| Peptide amphiphiles have been extensively used as versatile building blocks for the formation of nano-sized fibrous assemblies directed by the interplay of hydrophobic and hydrogen bonding interactions, a spontaneous and thus more or less uncontrolled process. Now, we would like to take the control over the organization of these assemblies one step further by creating structures which can be controlled in all dimensions, including the length of the fibre. Peptides will be tuned to assemble and disassemble in a controlled fashion through the connection of polymerisable hydrophobic moieties. We and others have shown that the incorporation of hydrophobic alkyl tails can induce and stabilise self-assembly of peptides. Furthermore, it has been demonstrated by us that such peptide amphiphile assemblies are amenable to manipulation to introduce higher order organisation such as alignment by a magnetic field. Moreover, the incorporation of polymerisable (e.g. by UV light) moieties in the hydrophobic elements allows us to further stabilise the fibres at specific sites. By exploiting this introduced difference in stability within the fibres in combination with control over the molecular order, established through alignment of the assemblies, we hope to be able to prepare highly defined supramolecular materials, gaining influence on all dimensions: First peptide fibres will be aligned via an external force, such as shearing or a magnetic field. Subsequently, irradiating the aligned fibres with spatially addressed UV light will lead to enhanced stability of the irradiated areas when a diacetylene moiety is introduced in the hydrophobic tails. The non-exposed areas will remain dynamic in nature which allows us to wash these non-crosslinked parts away. It will therefore be possible to ?cut? the nanofibres into pieces of highly defined length by using an appropriate grating as a mask. This could also be achieved by means of holography creating an intensity pattern or more interestingly by means of polarisation holography creating an pattern in which the direction of the polarisation of the light changes in space. Because the polymerisation of the diacetylenes after alignment is sensitive to the direction of the polarisation plane of the incident light also in this manner the fibres can be polymerised locally. This technique at first does not give any major benefit over the classical lithography approach. However, when we combine this technique with a intensity modulation of the light that is in line with the polarisation modulation in space the samples need not be aligned at all in order to be able to ?cut? the fibres into pieces of defined length. Regardless of the adopted strategy we will be able to construct nanoscale ?needles? of which the aspect ratio can be tuned. Conceivably, the tendency to align magnetically for such samples will differ markedly from the larger structures they have been derived from and could be tuned by altering the size of the assemblies. Typically, such structures are to be expected to display distinctive liquid crystalline behaviour of which the properties will be investigated in relation to shape and size of the assemblies. Hence, combining a bottom-up (self-assembly) and a top-down (lithography/holography) approach the project will not only offer a novel starting point in the design of devices with a nanoscale architecture but will also provide insight into key challenges and fundamental issues of areas such as (peptide) self-assembly and liquid crystalline behaviour. |
