The structure factor, viscosity, and diffusivity of four (styrene-b-isoprene-b-styrene-b-isoprene) tetrablock copolymers have been examined as functions of temperature (T). The copolymers have styrene compositions (f) of 23, 42, 60, and 80 vol % and total degrees of polymerization ca. 120; polystyrene and polyisoprene homopolymers with similar degrees of polymerization have been used for comparison. Small angle neutron scattering (SANS) measurements in the disordered state are well-described by the appropriate Leibler/RPA structure factors, and extrapolation of the inverse peak intensities to lower T yields estimates of the order-disorder transition temperatures, which are at or below -50 degrees C. Consequently, over the T range of interest (25-180 degrees C) and over length scales greater than the chain dimensions, the tetrablocks provide homogeneous matrices containing varying amounts of styrene and isoprene, in which the f and T dependence of segmental friction may be examined. The diffusivity (determined by pulsed-field-gradient NMR and forced Rayleigh scattering) and viscosity provide estimates of the effective monomeric friction factor zeta(eff)(f,T) via the Rouse model; the two dynamic properties yield equivalent values of zeta(eff). The T dependence of zeta(eff) is well-described by the WLF function, with the f dependence almost entirely contained in the composition dependence of the glass transition temperature (T-g). Thus, when compared at constant T - T-g, zeta(eff)(f) is only slightly larger than zeta(PS)degrees or zeta(PI)degrees, in marked contrast to the results for miscible blends such as PS/PVME and PS/PPO. Prediction of zeta(eff)(f,T) on the basis of the homopolymer values alone, i.e., zeta(PS)degrees (T) and zeta(PI)degrees(T) is only successful when T-g(f) is incorporated explicitly. An approach using equation of state estimates oi;free volume is significantly less successful, implying that the most important determinant of local friction in the mixture is the effective T-g sensed by each chain; T-g(f) does not represent an iso-free volume state.