Poly ethylene glycol

2 Poly(ethylene glycol)-Polystyrene Graft Polymers 

In swollen Tentagel and related supports, the PEG chains are more mobile than the cross-linked polystyrene matrix. This enables the recording of well-resolved NMR spectra of samples linked to Tentagel [5,7,133-135]. Polystyrene and other less mobile 

Unfortunately, PEG-grafted polystyrene supports have some disadvantages, the most critical being the low loading and the release of PEG upon treatment with TFA [9,62,141] or upon heating [142]. Further, because of their high PEG content, these supports can sometimes become adherent and are difficult to dry [9]. Increased stability towards acid has been achieved with PEG-grafted polystyrene devoid of benzylic C-O bonds [12,51,62,132], 

Despite the drawbacks of soluble supports mentioned in the introduction to this chapter, soluble PEG has often been used as a support for the synthesis of both biopolymers [6,148-153] and small organic molecules [18,154-158], Related supports with higher loadings have been described [159], in which 3,5-bis(chloromethyl)phenoxy groups were linked to both ends of PEG5000. 

Cross-linked, insoluble PEG can be prepared by copolymerizing PEG with epi-chlorohydrin [107,160] or with the tosylate of 3-methyl-3-(hydroxymethyl)oxetane [161,162], These supports are highly permeable and hydrophilic, and enable the use of 

The attachment of PEG to bioactive macromolecules is called PEGylation and provides various benefits [312]. These include better water solubility, enhanced resistance to proteolysis, decrease of immimogenicity, antigenicity, toxicity of drugs and slower rate of kidney clearance [313]. PEG has been approved for use in drugs, food and cosmetics [314]. The monodispersity of todays available PEGs eliminates former risks that were related to impurities foimd during chemical synthesis of PEG. 

The degradation of the PEG-based drug derivative is accomplished by breakage of the conjugate and subsequent release of the bound content in a controlled way [315]. As a result, PEG acts as a shield that covers and carries the eventual drug and at the end contributes to its longer shelf life and sustained blood levels after its release [316]. 

PEGylated drugs include conjugation with enzymes, peptides, proteins, antibodies, oligonucleotides, anticancer agents and small organic molecules [317]. 

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Poly(ethylene glycol) sesquiester of tall oil acids[6179l-30-8]... 

Materials that typify thermoresponsive behavior are polyethylene—poly (ethylene glycol) copolymers that are used to functionalize the surfaces of polyethylene films (smart surfaces) (20). When the copolymer is immersed in water, the poly(ethylene glycol) functionaUties at the surfaces have solvation behavior similar to poly(ethylene glycol) itself. The abiUty to design a smart surface in these cases is based on the observed behavior of inverse temperature-dependent solubiUty of poly(alkene oxide)s in water. The behavior is used to produce surface-modified polymers that reversibly change their hydrophilicity and solvation with changes in temperatures. Similar behaviors have been observed as a function of changes in pH (21—24). 

Other examples of materials that respond smartly to changes in temperature are the poly(ethylene glycol)s-modifted cottons, polyesters, and... 

Alternatively a bonded poly(ethylene glycol) capillary column held at 35°C for 5 min and programmed to 190°C at 8°C/min may be employed to determine all components but water. The Kad-Eischer method for water gives inaccurate results. 

Two-Phase Aqueous Extraction. Liquid—Hquid extraction usually involves an aqueous phase and an organic phase, but systems having two or more aqueous phases can also be formed from solutions of mutually incompatible polymers such as poly(ethylene glycol) (PEG) or dextran. A system having as many as 18 aqueous phases in equiHbrium has been demonstrated (93). Two-phase aqueous extraction, particularly useful in purifying biological species such as proteins (qv) and enzymes, can also be carried out in combination with fermentation (qv) so that the fermentation product is extracted as it is formed (94). 

Halex rates can also be increased by phase-transfer catalysts (PTC) with widely varying stmctures quaternary ammonium salts (51—53) 18-crown-6-ether (54) pytidinium salts (55) quaternary phosphonium salts (56) and poly(ethylene glycol)s (57). Catalytic quantities of cesium duoride also enhance Halex reactions (58). 

Ghdants are needed to faciUtate the flow of granulation from the hopper. Lubricants ensure the release of the compressed mass from the punch surfaces and the release/ejection of the tablet from the die. Combinations of siUcas, com starch, talc (qv), magnesium stearate, and high molecular weight poly(ethylene glycols) are used. Most lubricants are hydrophobic and may slow down disintegration and dmg dissolution. 

Anaerobically, poly(ethylene glycol) degrades slowly, although molecular weights up to 2000 daltons have been reported (177,178) to biodegrade. 

The biodegradation of poly(alkylene glycols) is hindered by their lack of water solubiUty, and only the low oligomers of poly(propylene glycol) are biodegradable with any certainty (179—181), as are those of poly(tetramethylene glycol) (182). A similar xo-oxidation mechanism to that reported for poly(ethylene glycol) has been proposed. 

Other blends such as polyhydroxyalkanoates (PHA) with cellulose acetate (208), PHA with polycaprolactone (209), poly(lactic acid) with poly(ethylene glycol) (210), chitosan and cellulose (211), poly(lactic acid) with inorganic fillers (212), and PHA and aUphatic polyesters with inorganics (213) are receiving attention. The different blending compositions seem to be limited only by the number of polymers available and the compatibiUty of the components. The latter blends, with all natural or biodegradable components, appear to afford the best approach for future research as property balance and biodegradabihty is attempted. Starch and additives have been evaluated ia detail from the perspective of stmcture and compatibiUty with starch (214). 

Reactive (unsaturated) epoxy resins (qv) are reaction products of multiple glycidyl ethers of phenoHc base polymer substrates with methacrylic, acryhc, or fumaric acids. Reactive (unsaturated) polyester resins are reaction products of glycols and diacids (aromatic, aUphatic, unsaturated) esterified with acryhc or methacrylic acids (see POLYESTERS,unsaturated). Reactive polyether resins are typically poly(ethylene glycol (600) dimethacrylate) or poly(ethylene glycol (400) diacrylate) (see PoLYETPiERs). 

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