Graft copolymers having pendant thiuram disulfide functions

A graft copolymer having grafts containing vinyl or diene sequences, said copolymer comprising a chain linkage comprising repeating units of:

• ##STR22## wherein:
• R.sub.1 represents a hydrogen atom or a monovalent organic radical which is an alkyl, cycloalkyl or aryl radical or a combination of at least two of the aforesaid radicals;
• a ##STR23## radical, where R.sub.7 represents hydrogen, an alkyl, cycloalkyl, or aryl radical or a combination of at least two of the aforesaid radicals;
• or a radical substituted by at least one halogen atom, said radical being an alkyl, cycloalkyl or aryl radical or a combination of at least two of the aforesaid radicals;
• A represents a single bond;
• an alkylene, cycloalkylene or arylene radical or a combination of at least two of the aforesaid radicals;
• or a ##STR24## radical, where B represents an alkylene, cycloalkylene or arylene radical or a combination of at least two of the aforesaid radicals;
• R.sub.2, R.sub.3 and R.sub.4 each represent independently an unsubstituted alkyl, cycloalkyl or aryl radical or a combination of at least two of the aforesaid radicals or at least one of R.sub.3 and R.sub.4 is substituted by at least one hydroxyl or carboxylic acid group, or at least one of R.sub.3 and R.sub.4 represents a polyoxyethylene or polyester sequence derived from a polyoxyethylene or a polyester terminated by a hydroxyl function, respectively;
• all of said alkyl, cycloalkyl, aryl radicals and their combinations, alkylene, cycloalkylene, arylene radicals and their combinations optionally containing at least one heteroatom, and/or at least one ##STR25## radical, where R represents alkyl, cycloalkyl or aryl radicals or a combination of at least two of said radicals;
• and
• where Po represents a vinyl or diene polymer sequence, said chain linkage optionally containing a random distribution of units derived from at least one vinylic monomer.