Crystallization of droplet dispersions and polymer layers

This section has shown examples of how through MD isolation and confinement, which typically results from the self-assembly of block copolymers, crystalline phases can change their nucleation behavior from heterogeneous to superficial, or homogeneous nucleation and their crystallization kinetics can also change from a complex process to a simple first-order process dominated by nucleation. Intermediate behavior is common, when percolated and isolated phases coexist. In many cases fractionated crystallization can be found as well as fractionated melting (although this last case has only been documented once for nanometric PEO droplets within PB-/ -PEO or PE-fo-PEO as presented above). 

The study of droplet dispersions is the oldest strategy to study nucleation changes induced by producing isolated clean phases of crystahizable materials. Many of these pioneering studies [1-10] demonstrated that obtaining the homogeneous nucleation temperature of a polymeric material can be very difficult and that the influence of superficial nucleation can be also quite 

in recent years, micro- and nanolayers have offered a great opportunity to analyze the influence of film thickness (and the influence of the interface with a foreign material—substrate) on polymer crystallization and final morphology. Generally, the crystallization process is only affected when the film thickness is less than the average spherulitic dimension in that case the 

Instantaneous nucleation and quick crystal growth in isolated droplets whose thickness is greater or equal to 5 nm. The crystallization temperatures observed were in the range of 38°C to 37°C, and the crystallization temperature has a dependence on droplet volume. 

Nucleation and slow growth where only one nucleus is formed inside the droplets. This behavior was observed in droplets that had a thickness of between 2 and 3 nm and a diameter of around 700 nm. The crystallization temperature was 34.8°C. 

---

A further means of achieving efficient light scattering in a liquid crystal device is to disperse a nematic material in a plastic matrix [63, 64]. The plastic is chosen so as to have a refractive index which is equal to no of the liquid crystal. One fabrication route [63] involves forming an emulsion of liquid crystal in a water-borne polymer system, which is then coated onto a substrate and dried. The product is a plastic film containing many small, separate droplets of liquid crystal. Alternatively, the liquid crystal may be dissolved in a reactive monomer [65], which is polymerized in a thin layer. As the polymer forms, the liquid crystal is expelled from solution and forms a similar array of droplets. Another route uses a polymer in... 

In this type of device the liquid crystal interpenetrates the fibres of the non-woven mat, in contrast to CPDLCs and polymer dispersed liquid crystals (PDLCs) where it stays confined in layers or droplets, resulting in enhanced electro-optical properties. 

---