Unique Self-assembly Behavior Research Articles

Recent Advances of Natural Pentacyclic Triterpenoids as Bioactive Delivery System for Synergetic Biological Applications.

Bioactive compounds have drawn much attention according to their various health benefits. However, poor dissolvability, low stability and limited bioavailability largely narrow their applications. Although a variety of nontoxic ingredients have been rapidly developed as vehicles to deliver bioactive compounds in the last few years, most of them are non-bioactive. Pentacyclic triterpenoids, owing to their unique self-assembly and co-assembly behaviors and different physiological functions, can construct bioactive carriers due to their higher biodegradability, biocompatibility and lower toxicity. In this paper, the basic classification, biological activities and physicochemical properties of pentacyclic triterpenoids were summarized. Additionally, applications of self-assembled and co-assembled pentacyclic triterpenoids as bioactive delivery systems to load bioactive components and future research directions were discussed. This study emphasizes the potential of pentacyclic triterpenoids as bioactive delivery systems, offering a new perspective for constructing self- or co-assemblies for further synergetic biological applications.

Molecular packing regulation of dopant-free hole transport polymers for efficient perovskite solar cells

Spiro-OMeTAD is a primary hole transport material (HTM) employed in most state-of-the-art regular perovskite solar cells (PSCs). The essential reliance on hygroscopic ionic dopants to enhance the conductivity and mobility of Spiro-OMeTAD has dramatically compromised the stability of PSCs. Here, we demonstrated excellent photovoltaic performance of PSCs by developing two dopant-free polymers, namely L1 and L2, using thieno[3,2-b]thiophene as a building block. It is found that the n-hexyl-modified thiophene side chains endow the polymer L2 with favorable crystallinity, unique self-assembly behavior, and a preferable face-on stacking orientation. After the addition of a small amount (10 %) of PM6 to create a polymer alloy named LPA, the above properties were further improved, and the resulting film exhibited a distinct fibrous morphology, resulting in increased hole mobility and effective defect passivation. Consequently, PSCs employing LPA as a dopant-free HTM afforded a high efficiency of 23.81 %. Importantly, LPA-based PSCs exhibit significantly enhanced operational stability with a T80 lifetime of 1572 h at 55 °C. This work provides a crucial guideline for the design of dopant-free polymers, thereby advancing the practical application of PSCs.

High-substituted hydroxypropyl cellulose prepared by homogeneous method and its clouding and self-assembly behaviors

Hydroxypropyl cellulose (HPC) is a sustainable cellulose derivative valued for its excellent biocompatibility and solubility and is widely used in various fields. Recent scientific research on high-substituted HPC mainly focused on its efficient preparation and phase transition behavior. Herein, a novel strategy of high-substituted HPC synthesis was demonstrated by employing DMSO/TBAF·3H2O as a cellulose solvent, exhibiting more efficiency than traditional approaches. High-substituted HPC prepared has remarkable thermal stability, exceptional hydrophilicity, and satisfactory solubility. Phase transition behavior of HPC with varying molar degrees of substitution (MS) was delved and a notable negative correlation between MS and cloud point temperature (TCP), was revealed, particularly evident at an MS of 12.3, where the TCP drops to 33 °C. Moreover, a unique self-assembly behavior featuring structural color and responsiveness to force in a solvent-free environment emerged when the MS exceeded 10.4. These insights comprehensively strengthen the understanding and knowledge of high-substituted HPC, simultaneously paving the way for further HPC investigation and exploitation.

Azaylide-based gemini amphiphiles displaying unique self-assembling behavior via an even-odd effect of alkyl linker chain length.

Herein, we report a straightforward synthesis of azaylide-based gemini amphiphiles using bis(diphenylphosphino)alkanes via the Staudinger reaction. The prepared gemini amphiphiles exhibited an even-odd effect in their self-assembly behavior depending on the length of the alkyl linkers. Furthermore, the assembled micelles had high host capability toward hydrophobic guests in water.

New Insight into the Structural Nature of Diphenylalanine Nanotube through Comparison with Amyloid Assemblies.

