Reversible Lamellar Thickening Induced by Crystal Transition in Poly(butylene succinate)

Bioinspired Nanolayered Structure Tuned by Extensional Stress: A Scalable Way to High-Performance Biodegradable Polyesters

The nacre-inspired multi-nanolayer structure offers a unique combination of advanced mechanical properties, such as strength and crack tolerance, making them highly versatile for various applications. Nevertheless, a significant challenge lies in the current fabrication methods, which is difficult to create a scalable manufacturing process with precise control of hierarchical structure. In this work, a novel strategy is presented to regulate nacre-like multi-nanolayer films with the balance mechanical properties of stiffness and toughness. By utilizing a co-continuous phase structure and an extensional stress field, the hierarchical nanolayers is successfully constructed with tunable sizes using a scalable processing technique. This strategic modification allows the robust phase to function as nacre-like platelets, while the soft phase acts as a ductile connection layer, resulting in exceptional comprehensive properties. The nanolayer-structured films demonstrate excellent isotropic properties, including a tensile strength of 113.5 MPa in the machine direction and 106.3 MPa in a transverse direction. More interestingly, these films unprecedentedly exhibit a remarkable puncture resistance at the same time, up to 324.8 N mm-1, surpassing the performance of other biodegradable films. The scalable fabrication strategy holds significant promise in designing advanced bioinspired materials for diverse applications.

Synthesis and Properties of Polybutylene (Succinate)-b-poly(dimethylsiloxane) with Unprecedented Combined Performance and Functions

The excellent combined properties of poly(butylene succinate) (PBS) make it a promising biodegradable plastic. However, the lack of functionality and low impact strength limit its application. Poly(dimethylsiloxane) (PDMS) was introduced to prepare new high-performance and functional poly(butylene succinate)-b-poly(dimethylsiloxane) (PBS-b-PDMS) in this work. The resulting PBS-b-PDMS was found to possess high molecular weight, narrow molecular weight distribution, and excellent combined performance. PBS-b-PDMS had good thermal properties. The decomposition temperature of 5% weight loss (T5%) increased from 324 to 344 °C, and the temperatures at the maximum weight loss rate (Tmax) values increased from 385.1 to 396.7 °C. The impact strength increased significantly from 7.8 kJ/m2 of PBS to 53.9 kJ/m2 of PBS-b-PDMS. As the PDMS block endows copolymers with low surface energy and good liquid resistance, PBS-b-PDMS has excellent antismudge, self-cleaning, and solvent resistance. Finally, to minimize the surface energy, PDMS blocks preferentially enrich the surface, which imparts the polymers with self-cleaning properties.

High-Molecular-Weight and Light-Colored Disulfide-Bond-Embedded Polyesters: Accelerated Hydrolysis Triggered by Redox Responsiveness

Disulfide bonds have attracted considerable attention due to their reduction responsiveness, but it is crucial and challenging to prepare disulfide-bond-based polyesters by melt polycondensation. Herein, the inherently poor thermal stability of the S-S bond in melting polycondensation was overcome. Moreover, poly(butylene succinate-co-dithiodipropionate) (PBSDi) with a light color and high molecular weights (Mn values up to 84.7 kg/mol) was obtained. These polyesters can be applied via melt processing with Td,5% > 318 °C. PBSDi10-PBSDi40 shows good crystallizability (crystallinity 56-38%) and compact lamellar thickness (2.9-3.2 nm). Compared with commercial poly(butylene adipate-co-terephthalate) (PBAT), the elevated mechanical and barrier performances of PBSDi make them better packaging materials. For the degradation behavior, the disulfide monomer obviously accelerates the enzyme degradation but has a weaker effect on hydrolysis. In 0.1 mol/L or higher concentrations of H2O2 solutions, the oxidation of disulfide bonds to sulfoxide and sulfone groups can be realized. This process results in a stronger nucleophilic attack, as confirmed by the Fukui function and DFT calculations. Additionally, the greater polarity and hydrophilicity of oxidation products, proved by noncovalent interaction analysis, accelerate the hydrolysis of polyesters. Moreover, glutathione-responsive breakage, from polymers to oligomers, is confirmed by an accelerated decline in molecular weight. Our research offers fresh perspectives on the effective synthesis of the disulfide polyester and lays a solid basis for the creation of high-performance biodegradable polyesters that degrade on demand.

