High mobility organic semiconductor formulations with excellent uniformity across large area substrates are prepared via the use of formulations containing small molecule and high permittivity semiconducting oligomers. The use of these high-k ( k > 3.3) oligomers allows control of the wetting via the manipulation of the surface energy of the substrate being coated. Organic thin fi lm transistors results with mobilities of up to 5 cm 2 V −1 s −1 , standard deviation <10 %, on/off ratios of 10 9 are presented.

Summary: Environmental scanning electron microscopy (ESEM) was used to study the film formation mechanisms and extent of coalescence of three acrylic latex compositions with different glass transition temperatures (Tg), here defined as standard‐low Tg, standard‐high Tg (both carboxymethyl cellulose‐ stabilised) and novel (stabilised with a novel polysaccharide derived from agricultural waste). The ESEM analysis revealed that the microstructure of the standard – low‐Tg system consisted of individual particles in dispersion and upon evaporation a continuous film formed, whereas in the case of the standard ‐ high Tg latex particle deformation was not observed, but particle aggregation resulted in the formation of crystal‐like structures that have formed via the formation of stacking faults. However, in the case of the novel system the microstructure consisted of individual particles and clusters and during evaporation a discontinuous film formed with voids present within its structure and some of the clusters accumulating on the surface of the specimens.

No abstract

Recently there has been renewed interest in moulding and embossing of polymers as potentially cheap methods of mass producing passive waveguide devices.1,2 Manufacturing components with good optical performance by these methods requires careful control of the fabrication process and the use of materials with optimised properties. Ideally the materials should have low intrinsic optical loss at 1.3 and 1.55 micron, should be refractive index matched to silica, and should provide acceptable thermal stability. Also, they must be processible. We have synthesised deuterated and non-deuterated fluoromethacrylate resins, which satisfy these criteria. They have intrinsic losses of 0.1 dB/cm at 1.3 micron and 0.6 dB/ cm at 1.55 micron whilst their refractive index is 1.45 at both wavelengths. Furthermore, their reflective index can be tuned by changing the amount of fluorine in the resin formulation. We have produced single mode waveguide power splitters using this material by embossing.

As the use of fibre optic networks increases in telecoms, datacoms, avionic and automotive areas, there will be increased demand for passive optical components, such as splitters, combiners, multiplexers and demultiplexers. However, for widespread application, fibre networks must be economically attractive in comparison with alternative solutions and so these passive components must be available at low cost. Polymer device fabrication techniques offer the potential to achieve these low cost targets and so are receiving increasing interest.