Polymer Domains Research Articles

Plant Organellar DNA Polymerases Evolved Multifunctionality through the Acquisition of Novel Amino Acid Insertions.

The majority of DNA polymerases (DNAPs) are specialized enzymes with specific roles in DNA replication, translesion DNA synthesis (TLS), or DNA repair. The enzymatic characteristics to perform accurate DNA replication are in apparent contradiction with TLS or DNA repair abilities. For instance, replicative DNAPs incorporate nucleotides with high fidelity and processivity, whereas TLS DNAPs are low-fidelity polymerases with distributive nucleotide incorporation. Plant organelles (mitochondria and chloroplast) are replicated by family-A DNA polymerases that are both replicative and TLS DNAPs. Furthermore, plant organellar DNA polymerases from the plant model Arabidopsis thaliana (AtPOLIs) execute repair of double-stranded breaks by microhomology-mediated end-joining and perform Base Excision Repair (BER) using lyase and strand-displacement activities. AtPOLIs harbor three unique insertions in their polymerization domain that are associated with TLS, microhomology-mediated end-joining (MMEJ), strand-displacement, and lyase activities. We postulate that AtPOLIs are able to execute those different functions through the acquisition of these novel amino acid insertions, making them multifunctional enzymes able to participate in DNA replication and DNA repair.

Construction of a highly error-prone DNA polymerase for developing organelle mutation systems.

A novel family of DNA polymerases replicates organelle genomes in a wide distribution of taxa encompassing plants and protozoans. Making error-prone mutator versions of gamma DNA polymerases revolutionised our understanding of animal mitochondrial genomes but similar advances have not been made for the organelle DNA polymerases present in plant mitochondria and chloroplasts. We tested the fidelities of error prone tobacco organelle DNA polymerases using a novel positive selection method involving replication of the phage lambda cI repressor gene. Unlike gamma DNA polymerases, ablation of 3′–5′ exonuclease function resulted in a modest 5–8-fold error rate increase. Combining exonuclease deficiency with a polymerisation domain substitution raised the organelle DNA polymerase error rate by 140-fold relative to the wild type enzyme. This high error rate compares favourably with error-rates of mutator versions of animal gamma DNA polymerases. The error prone organelle DNA polymerase introduced mutations at multiple locations ranging from two to seven sites in half of the mutant cI genes studied. Single base substitutions predominated including frequent A:A (template: dNMP) mispairings. High error rate and semi-dominance to the wild type enzyme in vitro make the error prone organelle DNA polymerase suitable for elevating mutation rates in chloroplasts and mitochondria.

Universality in Spatio-Temporal High-Mobility Domains Across the Glass Transition from Bulk Polymers to Single Chains

We use molecular dynamics simulations to characterize spatio-temporal, high-mobility domains in various bulk polymers, thin slabs, and isolated chains as liquid samples are cooled across the glass ...

Formation of Large Crystalline Domains in a Semiconducting Polymer with Semi-fluorinated Alkyl Side Chains and Application to High-Performance Thin-Film Transistors.

The semi-fluorinated alkyl (SFA) side chain introduced thienylenevinylene (TV)-based p-type polymer, PC12TVC5F7T, was synthesized for use in organic thin-film transistors (OTFTs). Herein, we investigated the influence of SFA side chains on the morphology, molecular orientation, and crystalline structure using a combination of atomic force microscopy (AFM), scanning electron microscopy (SEM), two-dimensional (2D) grazing-incidence wide-angle X-ray scattering (GIWAXS), and density functional theory (DFT) calculations. Interestingly, the incorporation of SFA side chains led to the evolution of plate-like large-sized domains and also strongly intermolecular stacked high crystalline structures. Furthermore, due to the strong interactions between SFA side chains, several (00h) peaks could be observed for PC12TVC5F7T, in spite of their fairly large dihedral angle. As a result, due to the well-developed microstructure of PC12TVC5F7T, the OTFT devices based on it exhibited a high hole mobility of 1.91 cm2 V-1 s-1, which is an outstanding value among the poly(thiophene) derivative polymers. These observations indicate that large-sized domains and strongly intermolecular stacked high crystalline structures, which are beneficial for charge carrier transport, could be attained by the introduction of SFA side chains, further enhancing the performance of the OTFTs.