Stress-Stabilized Crystalline Phases of Ultrahigh Molecular Weight Polyethylene under Tensile Stress

Ultrahigh molecular weight polyethylene (UHMWPE) is a semicrystalline polymer renowned for its exceptional mechanical properties, making it a popular material in various high-tech fields. Its mechanical attributes are predominantly governed by its crystalline structures, which may experience alterations in the chain conformation and interchain packing during mechanical deformation. This phenomenon leads to the emergence of distinct polymorphs with unique lattice structures. The investigation of stress-stabilized crystal structures of UHMWPE under tensile stress currently poses challenges with certain aspects remaining unclear. To address this, in this study, time-resolved X-ray wide-angle scattering (TR-WAXS) experiments of biaxially stretched UHMWPE films under in situ tensile conditions were conducted. Experimental results revealed two distinct stress-stabilized crystal phases of UHMWPE that differed from those previously reported. These stress-stabilized phases have been identified as the stress-stabilized orthorhombic crystal phase and the stress-stabilized monoclinic crystal phase, and their corresponding lattice parameters have been accurately calculated through an ab initio computational method. These findings provide deeper insights into UHMWPE's behavior under mechanical strain, opening other avenues for further academic exploration and potential applications in cutting-edge fields.

Robust, Fully Biodegradable Films of Polyesters Realized by In Situ Formation of an Interconnected Multi-Nanolayer Structure under Extensional Flow

Multilayer structures are not only applied to manipulate properties of synthetic polymer materials such as rainbow films and barrier films but also widely discovered in natural materials like nacre. In this work, in situ formation of an interconnected multi-nanolayer (IMN) structure in poly(butylene adipate-co-terephthalate) (PBAT)/poly(butylene succinate) (PBS) cocontinuous blends is designed by an extensional flow field during a "casting-thermal stretching" process, combining the properties of two components to a large extent. Hierarchical structures including phase morphology, crystal structure, and lamellar crystals in IMN films have been revealed, which clearly identifies the crucial role of extensional flow. The oriented PBAT phase in the IMN structure can be beneficial to the epitaxial growth of PBS crystals onto the PBAT nanolayers, thus improving interfacial adhesions. Furthermore, intense extensional stress can also promote crystallinity and thicken the lamellar structure. Given such distinct features in the fully biodegradable films, a simultaneous enhancement in tear strength, tensile strength, and puncture resistance has been achieved. To the best of our knowledge, the tear strength of IMN films about 285.9 kN/m is the highest level in the previous works of this system. Moreover, the proposed fabrication way of the IMN structure is facile and scalable, which is highly expected to be an efficient strategy for development of structured biodegradable polymers with excellent comprehensive properties.

Ductile poly(lactic acid)-based blends derived from poly(butylene succinate-co-butylene 2,5-thiophenedicarboxylate): Structures and properties

Because of superior tensile strength, biodegradability, and biocompatibility, poly(lactic acid) (PLA) has emerged as one among the growth-oriented biodegradable materials. But it has been limited to some extent in practical applications due to poor ductility. Consequently, in order to improve the drawback of poor ductility of PLA, ductile blends were obtained by melt-blending of poly(butylene succinate-co-butylene 2,5-thiophenedicarboxylate) (PBSTF25) with PLA. PBSTF25 has a good improvement on the ductility of PLA due to its excellent toughness. Differential scanning calorimetry (DSC) showed that PBSTF25 promoted the cold crystallization of PLA. Wide-angle X-ray diffraction (XRD) results revealed that PBSTF25 experienced stretch-induced crystallization throughout the stretching procedure. Scanning electron microscopy (SEM) showed neat PLA had a smooth fracture surface, but the blends had rough fracture surface. PBSTF25 can improve the ductility and processing properties of PLA. When the addition of PBSTF25 reached 20 wt%, tensile strength was 42.5 MPa and elongation at break increased to 156.6 %, approximately 19 times as much as PLA. The toughening effect of PBSTF25 was better than that of poly(butylene succinate).