Diphenylalanine (FF) nanotubes are a star material in the field of peptide self-assembly and have demonstrated numerous intriguing applications. Due to its resemblance to amyloid assembly, the FF nanotube is widely regarded as a simplified mimic of amyloids. Yet, whether FF nanotube truly possesses amyloid structure remains an open question. To better understand the structural nature of FF nanotube, we herein performed a comparative structural investigation between FF nanotube and typical amyloid systems by Aβ1-40, Aβ1-42, Aβ16-22, Aβ13-23, α-synuclein, and lysozyme using Fourier transform infrared spectroscopy. Through this comparative investigation, we obtained clear evidence to support that the FF nanotube does not possess a β-sheet structure, a key structural characteristic of amyloid assembly, thus revealing the non-amyloid structural nature of the FF nanotube. At last, in light of our new finding, we further discussed the unique self-assembly behaviors of FF during nanotube formation and the implications of our work for FF nanotube related applications.

Performance evaluation of polymer nanolatex particles as fluid loss control additive in water-based drilling fluids

The development of various nanoparticles and their successful application in oil and gas drilling engineering is an extremely interesting and crucial area of research, particularly in the field of drilling fluids. In this study, styrene, butyl acrylate, acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid were used as the main raw materials to synthesize a polymer nanolatex (SBAA) employing a conventional emulsion polymerization approach (one-pot method). SEM, TEM, and PSD experiments demonstrated that SBAA is a nanoparticle with a particle size of around 150 nm and a distinct core-shell structure. The TGA analysis revealed that SBAA had a decomposition temperature of 296 °C. Particularly, the unique self-assembly behavior of nanolatex particles is discussed for the first time using TEM and UV–Vis experiments. Additionally, filtration and permeability plugging tests were used to evaluate the filter loss reduction and micro-pore plugging ability of the SBAA in water-based drilling fluids. The findings showed that SBAA could reduce the medium pressure filtration loss by around 33% compared with the basic bentonite fluid, and the reduction rate after aging at 200 °C is around 41%. Particularly, it can reduce the filtrate loss velocity of water-based drilling fluid in heterogeneous pores, and the effects of filtration reduction and mud cake quality enhancement outperform those of commercial nanosilica particles. This study offers a novel reference approach for developing novel nanomaterials for water-based mud to plug microscopic pores and maintain wellbore stability.

Short Peptides Derived from a Block Copolymer-like Barnacle Cement Protein Self-Assembled into Diverse Supramolecular Structures

Peptides capable of self-assembling into different supramolecular structures have potential applications in a variety of areas. The biomimetic molecular design offers an important avenue to discover novel self-assembling peptides. Despite this, a lot of biomimetic self-assembling peptides have been reported so far; to continually expand the scope of peptide self-assembly, it is necessary to find out more novel self-assembling peptides. Barnacle cp19k, a key underwater adhesive protein, shows special block copolymer-like characteristics and diversified self-assembly properties, providing an ideal template for biomimetic peptide design. In this study, inspired by Balanus albicostatus cp19k (Balcp19k), we rationally designed nine biomimetic peptides (P1-P9) and systematically studied their self-assembly behaviors for the first time. Combining microscale morphology observations and secondary structure analyses, we found that multiple biomimetic peptides derived from the central region and the C-terminus of Balcp19k form distinct supramolecular structures via different self-assembly mechanisms under acidic conditions. Specifically, P9 self-assembles into typical amyloid fibers. P7, which resembles ionic self-complementary peptides by containing nonstrictly alternating hydrophobic and charged amino acids, self-assembles into uniform, discrete nanofibers. P6 with amphipathic features forms twisted nanoribbons. Most interestingly, P4 self-assembles to form helical nanofibers and novel ring-shaped microstructures, showing unique self-assembly behaviors. Apart from their self-assembly properties, these peptides showed good cytocompatibility and demonstrated promising applications in biomedical areas. Our results expanded the repertoire of self-assembling peptides and provided new insights into the structure-function relationship of barnacle cp19k.

