Controlling and Evaluating the Structure and Morphology of Polymers on Multiple Scales

Crystalline polymers spontaneously form hierarchical structures although the precise manner in which these scales of structure are interconnected especially terms of the formation and evolution of the complete structure remains unclear. We have set out to control these scales of structure by introducing additional components which self-assemble in to nano-scale units which then direct the crystallisation of the polymer matrix. In other words, we first assemble a low concentration top-level structure which is designed to template or direct the sub-sequent crystallisation of the matrix polymer. This top level structure takes on the role of controlling the structure. We have set out to both establish the design principles of such structures and to develop experimental procedures which allow us to follow the formation of such complex hierarchical polymer structures. In particular we focus of the relationships between these different levels of structure and time sequence of events required for the structure to evolve in the targeted manner. In this programme, we have exploited time-resolving small-angle X-ray scattering and electron microscopy together with neutron scattering to probe and quantify the different scales of structure and their evolution. We highlight new neutron scattering instrumentation which we believe have great potential in the growing field of hierarchical structures in polymers. The addition of small quantities of nanoparticles to conventional and sustainable thermoplastics leads to property enhancements with considerable potential in a number of areas Most engineered nano-particles are highly stable and these exist as nano-particles prior to compounding with the polymer resin, they remain as nano- particles during the active use as well as in the subsequent waste and recycling streams. In this work we also explore the potential for constructing nano-particles within the polymer matrix during processing from organic compounds selected to provide nanoparticles which can effectively control the subsequent crystallization process. Typically these nano-particles are rod-like in shape.

Long-term live-cell microscopy with labeled nanobodies delivered by laser-induced photoporation

Fluorescence microscopy is the method of choice for studying intracellular dynamics.However,its success depends on the.availability of specific and stable markers.A prominent example of markers that are rapidly gaining interest are nanobodies(Nbs.-15 kDa),which can be functionalized with bright and photostable organic fluorophores.Due to their relatively small size and high specificity,Nbs offer great potential for high-quality long-term subcellular imaging,but suffer from the fact that they cannot spontaneously cross the plasma membrane of live cells.We have recently discovered that laser-induced photoporation is well suited to deliver extrinsic labels to living cells without compromising their viability.Being a laser-based technology,it is readily compatible with light microscopy and the typical cell recipients used for that.Spurred by these promising initial results,we demonstrate here for the first time successful long-term imaging of specific subcellular structures with labeled nanobodies in living cells.We illustrate this using Nbs that target GFP/YFP-protein constructs accessible in the cytoplasm,actin-bundling protein Fascin,and the histone H2A/H2B heterodimers.With an efficiency of more than 80%labeled cells and minimal toxicity(-2%),photoporation proved to be an excellent intracellular delivery method for Nbs.Time-lapse microscopy revealed that cell division rate and migration remained unaffected,confirming excellent cell viability and functionality.We conclude that laser-induced photoporation labeled Nbs can be easily delivered into living cells,laying the foundation for further development of a broad range of Nbs with intracellular targets as a toolbox for long-term live-cell microscopy.

Nonpolar Al_(x)Ga_(1−x)N/Al_(y)Ga_(1−y)N multiple quantum wells on GaN nanowire for UV emission

Nonpolar m-plane AlGaN offers the advantage of polarization-free multiple quantum wells(MQWs)for ultraviolet(UV)emission and can be achieved on the sidewalls of selective area grown GaN nanowires.We reveal that the growth of AlGaN on GaN nanowires by metal organic chemical vapor deposition(MOCVD)is driven by vapor-phase diffusion,and consequently puts a limit on the pitch of nanowire array due to shadowing effect.An insight into the difficulty of achieving metal-polar AlGaN nanowire by selective area growth(SAG)in MOCVD is also provided and can be attributed to the strong tendency to form pyramidal structure due to a very small growth rate of{1011}semipolar planes compared to(0001)c-plane.The nonpolar m-plane sidewalls of GaN nanowires obtained via SAG provides an excellent platform for growth of nonpolar AlGaN MQWs.UV emission from mplane Al_(x)Ga_(1−x)N/Al_(y)Ga_(1−y)N MQWs grown on sidewalls of dislocation-free GaN nanowire is demonstrated in the wavelength range of 318–343 nm.