Toughened poly(butylene succinate)/polylactide/poly(vinyl acetate) ternary blend without sacrificing the strength

In this paper, poly(butylene succinate) (PBS)/polylactide (PLA)/poly(vinyl acetate) (PVAc) ternary blends were prepared via directly blending. The content of PBS in each sample was fixed at 30 wt% and that of PVAc was different, 2, 4 or 6%. PBS/PLA (30/70, g/g) and PLA/PVAc (66/4, g/g) were also prepared for comparison. XRD and DSC results showed that PVAc was miscible with PLA, and the crystallinity (X c ) of PLA in PBS/PLA increased by adding PBS, but X c of PBS and PLA in PBS/PLA/PVAc ternary blends reduced by adding PVAc. SEM images showed that PBS was dispersed as droplets in each blend The addition of PVAc improved the compatibility between PBS and PLA, and the fracture surfaces of the ternary blends became rougher than that of PBS/PLA. The tensile and impact tests results showed that PVAc could enhance PLA and the highly toughened PBS/PLA blend. Finally, PBS/PLA/PVAc blend with 2% of PVAc was highly toughened without sacrificing its strength. Its strength was the same as that of PBS/PLA, while the elongation at break and impact strength of the former were 2.8 and 2.5 times those of the latter.

High Mechanical Properties of Stretching Oriented Poly(butylene succinate) with Two-Step Chain Extension

The structure, morphology, fracture toughness and flaw sensitivity length scale of chain-extended poly(butylene succinate) with various pre-stretch ratios were studied. PBS modification adopted from a multifunctional, commercially available chain-extension containing nine epoxy groups (ADR9) as the first step chain extension and hydroxyl addition modified dioxazoline (BOZ) as the second step. Time-temperature superposition (TTS) studies show that the viscosity increased sharply and the degree of molecular branching increased. Fourier transform infrared spectroscopy (FT-IR) confirm successful chain extension reactions. The orientation of the polymer in the pre-stretch state is such that spherulites deformation along the stretching direction was observed by polarized light optical microscopy (PLOM). The fracture toughness of sample (λ_fix = 5) is Γ ≈ 10⁶ J m^-2 and its critical flaw sensitivity length scale is Γ/W_c ≈ 0.01 m, approximately 5 times higher than PBS without chain-extension (Γ ≈ 2 × 10⁵ J m^-2 and Γ/W_c ≈ 0.002 m, respectively). The notch sensitivity of chain-extended PBS is significantly reduced, which is due to the orientation of spherulites more effectively preventing crack propagation. The principle can be generalized to other high toughness material systems.

Micellization of a starch-poly(1,4-butylene succinate) nano-hybrid for enhanced energy storage

In this work, we report on a reverse micellization approach to prepare uncarbonized starch and poly(1,4-butylene succinate) hybrids with exceptional charge storage performance. Uncarbonized starch was activated through protonation, hybridized with poly (1,4-butylene succinate), configured into conductive reverse micelles, and incorporated with magnetite nanoparticles. Before magnetite incorporation, the maximum specific capacitance (C sp), energy density (E d), power density (P d) and retention capacity (%) of the reverse micelles were estimated to be 584 F g-1, 143 W h kg-1, 2356 W kg and 97.5%. After magnetite incorporation, we achieved a maximum supercapacitive performance of 631 F g-1, 204 W h kg-1, 4371 W kg-1 and 98%. We demonstrate that the use of magnetite incorporated St-PBS reverse micelles minimizes the contact resistance between the two supercapacitor electrodes, resulting in high charge storage capacity.

Properties and Skin Compatibility of Films Based on Poly(Lactic Acid) (PLA) Bionanocomposites Incorporating Chitin Nanofibrils (CN)

Nanobiocomposites suitable for preparing skin compatible films by flat die extrusion were prepared by using plasticized poly(lactic acid) (PLA), poly(butylene succinate-co-adipate) (PBSA), and Chitin nanofibrils as functional filler. Chitin nanofibrils (CNs) were dispersed in the blends thanks to the preparation of pre-nanocomposites containing poly(ethylene glycol). Thanks to the use of a melt strength enhancer (Plastistrength) and calcium carbonate, the processability and thermal properties of bionanocomposites films containing CNs could be tuned in a wide range. Moreover, the resultant films were flexible and highly resistant. The addition of CNs in the presence of starch proved not advantageous because of an extensive chain scission resulting in low values of melt viscosity. The films containing CNs or CNs and calcium carbonate resulted biocompatible and enabled the production of cells defensins, acting as indirect anti-microbial. Nevertheless, tests made with Staphylococcus aureus and Enterobacter spp. (Gram positive and negative respectively) by the qualitative agar diffusion test did not show any direct anti-microbial activity of the films. The results are explained considering the morphology of the film and the different mechanisms of direct and indirect anti-microbial action generated by the nanobiocomposite based films.

