Hydrophilic and hydrophobic segments

A. Audibert, J. Lecourtier, L. C. Bailey, and G. Maitland. Use of polymers having hydrophilic and hydrophobic segments for inhibiting the swelling of reactive argillaceous formations (Tutilisation d un... 

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]. 

Title Multiblock Copolymers Containing Hydrophilic and Hydrophobic Segments for Proton Exchange Membrane... 

Reduced Surface Tension. Just as surfactants self-organize in the bulk solution as a result of their hydrophilic and hydrophobic segments, they also preferentially adsorb and organize at the solution—vapor interface. In the case of aqueous surfactant solutions, the hydrophobic tails protrude into the vapor and leave only (he hydrophilic head groups in contact with the solution. The favorable energetics of the arrangement can be seen by the reduction in Ihe interracial free energy per unit area, nr surface tension, it. 

Block copolymers that consist of hydrophilic and hydrophobic segments are typical amphiphilic polymers, a variety of which have been synthesized by living cationic polymerization. Figure 9 schematically illustrates the structures of some of these amphiphilic polymers thus far obtained though the examples therein are based on poly(vinyl ether) segments, any other appropriate segments may be incorporated. As seen in the illustrations, macromolecular amphiphiles are not necessarily linear AB- and ABA-type block copolymers but may be graft, multiarmed, and network polymers, where the basic components are amphiphilic block copolymers. 

Tschierske and coworkers reported on new complex liquid crystalline phases of polyphilic block molecules or their metal complex [91-93]. These triblock rod-coil molecules consist of a rod-like p-terphenylene unit, and two hydrophobic alkyl chains at both ends of the rod, and oligo(ethylene glycol) with a terminal carbohydrate unit at a lateral position of the rod [94]. Depending on the size of the hydrophilic and hydrophobic segments, a series of unusual liquid crystalline phases were detected (Fig. 18). When the carbohydrate unit is directly conjugated to the rod building block, a simple smectic (Sa) phase was observed. In this liquid crystalline phase, the molecules are... 

Compared to low molecular weight amphiphiles, the size of polymeric amphi-philes allows for much more diverse arrangements of the hydrophilic and hydrophobic segments, as exemplified in Fig. 1. Accordingly, micellar polymers are characterized by versatile molecular architectures, giving rise to distinct subgroups. Diblock-copolymers with a clear separation of the hydrophilic... 

Polymers can also form gels, such as gelatin, as a solid suspension. Entangled polymer chains trap solvent. Some polymer mixtures form solid-insolid solutions, such as poly(ethylene) and poly(propylene) blends in clothing fabrics. Polymers can also be surfactants, such as starch with hydrophilic and hydrophobic segments. 

Example Both hydrophilic and hydrophobic segments located in the active-site are precisely and rapidly identified by determining the electrostatic potential at various surface-grid points or by graphical analysis. 

There is no coupling agent between the hydrophilic and hydrophobic segments. The pol5mer is formed by a one-pot ringopening pol5meiization technique (8). 

White, D., Coca, S., and O Dwyer, J. B. (2001). Pigment dispersions containing dispersants prepared by controlled radical pol5mierization having hydrophilic and hydrophobic segments. In PCT Int. Appl. WO 0144389, Ppg Industries Ohio, Inc., USA, 40 pp. 

It is worth pointing out that despite the similar arrangement of the hydrophilic and hydrophobic segments of surfactant molecules at the water/hydrocarbon interface, there is a principal difference in the driving force of the adsorption from the aqueons phase and from the liquid hydrocarbon phase (Figure 2.6). 

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