3D-printing of segregated carbon nanotube/polylactic acid composite with enhanced electromagnetic interference shielding and mechanical performance

Construction of segregated structures within conductive polymer composites (CPCs) is a prospective strategy to enhance electromagnetic interference (EMI) shielding effectiveness (SE). However, the CPCs of segregated structures frequently experience worsened mechanical performances due to weak interface reactions between adjacent polymer domains, which are hindered by conductive fillers. Herein, 3D-printed segregated carbon nanotube (CNT)/polylactic acid (PLA) composite was firstly exploited to develop high mechanical properties while achieving good performance for electromagnetic interference shielding. Within the final 3D-printed CNT/PLA composite, CNTs coated on 3D-printed PLA scaffold were translated to interconnected conductive network after compression. Thus, EMI SE of composite was as high as 67.0 dB when 5.0 wt% CNTs were loaded. Furthermore, 3D-printed PLA scaffold with a highly continuous structure also benefited the mechanical robustness of the segregated composite, revealing the bending strength (87.8 MPa) and Young's modulus (4.43 GPa), which were 101% and 43% higher than 43.7 MPa and 3.08 GPa for the conventional CNT/PLA composite. Moreover, the regulation of 3D-printed PLA scaffolds results in promising CNT/PLA composites with tunable EMI SE. This work suggests that 3D printing technology is an effective and easy approach to develop the outperformance of CPCs for different radiation source fields and electronic devices.

Understanding the Effect of Multiple Domain Deletion in DNA Polymerase I from Geobacillus Sp. Strain SK72

The molecular structure of DNA polymerase I or family A polymerases is made up of three major domains that consist of a single polymerase domain with two extra exonuclease domains. When the N-terminal was deleted, the enzyme was still able to perform basic polymerase activity with additional traits that used isothermal amplification. However, the 3′-5′ exonuclease domain that carries a proofreading activity was disabled. Yet, the structure remained attached to the 5′-3′ polymerization domain without affecting its ability. The purpose of this non-functional domain still remains scarce. It either gives negative effects or provides structural support to the DNA polymerase. Here, we compared the effect of deleting each domain against the polymerase activity. The recombinant wild type and its variants were successfully purified and characterized. Interestingly, SK72-Exo (a large fragment excluding the 5′-3′ exonuclease domain) exhibited better catalytic activity than the native SK72 (with all three domains) at similar optimum temperature and pH profile, and it showed longer stability at 70 °C. Meanwhile, SK72-Exo2 (polymerization domain without both the 5′-3′ and 3′-5′ exonuclease domain) displayed the lowest activity with an optimum at 40 °C and favored a more neutral environment. It was also the least stable among the variants, with almost no activity at 50 °C for the first 10 min. In conclusion, cutting both exonuclease domains in DNA polymerase I has a detrimental effect on the polymerization activity and structural stability.

Effective ion mobility in anion exchange ionomers: Relations with hydration, porosity, tortuosity, and percolation

The effective mobility of hydroxide, chloride and fluoride ions is reported in various anion exchange membranes (AEM) with a backbone of polysulfone (PSU) or poly (2,6-dimethyl-1,4-phenylene)oxide (PPO). The concentration dependence of the effective mobility is used to derive the porosity (π), tortuosity (τ), and percolation thresholds and to plot the ionic conductivity vs the hydration number. Semi-logarithmic plots of the effective ion mobility u(i) vs the square root of concentration √c(i) for hydroxide, fluoride and chloride ions in various PSU- and PPO-based ionomers at 25 and 60 °C show linear relations, from which the ratio π/τ can be determined. This existence of linear u(i) = f(√c(i)) plots is related to the very particular boundary conditions experienced by mobile ions, migrating in close vicinity to the immobile grafted counter-ions placed at the interfaces between polymer domains and electrolyte solution. The π/τ values for PSU-QA (0.29) and PPO-QA (0.38) are consistent with a relatively low hydrophilic-hydrophobic nanophase separation, which leads to channels with low diameter and high tortuosity. The tortuosity determined from a Bruggeman-type relation is 1.9 for PSU-QA and 1.6 for PPO-QA. The percolation thresholds φH2O,p, determined from the universal percolation equation near and above φH2O,p, are at a water volume fraction of 0.07 for PSU-TMA and 0.03 for PPO-QA indicating that these AEM have a two-dimensional structure of the hydrated domains. The prefactor, which should represent a good indication as to the maximum achievable ionic conductivity, is slightly below 100 mS/cm for both PSU-TMA and PPO-based ionomers. Plots of experimental and computed hydroxide and chloride ion conductivities as function of the hydration number (λ) show a maximum ionic conductivity for a value of the hydration number around 60, corresponding to optimal hydration conditions. At λ = 100, the ratio of conductivity between PSU-QA (OH− form) and PPO-QA (Cl− form) indicates that the degree of dissociation of ion pairs is about 30% lower for hydroxide than for chloride ions, which is consistent with the effective ionic radii of Cl− and OH−.

