Hydrophilic/hydrophobic copolymers surface properties

The hydrophilic, hydrophobic, and ionic nature of PVP can be modified by copolymerization to enhance the properties of PVP for certain applications. Nonionic, anionic, and cationic VP copolymers have all been commercialized. A wide range of vinyl pyrrolidone and vinyl acetate copolymers, which are non-ionic, have been made with optimized amphiphilicity and solubility in water or alcohol for the cosmetic and pharmaceutical industries. The surface activity of PVP can be further enhanced by copolymerization with acrylic acid. Vinyl pyrrolidone and acrylic acid copolymers, which are anionic in their major applications, with different molar rations have been developed with well-balanced surface, associative, and film-forming properties for industrial applications. 

Gervais et al. used x-ray photoelectron spectroscopy (XPS) to study the surface properties of polypeptide-block-polybutadiene-block-polypeptide triblock copolymers and found that the lamellar structures (which is as well observed by x-ray diffraction for these triblock systems) are perpendicular to the air-polymer interface. For more hydrophilic polypeptides they found that the surface is richer with polybutadiene whereas for hydrophobic polypeptides the surface resembled the block copolymer composition [87]. 

Recently, a new class of inhibitors (nonionic polymer surfactants) was identified as promising agents for drug formulations. These compounds are two- or three-block copolymers arranged in a linear ABA or AB structure. The A block is a hydrophilic polyethylene oxide) chain. The B block can be a hydrophobic lipid (in copolymers BRIJs, MYRJs, Tritons, Tweens, and Chremophor) or a poly(propylene oxide) chain (in copolymers Pluronics [BASF Corp., N.J., USA] and CRL-1606). Pluronic block copolymers with various numbers of hydrophilic EO (,n) and hydrophobic PO (in) units are characterized by distinct hydrophilic-lipophilic balance (HLB). Due to their amphiphilic character these copolymers display surfactant properties including ability to interact with hydrophobic surfaces and biological membranes. In aqueous solutions with concentrations above the CMC, these copolymers self-assemble into micelles. 

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