Application phase transition recovery

The previous ELP fusions all are examples of protein purification in which the ELP is covalently connected to the protein of choice. This approach is suitable for the purification of recombinant proteins that are expressed to high levels, but at very low concentrations of ELP the recovery becomes limited. Therefore this approach is not applicable for proteins expressed at micrograms per liter of bacterial culture, such as toxic proteins and complex multidomain proteins. An adjusted variant of ITC was designed to solve this problem. This variant makes use of coaggregation of free ELPs with ELP fusion proteins. In this coaggregation process, an excess of free ELP is added to a cell lysate to induce the phase transition at low concentrations of... 

Membrane separations involve the selective solubility in a thin polymeric membrane of a component in a mixture and/or the selective diffusion of that component through the membrane. In reverse osmosis (3) applications, which entail recovery of a solvent from dissolved solutes such as in desalination of brackish or polluted water, pressures sufficient to overcome both osmotic pressure and pressure drop through the membrane must be applied. In permeation (4), osmotic pressure effects are negligible and the upstream side of the membrane can be a gas or liquid mixture. Sometimes a phase transition is involved as in the process for dehydration of isopropanol shown in Fig. 1.8. In addition, polymeric liquid surfactant and immobilized-solvent membranes have been used. 

Performance polymers are used transitionally as solid-state materials in construction, transport, electrical engineering, etc., where their bulk mechanical, electrical, and thermal properties are exploited. At the same time, solutions of polymers are found in a large number of industrial processes and applications, from oil recovery to home and personal care products, agriculture, nutrition, etc. Polymerization processes are usually performed in a liquid phase with a subsequent purification of targeted product. 

SME of shape memory polyurethanes (SMPUs), the shape recoverability and shape fixing ability, ate dependent on the polyurethane network structure and phase transition of the SMPU, respectively. The roles played by the reversible phase and fixed phase are complex. Recovery stress is essential for most of the applications for SMPs since in practical applications the shape recovery can be impeded by external stimuli. 

Assessment of the mechanical properties and engineering applications of polymers is made by consideration of orientation, conformation and three-dimensional state of order of the polymer during the deformation processes. FT-Raman spectroscopy is also applied to the analysis of transient structural changes induced by polymer deformation. For a clear understanding of a deformation mechanism, characterization of structural changes is required online. Studies have been performed on a wide variety of polymers during elongation and recovery, to monitor phase transitions and alterations in crystallinity and anisotropy. Particularly useful for this purpose has been the simultaneous analysis of mechanical and spectroscopic properties, called rheooptical measurements. 

The temperature sensitivity of ELPs may be exploited in tissue engineering for those applications that may benefit from biomaterial formulations that are injectable and may be tri ered in some way to form a solid matrix after defect filling. The inherent thermal transition properties of ELPs provide a natural tri er for coacervation, and reversibility of the phase transition enables recovery of ELPs from applications that desire a scaffold-free outcome. 

Numerous polymers have been proposed as shape-memory polymers (SMPs), and many of them are based on polyurethanes. This is because of the intrinsic versatility of segmented copolyurethane systems. By suitable choice of diisocyanate and macrodiol, a wide variation in properties may be obtained, allowing the possibility of tuning the shape-memory response to suit different applications. Usually they are phase-segregated materials. For example, a dispersed rigid phase (usually based on the diisocyanate) provides physical crosslinks, while the macrodiol provides a soft amorphous phase with low glass transition that provides the trigger temperature for shape recovery [63]. 

Under normal conditions, the interphase is in the high-elastic state only in the case when its glass transition is below room temperature. The dimensions and composition of the interphase influence the glass transition temperature of the soft phase and of the interphase itself, as well as the melting point of the hard phase. These parameters are in turn decisive as far as the flexibility plateau is concerned. Hence, they influence the range of applicability of this elastomer and its mechanical memory (recovery). 

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