The effects of different inorganic salts on the structure and properties of ionic liquid plasticized starch/poly(butylene succinate) blends

1-Butyl-3-methylimidazole chloride ([BMIM]Cl) plasticized starch/poly(butylene succinate) (PBS) blends containing inorganic salts with different cations were prepared by a Haake mixer. The compatibility, thermal behaviors including crystallinity, crystallization temperature and melting temperature, thermal stability, and mechanical properties of these blends were systematically investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that the inorganic salts could interact strongly with [BMIM]Cl plasticized starch/PBS blends to improve their mechanical properties, while the thermal stability of the [BMIM]Cl plasticized starch/PBS blends was simultaneously reduced. The SEM results suggested that the compatibility of [BMIM]Cl plasticized starch and PBS was significantly improved with increasing inorganic salt content. Furthermore, by incorporating inorganic salts, the melting enthalpy (ΔH_m), crystallinity (X_c), and cold crystallization temperature (T_cc) of the blends were decreased.

1-Butyl-3-methylimidazole chloride ([BMIM]Cl) plasticized starch/poly(butylene succinate) (PBS) blends containing inorganic salts with different cations were prepared by a Haake mixer.

The Effects of Inorganic Salts with Different Anions on the Structure and Properties of Starch/Poly (Butylene Succinate) Blends Plasticized with Ionic Liquid

1-butyl-3-methylimidazole chloride ((BMIM) Cl) modified starch/poly (butylene succinate) (PBS) blends with different anions of inorganic salts were prepared by HAAKE mixer. The compatibility and thermal behaviors including crystallinity, crystallization and melting temperature, thermal stability and mechanical properties were systematically investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The results show that inorganic salts can produce a strong interaction with starch/PBS blends, which can improve the mechanical properties of starch/PBS blends, enhance the mechanical strength and elongation at break of starch/PBS blends, meanwhile, the thermal stability of starch/PBS blends decreased. The SEM images reveal that the compatibility of starch/PBS become better with the increase of inorganic salts. The melting and crystallization absorption peaks in the DSC curves show that the melting enthalpy (ΔH_m), crystallinity (X_c), and crystallization temperature (T_c) of the blends decrease and the cold crystallization temperature (T_cc) increase when inorganic salts is added. Moreover, inorganic salts with smaller anionic radius have much better effects on the starch/PBS blends plasticized with ((BMIM)Cl).

How Confinement Affects the Nucleation, Crystallization, and Dielectric Relaxation of Poly(butylene succinate) and Poly(butylene adipate) Infiltrated within Nanoporous Alumina Templates

This work describes the successful melt infiltration of poly(butylene succinate) (PBS) and poly(butylene adipate) (PBA) within 70 nm diameter anodic aluminum oxide (AAO) templates. The infiltrated samples were characterized by SEM, Raman, and FTIR spectroscopy. The crystallization behaviors and crystalline structures of both polymers, bulk and confined, were analyzed by differential scanning calorimetry (DSC) and grazing incidence wide angle X-ray scattering (GIWAXS). DSC revealed that a change in the nucleation process occurred from heterogeneous nucleation for bulk samples to homogeneous nucleation for infiltrated PBA and to surface-induced nucleation for infiltrated PBS. GIWAXS results indicate that PBS nanofibers crystallize in the α-phase, as well as their bulk samples. However, PBA nanofibers crystallize just in the β-phase, whereas PBA bulk samples crystallize in a mixture of α- and β-phases. The crystal orientation within the pores was determined, and differences between PBS and PBA were also found. Finally, broadband dielectric spectroscopy was applied to study the segmental dynamics for bulk and infiltrated samples. The glass temperature was found to significantly decrease in the PBS case upon infiltration, while that of PBA remained unchanged. These differences were correlated with the higher affinity of PBS to the AAO walls than PBA, in accordance with their nucleation behavior (surface-induced versus homogeneous nucleation, respectively).