Flexible photocatalytic membrane based on CdS/PMMA polymeric nanocomposite films: multifunctional materials.

In this study, poly(methyl methacrylate) with different doping nano-cadmium sulfide (CdS/PMMA) is prepared and characterized. CdS/PMMA polymeric nanocomposite films were synthesized using solution casting methodology. SEM and XRD are used for structure analysis for the studied nanocomposite films. XRD revealed the amorphous domains of PMMA polymer, which increased with increasing CdS nanoparticle contents. SEM revealed the CdS dispersion within the PMMA matrix. CdS nanoparticles in the PMMA matrix are expected to be aggregated due to the casting technique. The optical energy gap is found to be decreased after the CdS addition. ε' and ε″ have the same behavior with the applied frequency. Maxwell-Wagner interfacial polarization is the responsible factor for higher values of ε'-ε″ at the higher frequencies. Electrical conductivity behavior σAC tends to obtain a constant value at lower frequencies that approach from its DC conductivity values. After doping PMMA with nano-CdS, an exponential increase after a critical frequency value and the values of σAC was also increased. Besides, a significant reduction in laser energy power is identified by the reduction of the output power. CdS/PMMA can attenuate the laser power due to its nonlinear effect. CdS/PMMA nanocomposite can act as a photocatalyst to improve the performance of the photodegradation of Rhodamine B (RhB). Among the different CdS/PMMA nanocomposite films, 3.33wt% CdS/PMMA demonstrates the highest efficiency in visible photocatalysis of Rhodamine B. CdS/PMMA can be utilized as multifunctional materials use like laser optical limiting to reduce the power of laser sources and as a photocatalyst membranes.

In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells

AbstractThe development of polymer morphology and crystallinity of printed bulk heterojunction (BHJ) films doped with the different solvent additives 1,8‐diiodooctane (DIO) or diphenyl ether (DPE) is investigated with in situ grazing‐incidence small/wide‐angle X‐ray scattering. The solvent additives, having different boiling points, lead to a different film drying behavior and morphology growth states in the BHJ films of the benzothiadiazole‐based polymer (PPDT2FBT) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM). The phase demixing in the printed films is changing over time along with solvent evaporation. Polymer domains start aggregating to form larger domains in the liquid–liquid phase, while phase separation mainly occurs in the liquid–solid phase. The present work provides a profound insight into the morphology development of printed BHJ films doped with different solvent additives, which is particularly important for the large‐scale fabrication of organic photovoltaics.

Following In Situ the Evolution of Morphology and Optical Properties during Printing of Thin Films for Application in Non-Fullerene Acceptor Based Organic Solar Cells.

In situ printing gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situ with grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance.

Dynamic mechanical analysis of Scots pine and three tropical hardwoods

ABSTRACT Dynamic mechanical analysis (DMA) was used to investigate the viscoelastic behaviour of four species of wood, Scots pine, Gmelina, Obeche and Alstonia. Three frequencies (0.1, 1.0 and 10 Hz) were used over a temperature range of −150°C to +150°C. All the wood species showed tan δ peaks corresponding with secondary relaxations in the expected range. The low temperature (γ peak) was seen at −115°C to −83°C, differing between species and with frequency. β peaks relating to hemicellulose relaxations in association with water molecules were observed, at two locations for Scots pine and three locations in hardwoods. The α peak for lignin lay outside the temperature range studied. Differences in β peaks are proposed to relate to the composition of hemicellulose, and be influenced by structure and level of heterogeneity in the amorphous polymer domains; differing between the wood species studied, which is in-line with currently proposed cell wall polymer models.