Effect of A Limited Amount of D-Sorbitol on Pitch and Mechanical Properties of Cellulose Nanocrystal Films

A cellulose nanocrystal (CNC) suspension can form liquid crystal films with unique self-assembly behaviors. This gives CNC films a special iridescence, which has potential in many aspects, but the brittleness of pure CNC films limits their application. In this work, we propose a simple physical mixing method to obtain CNC film by adding D-sorbitol as a plasticizer. We first found that low D-sorbitol content (less than 6 wt% in CNC/DS composite solution) did not make a significant difference compared with pure CNC films in optical performance and, at the same time, the mechanical properties of the CNC films were improved. The various low contents of D-sorbitol can be well dispersed in CNC aqueous suspension, and the wavelength of the selectively reflected phenomenon is relatively stable and slightly decreased at 5 nm for concentrations from 0 to 6%. This phenomenon is opposite to that generally reported, where the wavelength of the selective reflected phenomenon increases obviously with the increase in plastic content. The pitch of the chiral structure decreased from 406 to 362 nm with an increase in D-sorbitol concentration. When the content of D-sorbitol reached 4%, the tensile strength, elongation at break, and Young modulus increased to 39.9 Mpa, 3.00%, and 2.99 GPa, respectively.

DNA-π Amphiphiles: A Unique Building Block for the Crafting of DNA-Decorated Unilamellar Nanostructures.

The unparalleled ability of DNA to recognize its complementary strand through Watson and Crick base pairing is one of the most reliable molecular recognition events found in natural systems. This highly specific sequence information encoded in DNA enables it to be a versatile building block for bottom-up self-assembly. Hence, the decoration of functional nanostructures with information-rich DNA is extremely important as this allows the integration of other functional molecules onto the surface of the nanostructures through DNA hybridization in a highly predictable manner. DNA amphiphiles are a class of molecular hybrids where a short hydrophilic DNA is conjugated to a hydrophobic moiety. Since DNA amphiphiles comprise DNA as the hydrophilic segment, their self-assembly in aqueous medium always results in the formation of nanostructures with shell made of DNA. This clearly suggests that self-assembly of DNA amphiphiles is a straightforward strategy for the ultradense decoration of a nanostructure with DNA. However, initial attempts toward the design of DNA amphiphiles were primarily focused on long flexible hydrocarbon chains as the hydrophobic moiety, and it has been demonstrated in several examples that they typically self-assemble into DNA-decorated micelles (spherical or cylindrical). Hence, molecular level control over the self-assembly of DNA amphiphiles and achieving diverse morphologies was extremely challenging and unrealized until recently.In this Account, we summarize our recent efforts in the area of self-assembly of DNA amphiphiles and narrate the remarkable effect of the incorporation of a large π-surface as the hydrophobic domain in the self-assembly of DNA amphiphiles. Self-assembly of DNA amphiphiles with flexible hydrocarbon chains as the hydrophobic moiety is primarily driven by the hydrophobic effect. The morphology of such nanostructures is typically predicted based on the volume ratio of hydrophobic to hydrophilic segments. However, control over the self-assembly and prediction of the morphology become increasingly challenging when the hydrophobic moieties can interact with each other through other noncovalent interactions. In this Account, the unique self-assembly behaviors of DNA-π amphiphiles, where a large π-surface acts as the hydrophobe, are described. Due to the extremely strong π-π stacking in aqueous medium, the assembly of the amphiphile is found to preferably proceed in a lamellar fashion (bilayer) and hence the morphology of the nanostructures can easily be tuned by the structural modification of the π-surface. Design principles for crafting various DNA-decorated lamellar nanostructures including unilamellar vesicles, two-dimensional (2D) nanosheets, and helically twisted nanoribbons by selecting suitable π-surfaces are discussed. Unilamellar vesicular nanostructures were achieved by using linear oligo(phenylene ethynylene) (OPE) as the hydrophobic segment, where lamellar assembly undergoes folding to form unilamellar vesicles. The replacement of OPE with a strongly π-stacking hydrophobe such as hexabenzocoronene (HBC) or tetraphenylethylene (TPE) provides extremely strong π-stacking compared to OPE, which efficiently directed the 2D growth for the lamellar assembly and led to the formation of 2D nanosheets. A helical twist in the lamella was achieved by the replacement of HBC with hexaphenylbenzene (HPB), which is the twisted analogue of HBC, directing the assembly into helically twisted nanoribbons. The most beneficial structural feature of this kind of nanostructure is the extremely dense decoration of their surface with ssDNA, which can further be used for DNA-directed organization of other functional nanomaterials. By exploring this, their potential as a nanoscaffold for predefined assembly of plasmonic nanomaterials into various plasmonic 1D, 2D, and 3D nanostructures through DNA hybridization is discussed. Moreover, the design of pH-responsive DNA-based vesicles and their application as a nanocarrier for payload delivery is also demonstrated.