Structural evolution and phase transition of uniaxially stretched poly(butylene adipate-co-butylene terephthalate) films as revealed by in situ synchrotron radiation small and wide angle X-ray scattering

Structural evolution and phase transition of poly(butylene adipate-co-butylene terephthalate) during uniaxial stretching.

Stress-oscillation behaviour of semi-crystalline polymers: the case of poly(butylene succinate)

Stress oscillation has been observed in a number of linear thermoplastic polymers during the cold-drawing process, where the polymers exhibit periodic self-excited oscillatory neck propagation. However, the origin of the mechanical stress oscillation process and its relationship with the crystalline morphology of the polymer are still under debate. In this work, we revisit the stress oscillation behavior by studying a semi-crystalline polyester, poly(butylene succinate) (PBS), a biodegradable polymer suitable for biomedical and packaging applications. Stress oscillation of PBS is observed when deformed at a range of elongation rates from 10 to 200 mm min-1, and the fluctuation magnitude decays as the deformation temperature increases from 23 to 100 °C. Periodic transparent/opaque bands form during necking of PBS, which consists of alternating regions of highly oriented crystalline zones and microcavities due to crazing and voiding, although the degree of crystallinity did not change significantly in the bands. Simultaneous small- and wide-angle X-ray scattering confirms that the alternating stress increases, as shown in the stress-strain curves, correspond to the appearance of the transparent bands in the sample, and the abrupt drop of the stress is the result of voiding during the neck propagation. The voiding and cavitation are ultimately responsible for the stress oscillation process in PBS. The in-depth analysis of this work is important in understanding and controlling the occurrence of instabilities/cavitation during polymer processing such as film blowing, biaxial stretching and injection moulding of biodegradable polymer materials.

Stress-induced crystal transition of poly(butylene succinate) studied by terahertz and low-frequency Raman spectroscopy and quantum chemical calculation

We measured terahertz (THz) and low-frequency Raman spectra of Poly (butylene succinate) (PBS) which shows the crystal transition from α to β by stretching. For the assignment of the absorption peaks in the low-frequency region, we performed quantum chemical calculations with Cartesian-coordinate tensor transfer (CCT) method. Four major peaks appeared in the THz spectra of PBS at around 58, 76, 90, and 100cm^-1, and in the low-frequency Raman spectra a peak was observed at 88cm^-1. The THz peak at 100cm^-1 and the Raman peak at 88cm^-1 show a shift to a lower wavenumber region with increasing temperature. The quantum chemical calculation of β crystal form reveals the new peak appears above 100cm^-1. It was found that two kinds of peaks overlapped at around 100cm^-1 in the THz spectra of PBS. One of them can be assigned to a weak hydrogen bond between the C=O and CH₂ groups in the intermolecular chains, which is perpendicular to the molecular chain of the α crystal form. Another one showed a parallel polarization which can be assigned to the intramolecular interaction between O (ether) and H-C groups in the β crystal form. The position of the peak at around 100cm^-1 in the perpendicular polarization changed to a lower wavenumber region with stretching, because of the weakening of the intermolecular hydrogen bonding by increasing the interatomic distances. On the other hand, that of the parallel polarization shifts to a higher wavenumber region because of the shortening of the interatomic distance from α to β crystal form (the strength of the intramolecular hydrogen bonding became stronger) by stretching.