4D-STEM Quantification of Nanoscale Ordered Domains in Organic Semiconducting Polymers

Journal Article 4D-STEM Quantification of Nanoscale Ordered Domains in Organic Semiconducting Polymers Get access Gabriel Calderon Ortiz, Gabriel Calderon Ortiz The Ohio State University, Columbus, Ohio, United States Search for other works by this author on: Oxford Academic Google Scholar Menglin Zhu, Menglin Zhu The Ohio State University, Columbus, Ohio, United States Search for other works by this author on: Oxford Academic Google Scholar Letian Dou, Letian Dou Purdue University, West Lafayette, Indiana, United States Search for other works by this author on: Oxford Academic Google Scholar Jinwoo Hwang Jinwoo Hwang The Ohio State University, Columbus, Ohio, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 1740–1742, https://doi.org/10.1017/S1431927620019170 Published: 01 August 2020

Conformation-dependent membrane permeabilization by neurotoxic PrP oligomers: The role of the H2H3 oligomerization domain

The relationship between prion propagation and the generation of neurotoxic species and clinical onset remains unclear. Several converging lines of evidence suggest that interactions with lipids promote various precursors to form aggregation-prone states that are involved in amyloid fibrils. Here, we compared the cytotoxicities of different soluble isolated oligomeric constructs from murine full-length PrP and from the restricted helical H2H3 domain with their effects on lipid vesicles. The helical H2H3 domain is suggested to be the minimal region of PrP involved in the oligomerization process. The discrete PrP oligomers of both the full-length sequence and the H2H3 domain have de novo β-sheeted structure when interacting with the membrane. They were shown to permeabilize synthetic negatively charged vesicles in a dose-dependent manner. Restricting the polymerization domain of the full-length PrP to the H2H3 helices strongly diminished the ability of the corresponding oligomers to associate with the lipid vesicles. Furthermore, the membrane impairment mechanism occurs differently for the full-length PrP oligomers and the H2H3 helices, as shown by dye-release and black lipid membrane experiments. The membrane damage caused by the full-length PrP oligomers is correlated to their neuronal toxicity at submicromolar concentrations, as shown by cell culture assays. Although oligomers of synthetic H2H3 could compromise in vitro cell homeostasis, they followed a membrane-disruptive pattern that was different from the full-length oligomers, as revealed by the role of PrPC in cell viability assays.

Enhanced electromagnetic interference shielding and mechanical properties of segregated polymer/carbon nanotube composite via selective microwave sintering

Formation of segregated structure in conductive polymer composites (CPCs) is an efficient strategy to achieve high electrical conductivity at relatively low filler loading. Nevertheless, not every polymer can meet the requirements for the conventional hot compression molding (CM), and it will always result in the weak interfacial bonding among the polymer domains. Herein, a clean and energy-saving approach based on selective microwave sintering (SMS) was proposed to fabricate the segregated poly(ethylene-co-octene) (POE)/carbon nanotube (CNT) composites with significantly enhanced electromagnetic interference (EMI) shielding and mechanical performance. CNT nanoparticles were selectively dispersed and coated on the surface of POE granules under an external force field. The coated CNT layer served as the microwave absorber, thus inducing the local melting and welding of the neighboring POE domains without destroying the original CNT segregated network. In this way, the intense inter-diffusion and entanglement of POE chains occurred in the interface regions to ensure high-quality sintering among POE granules. The prepared conductive POE/CNT composites were endowed with the significantly enhanced mechanical properties, showing nearly 2 times of tensile strength and over 10 times of elongation at break than the samples prepared by hot compaction. Also, the SMS composites with only 2.10 vol% CNT exhibited the excellent electrical conductivity of 26.0 S/m and EMI SE of 34.7 dB at the frequency of 12.0 GHz, respectively. What's more, the sintering process, reinforcement mechanism, and fusion behavior among neighboring polymer granules were intensively investigated via infrared thermography and COMSOL simulation.

