Two decades ago, the concept of molecular reinforcement of thermoplastics was advanced: it was predicted that thermoplastics of regular flexible-coil polymers are strongly reinforced by rigid-rod polymer chains that are molecularly dispersed in the thermoplastic matrix, acting as "molecular fibres". However, it proved difficult to test this concept because rigid-rod and flexible-coil polymers are usually demixed. Rigid-rod chains do not dissolve in normal thermoplastic matrices bur form a separate phase. A related concept bearing more promise, i.e. the "micellar reinforcement", is;introduced in this paper: rigid chains that are provided with flexible grafts can form reinforcing cylindric micelles in thermoplastic matrices. The micelles of such rod-coil graft copolymers have a thickness on the submicroscopic scale, not far above the molecular scale. This concept was explored in a polyester-polystyrene system based on rigid-chain polyesters (PES) containing double-bond units. Graft copolymers PSgPES were prepared by a mechanism of "grafting-through" which amounts to a random copolymerisation of styrene and the double bonds in the PES chains. Synthetic problems were (i) achieving high molecular weights, in particular of the PS chains, and (ii) avoiding crosslinking which occurs easily via multigrafting. After attempts with initiators in the bulk and in solution, thermal polymerisation without an initiator yielded long-chained PSgPES graft copolymer products with only moderate shares of ungrafted PS and RES byproducts. These graft products formed cylindric micelles of PES in a PS matrix which doubled the modulus of PS.