Spin-dependent non-singlet structure functions in next-to-leading order

We study in detail the flavor-non-singlet component of polarized structure functions in the framework of a consistent and complete next-to-leading order (${\cal O}(\alpha_s))$ analysis. In this context, we discuss some important features of the calculation of the next-to-leading order corrections. Particular emphasis is put on the $Q^2$-evolution of sum-rules for the first moments of the non-singlet structure functions which, as we show, could serve to explore $SU(2)$ and $SU(3)$ breaking effects in relations between baryonic $\beta$-decay matrix elements and in the proton's polarized sea. Furthermore we make predictions for polarized non-singlet structure functions measurable in a conceivable $\vec{e}\vec{p}$ collider mode of HERA.