Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

In the past decade, mesoporous silica nanoparticles (MSNs) have attracted more and more attention for their potential biomedical applications. With their tailored mesoporous structure and high surface area, MSNs as drug delivery systems (DDSs) show significant advantages over traditional drug nanocarriers. In this review, we overview the recent progress in the synthesis of MSNs for drug delivery applications. First, we provide an overview of synthesis strategies for fabricating ordered MSNs and hollow/rattle-type MSNs. Then, the in vitro and in vivo biocompatibility and biotranslocation of MSNs are discussed in relation to their chemophysical properties including particle size, surface properties, shape, and structure. The review also highlights the significant achievements in drug delivery using mesoporous silica nanoparticles and their multifunctional counterparts as drug carriers. In particular, the biological barriers for nano-based targeted cancer therapy and MSN-based targeting strategies are discussed. We conclude with our personal perspectives on the directions in which future work in this field might be focused.

Mesoporous Silica Nanoparticles: Synthesis, Biocompatibility and Drug Delivery

A mean-field phase diagram for conformationally symmetric diblock melts using the standard Gaussian polymer model is presented. Our calculation, which traverses the weak- to strong-segregation regimes, is free of traditional approximations. Regions of stability are determined for disordered (DIS) melts and for ordered structures including lamellae (L), hexagonally packed cylinders (H), body-centered cubic spheres (QIm3m), close-packed spheres (CPS), and the bicontinuous cubic network with Ia3d symmetry (QIa3d). The CPS phase exists in narrow regions along the order−disorder transition for χN ≥ 17.67. Results suggest that the QIa3d phase is not stable above χN ∼ 60. Along the L/QIa3d phase boundaries, a hexagonally perforated lamellar (HPL) phase is found to be nearly stable. Our results for the bicontinuous Pn3m cubic (QPn3m) phase, known as the OBDD, indicate that it is an unstable structure in diblock melts. Earlier approximation schemes used to examine mean-field behavior are reviewed, and compa...

Unifying Weak- and Strong-Segregation Block Copolymer Theories

Good control of the morphology, particle size, uniformity and dispersity of mesoporous silica nanoparticles (MSNs) is of increasing importance to their use in catalyst, adsorption, polymer filler, optical devices, bio-imaging, drug delivery, and biomedical applications. This review discusses different synthesis methodologies to prepare well-dispersed MSNs and hollow silica nanoparticles (HSNs) with tunable dimensions ranging from a few to hundreds of nanometers of different mesostructures. The methods include fast self-assembly, soft and hard templating, a modified Stober method, dissolving–reconstruction and modified aerogel approaches. In practical applications, the MSNs prepared by these methods demonstrate good potential for use in high-performance catalysis, antireflection coating, transparent polymer–MSNs nanocomposites, drug-release and theranostic systems.

Synthesis of mesoporous silica nanoparticles

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Crystallization assisted self-assembly of semicrystalline block copolymers

The self-assembly of poly(e-caprolactone)-b-poly(ethylene oxide) block copolymers (PCLnPEO44 and PCLnPEO113) with narrow polydispersity in aqueous medium was studied using transmission electron microscopy In this system, the formed micelles are composed of a crystalline PCL core and a soluble PEO corona We demonstrated that the PCL-b-PEO block copolymers can form micelles with abundant morphologies, depending on the lengths of the blocks and composition It is observed that for PCLnPEO44 the micellar morphology changes from spherical, rodlike, wormlike, to lamellar, as the length of the PCL block increases In contrast, most of PCLnPEO113 (n = 21−147) block copolymers form spherical micelles, and only PCL232PEO113 exhibits mixed spherical and lamellar micellar morphologies The effect of microstructure on micellar morphology was semiquantitatively interpreted in terms of reduced tethering density (σ) It is found that lamellar micelles are formed when σ is smaller than a critical value of between 30 an

Micellar Morphologies of Poly(ε-caprolactone)-b-poly(ethylene oxide) Block Copolymers in Water with a Crystalline Core

Structure and properties of polypropylene/poly(ethylene-co-propylene) in-situ blends synthesized by spherical Ziegler–Natta catalyst

In this study, three cationic surfactants (hexadecyltrimethylammonium chloride, hexadecyldimethylbenzylammonium chloride, and octadecyltrimethylammonium chloride) were used to modify montmorillonite and polyethylene (PE)/maleic anhydride grafted polyethylene (PE-g-MAH)/organic-montmorillonite (Org-MMT) nanocomposites, prepared by two blending processes (direct-melt blending and solution blending). X-ray diffractometry and transmission electron microscopy were used to investigate the intercalation behavior and microstructure of composites. Mechanical properties were also tested. It was found that the intercalation effect of PE/PE-g-MAH/Org-MMT could be enhanced by increasing the content of PE-g-MMT, using the silicate modified by a cationic surfactant with a benzyl group or long alkyl chain, adopting the solution-blending method or using high-density polyethylene as matrix. The degree of crystallinity of composites and the crystalline thickness perpendicular to the crystalline plane [like (110) and (200)] decreased with increasing amounts of PE-g-MAH and, under certain prescription, the crystalline thickness of the composite made by the solution method was much smaller than that made by direct-melt blending. This clearly showed that Org-MMT and PE-g-MAH had a heterogeneous nucleation effect on crystallization of PE from the melt, resulting in a decrease of crystalline thickness, and the heterogeneous nucleation effect was more evident in the nanocomposite made by the solution-blending method than in that made by the direct-melt intercalation process. The tensile strength initially increased and then decreased with increasing contents of PE-g-MAH. The maximum value in tensile strength (23.3 MPa) was achieved when the concentration of PE-g-MAH was 6 wt %. The impact strength increased concomitantly with the content of PE-g-MAH; it was 122.2 J/m when the concentration of PE-g-MAH was 9 wt %.© 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3974–3980, 2004

Polyethylene/maleic anhydride grafted polyethylene/organic‐montmorillonite nanocomposites. I. Preparation, microstructure, and mechanical properties

Poly(vinylidene difluoride)/organically modified montmorillonite (PVDF/OMMT) composite nanofibers were prepared by electrospinning the solution of PVDF/OMMT precursor in DMF. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) show that in the bulk of the PVDF/OMMT precursor OMMT platelets are homogeneously dispersed in PVDF and can be both intercalated and exfoliated. It is found that the diameter of the PVDF/OMMT composite nanofibers is smaller than that of the neat PVDF fibers because the lower viscosity of PVDF/OMMT solution, which is attributed to the possible adsorption of PVDF chains on OMMT layers and thus reduction in number of entanglement. The crystal structure of the composite nanofibers was investigated using WAXD and Fourier transform infrared (FT-IR) and compared with that of thin film samples. The results show that the nonpolar α phase is completely absent in the electrospun PVDF/OMMT composite nanofibers, whereas it is still present in the neat PVDF electrospun ...

Jun-Ting Xu

Papers

Crystallization assisted self-assembly of semicrystalline block copolymers

Micellar Morphologies of Poly(ε-caprolactone)-b-poly(ethylene oxide) Block Copolymers in Water with a Crystalline Core

Structure and properties of polypropylene/poly(ethylene-co-propylene) in-situ blends synthesized by spherical Ziegler–Natta catalyst

Polyethylene/maleic anhydride grafted polyethylene/organic‐montmorillonite nanocomposites. I. Preparation, microstructure, and mechanical properties

Cooperative effect of electrospinning and nanoclay on formation of polar crystalline phases in poly(vinylidene fluoride).