Method for preparing amorphous polymer chains in elastomers

A method for preparing an amorphous polymer chain in an elastomer having substantially no hard segments and being millable on conventional rubber machinery, which polymer chain results in elastomer after being cross-linked, comprising the steps of:

• forming a crystallizable oligomer having a repeating unit comprising regularly arranged monomer units;
• and
• reacting said repeating unit at both ends thereof to effect extensions of its chain length;
• wherein said method further comprises the steps of:
• selecting the kind of said monomer units to be introduced into said repeating unit;
• selecting the number of said monomer units in said oligomer from a predetermined range, in order to prevent crystallization by the linkage units and to avoid not having a lower glass transition temperature, so that the number of said monomer units in said oligomer is not higher or lower than the predetermined range;
• selecting the molecular weight distribution of said repeating unit, comprising said monomer units being as small as possible in order to avoid a molecular weight more or less than a predetermined range, thereby causing local crystallization and avoiding not having a lower glass transition temperature;
• selecting a linkage unit, selected from urethane linkage units and amide linkage units, comprising a compound which reacts with the terminals of said repeating units and inhibits crystallization of said repeating unit after the reaction;
• whereby controlling crystallizability of said polymer chain such that a portion including said oligomer has an elastic phase where the crystallizability of said oligomer is limited under normal operational conditions so that it shows rubber elasticity and a highly oriented phase where said portion including said oligomer behaves like a crystallized oligomer when deformed excessively.