2D crystal drive assembly prepared using techniques and 3D structures of polycyclic

In recent years, a flexible explore ~ ​​crystallinity crystalline block copolymer solution in the drive assembly (CDSA) behavior has become a hot research self-assembly. This technology was first proposed by Professor Ian manners, its main advantage is actively growing polymer assemblies in solution may be, which provides possibilities for the preparation of controlled size and morphology of the polymer morphologies assembled. Some of the one-dimensional drawing micelle, multiblock, patchy and asymmetric co-micelles have been widely reported, while some complex structure has begun to emerge, such as two-dimensional, mixed and mesopores structure. However, the polymer to be prepared independently of the assembly of 3D structure by CDSA still rarely reported. 利用结晶驱动组装技术制备2D和3D的多环结构 Recently, East China University of Professor Gerald Guerin reported A method for the preparation of 2D and 3D multi-ring structures using CDSA technology , the article in entitled \”Formation of 2D and 3D multi-tori mesostructures via crystallization-driven self-assembly\” published in the Journal of Science child \” Sci. Adv. \” on. Which describes the system How to prepare a powdered flowers class 3D assembly technique by CDSA block copolymer. while adding a mixed solvent of preparing such micelle third solvent, a mesoporous morphology of this assembly in a corresponding change will occur, as a higher sphericity can be obtained mesoporous structure, or to form an annular layered structure Wait. More importantly, Once such mesoporous materials 3D transferred onto the substrate, its shape can maintain long-term stability at room temperature.

利用结晶驱动组装技术制备2D和3D的多环结构
Preparation and characterization of the structure of FIG. 1. 3D ring.

Preparation method

As shown, by 8 μL of PFS26-b-PS306 in THF (c = 10 mg ml -1) rapidly injection 1 mL 1, and in acetone / decane solution preheated 20 min 35 ℃, followed by addition of 20 μL columnar gumPFS55-b-PI500 beam decane solution, and after 35 ℃ for 1 hour, to obtain this micelle. This scheme can be obtained in isolated annulus and having a wide size distribution, having a diameter of 20 μm polycyclic spherical shell surface. These look like shell broken hollow spheres, adhesion of smaller annulus formed. Meanwhile annulus consisting sphere having a narrow size distribution, an inner diameter of about 400 nm, and an outside diameter of about 1 μm.

利用结晶驱动组装技术制备2D和3D的多环结构
Figure 2. different holding times resulting multi-dimensional mesoporous structure

mechanism discussed:

this interesting phenomenon stimulated the enthusiasm of scientists to explore, On the first guess that these special 3D multi-ring structure is joined to PFS26 -b-PS306 micelles formed by a large number of small ring CDSA, these small rings attached to each in turn, by the subsequent addition of the micelle PFS26 -b-PS306 pick from. In order to explore the real reason for this structure is formed, characterized in author shorter holding time such as 30 s and 5 min of micelle morphology (FIG. 2), but the results showed that within 30 s of the assembled body that is to present some maldistribution, large broken surface polycyclic structure. Broken on these structures can be observed very small holes, and when the time is extended to time of 5 min, still can be observed a large surface broken polycyclic structures, but also can be clearly observed increased inner diameter of the aperture at this time. This result overturned the original authors speculate, indicating that the formation of this self-assembly follow a unique way. To further understand the process of assembling the multi-level structure, the authors studied the kinetics of formation of this plurality of toroidal structure. Can be observed by HRTEM (FIG. 3), within a very short incubation time (0.5 minutes), these structures are composed of many pit-like class consisting of micelles. When the holding time of 5 minutes, these structures are still many small spherical micelles composed, but we can occasionally find some curved elongated micelles. When these samples were further incubated for some time, these curved elongated micelles increases gradually, and a one-dimensional presentation of the micelles start concentrically, and with some spherical micelles coexist. After 20 minutes, the overwhelming majority of spherical micelles have disappeared, to be replaced by a number of concentric elongated micelles. After 30 minutes incubation, the annulus gradually become clear. Thereafter holding time, shape remains unchanged. This slenderMicelles are typically assembled by block polymer CDSA come inside colloidal crystalline, wherein the crystallization PFS blocks plays a key role in the formation of these rod-like structure of the seed, the results of XRD analysis also its this confirmed the crystallization nucleation of the micelles.

Research 利用结晶驱动组装技术制备2D和3D的多环结构
Figure 3. The assembled structure of the surface of a polycyclic kinetics.

In the 3D mesoporous assembly body, occasionally can be observed assembly is damaged, which also tend to crack rather than micelles through between the annular micelles, this result indicates that these ring the overall structure is stable, moreover, these rings are asymmetric surface, while exhibiting expansion, contraction while bending form, it appears to sustain growth in the overall shape of the stone. (FIG. 4) In general, this assembly process spent powdered micelles PFS26 -b-PS306 is first formed micelle amorphous core, which in turn form unevenness size, micron category raspberry-shaped balloon bubble. In the second step, the elongated micelle nucleation PFS55 -b-PI500 re-energize the crystal structure similar to the pit, and then formed into a cylindrical form transition spheres. And when PFS26-b-PS306 micelles extending growth, which takes place along the path of least radius of curvature, and grown along the equatorial plane of the sphere. In addition, different authors also found that the selective solvent is added by mixing a solvent, this 3D topography annular micelles also be affected, such as the available number of broken spherical annular mesh layer and the like.

利用结晶驱动组装技术制备2D和3D的多环结构 4. Multi mechanism toroidal structure formed
FIG Research

Summary:

In this report, we describe a technique be prepared by CDSA the method has a multi-ring structure 3D. Formation of this structure is a multi-step assembly of the accumulation result, first PFS26 -b-PS306 be self-assembled into vesicles micron level, under the premise of micelles without nuclei, the film still exhibits an amorphous state, but with Over time, a large perforated film can be obtained. However, under the premise of presence PFS55 -b-PI500 nuclei, vesicles such structure will change from a spherical to cylindrical, elongated nuclei eventually form micelles. At the same time due to the shorter the nucleation time, the growth of the micelles is restricted, to thereby obtain an annular structure. While this third solvent mixed solvent is added, this form of assembly also mesoporousChanges, such as a higher sphericity can be obtained mesoporous structure, or the like to form an annular monolayer. The process of assembling this solution proved the great potential of new functional materials were prepared using the CDSA, but also for the use of bottom-up assembly solutions to produce more complex structure assembly paved the way. DOI: 10.1126 / sciadv.aaz7301

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