Morphology, Nucleation, and Isothermal Crystallization Kinetics of Poly(Butylene Succinate) Mixed with a Polycarbonate/MWCNT Masterbatch

In this study, nanocomposites were prepared by melt blending poly(butylene succinate) (PBS) with a polycarbonate (PC)/multi-wall carbon nanotubes (MWCNTs) masterbatch, in a twin-screw extruder. The nanocomposites contained 0.5, 1.0, 2.0, and 4.0 wt% MWCNTs. Differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) results indicate that the blends are partially miscible, hence they form two phases (i.e., PC-rich and PBS-rich phases). The PC-rich phase contained a small amount of PBS chains that acted as a plasticizer and enabled crystallization of the PC component. In the PBS-rich phase, the amount of the PC chains present gave rise to increases in the glass transition temperature of the PBS phase. The presence of two phases was supported by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis, where most MWCNTs aggregated in the PC-rich phase (especially at the high MWCNTs content of 4 wt%) and a small amount of MWCNTs were able to diffuse to the PBS-rich phase. Standard DSC scans showed that the MWCNTs nucleation effects saturated at 0.5 wt% MWCNT content on the PBS-rich phase, above this content a negative nucleation effect was observed. Isothermal crystallization results indicated that with 0.5 wt% MWCNTs the crystallization rate was accelerated, but further increases in MWCNTs loading (and also in PC content) resulted in progressive decreases in crystallization rate. The results are explained by increased MWCNTs aggregation and reduced diffusion rates of PBS chains, as the masterbatch content in the blends increased.

Double Crystalline Multiblock Copolymers with Controlling Microstructure for High Shape Memory Fixity and Recovery

The shape memory performance of double crystalline poly(butylene succinate)-co-poly(ε-caprolactone) (PBS-co-PCL) multiblock copolymers with controlling microstructure was studied, and the corresponding microstructure origin was further quantitatively analyzed by wide and small-angle X-ray scattering (WAXS and SAXS) experiments. It was found that the multiblock copolymer with higher PCL content, proper deformation strain, and inhibited crystallization of PBS (lower crystallinity and smaller crystal size, which could be realized by quenching from the melt) would exhibit better shape memory fixity and recovery performance. WAXS and SAXS results revealed that the shape fixity ratio (R_f) was closely related with the relative crystallinity of the PCL component, while the shape recovery ratio (R_r) strongly relied on the deformation and recovery behavior of the PBS and PCL components that changed along with compositions and deformation strains. For the copolymer with higher PCL content (BS₃₀CL₇₀), at the lower deformation strain (0% ∼ 90%), both the PBS and PCL components after recovery had no orientation (labeled as stage I), resulting in almost complete recovery; with the deformation strain increasing (90% ∼ 200%), it was the irreversible deformation of the PCL component that largely took responsibility for the decreased R_r (stage II). On the contrary, when the PCL content decreased to 50 wt % (BS₅₀CL₅₀), stage I (0% ∼ 50%) and stage II (50% ∼ 100%) appeared in much lower strains; with the deformation strain increasing (100% ∼ 200%), the irreversible deformation of both PBS and PCL components was mainly responsible for the further reduction of R_r (stage III). It could exhibit excellent shape memory performance for biodegradable double crystalline multiblock copolymers by controlling the composition, deformation strain, and crystallization, which might have wide application prospects in biomedical areas.

Tuning the crystalline and mesophase structure of olefin block copolymer through self-nucleation and annealing treatments

As a type of novel semi-crystalline block copolymers, the final properties of olefin block copolymers (OBCs) greatly depend on the crystalline and phase-separated structures. In the present work, we systematically investigated the influence of self-nucleation and annealing on the lamellar and mesophase-separated structure of OBCs. According to the crystalline and melting behavior after self-nucleation and annealing treatments, four different regimes can be recognized with the self-seeding temperature Ts varying from 125 to 109 °C. In regime A, only self-nucleation occurs, while it coexists with lamellar thickening in regime B. In regime C, there is only lamellar thickening behavior. The lamellar thickening induced inconsecutive lamellar crystals observed revealed that the rearrangement of the hard blocks, which are next to the soft blocks and trapped in the intermediate regime between crystalline and amorphous phases, into neighboring lamellar crystals should be the mechanism for the lamellar thickening of the OBCs. Surprisingly, no lamellar thickening occurs and a new small melting peak appears at lower temperatures in regime D. Considering the block dispersity of OBCs, the emergence of a small melting peak at lower temperatures can be attributed to the crystallization of the ethylene sequence with relatively weaker crystallization abilities, which are not able to crystallize in a standard crystalline state. Based on these findings, we gained some new understandings on lamellar thickening behavior of OBCs and established the self-nucleation and annealing process as a powerful tool for tuning the crystalline and phase-separated structures of OBCs.