In the compounds of formula B1 and B2, R1 is in particular a poly propylene oxide chain or a poly tetramethylene oxide chain, but it can also represent a chain derived from dicarboxylic acids, {HEAD ~ diols}, {TAIL ~ diamines} or diisocyanates etc., by well known methods of poly condensation 
In the compounds of formula B1 and B2 , R1 is in particular a poly propylene oxide chain or a poly tetramethylene oxide chain , but it can also represent a chain derived from dicarboxylic acids , { HEAD ~ diols } , { TAIL ~ diamines } or diisocyanates etc . , by well known methods of poly condensation
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