In recent years the self-assembly of block copolymers has received considerable attention, which has resulted in many exciting discoveries. [1] By careful selection of the type of blocks employed, the properties of these polymers can be readily tuned, making them potentially interesting systems from both an academic and industrial point of view. When a good solvent is chosen for only one of the blocks, aggregation will occur, thus leading to phase separation. A great number of parameters can be varied, which alter the aggregation architecture, namely, temperature, solvent, block length, ratio of one block to another, concentration, and pH. [2] Consequently, a wide variety of morphologies has been reported for this type of self-assembled macromolecules, for example, spheres, rods, lamellae, films, and patterned surfaces, [3] which have a considerable potential in a wide range of applications in the fields of optoelectronics and biomedicine. [4] Rod-coil diblock copolymers, consisting of a flexible and a rigid block, constitute a special class of block copolymers. [2, 3] Recently, we have shown that polyisocyanopeptides can be used as the rigid component in such systems. [5,6] These isocyanide polymers have a very high persistence length, which originates from the well-defined helical b-sheet arrangement of the polymer side chains. [7] Charged diblock copolymers of styrene and isocyano-l-alanyl-l-alanine, and of styrene and isocyano-l-alanyl-l-histidine have also been prepared and found to self-assemble in water to form a variety of structures such as vesicles, multilayers and even helical aggregates. [5] Herein, we describe the aggregation behavior of a rodcoil diblock copolymer derived from an isocyanoamino acid containing a thiophene group. This diblock copolymer consists of 40 styrene and 50 3-(isocyano-l-alanyl-amino-ethyl)thiophene (PS-PIAT) units and is an amphiphile in both organic and aqueous solvents because of only a slight difference in polarity between the two blocks (Figure 1 a,b). The thiophene rings in PS-PIAT are present as functional groups that can be polymerized after aggregation, [8] to form stable polymerized morphologies with possibly interesting applications, for example, as conducting materials.
PS-PIAT was synthesized and characterized following procedures previously reported by us. [5] As a result of the amide functional groups in the PIAT side chains the thiophene groups are arranged in four stacks, which run parallel to the helical polymer backbone (Figure 1 c). When PS-PIAT is dissolved in CHCl 3 it forms vesicles as was shown by transmission electron microscopy (TEM). [9] Upon drying, the spherical shape of the vesicles was not retained, as we concluded from the collapsed structures that were visible after platinum shadowing of the TEM grids (Figure 2 a, inset I). Aggregation of the diblock copolymer molecules is induced by the poor solubility of the polyisocyanide block in CHCl 3 . The formed vesicles have a high polydispersity, with diameters varying between 2 and 22 mm, with an average diameter of 7 mm, and an average membrane thickness, as determined from the TEM images, of 27 AE 5 nm, which is approximately twice the length of a single, stretched, PS-PIAT molecule. We propose that the vesicle membrane is composed of a bilayer, in which the polyisocyanide blocks are located in the center of the membrane and the polystyrene blocks are directed towards the solvent (Figure 2 b). In separate experiments PS-PIAT was added to a dispersion of (FeCl 3 ) in CHCl 3 to polymerize the thiophene groups of the [*] Dr.