Novel anionic polymerization initiator, use thereof for synthesizing a diene elastomer having an alkyne function at the chain end, and funcionalized diene elastomer

A process for the synthesis of a diene elastomer bearing, at one or each of its chain ends, a group comprising an alkyne functional group, comprising the anionic polymerization of at least one conjugated diene monomer initiated by an organometallic compound comprising an alkyne bond of formula 1:

• wherein
• Met, which can be borne by the ortho, meta or para position with respect to the group comprising the carbon-carbon triple bond, denotes an alkali metal, and
• R1 and R2, and also R3 and R4, which can be borne by the ortho, meta or para position, denote, independently of one another, a hydrogen atom, a C1-C15 alkyl group, a C5-C15 cycloalkyl group, a C6-C15 aryl group or a C7-C15 arylalkyl group which can be separated from the aromatic nucleus by a heteroatom, such as O or S, and
• R5 denotes a C1-C5 alkyl group, a C5-C15 cycloalkyl group, a C6-C15 aryl group, a C7-C15 arylalkyl group or a protective group for the alkyne functional group.

A diene elastomer bearing, at one or each of its chain ends, a group comprising an alkyne functional group, corresponding to the following formula 3:

• (A-E)n-X Formula 3
• wherein:
• X denotes a hydrocarbon group of valency n or a group resulting from a functionalization, coupling or star-branching agent comprising at least one atom chosen from O, N, Si or Sn;
• A is a monovalent radical corresponding to the following formula 2:
• wherein:
• R1 and R2, and also R3 and R4, which can be borne by the ortho, meta or para position, denote, independently of one another, a hydrogen atom, a C1-C15 alkyl group, a C5-C15 cycloalkyl group, a C6-C15 aryl group or a C7-C15 arylalkyl group which can be separated from the aromatic nucleus by a heteroatom, such as O or S,
• R5 denotes a hydrogen atom, a C1-C5 alkyl group, a cycloalkyl group, a C6-C15 aryl group, a C7-C15 arylalkyl group or a protective group for the alkyne functional group, and
• * indicates a point of bonding with the elastomer E,
• E, which can be borne by the ortho, meta or para position of A with respect to the group comprising the carbon-carbon triple bond, denotes the diene elastomer, and
• n is an integer ranging from 1 to 12.