Process for preparing high-reactivity isobutene homo- or copolymers

A process for preparing a high-reactivity isobutene homo- or copolymer, the process comprising:

• polymerizing isobutene or an isobutene-comprising monomer mixture in the presence of a complex, comprising
• a donor, and
• an aluminum trihalide or an alkylaluminum halide, to obtain the isobutene homo- or copolymer having a content of terminal vinylidene double bonds per polyisobutene chain end of at least 70 mol %,
• wherein the donor comprises a mixture of at least two ethers each of the general formula. R1—O—R2,
• wherein R1 and R2 are each independently selected from the group consisting of C1- to C20-alkyl radicals, C5- to C8-cycloalkyl radicals, C6- to C20-aryl radicals, and C7- to C20-arylalkyl radicals,
• wherein in at least one ether, R1 and R2 independently of another comprise a halogen atom, and
• wherein an acid employed in the process comprises only a carboxylic acid, a mineral acid, aluminum trihalide, alkylaluminum dihalide, dialkyl aluminum halide or a mixture thereof.