Coal-derived nanomaterials for enhanced NAPL flow in porous media

This study investigates the synthesis and characterization of high value-added carbonaceous nanomaterials from coal and explores their application as flow enhancers in subsurface formations containing non-aqueous phase liquids (NAPLs) such as crude oils. A modified Hummer’s method is used to exfoliate coal and extract graphene oxide nanosheets. Dodecylamine is then grafted to one side of the nanosheets using starch as a template. The reaction products are engineered carbon nanosheets (E-CNS) with an amphiphilic character that endues them with both surfactant-like and nanoparticle-like properties, including high interfacial activity and stability in water. As a result, the engineered nanosheets are able to reduce the NAPL/water interfacial tension by more than 60%, enhancing NAPL emulsification and its mobilization through small pores. They also promote NAPL solubilization by reversing wettability of both aged quartz and calcite from NAPL-wet towards neutral-wet to weakly water-wet conditions. The E-CNS exhibit a unique self-assembly behavior at the NAPL/water interface, flattening the curvature of both concave and convex menisci in glass tubes. Compared to waterflooding, nanofluid flooding can enhance NAPL recovery by 13% and 6% in Edwards limestone and Berea sandstone, respectively, with minimum rock retention, which demonstrates their potential application in aquifer remediation or enhanced oil recovery processes.

Solution Self-Assembly of Chalcogen-Bonding Polymer Partners.

Chalcogen bonding is regarded as a form of noncovalent interaction; however, harnessing chalcogen bonds to drive macromolecular self-assembly remains unexplored. Here we report two classes of chalcogen-bonding partner polymers and their unique self-assembly behaviors in THF/H2O solution. Using simple poly(4-vinylphenyl chalcogenide) (P4VCh, Ch = Te or Se) as the donor polymer and poly(ethylene oxide)-block-poly(4-vinylpyridine N-oxide) (PEO-b-P4VO) as the acceptor polymer, they can form donor-acceptor noncovalent complexes and further aggregate into tubular and spherical assemblies through interchain Te···O and Se···O chalcogen-chalcogen interactions. The small distinction in binding affinity of chalcogen bonds can dictate the assembly of different geometries. Moreover, mixing the strong and weak chalcogen-bonding pairs in various ratios can allow us to obtain ergodic phase evolution with tunable dimensionality and morphology.

A unique polymersome covered by loop-cluster polyamine corona.

In this work, we synthesized a new comb-like copolymer (c-iMP) possessing amphiphilic diblock side chains consisting of poly(methyloxazoline) (PMOZ) and poly(phenyloxazoline) (PPOZ) via reversible addition-fragmentation chain-transfer (RAFT) polymerization of p-choloromethylstyene (CMS) and cationic ring-opening polymerization (CROP) of 2-methyl-2-oxazoline (MOZ) and 2-phenyl-2-oxazoline (POZ). Then, by performing selective hydrolysis of the hydrophilic PMOZ block, the PMOZ block was transformed into PEI (polyethylenimine) from which comb-like copolymers (c-iEP) possessing two blocks of PEI (E) and PPOZ (P) were produced. The comb-copolymers c-iEP showed unique self-assembling behavior in water to give an unusual polymersome covered by a loop-cluster polyamine corona. The polymersome showed extreme toughness and stability without collapse and fusion even at dry conditions and could be transformed into capsules. This is the first example of polymesome without free-ends on the vesicle wall which could include Ag ions inside and could deposit silica around the wall to form hybrid hollow spheres.

Supramolecular microtubes based on 1,3,5-benzenetricarboxamides prepared by self-assembly upon heating.

A series of three 1,3,5-benzenetricarboxamides with peripheral tertiary N,N-dialkyl-ethylamino substituents with different length of the alkyl groups is reported. In particular, the N1,N3,N5-tris[2-(diethylamino)-ethyl]-1,3,5-benzenetricarboxamide exhibits phase separation followed by self-assembly upon heating from aqueous solution into well-defined supramolecular fiber-like structures in the form of microtubes.