Influence of 3D morphology on the performance of all-polymer solar cells processed using environmentally benign nonhalogenated solvents

Advancing the photovoltaic performance of all-polymer solar cells (APSCs) requires a comprehensive understanding of the dependence of the properties of photoactive blend films on the solvents used to process them. We have studied the correlation between the morphology of PTB7-Th:PNDI2OD-T2 blend films prepared using six different processing solvents. Three-dimensional (3D) transmission electron microscopy tomography (TEMT) revealed the influence of the 3D morphology of the PTB7-Th:PNDI2OD-T2 blend films on their photovoltaic performance. The high-performing toluene (TOL)- and o -xylene (XY)-processed blend films displayed power conversion efficiencies (PCEs) of ~4%, which contained nanoscopically networked fibrous PNDI2OD-T2 polymer domains. The films processed using the other solvents exhibited partly disconnected domains or unfavorable vertical phase separation. In addition, the use of N -dimethylformamide (DMF), N , N -dimethylacetamide (DMAc), or N -methyl-2-pyrrolidone (NMP) as a solvent additive in XY solution resulted in a substantial improvement in the PCEs to 6.1%. This large enhancement was attributed to the formation of the better-interconnected narrower crystalline fibrillary structure of PNDI2OD-T2 chains with the aid of solvent additives, as clearly elucidated by 3D-TEMT imaging. This work highlights that APSCs processed from benign nonhalogenated solvents with appropriate additives can outperform APSCs processed from toxic halogenated solvents by affording a favorable blend morphology and that 3D TEMT imaging is a powerful and essential tool for characterizing the true morphology of photoactive layers. • Three-dimensional transmission electron microscopy revealed nanoscopic morphology. • 3D morphology is a key in determining the performance of all-polymer solar cells. • Environmentally benign nonhalogenated solvents performed better than halogen solvents. • The use of DMAc solvent additive greatly improved the photovoltaic.

Solvent-Responsive and Reversible Structural Coloration in Nanostructured Block Polymer Films

Structural coloration, the vibrant colors in many biological systems, results from periodically ordered nanostructures, giving rise to a photonic band gap in which specific wavelengths are either reflected or transmitted. In many of the current materials, structural coloration is a result of the static morphology, and modifications of the materials are directed toward tuning the reflected wavelength. Recently, excitement in the ability to create materials exhibiting responsive and reversible structural coloration for manipulating light at the nanoscale has been motivated by biological systems that utilize changes in coloration for camouflage or communication between other animals. Here, we establish the effect of solvent swelling and deswelling on the photonic band gap of nanostructured films containing a lamellar-forming diblock copolymer, poly­(1,2-butadiene)-block-poly­(ethylene oxide) (1,2PBD-PEO). The large chemical incompatibility between 1,2PBD and PEO domains (resulting in a high-χ system) allows to strategically and independently swell either one or both domains while maintaining the same lamellar morphology. The influence of solvent, leading to wavelength-specific reflection, entails changes in both the domain spacing and refractive index. A good solvent for both 1,2PBD and PEO domains, such as tetrahydrofuran, leads to a prominent increase in the domain spacing, and as a result, a shifting of the reflected light to green from an initially colorless and translucent film. For selective solvents such as water and hexane, only one domain swells (PEO or 1,2PBD domain, respectively), resulting in asymmetric changes in domain spacing. Additionally, the existence of PEO crystals plays an essential role in the ability of solvents to swell polymer domains. The structural and refractive index transformations on swelling with solvents leading to changes in the reflected wavelength and intensity are found to be reversible on the evaporation of solvents, enabling cyclic swelling and deswelling of the nanostructure. The work presented here highlights the necessary parameters for tuning the photonic band gap properties in self-assembled polymer materials using a combination of solvent quality (e.g., degree of polymer domain swelling) and variations in the effective refractive indices between domains.

One-pot solvothermal synthesis of silane-functionalized carbon nanodots as compatibilizers for the immiscible TPU/MVQ blends

Herein, silane-functionalized carbon nanodots (Si-CDs) with different sizes and surface grafting density were successfully fabricated by a facile and cost-effective one-pot solvothermal treatment and incorporated for the first time as novel compatibilizers into the thermoplastic polyurethane/methyl vinyl silicone rubber (TPU/MVQ) blends. As obtained fluorescent Si-CDs with a size of 2 nm and functionalized with maximum amido and silane chains, called Si-CDs-High, displayed better compatibilizing efficiency than other Si-CDs with large size and low grafting density. The average diameter of MVQ domain in the blend reduced sharply from 2.51 ± 1.03 μm to 0.91 ± 0.28 μm at a small content of 1 wt% of Si-CDs-High. As effective compatibilizers, Si-CDs-High were located at the interface and formed a stable interface layer between TPU and MVQ phases and the thickness of interface was quantitatively identified by using Atomic Force Microscope. The superior compatibilizing efficiency of Si-CDs-High can be attributed that such Si-CDs with sufficient chains and groups can not only prevent coalescence of polymer domains by rigid nanoparticle core but also enhance interfacial adhesion due to the molecular entanglements and hydrogen bonding. Furthermore, the polymer blends with Si-CDs-High exhibited enhanced mechanical property, thermal stability and tunable fluorescent properties. This strategy compatibilized by fluorescent Si-CDs paves a new possibility for advanced blend nanocomposites.

