Applications of Amphiphilic Copolymers

Application of amphiphilic block copolymers for nanoparticle formation has been developed by several research groups. R. Schrock et al. prepared nanoparticles in segregated block copolymers in the sohd state [39] A. Eisenberg et al. used ionomer block copolymers and prepared semiconductor particles (PdS, CdS) [40] M. Moller et al. studied gold colloidals in thin films of block copolymers [41]. M. Antonietti et al. studied noble metal nanoparticle stabilized in block copolymer micelles for the purpose of catalysis [36]. Initial studies were focused on the use of poly(styrene)-folock-poly(4-vinylpyridine) (PS-b-P4VP) copolymers prepared by anionic polymerization and its application for noble metal colloid formation and stabilization in solvents such as toluene, THF or cyclohexane (Fig. 6.4) [42]. 

In Chapter 4, Massignani, Lomas and Battaglia review the fabrication processes used to form polymersomes, membrane-enclosed structures that are formed through self-assembly of amphiphilic copolymers. The resulting molecular properties, methods to control their size, loading strategies and applications of polymersomes are also detailed. 

Like small amphiphile nanotubes [14], block copolymer nanotubes should have potential applications in controlled deUvery and release [97,98], in encapsulation [99], and in nanoelectronics [100] etc. Although there have been reports on laboratory use of block copolymer nanofibers as vehicles for drug delivery [101], as scaffolds for cell growth [88,102], as precursors for ceramic magnetic nanowires [103,104], and as precursors for carbon nanofibers [105,106[, practical applications of block copolymer nanotubes have not been reported. This is probably due to the difficulty in making such structures. Their preparation from the self-assembly of block copolymers and interests from industry will likely change the scenery of nanotube appUca-tions in the futme. 

SYNTHESIS OF AMPHIPHILIC COPOLYMERS BASED ON ACRYLATES BY FREE-RADICAL POLYMERIZATION AND THEIR APPLICATION IN ALKYD EMULSIONS... 

There have been a small number of recent reports on the applications of amphiphilic block copolymer micelles as nanoreactors. One recent example has reported that the assembly of a grafted amphiphile into a polymer micelle in... 

Abstract Self-assembly phenomena in block copolymer systems are attracting considerable interest from the scientific community and industry alike. Particularly interesting is the behavior of amphiphilic copolymers, which can self-organize into nanoscale-sized objects such as micelles, vesicles, or tubes in solution, and which form well-defined assemblies at interfaces such as air-liquid, air-solid, or liquid-solid. Depending on the polymer chemistry and architecture, various types of organization at interfaces can be expected, and further exploited for applications in nanotechnology, electronics, and biomedical sciences. 

Due to the large number of amphiphilic copolymers claimed for potential applications as drug release micelles, we shall consider at first the A-B and A-B-A structures, where some of them are specifically functionalized with targeting groups, followed by the more recently developed copolymer structures, for example star, graft A-B-C and polymer complexes. 

In a similar manner, several nanoparticles have been produced in the presence of block copolymers in selective solvents so as to form micelles that encapsulate particles such as metal salts. Consequently, these micelles are chemically converted to finely disperse colloidal hybrid polymer/metal particles with interesting catalytic, non-linear optic, semiconductor and magnetic properties [1, 20]. Finally, another area of potential application of amphiphilic block copolymers is that involving surface modification through the adsorption of block copolymer micelles or film formation. The use of a suitable micellar system allows for the alteration of specific surface characteristics, such as wetting and biocompatibility, or even enables the dispersion and stabilisation of solid pigment particles in a liquid or solid phase [1, 178]. 

ELP-based triblock copolypeptides have also been used to produce stimulus-responsive micelles, and Chaikof and coworkers envisioned the possible application of these micelles as controlled drug delivery vehicles. These amphiphilic triblock copolymers were constructed from two identical hydrophobic ELP endblocks and a hydrophilic ELP midblock. Below the transition temperature, loose and monodispersed micelles were formed that reversibly contracted upon heating, leading to more compact micelles with a reduced size [90]. 

Finally, we have designed and synthesized a series of block copolymer surfactants for C02 applications. It was anticipated that these materials would self-assemble in a C02 continuous phase to form micelles with a C02-phobic core and a C02-philic corona. For example, fluorocarbon-hydrocarbon block copolymers of PFOA and PS were synthesized utilizing controlled free radical methods [104]. Small angle neutron scattering studies have demonstrated that block copolymers of this type do indeed self-assemble in solution to form multimolecular micelles [117]. Figure 5 depicts a schematic representation of the micelles formed by these amphiphilic diblock copolymers in C02. Another block copolymer which has proven useful in the stabilization of colloidal particles is the siloxane based stabilizer PS-fr-PDMS [118,119]. Chemical... 

Recently, many studies have focused on self-assembled biodegradable nanoparticles for biomedical and pharmaceutical applications. Nanoparticles fabricated by the self-assembly of amphiphilic block copolymers or hydrophobically modified polymers have been explored as drug carrier systems. In general, these amphiphilic copolymers consisting of hydrophilic and hydrophobic segments are capable of forming polymeric structures in aqueous solutions via hydrophobic interactions. These self-assembled nanoparticles are composed of an inner core of hydrophobic moieties and an outer shell of hydrophilic groups [35, 36]. 

The problems related to the colloidal stability of amphiphilic polymers in water are reviewed by Aseyev, Tenhu, and Winnik in the first chapter of volume 196. The focus is on the derivatives of thermally responsive smart macromolecules - both on copolymers and homopolymers - which are present in a solution as stable micelles potentially having various applications. 

Here, we focus on one class ofblock copolymers synthesized by this method polystyrene-6-poly(vinylperfluorooctanic acid ester) block copolymers (Figure 10.33). After describing the synthesis and characterization, we will treat some properties and the potential applications of this new class ofblock copolymers. The amphiphilicity of the polymers is visualized by the ability to form micelles in diverse solvents that are characterized by dynamic light scattering (DLS). Then the use of these macromolecules for dispersion polymerization in very unpolar media is demonstrated by the polymerization of styrene in 1,1,2-trichlorotrifluoroethane (Freon 113). 

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