One polymer composition, various morphologies: the decisive influence of conditions on the polymerization-induced self-assembly (PISA) of N-acryloyl thiomorpholine.

Polymerization-induced self-assembly (PISA) represents a powerful technique for the preparation of nanostructures comprising various morphologies. Herein, we demonstrate that the recently introduced monomer N-acryloylthiomorpholine (NAT) features a unique self-assembly behaviour during an aqueous PISA. The one-pot, aqueous RAFT dispersion polymerization starting from short poly(N-acryloylmorpholine) (PNAM) enables access to all common solution morphologies including spheres, worms, vesicles and lamellae, at very low molar masses (< 8 kDa). Moreover, all these structures can be obtained for the same polymer composition and size by the variation of the polymerization temperature and concentration of the monomer. This exceptional self-assembly behavior is associated with the combination of a high glass transition temperature, excellent water solubility of the monomer, and the early onset of aggregation during the polymerization, which stabilizes the morphology at different stages. This PISA system opens up new opportunities to reproducibly create versatile, functional nanostructures and enables an independent evaluation of morphology-property relationships, as it is exemplarily shown for the oxidative degradation of spherical and wormlike micelles, as well as vesicles.

Thermally stable core-shell star-shaped block copolymers for antifouling enhancement of water purification membranes

Star-shaped block copolymers (SPs), consisting of a hydrophobic core and hydrophilic arms, are a new material architecture introduced to the area of antifouling coatings for water filtration membranes. The unique self-assembly behavior of these SPs on hydrophobic membranes surface allows the formation of an ultrathin coating (less than 15 nm), rendering a highly hydrophilic antifouling membrane surface. Here, we have judiciously examined several important structural and process parameters, such as the chemical composition of SPs and surface properties (e.g., surface potential, coverage, and wettability) driven by a mono- or bi-layered assembly of SPs, to acquire a highly hydrophilic and thermally stable antifouling coating on a hydrophobic ultrafiltration (polysulfone, PSF) membrane for oil sands produced water treatment. Among three types of SPs (e.g., SP1 with 100% amine, SP2 with 55% amine/45% PEG, and SP3 with 35% carboxylic acid/65% PEG moieties in the arms) and their variable coating conditions, the bilayer coating comprised of SP3 top-layer and SP1 bottom-layer exhibited the best hydrophilicity and anti-oil fouling efficiency showing 2–4 times higher water flux compared to an unmodified PSF membrane during the filtration of synthetic oil-water emulsions conducted in both constant flux mode and constant pressure mode. Outstanding antifouling efficiency of the bilayer coating toward natural organic matters (NOMs) was also verified by using bovine serum albumin (BSA) and humic acid (HA) as the model foulants. The bilayer-coated membrane retained more than 80% and 90% (for nano and micron size oil emulsion, respectively) of its initial antifouling efficiency even after rigorous thermal treatment for an extended period (80 °C for 1 week), which demonstrates its feasibility for high-temperature membrane operation.

Impact of Rigidity on Molecular Self-Assembly.

Rigid, cage-like molecules, like diamondoids, show unique self-assembly behavior, such as templating 1-D nanomaterial assembly via pathways that are typically blocked for such bulky substituents. We investigate molecular forces between diamondoids to explore why molecules with high structural rigidity exhibit these novel assembly pathways. The rigid nature of diamondoids significantly lowers configurational entropy, and we hypothesize that this influences molecular interaction forces. To test this concept, we calculated the distance-dependent impact of entropy on assembly using molecular dynamics simulations. To isolate pairwise entropic and enthalpic contributions to assembly, we considered pairs of molecules in a thermal bath, fixed at set intermolecular separations but otherwise allowed to freely move. By comparing diamondoids to linear alkanes, we draw out the impact of rigidity on the entropy and enthalpy of pairwise interactions. We find that linear alkanes actually exhibit stronger van der Waals interactions than diamondoids at contact, because the bulky structure of diamondoids induces larger net atomic separations. Yet, we also find that diamondoids pay lower entropic penalties when assembling into contact pairs. Thus, the cage-like shape of diamondoids introduces an enthalpic penalty at contact, but the penalty is counterbalanced by entropic effects. Investigating the distance dependence of entropic forces provides a mechanism to explore how rigidity influences molecular assembly. Our results show that low entropic penalties paid by diamondoids can explain the effectiveness of diamondoids in templating nanomaterial assembly. Hence, tuning molecular rigidity can be an effective strategy for controlling the assembly of functional materials, such as biomimetic surfaces and nanoscale materials.

