Immobilization systems polyethylene

Some active materials are carriers for drugs (drug delivery systems), some have immobilized peptides to enable cell adhesion or migration, some are degradable by hydrolysis or by specific enzyme action. Some contain bioactive agents (e.g., heparin, thrombomodulin) to prevent coagulation or platelet activation while others incorporate bioactive groups to enhance osteo-conduction. Many include polyethylene oxide to retard protein adsorption and this is perhaps the closest we have come to a kind of inertness. 

An evanescent wave biosensor was devised for determination of analytes capable of intercalation in dsDNA in a FIA system. A polyethylene lensed optical fiber is coated with a thin polymeric layer containing dsDNA which is immobilized there. The fiber is placed in a FLA system immersed in a solution of ethidium bromide (144), which undergoes intercalation in the dsDNA. The fluorescence signal of 144 is thus enhanced about a 1000-fold relative to the evanescent wave fluorescence measurement without the coating and is dependent on the concentration in solution. If an analyte is present in the same solution, it competes with 144 for intercalation in the DNA and causes fluorescence quenching, which can be measured and correlated to the analyte concentration. This method was applied to determination of various analytes, including 4, 6-diamidino-2-phenylindole dihydrochloride (145)247. 

Ind-amido titanium complexes with o -alkenyl functions in position 2 of the indenyl ring have been synthesized and characterized. After activation with MAO, these complexes were used as homogeneous and heterogeneous catalysts for the homopolymerization of ethylene and propylene and the co-polymerization of ethylene and 1,7-octadiene.406 A series of alkyl-, u -alkenyl-, and u -phenylalkyl-substituted Cp- and Ind-amido dichloro titanium complexes have been synthesized and characterized. The cj-phenylalkyl-substituted complexes react with LiBu to give metallacycles via a CH activation reaction on the ortho-position of the phenyl group (Scheme 305).741 742 After activation with MAO, these complexes catalyze ethylene polymerizations. The substituents on the aromatic system influence the polymerization activity of the catalysts and the properties of the polyethylene. The u -alkenyl-substituted catalysts show self-immobilization in ethylene polymerization. 

Bis-Cp titanium derivatives supported on MgCl2/AlR (OEt)3 , activated with MAO or borate activators, have been used as catalytic systems for the polymerization of a-olefins.475 Supports of type MgCl2/AlR (OEt)3 have been shown to be effective for the immobilization and activation of Cp2TiCl2 and other single-site olefin polymerization catalysts without the use of MAO or a borate activator. Polyethylene with a spherical particle morphology and narrow molecular weight distribution has been obtained.1... 

V(L)Cl2(TpMs )] (L = N Bu L = O) were in situ supported onto SiC>2 and onto MAO and trimethylaluminum. All catalyst systems were shown to be active in ethylene polymerization. The systems were stable at different [A1]/[V] molar ratios and polymerization temperatures.21 Branched polyethylene/high-density polyethylene blends were prepared using the combined [NiChfa-diimine)] and V(T(Tp-vls )(N Bu) catalysts. The polymerization reactions were performed in hexane or toluene at three different polymerization temperatures (CPC, 30°C and 50°C) and several nickel molar fractions, using MAO as cocatalyst.22 TpMs- and TpMs -imido vanadium (V) were immobilized onto a series of inorganic supports All the systems were shown to be active in ethylene polymerization in the presence of MAO or TiBA/MAO mixture.23... 

The same group also reported a disperse system consisting of N-oxyl-immobilized polyethylene particles as disperse phase and aqueous NaHC03-NaBr as disperse medium [19]. N-Oxyl-immobilized poly(p-phenylenebenzobisthiazolc) network polymer particles (PBZTNT-N-oxyl) have also been developed. The polymer is effective for the anodic oxidation of alcohols to afford the corresponding ketones, aldehydes, and/ or carboxylic adds [20]. These achievements nicely demonstrate the potential of liquid-solid disperse systems for eledroorganic synthesis. 

The activity of some polyethylene glycols bonded with macroporous copolymers of glycidylmethacrylate during the interfacial catalysis of the model reaction of sodium phenolate with n-BuBr, were investigated [79]. Rate constants of phenol alkylation in the aqueous system NaOPh-n-BuBr (in toluene)-PEG were measured at 60°C as a function of the molecular weight of PEG and its concentration. The obtained results were compared with the data on the kinetics of the reaction occurring in the presence of soluble PEG. Upon the insertion of immobilized and soluble PEG, alkylation rates increased 168 and 139 fold, respectively. The increase of the catalytic activity of immobilized PEG, which corresponded to a rise in the molecular weight of the polymer, was caused by an increase in the PEG ability to sorb alkali metal cations. 

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