Block Copolymer Assembly via Kinetic Control

Department of Materials Science and Engineering and Delaware Biotechnology Institute, University of Delaware, Newark, Delaware 19716, USA.
Science (Impact Factor: 33.61). 09/2007; 317(5838):647-50. DOI: 10.1126/science.1141768
Source: PubMed


Block copolymers consist of two or more chemically different polymer segments, or blocks, connected by a covalent linkage. In solution, amphiphilic blocks can self-assemble as a result of energetic repulsion effects between blocks. The degree of repulsion, the lengths of the block segments, and the selectivity of the solvent primarily control the resultant assembled morphology. In an ideal situation, one would like to be able to alter the morphology that forms without having to change the chemistry of the block copolymer. Through the kinetic manipulation of charged, amphiphilic block copolymers in solution, we are able to generate different nanoscale structures with simple block copolymer chemistry. The technique relies on divalent organic counter ions and solvent mixtures to drive the organization of the block copolymers down specific pathways into complex one-dimensional structures. Block copolymers are increasingly used as templating materials; thus, the ability to control the formation of specific patterns and structures is of growing interest and applicability.

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    • "Nonspherical particles have attracted increasing attention for their potential applications in drug-delivery systems.8 Many methods, such as film hydration, emulsion, template, microfluidic, mechanical stretching, and self-assembly can be used in the preparation of nonspherical particles.9–18 It is of great importance to develop a simple method to prepare nonspherical particles with a high yield.8 "
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    ABSTRACT: Controlled-release carriers for local drug delivery have attracted increasing attention for inner-ear treatment recently. In this paper, flower-shaped bovine serum albumin (FBSA) particles were prepared by a modified desolvation method followed by glutaraldehyde or heat denaturation. The size of the FBSA particles varied from 10 μm to 100 μm, and most were 50-80 μm. Heat-denatured FBSA particles have good cytocompatibility with a prolonged survival time for L929 cells. The FBSA particles were utilized as carriers to investigate the release behaviors of the model drug - rhodamine B. Rhodamine B showed a sustained-release effect and penetrated the round-window membrane of guinea pigs. We also confirmed the attachment of FBSA particles onto the round-window membrane by microscopy. The FBSA particles, with good biocompatibility, drug-loading capacity, adhesive capability, and biodegradability, may have potential applications in the field of local drug delivery for inner-ear disease treatment.
    International Journal of Nanomedicine 07/2014; 9(1):3193-201. DOI:10.2147/IJN.S59807 · 4.38 Impact Factor
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    • "Discoidal micelles and nematic phase from such micelles have been detected in ternary mixtures of lauric acid with anionic and zwitterionic surfactants [16]. Disc-shaped aggregates are formed also in solutions of diblock and triblock copolymers [17] [18] [19] [20] [21] [22]. Such aggregates are formed also by phospholipids dispersed in water [23] [24] and in aqueous surfactant/lipid systems [25]. "
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    ABSTRACT: The ladder model of growth of cylindrical micelles gives expressions for the micellar size distribution and for the mean aggregation number, which are in good agreement with the experiment. Here, we consider this model and its extension to the case of disclike micelles. In analogy with the modeling of elongated micelles as sphero-cylinders, the disclike micelles can be modeled as toro-discs. Upon micelle growth, the hemispherical caps of a cylindrical aggregate remain unchanged, whereas the semitoroidal periphery of a disclike micelle expands. This effect can be taken into account in the expression for the size distribution of the disclike micelles, which predicts the dependence of the micelle mean aggregation number on the surfactant concentration. It turns out that disclike micelles could form in a limited range of surfactant concentrations, and that their mean aggregation number cannot exceed a certain maximal value. Large disclike micelles can exist only near the border with the domain of cylindrical micelles. Then, small variations in the experimental conditions could induce a transformation of the disclike micelles into cylindrical ones.
    Current Opinion in Colloid & Interface Science 12/2013; 18(6):524–531. DOI:10.1016/j.cocis.2013.11.002 · 5.84 Impact Factor
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    • "Usually , when these copolymers are dissolved in water, spherical micelles are formed, where the hydrophobic blocks comprise the water-insoluble core, while the hydrophilic blocks form a protective hydrophilic corona. This feature makes such polymeric materials attractive for a large variety of potential applications [1] [2] [3] [4] [5] [6], like pharmaceuticals, cosmetics, paints, coating and drug delivery systems. In particular , block copolymers based on the inexpensive monomer sodium styrene sulfonate, SSNa, are of great practical interest, as they are used in several applications, including ion exchange or fuel cell membranes [7] [8]. "
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    ABSTRACT: A series of poly(sodium styrene sulfonate)-b-poly(methyl methacrylate), PSSNa-b-PMMA, amphiphilic diblock copolymers have been synthesized through atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in N,N-dimethylformamide/water mixtures, starting from a PSSNa macroinitiator. The kinetics of the polymerization was followed by 1H NMR, while the chemical composition of the copolymers was verified by a variety of techniques, such as 1H NMR, FTIR and TGA. The MMA content of the copolymers ranges from 0 up to 60mol%, while the number–average molecular weight of the PSSNa macroinitiator was 9000g/mol. The self-association of the diblock copolymers in aqueous solution was compared to the respective behavior of similar random P(SSNa-co-MMA) copolymers through optical density measurements, pyrene fluorescence probing, dynamic light scattering and surface tension measurements. It is shown that the diblock copolymers form micellar structures in water, characterized by an increasing hydrophobic character and a decreasing size as the length of the PMMA block increases. These micelle-like structures turn from surface inactive to surface active as the length of the PMMA block increases. Moreover, contrary to the MMA-rich random copolymers, the respective diblock copolymers form water insoluble polymer/surfactant complexes with cationic surfactants such as hexadecyltrimethyl ammonium bromide (HTAB), leading to materials with antimicrobial activity.
    European Polymer Journal 04/2011; 47(4):752-761. DOI:10.1016/j.eurpolymj.2010.09.034 · 3.01 Impact Factor
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