Binary Self-Assembly of Conjugated Block Copolymers and Quantum Dots at the Air-Liquid Interface into Ordered Functional Nanoarrays.

Controlling the nanoscale morphology of conducting polymer/nanoparticle hybrid films is a highly desired but challenging task. Here, we report that such functional hybrid films with unprecedented structural order can be formed through the self-assembly of conjugated block copolymers and CdSe quantum dots at the air-water interface. The one-step assembly of quantum dots and block copolymers composed of polythiophene and polyethylene glycol (P3HT-b-PEG) at the fluidic interface generated a highly ordered assembly structure of P3HT nanowires and one-dimensional quantum dot arrays. Structure analyses revealed a unique self-assembly behavior and size dependency, which are distinct from the conventional self-assembly of coil-type polymers on solid substrates. Interestingly, hydrophobic quantum dots reside at the interface between P3HT and PEG domains without disrupting the P3HT packing structure, which is advantageous for the optoelectronic properties. Furthermore, large particles bridge the P3HT nanowires at both ends, while small particles decorate each P3HT/PEG interfaces, thus forming tight p-n junctions for a broad size range of nanoparticles. The nanoparticle-incorporated hybrid films showed more than an order of magnitude higher photocurrent and light sensitivity compared to polymer-only films, consistent with the assembly structure with close contact between the organic and inorganic semiconductors.

Pathway Control in Cooperative vs. Anti‐Cooperative Supramolecular Polymers

Controlling the nanoscale morphology in assemblies of π-conjugated molecules is key to developing supramolecular functional materials. Here, we report an unsymmetrically substituted amphiphilic PtII complex 1 that shows unique self-assembly behavior in nonpolar media, providing two competing anti-cooperative and cooperative pathways with distinct molecular arrangement (long- vs. medium-slipped, respectively) and nanoscale morphology (discs vs. fibers, respectively). With a thermodynamic model, we unravel the competition between the anti-cooperative and cooperative pathways: buffering of monomers into small-sized, anti-cooperative species affects the formation of elongated assemblies, which might open up new strategies for pathway control in self-assembly. Our findings reveal that side-chain immiscibility is an efficient method to control anti-cooperative assemblies and pathway complexity in general.

Single-chain tethered nanoparticles with tunable softness: scalable synthesis and unique self-assembly behavior

A scalable method to prepare single-chain tethered nanoparticles with tunable softness, which results in unique self-assembly behaviors.

Ionic-surfactants-based thermotropic liquid crystals.

Thermotropic liquid crystals (TLCs) are a series of soft materials with ordered arrangements of repeating structural units in a certain range of temperature. Specifically, the TLCs constructed by the electrostatic combination between ionic surfactants and other oppositely charged groups have received great attention in the field of optoelectronic devices, material transportation and separation, smart materials as well as biosensing. As typical amphiphilic molecules, ionic surfactants with charged head-groups and long alkyl tails exhibit unique self-assembly behaviors, being preferable as flexible building blocks of TLCs. In this review, we have discussed the TLCs formed by salt-free catanionic surfactants and ionic surfactants with other functional groups, including metal ions, nanoclusters, biomolecules, and polyelectrolytes. The design of such TLC molecules, the influencing factors of the mesophases, and the related applications of the TLCs are discussed in detail. Because of their easy preparation and variable structure, these TLCs are expected to greatly widen the application scope of the relevant functional molecules. At the end of this review, we put forward some ideas with regard to the aspects that are required to be improved and propose the possible development trend in this direction. It is expected that through this review, the important roles of ionic surfactants in building TLCs will be highlighted and thus, more studies will be inspired to exploit more TLCs based on ionic surfactants with excellent properties.