Oxyethylene-chain crosslinking

Irradiation Procedure. 30% w/w solutions of poloxamer were prepared in distilled water by the cold process and saturated with nitrous oxide. This agent is a known scavenger of hydrated electrons and is known to enhance crosslinking of poly(oxyethylene) chains (9). Vials containing these solutions were irradiated at ambient temperature in a 2000 Ci ° Co source at a dose rate of 0.5 Mrad h- Physicochemical measurements were performed on solutions prepared by dilution of these irradiated samples. 

The length of a crosslinker is the distance between the polymerisable units and this defines the maximum distance between the two crosslink points attaching two polymer chains. Varying the length of an alkyl or oxyethylene chain between two methacrylate units showed that the shortest crosslinker ethylene... 

PS = insoluble polymeric matrix crosslinked polystyrene POE = hydrophilic spacer poly(oxyethylene) chain X = anchoring group -O-... 

Another factor has to be considered. When the macromonomer chain segments can give rise to transfer reactions, the probability of such events is enhanced because the number of chain segments per unsaturation is high. Homopolymerization of such macromonomers should be expected to involve additional branching and possibly crosslinking. A typical example is that of PEO macromonomers because oxyethylene units are known to induce transfer reactions U3). 

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