactions stirred with PTFE stir bars are highly functionalized; however, the utilization of spectroscopic techniques, such as Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, tells otherwise. Furthermore, in the case of CNTs, we determined that using Raman spectroscopy alone for analysis is not sufficient to demonstrate successful chemical modification.
Amphiphilic Bottlebrush Block Copolymers: Analysis of Aqueous Self-Assembly by Small-Angle Neutron Scattering and Surface Tension Measurements
(American Chemical Society, 2019) Alaboalirat, Mohammed; Qi, Luqing; Arrington, Kyle J.; Qian, Shuo; Keum, Jong K.; Mei, Hao; Littrell, Kenneth C.; Sumpter, Bobby G.; Carrillo, Jan-Michael Y.; Verduzco, Rafael; Matson, John B.
A systematic series of 16 amphiphilic bottlebrush block copolymers (BCPs) containing polystyrene and poly(N-acryloylmorpholine) (PACMO) side chains were prepared by a combination of atom-transfer radical polymerization (ATRP), photoiniferter polymerization, and ring-opening metathesis polymerization (ROMP). The grafting-through method used to prepare the polymers enabled a high degree of control over backbone and side-chain molar masses for each block. Surface tension measurements on the self-assembled amphiphilic bottlebrush BCPs in water revealed an ultralow critical micelle concentration (cmc), 1–2 orders of magnitude lower than linear BCP analogues on a molar basis, even for micelles with >90% PACMO content. Combined with coarse-grained molecular dynamics simulations, fitting of small-angle neutron scattering traces (SANS) allowed us to evaluate solution conformations for individual bottlebrush BCPs and micellar nanostructures for self-assembled macromolecules. Bottlebrush BCPs showed an increase in anisotropy with increasing PACMO content in toluene-d8, which is a good solvent for both blocks, reflecting an extended conformation for the PACMO block. SANS traces of bottlebrush BCPs assembled into micelles in D2O, a selective solvent for PACMO, were fitted to a core–shell–shell model, suggesting the presence of a partially hydrated inner shell. Results showed an average micelle diameter of 40 nm with combined shell diameters ranging from 16 to 18 nm. A general trend of increased stability of micelles (i.e., resistance to precipitation) was observed with increases in PACMO content. These results demonstrate the stability of bottlebrush polymer micelles, which self-assemble to form spherical micelles with ultralow (<70 nmol/L) cmc’s across a broad range of compositions.
Amplification of USP13 drives ovarian cancer metabolism
(Springer Nature, 2016) Han, Cecil; Yang, Lifeng; Choi, Hyun Ho; Baddour, Joelle; Achreja, Abhinav; Liu, Yunhua; Li, Yujing; Li, Jiada; Wan, Guohui; Huang, Cheng; Ji, Guang; Zhang, Xinna; Nagrath, Deepak; Lu, Xiongbin
Dysregulated energetic metabolism has been recently identified as a hallmark of cancer. Although mutations in metabolic enzymes hardwire metabolism to tumourigenesis, they are relatively infrequent in ovarian cancer. More often, cancer metabolism is re-engineered by altered abundance and activity of the metabolic enzymes. Here we identify ubiquitin-specific peptidase 13 (USP13) as a master regulator that drives ovarian cancer metabolism. USP13 specifically deubiquitinates and thus upregulates ATP citrate lyase and oxoglutarate dehydrogenase, two key enzymes that determine mitochondrial respiration, glutaminolysis and fatty acid synthesis. The USP13 gene is co-amplified with PIK3CA in 29.3% of high-grade serous ovarian cancers and its overexpression is significantly associated with poor clinical outcome. Inhibiting USP13 remarkably suppresses ovarian tumour progression and sensitizes tumour cells to the treatment of PI3K/AKT inhibitor. Our results reveal an important metabolism-centric role of USP13, which may lead to potential therapeutics targeting USP13 in ovarian cancers.
An experimental and computational study of donor–linker–acceptor block copolymers for organic photovoltaics
(Wiley, 2018) Hu, Zhiqi; Jakowski, Jacek; Zheng, Chenyu; Collison, Christopher J.; Strzalka, Joseph; Sumpter, Bobby G.; Verduzco, Rafael
Block copolymers with donor and acceptor conjugated polymer blocks provide an approach to dictating the donor–accepter interfacial structure and understanding its relationship to charge separation and photovoltaic performance. We report the preparation of a series of donor‐linker‐acceptor block copolymers with poly(3‐hexylthiophene) (P3HT) donor blocks, poly((9,9‐dioctylfluorene)‐2,7‐diyl‐alt‐[4,7‐bis(thiophen‐5‐yl)‐2,1,3‐benzothiadiazole]‐2′,2″‐diyl) (PFTBT) acceptor blocks, and varying lengths of oligo‐ethylene glycol (OEG) chains as the linkers. Morphological analysis shows that the linkers increase polymer crystallinity while a combination of optical and photovoltaic measurements shows that the insertion of a flexible spacer reduces fluorescence quenching and photovoltaic efficiencies of solution processed photovoltaic devices. Density functional theory (DFT) simulations indicate that the linking groups reduce both charge separation and recombination rates, and block copolymers with flexible linkers will likely rotate to assume a nonplanar orientation, resulting in a significant loss of overlap at the donor–linker–acceptor interface. This work provides a systematic study of the role of linker length on the photovoltaic performance of donor–linker–acceptor block copolymers and indicates that linkers should be designed to control both the electronic properties and relative orientations of conjugated polymers at the interface.

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