Hydrophobic hybrid polymer

Figure 5. Modification of (partially hydrolyzed) GPTMS with 1,1,2,2-tetrahydro-perfluorooctyltriethoxysilane to create highly hydrophobic hybrid polymers.

It has been shown that the use of hydrophobic organo-tin catalysts, a solvent of the polyaddition medium or an off-stoichiometric ratio of the isocyanate and the diol component allows a considerable increase in the molecular weight of the polymer. It was also shown that hybrid polymer nanoparticles based on polystyrene/ polyurethane (PS/PU) or poly(butyl acrylate)/polyurethane (PBA/PU) can be synthesized using a one-pot procedure [26]. 

In order to obtain hydrophobic materials, fluorosilanes in quantities of < 1 mol% were added to the coating sols (see Fig. 21-11, compounds 9,10). This has a favorable effect on the barrier properties to polar permeants such as water vapor (PES/SiO /hybrid polymer WVTR 0.18 g/m d PES/SiO /hydrophobic hybrid polymer WVTR 0.03 g/m d, layer thickness in both cases 4 fim). 

Historically, after the development of oligopeptide-based vesicles, several groups developed and characterized vesicles using polypeptide hybrid systems consisting of polypeptide and synthetic polymer blocks [17-19]. Soon thereafter, vesicles formed entirely from polypeptides, such as poly(L-lysine)-h-poly(L-leucine) and poly(L-lysine)-h-poly(L-glutamate), were developed [20, 21]. This review will focus on recent developments in the formation of vesicles composed of polypeptide hybrid or polypeptide systems, as well as the potential promise of these systems as effective dmg delivery vehicles. A specific example of a polypeptide-based vesicle is shown in Fig. 1, where the hydrophobic segment is a-helical and the hydrophilic segment is a random coil. 

A wide range of additives can also be introduced into the sol-gel matrices in order to modulate the hydrophobicity of the materials and to improve enzyme stability, activity and accessibility, leading to hybrid or even composite sol-gel matrices. Polymers [157,179,180] such as polyethyleneglycol, polyvinylpyrrolidone, polyvinylalcohol, polyglycidol, polyethyleneimine, polyacrylate have been simultaneously entrapped with enzymes in a siloxane matrix, as well as organic additives (sugar, amino add)... 

Jeong JH, Park TG. Novel polymer-DNA hybrid polymeric micelles composed of hydrophobic poly(DL-lactic acid-co-glycolic acid) and hydrophiUc oligonucleotides. Bioconjugate Chem 2001 12 917-923. 

The second article by Kawahara and his coworkers focuses on polyolefin (PO)-based hybrid materials (POH), in view of their synthesis, structures, and properties. POs are currently the most widely and conveniently used polymeric materials as recognized by the production amount of over one hundred million tons annually in the world, due to the cheap price yet good properties. They are basically hydrocarbon polymers, and hence hydrophobic and less polar. These basic properties are to be modified by introducing a polar function for a wider use in practical applications. Preparation of POHs is one of the best ways to... 

The use of a polymer species as a way to control diffusion to the inside of mesoporous silica was also employed by Lopez and coworkers.67 In this work the researchers polymerized iV-isopropyl acrylamide on mesoporous silica by atom transfer radical polymerization, and took advantage of the changes the polymer experiences upon thermal treatment. The authors discovered that the hybrid material could take up more fluorescein than nonfunctionalized material at temperatures above 45°C. At that temperature the polymer is in a collapsed hydrophobic state and partially covers the negatively charged surface of silica that otherwise repels the negatively charged fluorescein dye. At temperatures below 30°C the polymer exists in a hydrated state in which the chains are expanded. Interestingly, the fluorescein loaded hybrid particles were... 

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