Curable compositions containing isocyanate-based tougheners

A homogenous curable composition comprising:

• A) an N-arylated benzoxazine component, and
• B) a prepolymer of the following structure:
• P—(X—CO—NH—D—NH—CO—Y—E)z,
• wherein
• P is a z-valent residue,
• X and Y independently are selected from the group consisting of NR′, O and S, wherein R′ is hydrogen or a residue selected from the group consisting of aliphatic, heteroaliphatic, araliphatic, heteroaraliphatic, aromatic and heteroaromatic residues,
• D is a divalent residue of a diisocyanate comprising two isocyanate groups having different reactivity, from which the two isocyanate groups with different reactivity have been removed to form two binding sites being valences,
• E is an end-capping residue, selected from the group consisting of aliphatic, heteroaliphatic, araliphatic, heteroaraliphatic, aromatic and heteroaromatic residues, and
• z is an integer of 1 to 12,
• wherein the homogenous curable composition exhibits upon curing G1c of 450 J/m2 or more according to ASTM 05045-96 using single etch notch bending test specimens sized 56 mm×12.7 mm×3.2 mm