Transdermal progesterone delivery study from waterborne poly(urethane-urea)s nanocomposites films based on montmorillonite clay and reduced graphene oxide

Waterborne poly(urethane-urea)s nanocomposites films based on montmorillonite (Mt) clay, reduced graphene oxide (rGO) or Mt/rGO hybrids were investigated as a new system for transdermal delivery of progesterone (P4). Polymer matrices were prepared from poly(ethylene glycol-block-propylene glycol) (PEG-b-PPG) (containing 7% PEG-based segments), and poly(propylene glycol) (PPG), as soft segments. Cast films-drug interaction was investigated by X-ray diffraction (XRD), low-field nuclear magnetic resonance (NMR) relaxometry, and Fourier-transform infrared spectrometry (FTIR). In vitro release tests and ex vivo permeation tests using pig ear skin were evaluated. XRD and NMR results showed that P4 crystals affected the morphology of amorphous polymeric domains. FTIR data suggested that the presence of P4 decreased the strength of hydrogen bonds in nanocomposites. Mt/rGO hybrid film promoted sustained drug permeation for 8 h, indicating the possibility of being applied as transdermal delivery system, due to the barrier to drug diffusion promoted by the hybrid system.

Improving the picture of atomic structure in nonoriented polymer domains using the pair distribution function: A study of polyamide 6

AbstractInvestigations of the atomic structures within polyamides started over 80 years ago and continue today. These weakly ordered materials diffract X‐rays poorly and typically require postprocessing to obtain idealized samples for structural studies. An important goal remains to develop techniques to study the local structure in its natural state, with atomic resolution, and with sensitivity to subtle changes due to synthesis conditions or other technologically relevant processing procedures. Here, we compare the structures of as‐produced, nonoriented polyamide 6 ([C6H11NO] n) from both hydrolytic and anionic processes. A total scattering pair distribution function approach is used to elucidate information about the atomic bonding, molecular conformation, chain packing, crystallite size, and ratio of ordered to disordered domain content. The results are compared with those from standard analytical methods.

Direct Correlation of Nanoscale Morphology and Device Performance to Study Photocurrent Generation in Donor-Enriched Phases of Polymer Solar Cells.

The nanoscale morphology of polymer blends is a key parameter to reach high efficiency in bulk heterojunction solar cells. Thereby, research typically focusing on optimal blend morphologies while studying nonoptimized blends may give insight into blend designs that can prove more robust against morphology defects. Here, we focus on the direct correlation of morphology and device performance of thieno[3,4-b]-thiophene-alt-benzodithiophene (PTB7):[6,6]phenyl C71 butyric acid methyl ester (PC71BM) bulk heterojunction (BHJ) blends processed without additives in different donor/acceptor weight ratios. We show that while blends of a 1:1.5 ratio are composed of large donor-enriched and fullerene domains beyond the exciton diffusion length, reducing the ratio below 1:0.5 leads to blends composed purely of polymer-enriched domains. Importantly, the photocurrent density in such blends can reach values between 45 and 60% of those reached for fully optimized blends using additives. We provide here direct visual evidence that fullerenes in the donor-enriched domains are not distributed homogeneously but fluctuate locally. To this end, we performed compositional nanoscale morphology analysis of the blend using spectroscopic imaging of low-energy-loss electrons using a transmission electron microscope. Charge transport measurement in combination with molecular dynamics simulations shows that the fullerene substructures inside the polymer phase generate efficient electron transport in the polymer-enriched phase. Furthermore, we show that the formation of densely packed regions of fullerene inside the polymer phase is driven by the PTB7:PC71BM enthalpy of mixing. The occurrence of such a nanoscale network of fullerene clusters leads to a reduction of electron trap states and thus efficient extraction of photocurrent inside the polymer domain. Suitable tuning of the polymer-acceptor interaction can thus introduce acceptor subnetworks in polymer-enriched phases, improving the tolerance for high-efficiency BHJ toward morphological defects such as donor-enriched domains exceeding the exciton diffusion length.